EPA/540/R-06/009 

 March 2006 

Compost-Free Bioreactor 

Treatment of Acid Rock Drainage 

Leviathan Mine, California 

Innovative Technology Evaluation Report 

National Risk Management Laboratory 

Office of Research and Development 

U.S. Environmental Protection Agency 

Cincinnati, Ohio 45268
__________________________________________________________________________ 

Notice 

The information in this document has been funded wholly or in part by the U.S. Environmental Protection 

Agency (EPA) in partial fulfillment of Contract No. 68-C-00-181 to Tetra Tech EM, Inc. It has been subject 

to the Agency’s peer and administrative review, and it has been approved for publication as an EPA 

document. Mention of trade names of commercial products does not constitute an endorsement or 

recommendation for use. 

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Foreword 

The U.S. Environmental Protection Agency (EPA) is charged by Congress with protecting the Nation’s land, 

air, and water resources. Under a mandate of national environmental laws, the Agency strives to formulate 

and implement actions leading to a compatible balance between human activities and the ability of natural 

systems to support and nurture life. To meet this mandate, EPA’s research program is providing data and 

technical support for solving environmental problems today and building a science knowledge base 

necessary to manage our ecological resources wisely, understand how pollutants affect our health, and 

prevent or reduce environmental risks in the future. 

The National Risk Management Research Laboratory (NRMRL) is the Agency’s center for investigation of 

technological and management approaches for preventing and reducing risks from pollution that threaten 

human health and the environment. The focus of the Laboratory’s research program is on methods and their 

cost-effectiveness for prevention and control of pollution to air, land, water, and subsurface resources; 

protection of water quality in public water systems; remediation of contaminated sites, sediments and ground 

water; prevention and control of indoor air pollution; and restoration of ecosystems. NRMRL collaborates 

with both public and private sector partners to foster technologies that reduce the cost of compliance and to 

anticipate emerging problems. NRMRL’s research provides solutions to environmental problems by: 

developing and promoting technologies that protect and improve the environment; advancing scientific and 

engineering information to support regulatory and policy decisions; and providing the technical support and 

information transfer to ensure implementation of environmental regulations and strategies at the national, 

state, and community levels. 

This publication has been produced as part of the Laboratory’s strategic long-term research plan. It is 

published and made available by EPA’s Office of Research and Development to assist the user community 

and to link researchers with their clients. 

 Sally C. Gutierrez, Director

 National Risk Management Research Laboratory 

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Abstract 

As part of the Superfund Innovative Technology Evaluation (SITE) program, an evaluation of the compostfree bioreactor treatment of acid rock drainage (ARD) from the Aspen Seep was conducted at the Leviathan 

Mine Superfund site located in a remote, high altitude area of Alpine County, California. The evaluation 

was performed by U.S. Environmental Protection Agency (EPA) National Risk Management Research 

Laboratory (NRMRL), in cooperation with EPA Region IX, and Atlantic Richfield Company (ARCO), the 

state of California, and the University of Nevada-Reno (UNR). The primary target metals of concern in the 

ARD include aluminum, copper, iron, and nickel; secondary target metals include selenium and zinc. 

Drs. Glenn Miller and Tim Tsukamoto of the UNR have developed a compost-free bioreactor technology in 

which sulfate-reducing bacteria are nurtured to generate sulfides which scavenge dissolved metals to form 

metal sulfide precipitates. Unlike compost bioreactors, this technology uses a continuous liquid carbon 

source and a rock matrix rather than a compost or wood chip matrix which is consumed by bacteria and 

collapses over time. The benefits include better control of biological activity and improved hydraulic 

conductivity and precipitate flushing. 

Evaluation of the compost-free bioreactor technology occurred between November 2003 and July 2005. The 

treatment system neutralized acidity and precipitated metal sulfides from ARD at flows up to 91 liters per 

minute (24 gallons per minute) on a year-round basis. Multiple sampling events were conducted during both 

gravity flow and recirculation modes of operation. During each sampling event, EPA collected chemical 

data from the system influent and effluent streams, documented metals removal and reduction in acidity 

between the bioreactors, settling ponds, and aeration channel, and recorded operational information pertinent 

to the evaluation of the treatment system. The treatment system was evaluated independently, based on 

removal efficiencies for primary and secondary target metals, comparison of effluent concentrations to EPA 

interim (pre-risk assessment and record of decision) discharge standards, and on the characteristics of and 

disposal requirements for the resulting metals-enriched solid wastes. Removal efficiencies of individual unit 

operations were also evaluated. 

The compost-free bioreactor treatment system was shown to be extremely effective at neutralizing acidity 

and reducing the concentrations of 4 of the 5 target metals in ARD flows at Leviathan Mine to below EPA 

interim discharge standards. During the demonstration, pilot testing to determine optimal sodium hydroxide 

addition resulted in exceedance of discharge standards for iron; however, after base optimization during 

gravity flow operations effluent iron concentrations met discharge standards. Iron also exceeded discharge 

standards during recirculation operations when base addition was stopped due to equipment failure or lack of 

adequate base supply. Although the influent concentrations for the primary target metals were up to 580 

fold above the EPA interim discharge standards, the treatment system was successful in reducing the 

concentrations of the primary target metals in the ARD to between 1 and 43 fold below the discharge 

standards. Removal efficiencies for the 5 primary target metals exceeded 85 percent; sulfate ion was 

reduced by 17 percent. The metal sulfide precipitates generated by this technology were not found to be 

hazardous or pose a threat to water quality and could be used as a soil amendment for site reclamation. 

Based on the success of bioreactor treatment at the Leviathan Mine site, ARCO will continue to treat ARD 

at the Aspen Seep. The state of California and ARCO are also evaluating the potential effectiveness, 

implementability, and costs for treatment of other ARD sources at the mine site. 

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Contents 

Notice ............................................................................................................................................................... i 

Foreword ............................................................................................................................................................ ii 

Abstract .............................................................................................................................................................iii 

Acronyms, Abbreviations, and Symbols .......................................................................................................... vii 

Conversion Factors............................................................................................................................................ ix 

Acknowledgements ............................................................................................................................................ x 

Section 1 Introduction .................................................................................................................................... 1 

 1.1 Project Background................................................................................................................ 1 

 1.2 The Site Demonstration Program and Reports....................................................................... 1 

1.3 Purpose of the Innovative Technology Evaluation Report .................................................... 3 

 1.4 Technology Description......................................................................................................... 3 

 1.5 Key Findings.......................................................................................................................... 7 

 1.6 Key Contacts.......................................................................................................................... 7 

Section 2 Technology Effectiveness ............................................................................................................. 10 

 2.1 Background.......................................................................................................................... 10 

2.1.1 Site Description ..................................................................................................... 10

2.1.2 History of Contaminant Release............................................................................ 12 

2.1.3 Previous Actions.................................................................................................... 12 

 2.2 Process Description.............................................................................................................. 12 

 2.3 Evaluation Approach ........................................................................................................... 14 

2.3.1 Project Objectives.................................................................................................. 14 

2.3.2 Sampling Program ................................................................................................. 15 

2.4 Field Evaluation Activities .................................................................................................. 16 

2.4.1 Mobilization Activities .......................................................................................... 16 

2.4.2 Operation and Maintenance Activities .................................................................. 16 

2.4.3 Process Modifications............................................................................................ 18 

2.4.4 Evaluation Monitoring Activities .......................................................................... 18 

2.4.5 Demobilization Activities...................................................................................... 19 

2.4.6 Lessons Learned .................................................................................................... 19 

 2.5 Technology Evaluation Results ........................................................................................... 20

2.5.1 Primary Objective No.1: Evaluation of Metals Removal Efficiencies ................. 20 

2.5.2 Primary Objective No.2: Comparison of Effluent Data to Discharge Standards.. 22 

2.5.3 Secondary Objectives for Evaluation of Bioreactor Treatment System Unit 

Operations ............................................................................................................. 23 

2.5.3.1 Operating Conditions........................................................................... 24 

2.5.3.2 Reaction Chemistry ............................................................................. 26 

2.5.3.3 Metals Removal By Unit Operation .................................................... 30 

2.5.3.4 Solids Separation ................................................................................. 33 

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Contents (continued) 

2.5.4 Evaluation of Solids Handling and Disposal ......................................................... 37 

2.5.4.1 Waste Characterization and Handling Requirements .......................... 37 

2.5.4.2 Bioreactor Treatment System Solids ................................................... 37 

Section 3 Technology Applications Analysis............................................................................................... 41 

 3.1 Key Features ........................................................................................................................ 41 

 3.2 Applicable Wastes .......................................................................................................... 42 

3.3 Factors Affecting Performance ............................................................................................ 42 

 3.4 Technology Limitations....................................................................................................... 42 

3.5 Range of Suitable Site Characteristics ................................................................................. 43 

 3.6 Personnel Requirements....................................................................................................... 44 

 3.7 Materials Handling Requirements ....................................................................................... 44 

 3.8 Permit Requirements .......................................................................................................... 44 

3.9 Community Acceptance....................................................................................................... 45 

3.10 Availability, Adaptability, and Transportability of Equipment ........................................... 45 

3.11 Ability to Attain ARARs ..................................................................................................... 45 

3.11.1 Comprehensive Environmental Response, Compensation, and Liability Act ....... 46 

3.11.2 Resource Conservation and Recovery Act ............................................................ 46 

3.11.3 Clean Air Act......................................................................................................... 48 

3.11.4 Clean Water Act .................................................................................................... 48 

3.11.5 Safe Drinking Water Act ....................................................................................... 48 

3.11.6 Occupational Safety and Health Act...................................................................... 48 

3.11.7 State Requirements................................................................................................ 49 

3.12 Technology Applicability To Other Sites ............................................................................ 49 

Section 4 Economic Analysis........................................................................................................................ 51 

 4.1 Introduction.......................................................................................................................... 51 

 4.2 Cost Summary...................................................................................................................... 51 

 4.3 Factors Affecting Cost Elements ......................................................................................... 52

4.4 Issues and Assumptions ....................................................................................................... 52 

 4.5 Cost Elements ...................................................................................................................... 52 

4.5.1 Site Preparation ..................................................................................................... 53

4.5.2 Permitting and Regulatory Requirements.............................................................. 53 

4.5.3 Capital and Equipment .......................................................................................... 53 

4.5.4 System Startup and Acclimation Costs.................................................................. 54 

4.5.5 Consumables and Supplies .................................................................................... 54 

4.5.6 Labor ..................................................................................................................... 54 

4.5.7 Utilities .................................................................................................................. 54 

4.5.8 Residual Waste Handling and Disposal................................................................. 55 

4.5.9 Analytical Services................................................................................................ 55 

4.5.10 Maintenance and Modifications ............................................................................ 55 

Section 5 Data Quality Review..................................................................................................................... 56 

 5.1 Deviations From TEP/QAPP ............................................................................................... 56 

5.2 Summary of Data Evaluation and PARCC Criteria Evaluation........................................... 57 

Section 6 Technology Status......................................................................................................................... 59 

References ....................................................................................................................................................... 60 

Appendix A Sample Collection And Analysis Tables .............................................................................. 61 

Appendix B Data Used To Evaluate Project Primary Objectives .......................................................... 69 

Appendix C Detailed Cost Element Spreadsheets.................................................................................... 76 

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Tables 

Table Page 

1-1 Bioreactor Treatment System Removal Efficiencies: Gravity Flow Operation....................................... 9 

1-2 Bioreactor Treatment System Removal Efficiencies: Recirculation Operation....................................... 9 

1-3 Determination of Hazardous Waste Characteristics for Bioreactor Solid Waste Streams ....................... 9 

2-1 Summary of Historical Metals of Concern ............................................................................................ 13 

2-2 Removal Efficiencies for the Bioreactor Treatment System - Gravity Flow Operation ........................ 21 

2-3 Removal Efficiencies for the Bioreactor Treatment System - Recirculation Operation ........................ 21 

2-4 EPA Interim Discharge Standards ......................................................................................................... 22 

2-5 Results of the Student’s-t Test Statistical Analysis for Maximum Daily Effluent Data ........................ 23 

2-6 Results of the Student’s-t Test Statistical Analysis for 4-Day Average Effluent Data .......................... 24 

2-7 Gravity Flow Unit Operation Parameters .............................................................................................. 25 

2-8 Recirculation Unit Operation Parameters .............................................................................................. 26 

2-9 Gravity Flow Unit Operation Reaction Chemistry ................................................................................ 27 

2-10 Impact of Temperature on Sulfate Reduction and Iron Removal During Gravity Flow Operations ..... 28 

2-11 Recirculation Unit Operation Reaction Chemistry ................................................................................ 29 

2-12 Impact of Temperature on Sulfate Reduction and Iron Removal During Recirculation Operations ..... 30 

2-13 Gravity Flow Unit Operation Dissolved Metals Removal Efficiencies................................................. 31 

2-14 Gravity Flow Unit Operation Metals and Sulfate Load Reduction........................................................ 31 

2-15 Recirculation Unit Operation Dissolved Metals Removal Efficiencies................................................. 33 

2-16 Recirculation Unit Operation Metals and Sulfate Load Reduction........................................................ 33 

2-17 Gravity Flow Operation Solids Separation Efficiencies ........................................................................ 34

2-18 Recirculation Operation Solids Separation Efficiencies........................................................................ 36 

2-19 Bioreactor Treatment System Waste Characterization .......................................................................... 39 

3-1 Determination of Hazardous Waste Characteristics for Bioreactor Solid Waste Streams..................... 45 

3-2 Federal Applicable or Relevant and Appropriate Requirements for the Bioreactor Treatment System 47 

3-3 Feasibility Study Criteria Evaluation for the Bioreactor Treatment System at Leviathan Mine............ 50 

4-1 Summary of Total and Variable Costs for Each Mode of Operation..................................................... 52 

4-2 Summary of Cost Elements ................................................................................................................... 53 

Figures 

Figure Page 

1-1 Site Location Map.................................................................................................................................... 2 

1-2 Bioreactor Treatment System, Gravity Flow Configuration Schematic .................................................. 5 

1-3 Bioreactor Treatment System, Recirculation Configuration Schematic .................................................. 6 

2-1 Site Layout............................................................................................................................................. 11 

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Acronyms, Abbreviations, and Symbols 

μg/L Microgram per liter 

μmhos/cm Micromhos per centimeter 

°C Degree Celsius 

ACQR Air quality control region 

AMD Acid mine drainage 

AQMD Air quality management district 

ARAR Applicable or relevant and appropriate requirements 

ARCO Atlantic Richfield Company 

ARD Acid rock drainage 

CAA Clean Air Act 

CERCLA Comprehensive Emergency Response, Compensation, and Liability Act 

CFR Code of Federal Regulations 

cm Centimeter 

CUD Channel under drain 

CWA Clean Water Act 

DI Deionized water 

DO Dissolved oxygen 

DOT Department of Transportation 

EE/CA Engineering evaluation cost analysis 

EPA U.S. Environmental Protection Agency 

HDPE High density polyethylene 

HRT Hydraulic residence time 

ICP Inductively coupled plasma 

ITER Innovative Technology Evaluation Report 

kg Kilogram 

kg/day Kilogram per day 

kW Kilowatt 

L Liter 

L/min Liter per minute 

3 m Cubic meter 

MCL Maximum contaminant level 

MCLG Maximum contaminant level goal 

MD Matrix duplicate 

mg/kg Milligram per kilogram 

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Acronyms, Abbreviations, and Symbols (continued) 

mg/L Milligrams per liter 

mL Milliliter 

ml/L Milliliter per liter 

ml/min Milliliter per minute 

MS Matrix spike 

mV Millivolt 

NCP National Oil and Hazardous Substances Pollution Contingency Plan 

NPDES National Pollutant Discharge and Elimination System 

NRMRL National Risk Management Research Laboratory 

O&M Operation and maintenance 

ORP Oxidation reduction potential 

OSHA Occupational Safety and Health Administration 

PARCC Precision, accuracy, representativeness, completeness, and comparability 

pH Negative logarithm of the hydrogen ion concentration 

POTW Publicly-owned treatment works 

PPE Personal protection equipment 

PQL Practical quantitation limit 

PUD Pit under drain 

QA/QC Quality assurance/quality control 

RCRA Resource Conservation and Recovery Act 

RPD Relative percent difference 

RWQCB California Regional Water Quality Control Board – Lahontan Region 

SARA Superfund Amendment and Reauthorization Act 

SCADA Supervisory Control and Data Acquisition 

SDG Sample delivery group 

SDWA Safe Drinking Water Act 

SITE Superfund Innovative Technology Evaluation 

SPLP Synthetic precipitation and leaching procedure 

STLC Soluble threshold limit concentration 

TCLP Toxicity characteristic leaching procedure 

TDS Total dissolved solids 

TEP/QAPP Technology Evaluation Plan/Quality Assurance Project Plan 

Tetra Tech Tetra Tech EM Inc. 

TOM Task order manager 

TSD Treatment, storage, and disposal 

TSS Total suspended solids 

TTLC Total threshold limit concentration 

UNR University of Nevada Reno 

USACE US Army Corp of Engineers 

WET Waste extraction test 

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Conversion Factors 

To Convert From To Multiply By 

Length: Centimeter 

 Meter 

 Kilometer 

Inch 

Foot 

Mile 

0.3937

3.281 

0.6214 

Area: Square Meter Square Foot 10.76 

Volume: Liter 

Cubic Meter 

Cubic Meter 

Gallon 

Cubic Foot 

Cubic Yard 

0.2642 

35.31 

1.308 

Flow: Liter per minute Gallon per minute 0.2642 

Mass: Kilogram 

Metric Ton 

Pound 

Short Ton 

2.2046 

1.1025 

Energy: Kilowatt-hour British Thermal Unit 3413 

Power: Kilowatt Horsepower 1.34 

Temperature: °Celsius (°Fahrenheit + 32) 1.8 

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Acknowledgements 

This report was prepared under the direction of Mr. Edward Bates, the U.S. Environmental Protection 

Agency (EPA) Superfund Innovative Technology Evaluation (SITE) project manager at the National Risk 

Management Research Laboratory (NRMRL) in Cincinnati, Ohio; and Mr. Kevin Mayer, EPA Region IX. 

This report was prepared by Mr. Matt Udell, Mr. Noel Shrum, and Mr. Matt Wetter of Tetra Tech EM Inc. 

(Tetra Tech) under Field Evaluation and Technical Support (FEATS) Contract No. 68-C-00-181. Field 

sampling and data acquisition was performed by Mr. Udell, Mr. Joel Bauman, Mr. Matt Wetter, and Ms. 

Sarah Piper of Tetra Tech. 

This project consisted of the demonstration of an innovative technology under the SITE program to 

evaluate the compost-free bioreactor treatment system developed by Drs. Glenn Miller and Tim Tsukamoto 

of the University of Nevada Reno. The technology demonstration was conducted on acid rock drainage at 

the Leviathan Mine Superfund site in Alpine County, California. The technology is currently being used as 

an interim action at the site, pending completion of a remedial investigation, feasibility study, and record of 

decision. This Innovative Technology Evaluation Report (ITER) interprets the data that were collected 

during the two-year demonstration period and discusses the potential applicability of the technology to 

other mine sites. 

The cooperation of the following people during the technology demonstration and review of this report are 

gratefully acknowledged: Mr. Scott Jacobs and Ms. Diana Bless of NRMRL, Drs. Glenn Miller and Tim 

Tsukamoto of the University of Nevada Reno, Mr. Roy Thun and Mr. John Pantano of ARCO, and Mr. 

Chris Stetler and Mr. Doug Carey of the California Regional Water Quality Control Board-Lahontan 

Region. 

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SECTION 1 

INTRODUCTION 

This section provides background information about the 

Superfund Innovative Technology Evaluation (SITE) Program 

and the SITE demonstration that was conducted at a mine site 

in Alpine County, California, discusses the purpose of this 

Innovative Technology Evaluation Report (ITER), and briefly 

describes the technology that was evaluated. Key contacts are 

listed at the end of this section for inquiries regarding 

additional information about the SITE Program, the evaluated 

technology, and the demonstration site. 

1.1 Project Background 

The U.S. Environmental Protection Agency (EPA), the states, 

and the Federal Land Management Agencies all need better 

tools to manage acid rock drainage (ARD) at abandoned mine 

sites. Over a 21-month period during 2003 and 2005, EPA 

evaluated the use of compost-free bioreactors for removal of 

high concentrations of metals from ARD generated at 

Leviathan Mine, located northwest of Monitor Pass in 

northeastern Alpine County, California (Figure 1-1). The 

compost-free bioreactor treatment SITE demonstration was 

conducted by EPA under the SITE Program, which is 

administered by EPA’s National Risk Management Research 

Laboratory (NRMRL), Office of Research and Development. 

The SITE demonstration was conducted by EPA in 

cooperation with EPA Region IX, the state of California, and 

Atlantic Richfield Company (ARCO). 

The compost-free bioreactor treatment system in operation at 

Leviathan Mine is an improvement to current wood chip, 

compost, and manure based bioreactors in place at many 

facilities. The treatment system was installed by the 

University of Nevada Reno (UNR) and ARCO from fall 2002 

through the spring 2003. The bioreactor treatment system was 

specifically designed by UNR to treat moderate flow rates of 

ARD containing hundreds of milligrams per liter (mg/L) of 

metals at a pH as low as 3.0. Without treatment, the ARD 

from the mine would otherwise be released to the 

environment. The SITE demonstration consisted of monthly 

sampling events of the bioreactor treatment system with 

periods of extended inaccessibility due to winter snowfall. 

Throughout the SITE demonstration, EPA collected chemical 

data on the system’s influent and effluent streams, 

documented metals removal and reduction in acidity within 

the system’s unit operations, and recorded operational 

information pertinent to the evaluation of the treatment 

system. EPA evaluated the treatment system based on 

removal efficiencies for primary and secondary target metals, 

comparison of effluent concentrations to interim discharge 

standards (pre-risk assessment and record of decision) 

mandated by EPA in 2002 and on the characteristics of 

resulting metals-enriched solid wastes. Removal efficiencies 

of individual unit operations were also evaluated. A summary 

of the SITE demonstration and the results of the bioreactor 

treatment technology evaluation are presented in Sections 2 

through 5 of this report. 

1.2 The SITE Demonstration Program and 

Reports 

In 1980, the U.S. Congress passed the Comprehensive 

Environmental Response, Compensation, and Liability Act 

(CERCLA), also known as Superfund. CERCLA is 

committed to protecting human health and the environment 

from uncontrolled hazardous waste sites. In 1986, CERCLA 

was amended by the Superfund Amendments and 

Reauthorization Act (SARA). These amendments emphasize 

the achievement of long-term effectiveness and permanence of 

remedies at Superfund sites. SARA mandates the use of 

permanent solutions, alternative treatment technologies, or 

resource recovery technologies, to the maximum extent 

possible, to clean up hazardous waste sites. 

State and Federal agencies, as well as private parties, have for 

several years now been exploring the growing number of 

innovative technologies for treating hazardous wastes. EPA 

has focused on policy, technical, and informational issues 

related to the exploring and applying new remediation 

technologies applicable to Superfund sites. One such 

initiative is EPA’s SITE Program, which was established to 

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accelerate the development, demonstration, and use of 

innovative technologies for site cleanups. The SITE 

Program's primary purpose is to maximize the use of 

alternatives in cleaning hazardous waste sites by encouraging 

the development and demonstration of new, innovative 

treatment and monitoring technologies. It consists of three 

major elements: the Demonstration Program, the Consortium 

for Site Characterization Technologies, and the Technology 

Transfer Program. 

The objective of the Demonstration Program is to develop 

reliable performance and cost data on innovative technologies 

so that potential users can assess the technology’s site-specific 

applicability. Technologies evaluated are either available 

commercially or are close to being available for full-scale 

remediation of Superfund sites. SITE demonstrations usually 

are conducted at hazardous waste sites under conditions that 

closely simulate full-scale remediation conditions, thus 

assuring the usefulness and reliability of the information 

collected. Data collected are used to assess: (1) the 

performance of the technology; (2) the potential need for preand post treatment of wastes; (3) potential operating problems; 

and (4) the approximate costs. The demonstration also 

provides opportunities to evaluate the long term risks and 

limitations of a technology. 

At the conclusion of a SITE demonstration, EPA prepares a 

Demonstration Bulletin, Technology Capsule, and an ITER. 

These reports evaluate all available information on the 

technology and analyze its overall applicability to other 

potential sites characteristics, waste types, and waste matrices. 

Testing procedures, performance and cost data, and quality 

assurance and quality standards are also presented. The 

Technology Bulletin consists of a one to two page summary of 

the SITE demonstration and is prepared as a mailer for public 

notice. The Technology Bulletin provides a general overview 

of the technology demonstrated, results of the demonstration, 

and telephone numbers and e-mail address for the EPA project 

manager in charge of the SITE evaluation. In addition, 

references to other related documents and reports are 

provided. The Technology Capsule consists of a more indepth summary of the SITE demonstration and is usually 

about 10 pages in length. The Technology Capsule presents 

information and summary data on various aspects of the 

technology including applicability, site requirements, 

performance, process residuals, limitations, and current status 

of the technology. The Technology Capsule is designed to 

help EPA remedial project managers and on-scene 

coordinators, contractors, and other site cleanup managers 

understand the types of data and site characteristics needed to 

effectively evaluate the technology’s applicability for cleaning 

Superfund sites. The final SITE document produced is the 

ITER. The ITER consists of an in-depth evaluation of the 

SITE demonstration including details on field activities and 

operations, performance data and statistical evaluations, 

economic analysis, applicability, and effectiveness, as 

discussed in the following section. 

1.3 Purpose of the Innovative Technology 

Evaluation Report 

The ITER is designed to aid decision-makers in evaluating 

specific technologies for further consideration as applicable 

options in a particular cleanup operation. The ITER should 

include a comprehensive description of the SITE 

demonstration and its results, and is intended for use by EPA 

remedial project managers, EPA on-scene coordinators, 

contractors, and other decision-makers carrying out specific 

remedial actions. 

To encourage the general use of demonstrated technologies, 

EPA provides information regarding the applicability of each 

technology to specific sites and wastes. The ITER includes 

information on cost and desirable site-specific characteristics. 

It also discusses advantages, disadvantages, and limitations of 

the technology. However, each SITE demonstration evaluates 

the performance of a technology in treating a specific waste 

matrix at a specific site. The characteristics of other wastes 

and other sites may differ from the characteristics at the 

demonstration site. Therefore, a successful field 

demonstration of a technology at one site does not necessarily 

ensure that it will be applicable at other sites. Data from the 

field demonstration may require extrapolation for estimating 

the operating ranges in which the technology will perform 

satisfactorily. Only limited conclusions can be drawn from a 

single field demonstration. 

This ITER provides information on new approaches to the use 

of a compost-free bioreactor treatment system to reduce the 

concentration of toxic metals and acidity in ARD at Leviathan 

Mine, and is a critical step in the development and 

commercialization of compost-free bioreactor treatment 

systems for use at other applicable mine sites. 

1.4 Technology Description 

Biological treatment of ARD relies on the biologically 

mediated reduction of sulfate to sulfide followed by metal 

sulfide precipitation. Biologically promoted sulfate-reduction 

has been attributed primarily a consortium of sulfate-reducing 

bacteria, which at Leviathan Mine utilizes ethanol as a carbon 

substrate to reduce sulfate to sulfide. This process generates 

hydrogen sulfide, elevates pH to about 7, and precipitates 

divalent metals as metal sulfides. The following general 

equations describe the sulfate-reduction and metal sulfide 

precipitation processes. 

- 2CH3CH2OH + 3SO42- → 3HS- + 3HCO3 + 3H2O (1) 

2CH3CH2OH + SO4

2- → 2 CH3COO- + HS-

 + H2O (2) 

HS- + M2+→ MS + 2H+ (3) 

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Here ethanol is the carbon source and SO4

2- is the terminal 

electron acceptor in the electron transport chain of sulfatereducing bacteria. Reaction No.1 causes an increase in 

alkalinity and a rise in pH, while reaction No.2 results in the 

generation of acetate rather than complete oxidation to 

carbonate. HS- then reacts with a variety of divalent metals 

(M2+), resulting in a metal sulfide (MS) precipitate. 

The reduction of sulfate to sulfide requires 8 electrons: 

H2SO4 + 8H+

 + 8e

- → H2S + 4H2O (4) 

Ethanol contributes 12 electrons per molecule oxidized, 

assuming complete oxidation to carbon dioxide. 

3H2O + C2H5OH → 12e

-

 + 2CO2 + 12H+ (5) 

However, incomplete oxidation of ethanol to acetate yields 

only 4 electrons per molecule oxidized. 

H2O + C2H5OH → 4e- + C2H3OOH + 4H+ (6) 

The moles of ethanol consumed per mole of sulfate reduced in 

the bioreactors at Leviathan Mine suggest that incomplete 

oxidation of ethanol is the predominant reaction. 

Compost-Free Bioreactor System Overview: At Leviathan 

Mine, the compost-free bioreactor treatment system consists 

of ethanol and sodium hydroxide feed stocks, a pretreatment 

pond, two bioreactors, a settling pond, a flushing pond, and an 

aeration channel. The heart of the treatment system is the 

two compost-free, sulfate-reducing bioreactors. A blanket of 

manure was added to the base of each bioreactor to support 

the startup of each bioreactor. The bioreactors are lined ponds 

filled with river rock (Figures 1-2 and 1-3). River rock was 

selected because of the stability of the matrix and the ease at 

which metal sulfide precipitates can be flushed from the 

matrix to the flushing pond. Each bioreactor consists of three 

influent distribution loops and three effluent collection loops 

located near the top, in the middle, and just above the bottom 

of the bioreactor to precisely control flow within the 

bioreactor media. ARD water can be drawn upward or 

downward through the aggregate to one of three effluent 

collection lines located at the opposite end of each bioreactor 

(Figures 1-2 and 1-3). 

The system was designed to treat ARD by gravity flow 

through successive sulfate-reducing bioreactors and 

precipitation of metal sulfides in a continuous flow settling 

pond (Figure 1-2). During the demonstration, an alternative 

mode of operation (recirculation) was also evaluated, which 

involved the direct contact of influent ARD with sulfide rich 

water from the bioreactors and precipitation of metal sulfides 

in the settling pond. A portion of the pond supernatant 

containing excess sulfate is then pumped to the head of the 

bioreactor system to generate additional sulfides (Figure 1-3). 

Compost-Free Bioreactor Operation: Operated in gravity 

flow mode (Figure 1-2), influent ARD passes through a flow 

control weir at flow rates ranging from 25 to 47 liters per 

minute (L/min), where sodium hydroxide is added to adjust 

the pH to approximately 4 to maintain a favorable 

environment for sulfate-reducing bacteria and ethanol is added 

to provide a carbon source for reducing equivalents for the 

sulfate-reducing bacteria. Precipitates that are formed at this 

state are settled out in the pretreatment pond. ARD flows 

through Bioreactor No.1 and Bioreactor No.2 to reduce sulfate 

to sulfide. Excess sulfide generated in the first bioreactor is 

passed, along with partially treated ARD water, through to the 

second bioreactor for additional metals removal. Effluent 

from the second bioreactor discharges to a continuous flow 

pond for extended settling of metal sulfide precipitates. 

Sodium hydroxide is added to the bioreactor effluent to 

consume mineral acidity and convert bisulfide to sulfide, 

which is necessary to precipitate iron as iron sulfide in the 

settling pond. 

Operated in recirculation mode (Figure 1-3), metal-rich ARD 

is routed around the two bioreactors to a flow control vault at 

the head of the continuous flow settling pond. The untreated 

ARD is mixed with sodium hydroxide and sulfide rich water 

from bioreactor No.2, and is then discharged to the settling 

pond. The combination of a neutral pH condition and high 

sulfide concentration promotes rapid generation and 

precipitation of metal sulfides in the settling pond rather than 

in the two bioreactors. Precipitation of metal sulfides 

downstream of the two bioreactors greatly reduces 

precipitation in the bioreactors and the need for flushing and 

the associated stress on the two bioreactors. A portion of the 

pond supernatant containing excess sulfate is then pumped to 

bioreactor No.1 at flow rates ranging from 114 to 227 L/min 

(influent to recirculation ratio of 1:2 to 1:6). Ethanol is added 

to the influent vault at the head of bioreactor No.1. Sulfaterich and metal-poor water from the holding pond then flows 

through the two bioreactors to promote additional sulfate 

reduction to sulfide. The pH of the supernatant recirculated 

through the bioreactors is near neutral, providing optimal 

conditions for sulfate-reducing bacteria growth. The system 

operated in recirculation mode requires about 49 percent less 

sodium hydroxide addition and 14 percent more ethanol than 

the gravity flow mode of operation. 

In both modes of operation, the effluent from the continuous 

flow settling pond flows through a rock lined aeration channel 

to promote gas exchange prior to effluent discharge. Metal 

sulfide precipitate slurry is periodically flushed from the two 

bioreactors to prevent plugging of the river rock matrix. The 

slurry is sent to a flushing pond for extended settling. Metal 

sulfide precipitates are periodically pumped out of the settling 

and flushing ponds and dewatered using bag filters. Metals in 

bag filter solids did not exceed Federal or state of California 

standards for characterization as a hazardous waste. 

4
Figure 1-2. Bioreactor Treatment System, Gravity Flow Configuration Schematic

5
Figure 1-3. Bioreactor Treatment System, Recirculation Configuration Schematic

6
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1.5 Key Findings 

The bioreactor treatment system is extremely effective at 

neutralizing acidity and reducing metals content in ARD, with 

resulting effluent streams that meet EPA interim discharge 

standards for the primary target metals and the secondary 

target metals. The bioreactor treatment system operated in 

gravity flow mode from November 2003 through mid-May 

2004 treating 9.24 million liters (2.44 million gallons) of ARD 

using 9,236 liters (L) of sodium hydroxide and 4,466 L of 

ethanol. The bioreactor treatment system operated in the 

recirculation mode from mid-May 2004 through July 2005 

treating 22.1 million liters (5.81 million gallons) of ARD 

using 22,029 L of sodium hydroxide and 10,617 L of ethanol. 

Although the influent concentrations for the primary target 

metals were up to 580 fold above EPA interim discharge 

standards, both modes of treatment system operation were 

successful in reducing the concentrations of the primary target 

metals in the ARD to between 1 and 43 fold below the 

discharge standards. Internal trials run to refine base addition 

requirements and to evaluate various sources of base addition 

lead to significant excursions of effluent iron concentrations 

above the EPA interim discharge standards during a portion of 

the evaluation. However, after base optimization during 

gravity flow operations effluent iron concentrations met 

discharge standards. Iron also exceeded discharge standards 

during recirculation operations when base addition was 

stopped due to equipment failure or lack of adequate base 

supply. In addition, the concentrations of the secondary target 

metals, with the exception of selenium, were reduced to below 

the discharge standards. For the gravity flow mode of 

treatment system operation, the average removal efficiency for 

the primary target metals was 94 percent over 6 sampling 

events. For the recirculation mode of treatment system 

operation, the average removal efficiency for the primary 

target metals was 96 percent over 7 sampling events. 

Removal efficiencies for arsenic were not calculated because 

the influent and effluent metals concentrations were not 

statistically different (p-value exceeded 0.05). In addition, the 

concentration of arsenic in system influent was well below 

discharge standards. 

Average removal efficiencies for secondary target metals 

ranged from 41 to 99 percent in both modes of operation; 

however, removal efficiencies were not calculated for arsenic, 

cadmium, chromium, lead, and selenium as the influent and 

effluent concentrations were not statistically different (p-value 

exceeded 0.05). In the case of arsenic, cadmium, chromium, 

lead, and selenium in the ARD, concentrations were near or 

below the EPA interim discharge standards in the influent; 

therefore, the treatment system was not optimized for removal 

of these metals resulting in lower removal efficiencies. 

Removal efficiencies for sulfate ranged from 8 to 35 percent 

with an average reduction in sulfate of 17 percent. There was 

on average a 9 percent increase in sulfate removal during 

recirculation operations when compared to gravity flow 

operations. 

Tables 1-1 and 1-2 present the average and range of removal 

efficiencies for filtered influent and effluent samples collected 

from the treatment system during both gravity flow and 

recirculation modes of operation. A summary of the average 

influent and effluent metals concentrations for each mode of 

operation is presented. The results of a comparison of the 

average effluent concentration for each metal to the EPA 

interim discharge standards is also presented; where a “Y” 

indicates that either the maximum concentration (based on a 

daily composite of three grab samples) and/or the average 

concentration (based on four daily composite samples) was 

exceeded; and an “N” indicates that neither discharge standard 

was exceeded. 

The bioreactor treatment system produced a relatively small 

quantity of metal sulfide sludge. During operation from 

November 2003 through July 2005, the bioreactor generated 

about 14.2 dry tons (12,900 kilograms [kg]) of sludge 

consisting mainly of iron sulfide. This equals about 1.7 dry 

tons (1,550 kg) of sludge per million gallons (0.45 dry ton 

[410 kg] per million liters) of ARD treated. The solid waste 

residuals produced by the treatment system were analyzed for 

potential hazardous waste characteristics. Total and leachable 

metals analyses were performed on the solid wastes for 

comparison to California and federal hazardous waste 

classification criteria. The characteristics of the solid waste 

stream are presented in Table 1-3. None of the solid wastes 

were found to be hazardous or a threat to water quality; 

however, the solids were disposed of off site pending 

designation of an on-site disposal area. 

In general, the limitations of the bioreactor treatment system 

implemented at Leviathan Mine were not related to the 

applicability of the technology, but rather to operational issues 

due to weather conditions (extreme cold and winter snow 

pack), maintenance problems (recirculation pump failures and 

reagent delivery), and the remoteness of the site (power 

supply, maintaining adequate supplies of consumables and 

replacement equipment). The technology is not limited by the 

sub-freezing temperatures encountered in the high Sierra 

Nevada during the winter months. However, biological 

activity did slow resulting is decreased sulfate reduction to 

sulfide. Effluent discharge standards were generally met as 

the flow of ARD entering the bioreactor treatment system also 

decreased during the winter. 

1.6 Key Contacts 

Additional information on this technology, the SITE Program, 

and the evaluation site can be obtained from the following 

sources: 

7
_______________________________________________________________________________________ 

EPA Contacts: 

Edward Bates, EPA Project Manager 

U.S. Environmental Protection Agency

National Risk Management Research Laboratory

Office of Research and Development 

26 West Martin Luther King Jr. Drive 

Cincinnati, OH 45268

(513) 569-7774

bates.edward@epa.gov 

Kevin Mayer, EPA Remedial Project Manager 

U.S. Environmental Protection Agency Region 9 

75 Hawthorne Street, SFD-7-2 

San Francisco, CA 94105

(415) 972-3176

mayer.kevin@epa.gov 

ARCO Contact: 

Roy Thun, Project Manager

BP Atlantic Richfield Company 

6 Centerpointe Drive, Room 6-164 

La Palma, CA 90623 

(661) 287-3855

thunril@bp.com 

State of California Contact: 

Richard Booth, Project Manager

California Regional Water Quality Control Board

Lahontan Region 

2501 Lake Tahoe Blvd. 

South Lake Tahoe, CA 96150

(530) 542-5470

RBooth@waterboards.ca.gov 

University of Nevada-Reno Contacts: 

Drs. Glenn Miller and Tim Tsukamoto

Department of Natural Resources and Environmental Science 

University of Nevada-Reno, Mail Stop 199

Reno, NV 89557-0187

(775) 784-4413

gcmiller@unr.edu 

timothyt@unr.edu 

8
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Table 1-1. Bioreactor Treatment System Removal Efficiencies: Gravity Flow Configuration 

Target 

Metal 

Number of 

Sampling 

Events 

Average 

Filtered Influent 

Concentration 

(μg/L) 

Standard 

Deviation 

Average 

Filtered Effluent 

Concentration 

(μg/L) 

Standard 

Deviation 

Exceeds 

Discharge 

Standard 

(Y/N) 

Average 

Removal 

Efficiency (1) 

(%) 

Range of 

Removal 

Efficiencies 

(%) 

Primary Target Metals 

Aluminum 6 37,467 2,011 103 78.8 N 99.7 99.5 to 99.9 

Arsenic 6 2.1 0.64 4.73 4.0 N NC NC 

Copper 6 691 51.2 4.8 1.6 N 99.3 99.1 to 99.7 

Iron 6 117,167 6,242 4,885 4,771 Y 95.8 65.6 to 99.9 

Nickel 6 487 33.5 65.5 35.9 N 86.6 72.1 to 92.6 

Secondary Target Metals 

Cadmium 6 0.61 0.27 <0.21 0.07 N 65.3 42.5 to 79 

Chromium 6 12.2 8.9 7.83 6.6 N NC NC 

Lead 6 3.64 2.5 4.69 2.9 N NC NC 

Selenium 6 13.9 3.1 11.2 2.6 Y NC NC 

Zinc 6 715 47.1 15.8 6.8 N 97.8 95.9 to 98.6 

(1) Average removal efficiency calculated using the average influent and average effluent concentration data. 

NC = Not calculated as influent and effluent concentrations were not statistically different 

μg/L = Microgram per liter 

Table 1-2. Bioreactor Treatment System Removal Efficiencies: Recirculation Configuration 

Target 

Metal 

Number of 

Sampling 

Events 

Average 

Filtered Influent 

Concentration 

(μg/L) 

Standard 

Deviation 

Average 

Filtered Effluent 

Concentration 

(μg/L) 

Standard 

Deviation 

Exceeds 

Discharge 

Standard 

(Y/N) 

Average 

Removal 

Efficiency(1) 

(%) 

Range of 

Removal 

Efficiencies 

(%) 

Primary Target Metals 

Aluminum 7 40,029 4,837 52.7 25.7 N 99.9 99.7 to 99.9 

Arsenic 7 7.43 6.5 6.51 4.9 N NC NC 

Copper 7 795 187 4.59 3.2 N 99.4 98.8 to 99.8 

Iron 7 115,785 13,509 2,704 3,000 Y 97.7 92.8 to 99.7 

Nickel 7 529 34.1 69.7 44.2 N 86.8 71.0 to 96.4 

Secondary Target Metals 

Cadmium 7 0.60 0.50 <0.20 0.09 N NC NC 

Chromium 7 11.1 6.3 6.38 5.2 N 42.5 21.2 to 84.8 

Lead 7 4.17 2.3 2.45 1.6 N 41.3 22.0 to 57.1 

Selenium 7 11.5 5.1 8.49 3.6 Y NC NC 

Zinc 7 776 51.7 8.91 7.4 N 98.9 97.7 to 99.8 

(1) Average removal efficiency calculated using the average influent and average effluent concentration data. 

NC = Not calculated as influent and effluent concentrations were not statistically different 

μg/L = Microgram per liter 

Table 1-3. Determination of Hazardous Waste Characteristics for Bioreactor Solid Waste Streams 

TTLC STLC TCLP 

Treatment 

System Solid Waste Stream 

Total Solid 

Waste Generated 

Pass or 

Fail 

Pass or 

Fail 

Pass or 

Fail Waste Handling Status 

Bioreactor 

Treatment 

System 

Dewatered Sludge 4.3 dry tons P P P Off-site Disposal 

Pretreatment Pond Moved into Flushing Pond P P P Moved into Flushing Pond 

Settling Pond 10 dry tons (estimated) P P P Pending Filtration 

Flushing Pond 4.3 dry tons (estimated) P P P Pending Filtration 

STLC = Soluble limit threshold concentration TTLC = Total threshold limit concentration 

TCLP = Toxicity characteristic leaching procedure 1 dry ton = 907 kilograms 

9
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SECTION 2 

TECHNOLOGY EFFECTIVENESS

The following sections discuss the effectiveness of the 

compost-free bioreactor treatment technology demonstrated at 

the Leviathan Mine site. The discussion includes a 

background summary of the site, description of the technology 

process and the evaluation approach, a summary of field 

activities, and results of the evaluation. 

2.1 Background 

Leviathan Mine is a former copper and sulfur mine located 

high on the eastern slopes of the Sierra Nevada Mountain 

range, near the California-Nevada border. Intermittent mining 

of copper sulfate, copper, and sulfur minerals since the mid1860s resulted in extensive acid mine drainage (AMD) and 

ARD at Leviathan Mine. During the process of converting 

underground workings into an open pit mine in the 1950s, 

approximately 22 million tons of overburden and waste rock 

were removed from the open pit mine and placed in the Aspen 

Creek drainage, contributing ARD to the Aspen Seep. 

Oxidation of sulfur and sulfide minerals within the mine 

workings and waste rock forms sulfuric acid (H2SO4), which 

liberates toxic metals from the mine wastes creating AMD and 

ARD. AMD and ARD at Leviathan Mine contain high 

concentrations of toxic metals and historically flowed directly 

to Leviathan Creek without capture or treatment. 

2.1.1 Site Description 

The Leviathan Mine property occupies approximately 102 

hectares in the Leviathan Creek basin, which is located on the 

northwestern flank of Leviathan Peak at an elevation ranging 

from 2,134 to 2,378 meters ( 7,000 to 7,800 feet) above mean 

sea level. Access to the mine site is provided by unpaved 

roads (United States Forest Service Road 52) from State 

Highway 89 on the southeast and from US Highway 395 south 

of Gardnerville, Nevada, on the northeast. Of the total 

property, approximately 1 million square meters (247 acres) 

are disturbed by mine-related activities. With the exception of 

approximately 85 thousand square meters on Forest Service 

lands, mine-related workings are located on property owned 

by the State of California. Figure 2-1 presents a map showing 

the layout of the Leviathan Mine site. 

The mine site lies within the Bryant Creek watershed and is 

drained by Leviathan and Aspen creeks, which combine with 

Mountaineer Creek 3.5 kilometers below the mine to form 

Bryant Creek, a tributary to the East Fork of the Carson River. 

The terrain in the Leviathan Creek basin includes rugged 

mountains and high meadowlands. The area has a climate 

typical of the eastern slope of the Sierra Nevada range 

characterized by warm dry summers with the bulk of the 

precipitation occurring as winter snow. Vegetation at the site 

is representative of the high Sierra Nevada floristic province, 

with scattered stands of mixed conifers or Jeffery pine on 

north-facing slopes. Aspen groves border parts of Leviathan 

and Aspen creeks, while shrub communities dominate flats 

and south facing slopes. 

Precipitation in the area around Leviathan Mine varies with 

elevation and distance from the crest of the Sierra Nevada 

mountain range. The heaviest precipitation is from November 

through April. Annual precipitation on western slopes of the 

Sierra Nevada averages about 140 centimeters (cm), varying 

from a low of about 51 cm to highs estimated in the range of 

165 to 178 cm in some of the more remote mountain areas 

near the easterly boundary of Leviathan Creek basin. There is 

little precipitation data for the mine site; therefore, a mean 

annual precipitation was estimated at 70.6 cm per year using 

local weather monitoring stations provided by the U.S. 

Geological Survey (EMC2 2004a). A large percentage of the 

precipitation which falls during the winter months occurs as 

snow. Snow pack accumulates from about November through 

March, with the maximum accumulation generally occurring 

about April 1. The average April 1 snow line is below an 

elevation of 1,525 meters. The snow pack generally begins to 

melt during March, but the period of major snowmelt activity 

is typically April through July. Winter snow pack is the 

source of about 50 percent of annual runoff. 

10
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Figure 2-1. Site L

a

y

o

ut 

11
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2.1.2 History of Contaminant Release 

Prior to 1984, the various sources of AMD and ARD 

discharging from the Leviathan Mine site included AMD from 

the floor of the mine pit flowing west into Leviathan Creek; 

AMD from Adit No. 5, located below the mine pit, flowing 

west into Leviathan Creek; ARD from the Delta Area (also 

known as Delta Seep), located adjacent to Leviathan Creek 

along the western edge of the mine area, flowing northwest 

into Leviathan Creek; and ARD from Aspen Seep, located 

along the northern portion of the site within the overburden 

piles, flowing north into Aspen Creek. Historically, the 

concentrations of five primary target metals, aluminum, 

arsenic, copper, iron, and nickel in the AMD and ARD 

released to Leviathan and Aspen creeks have exceeded EPA 

interim (pre-risk assessment and record of decision) discharge 

standards up to 3,000 fold. Historical concentrations for each 

source of AMD and ARD are presented in Table 2-1. 

When AMD was inadvertently released in large quantities 

from the Leviathan Mine site in the 1950s, elevated 

concentrations of toxic metals resulted in fish and insect kills 

in Leviathan Creek, Bryant Creek, and the east fork of the 

Carson River. The absence of trout among the fish killed in 

Bryant Creek and in the east fork of the Carson River 

immediately downstream from Bryant Creek indicated that 

continuous discharges from mining operations had eliminated 

the more sensitive trout fisheries that existed prior to open-pit 

operations. Various efforts were made between 1954 and 

1975 to characterize the impacts of Leviathan Mine on water 

quality at and below the site during and after open-pit mining 

operations (California Regional Water Quality Control Board 

– Lahontan Region [RWQCB] 1995). 

2.1.3 Previous Actions 

The Leviathan Mine Pollution Abatement Project was initiated 

by the state of California in 1979 with the preparation of a 

feasibility study. In 1982, the State contracted the design of 

the Pollution Abatement Program, which was then 

implemented in 1984 with physical actions that significantly 

reduced the quantity of toxic metals discharging from the mine 

site. Work conducted at the site included regrading overburden piles to prevent impounding and infiltration of 

precipitation and promote surface runoff; partially filling and 

grading the open pit; constructing a surface water collection 

system within the reworked mine pit to redirect 

uncontaminated surface water to Leviathan Creek; 

constructing a pit under drain (PUD) system beneath the pit 

(prior to filling and grading) to collect and divert surface water 

seeping into the pit floor; construction of five 

storage/evaporation ponds to collect discharge from the PUD 

and Adit No. 5; and rerouting Leviathan Creek by way of a 

concrete diversion channel to minimize contact of creek water 

with waste rock piles. During pond construction, previously 

unrecognized springs were encountered. To capture the 

subsurface flow from these springs, a channel under drain 

(CUD) was constructed beneath Leviathan Creek (RWQCB 

1995). Discharges of ARD to Aspen Creek were not 

addressed as a part of the project. Figure 2-1 presents a 

detailed site map of the mine site as it exists in 2004, after 

implementation physical work conducted at the mine site. 

Starting in 1996, pilot studies were conducted by UNR in 

coordination with the state of California to precipitate metals 

in ARD discharging from Aspen Seep using sulfate-reducing 

bacteria. The pilot studies evaluated wood chip and rock 

substrates, base addition, and a solids collection and removal 

strategies. The information developed during the pilot studies 

resulted in the design and construction of a full-scale compostfree bioreactor treatment system in the fall of 2002 through the 

summer of 2003. 

Starting in 1997, EPA initiated enforcement actions at the 

Leviathan Mine site to further mitigate potential releases of 

AMD and ARD from the various sources. In response to 

EPA’s 1997 action memorandum, the state of California 

implemented the active lime treatment system in 1999 to treat 

AMD that collects in the retention ponds. Since the 

installation of the active lime treatment system in 1999, no 

releases of AMD have occurred from the retention ponds to 

Leviathan Creek. In response to EPA’s July 21, 2001, action 

memorandum, ARCO implemented a semi-passive alkaline 

lagoon treatment system to treat ARD from the CUD. Figure 

2-1 presents a detailed site map of the mine site after 

construction of the lime and bioreactor treatment systems. 

In 2002, EPA prepared an additional action memorandum 

setting interim discharge standards for the five primary target 

metals and five secondary water quality indicator metals for 

discharge of treated water from the treatment systems to 

Leviathan Creek (EPA 2002). Discharge standards for the 

five primary metals of concern are presented in Table 2-1. 

The maximum daily standard equals the highest concentration 

of a target metal to which aquatic life can be exposed for a 

short period of time without deleterious effects. The four-day 

average standard equals the highest concentration of a target 

metal to which aquatic life can be exposed for an extended 

period of time (4 days) without deleterious effects. 

2.2 Process Description 

The bioreactor treatment system evaluated at Leviathan Mine 

was set up to treat ARD captured from Aspen Seep at the mine 

site. The treatment system consists of one 7,600 L ethanol and 

three 3,800 L sodium hydroxide feed stock tanks, a 

pretreatment pond, two bioreactors, a settling pond, a flushing 

pond, and an aeration channel. The system was designed to 

treat ARD by gravity flow through successive sulfate-reducing 

bioreactors and precipitation of metal sulfides in a continuous 

flow settling pond (Figure 1-2). System design flow is 114 

L/min. During the demonstration, an alternative mode of 

12
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Table 2-1. Summary of Historical Metals of Concern 

Analyte 

Number of 

Samples 

Detection 

Percentage 

Minimum 

Concentration 

(mg/L) 

Maximum 

Concentration 

(mg/L) 

Mean 

(mg/L) 

Standard 

Deviation 

(mg/L) 

Discharge Standards 

Maximum (a) 

(mg/L) 

Average (b) 

(mg/L) 

Aspen Seep 

Aluminum 34 100 0.073 65 51 14.2 4.0 2.0 

Arsenic 34 97.1 0 0.1 0.03 0.03 0.34 0.15 

Copper 21 95.2 0 1.8 1.3 0.55 0.026 0.016 

Iron 34 100 0.11 580 124 113 2.0 1.0 

Nickel 34 97.1 0 0.75 0.55 0.18 0.84 0.094 

Adit No. 5 

Aluminum 46 100 220 430 310 63.6 4.0 2.0 

Arsenic 45 100 8.6 28 16.2 5.5 0.34 0.15 

Copper 28 100 0.88 4.2 1.5 0.97 0.026 0.016 

Iron 45 100 120 2,400 815 369 2.0 1.0 

Nickel 46 100 4.4 10 6.1 1.6 0.84 0.094 

Combination of Ponds 1, 2 North, and 2 South 

Aluminum 29 100 3 4,900 1,199 1,036 4.0 2.0 

Arsenic 27 100 0.192 92 27.1 19.9 0.34 0.15 

Copper 9 100 2.4 35 8.1 10.2 0.026 0.016 

Iron 32 100 4 6,600 1,734 1,450 2.0 1.0 

Nickel 27 100 1.2 61 17.5 12 0.84 0.094 

Channel Under Drain 

Aluminum 60 100 29 68 48 10.6 4.0 2.0 

Arsenic 61 100 0.091 0.80 0.45 0.19 0.34 0.15 

Copper 37 97.3 0 0.13 0.026 0.035 0.026 0.016 

Iron 61 100 270 460 367 59.2 2.0 1.0 

Nickel 61 100 0.21 3.4 1.95 0.79 0.84 0.094 

Delta Seep 

Aluminum 18 100 0.89 4.7 1.68 0.88 4.0 2.0 

Arsenic 19 84.2 0.052 0.094 0.067 0.012 0.34 0.15 

Copper 17 35.3 0.0018 0.14 0.032 0.054 0.026 0.016 

Iron 19 100 18.0 33.0 21.5 3.9 2.0 1.0 

Nickel 18 100 0.41 0.563 0.49 0.05 0.84 0.094 

(a) Based on a daily composite of three grab samples 

(b) Based on the average of four daily composite samples 

mg/L = Milligram per liter 

operation (recirculation) was also evaluated, which involved 

the direct contact of ARD with sulfide rich water from the 

bioreactors and precipitation of metal sulfides in the settling 

pond. A portion of the settling pond supernatant containing 

excess sulfate is then pumped to the head of the bioreactor 

system to generate additional sulfides (Figure 1-3). 

The heart of the treatment system is the two compost-free, 

sulfate-reducing bioreactors. The bioreactors are ponds lined 

with 60 mil high density polyethylene (HDPE) and filled with 

20 to 40 cm river rock. River rock was selected because of the 

ease at which precipitates can be flushed through the matrix 

and the stability of the matrix. A blanket of manure was 

added to the base of each bioreactor to support the startup of 

each bioreactor. Each bioreactor consists of three 10 cm 

diameter influent distribution lines and three 10 cm effluent 

collection lines. The distribution and collection lines are 

located near the top, in the middle, and just above the bottom 

of the bioreactor to precisely control flow within the 

bioreactor media. ARD water can be drawn upward or 

downward through the aggregate to one of three effluent 

collection lines located at the opposite end of each bioreactor 

(Figures 1-2 and 1-3). 

Influent to the treatment system consists of ARD discharged 

from Aspen Seep. In gravity flow mode (Figure 1-2), influent 

13
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ARD from Aspen Seep passes through a flow control weir at 

flow rates ranging from 25 to 91 L/min, where a 25 percent 

sodium hydroxide solution (0.26 [ml/L] milliliter per liter or 

83 mg/L) is added to adjust the pH from 3.1 to approximately 

4 to maintain a favorable environment for sulfate-reducing 

bacteria and ethanol (0.43 ml/L or 339 mg/L) is added to 

provide a carbon source for reducing equivalents for the 

sulfate-reducing bacteria. The dosed influent discharges into a 

pretreatment pond (28 m3

 [cubic meter], 4 hour hydraulic 

residence time [HRT] at 114 L/min) to allow sufficient time 

for reagent contact and to stabilize the flow to the head of 

Bioreactor No.1. A small volume of metal precipitation also 

occurs within the pretreatment pond. ARD from the 

pretreatment pond then flows through Bioreactor No.1 (354 

m3 total volume, 150 m3 active volume) and Bioreactor No.2 

(200 m3

 total volume, 85 m3 active volume) to reduce sulfate 

to sulfide. The HRT for the two bioreactors are 22 hours for 

Bioreactor No.1 and 13 hours for Bioreactor No.2 at a design 

flow rate of 114 L/min. Excess sulfide generated in the first 

bioreactor is passed, along with partially treated ARD water, 

through to the second bioreactor for additional metals 

removal. Effluent from the second bioreactor discharges to a 

continuous flow pond (465 m3

 volume, 68 hour HRT at 114 

L/min) for extended settling of metal sulfide precipitates. A 

twenty-five percent sodium hydroxide solution (0.85 ml/L or 

270 mg/L) is added to the bioreactor effluent prior to the 

continuous flow settling pond to reduce acidity, raise the pH to 

7, and enhance metal sulfide precipitation. 

Operated in recirculation mode (Figure 1-3), metal-rich ARD 

influent from Aspen Seep passes through a flow control weir 

at which point the ARD flow is routed around the two 

bioreactors to a flow control vault at the head of the 

continuous flow settling pond. The untreated ARD is mixed 

with the sulfide-rich water from bioreactor No.2 followed by 

25 percent sodium hydroxide solution (0.5 ml/L or 159 mg/L), 

and is then discharged to the settling pond. The combination 

of a neutral pH condition and high sulfide concentrations 

promotes rapid precipitation of metal sulfides in the settling 

pond rather than in the two bioreactors. Precipitation of a 

majority of the metal sulfides downstream of the two 

bioreactors reduces precipitate formation in the bioreactors 

and the need for flushing and the associated stress on bacteria 

in the two bioreactors. A portion of the pond supernatant 

containing excess sulfate is then pumped to a holding pond at 

flow rates ranging from 114 to 227 L/min. Ethanol (0.5 ml/L 

or 395 mg/L) is added to the discharge from the holding pond, 

just prior to the head of bioreactor No.1. Sulfate-rich and 

metal-poor water from the holding pond then flows through 

the two bioreactors to promote additional sulfate reduction to 

sulfide. The pH of the supernatant recirculated through the 

bioreactors is near neutral, providing optimal conditions for 

sulfate-reducing bacteria growth (Tsukamoto 2005a). The 

system operated in recirculation mode requires about 49 

percent less sodium hydroxide and 14 percent more ethanol 

than the gravity flow mode of operation. 

During both modes of operation, the effluent from the 

continuous flow settling pond then flows through a rock lined 

aeration channel (46 meter long by 0.6 meter wide) to promote 

gas exchange prior to effluent discharge. Precipitate slurry is 

periodically flushed from the two bioreactors to prevent 

plugging of the river rock matrix. The slurry is sent to a 

flushing pond (510 m3 volume, 75 hour HRT at 114 L/min) for 

extended settling. The flushing pond can also be used for 

extended settling of the continuous flow settling pond effluent 

in the event of a system upset. Settled solids are periodically 

pumped out of the settling and flushing ponds and dewatered 

using 3 meter by 4.6 meter spun fabric bag filters. The bag 

filtration process relies on the build up of filter cake on the 

inside of each bag to remove progressively smaller particles. 

Effluent from the bag filters, including soluble metals and 

particles too small to be captured, flows by gravity back into 

the flushing pond. Metals in bag filter solids did not exceed 

Federal or state of California standards for characterization as 

a hazardous waste. The total system HRT is 107 hours at 

maximum design flow of 114 L/min, and 352 hours at an 

average flow rate of 37.9 L/min during the demonstration. 

2.3 Evaluation Approach 

Evaluation of the bioreactor treatment technology occurred 

between November 2003 and July 2005 on a year round basis. 

During the evaluation period, multiple sampling events of the 

treatment system were conducted in accordance with the 2003 

Technology Evaluation Plan/Quality Assurance Project Plan 

(TEP/QAPP) (Tetra Tech EM Inc [Tetra Tech] 2003). During 

each sampling event, EPA collected chemical data from the 

systems’ influent and effluent streams, documented metals 

removal and reduction in acidity within the systems’ unit 

operations, and recorded operational information pertinent to 

the evaluation of the treatment system. The treatment system 

was evaluated based on removal efficiencies for primary and 

secondary target metals, comparison of effluent concentrations 

to EPA interim discharge standards, and on the characteristics 

of and disposal requirements for the resulting metals-enriched 

solid wastes. Removal efficiencies of individual unit 

operations were also evaluated. The following sections 

describe in more detail the project objectives and sampling 

program. 

2.3.1 Project Objectives 

As discussed in the TEP/QAPP (Tetra Tech 2003), two 

primary objectives identified for the SITE demonstration were 

considered critical to the success of the bioreactor treatment 

technology evaluation. Seven secondary objectives were 

identified to provide additional information that is useful, but 

not critical to the technology evaluation. The primary 

objectives of the technology evaluations were to: 

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• Determine the removal efficiencies for primary target 

metals over the evaluation period 

• Determine if the concentrations of the primary target 

metals in the treated effluent are below the interim 

(pre-risk assessment and record of decision) 

discharge standards mandated in 2002 Action 

Memorandum for Early Actions at Leviathan Mine 

(EPA 2002) 

The following secondary objectives also were identified: 

• Document operating parameters and assess critical 

operating conditions necessary to optimize system 

performance 

• Monitor the general chemical characteristics of the 

ARD water as it passes through the treatment system 

• Evaluate operational performance and efficiency of 

solids separation systems 

• Document solids transfer, dewatering, and disposal 

operations 

• Determine capital and operation and maintenance 

(O&M) costs 

• Document winter operating procedures and 

effectiveness 

• Determine the volume and type of metal precipitate 

generated in the bioreactors and the optimal 

frequency and duration of bioreactor flushing 

2.3.2 Sampling Program 

Over the duration of the demonstration, EPA collected 

pretreatment, process, and post-treatment water samples from 

the treatment system. These samples were used to evaluate 

the primary and secondary objectives, as identified in the 

TEP/QAPP (Tetra Tech 2003). Sludge samples also were 

collected to document the physical and chemical 

characteristics of the sludge and to estimate the volume and 

rate of sludge generation. Summary tables documenting the 

water and sludge samples collected and the analyses 

performed for each mode of treatment system operation are 

presented in Appendix A. In addition to chemical analyses 

performed on the samples collected, observations were 

recorded on many aspects of the operations of each treatment 

system. The sampling program is summarized below by 

objective. 

Primary Objective 1: Determine the removal efficiency 

for each metal of concern over the demonstration period. 

To achieve this objective, influent and effluent samples from 

the treatment system were collected from strategic locations 

within the treatment system. The samples were filtered, 

preserved, and then analyzed for primary target metals: 

aluminum, arsenic, copper, iron, and nickel and secondary 

water quality indicator metals: cadmium, chromium, lead, 

selenium, and zinc. From the influent and effluent data 

collected, overall average removal efficiencies were calculated 

for each target metal over the period of the demonstration. 

The results of the removal efficiency calculations are 

summarized in Section 2.5.1. 

Primary Objective 2: Determine if the concentration of 

each target metal in the treated effluent is below the EPA 

interim discharge standard. Results from effluent samples 

collected to meet Primary Objective 1 were used to meet this 

objective. The sampling schedule was designed so that a 

composite of three grab samples were collected on each 

sampling day. Results from daily composite samples were 

compared against EPA’s daily maximum discharge standards 

(EPA 2002). In addition, 4-day running averages were 

calculated for each target metal for comparison against EPA’s 

four-day average discharge standards. To determine if the 

discharge standards were met, the effluent data were compared 

directly to the applicable standards as specified in Table 2-1. 

In addition, a statistical analysis was performed to determine 

whether or not statistically the results were below the 

discharge standards. The results of the comparison of effluent 

data to discharge standards are summarized in Section 2.5.2. 

Secondary Objective 1: Document operating parameters 

and assess critical operating conditions necessary to 

optimize system performance. To achieve this objective, 

system flow and recirculation rate data, ethanol and sodium 

hydroxide dosing data, and HRT data were recorded by the 

system operator and the SITE demonstration sampling team. 

The performance of individual unit operations was assessed by 

determining the reduction in target metal concentrations along 

the treatment system flow path. A description of system 

operating parameters and discussion of metals reduction 

within individual unit operations are presented in 

Section 2.5.3. 

Secondary Objective 2: Monitor the general chemical 

characteristics of the ARD water as it passes through the 

treatment system. To achieve this objective, the influent and 

effluent samples collected to meet Primary Objectives 1 and 2 

were analyzed for total iron, sulfate, total suspended solids 

(TSS), total dissolved solids (TDS), and total and bicarbonate 

alkalinity. Field measurements were also collected for ferrous 

iron, sulfide, pH, dissolved oxygen (DO), temperature, 

oxidation-reduction potential (ORP), and conductivity. 

Organic analysis for residual ethanol or metabolites was not 

conducted as a part of the sampling program. A discussion of 

these data and associated reaction chemistry are presented in 

Section 2.5.3. 

Secondary Objective 3: Evaluate operational performance 

and efficiency of solids separation systems. To achieve this 

objective, influent and effluent samples were collected from 

the bioreactors and settling ponds and were analyzed for 

15
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filtered and unfiltered metals, TSS, and TDS to assess target 

metal removal efficiencies, solids removal rates and 

efficiencies, HRT, and residual levels of solids in the effluent 

streams. The results of this evaluation are presented in 

Section 2.5.3. 

Secondary Objective 4: Document solids transfer, 

dewatering, and disposal operations. To achieve this 

objective, the system operator maintained a log of the volume 

and rate of solids transferred from the settling ponds for 

dewatering and disposal. Solids samples were collected after 

dewatering and analyzed for residual moisture content and 

total and leachable metals to determine waste characteristics 

necessary for waste classification prior to disposal. Leachable 

metals were evaluated using the California Waste Extraction 

Test (WET) (State of California 2004), the Method 1311: 

Toxicity Characteristic Leaching Procedure (TCLP) (EPA 

1997), and Method 1312: Synthetic Precipitation and 

Leaching Procedure (SPLP) (EPA 1997). An evaluation of 

solids handling is presented in Section 2.5.4. 

Secondary Objective 6: Document winter operating 

procedures and effectiveness. To achieve this objective, 

winter O&M activities were documented by the system 

operator. The system operator logged changes to system 

configuration; changes in influent flow and chemical dosing 

rates; changes in activity of sulfate-reducing bacteria; changes 

in solids settling efficiencies; operational problems and system 

down time; frequency of site visits and access difficulties; and 

consumables and equipment change out. Samples were also 

collected as specified in secondary objective No. 1, 2, 3, and 4 

to document the effect of winter conditions on the anaerobic 

wetland treatment system. The results of this evaluation are 

presented in Section 2.5.3. 

Secondary Objective SAW1: Determine the volume and 

type of metal precipitate generated in the bioreactors and 

the optimal frequency and duration of bioreactor flushing. 

To achieve this objective, the system operator documented the 

volume of metal precipitate flushed from each bioreactor and 

the overall rate and volume of metal precipitate accumulation 

in the flushing pond. Solids samples were collected from the 

flushing pond and analyzed for total metals to determine the 

type of metal precipitates formed. An evaluation of solids 

handling is presented in Sections 2.5.3 and 2.5.4. 

2.4 Field Evaluation Activities 

The following sections discuss activities required to conduct a 

technical evaluation of each mode of the bioreactor treatment 

system operation at the Leviathan Mine site. The discussion 

includes a summary of mobilization activities, O&M 

activities, process modifications, evaluation monitoring 

activities, demobilization activities, and lessons learned. 

2.4.1 Mobilization Activities 

The bioreactor treatment system was constructed between the 

fall of 2002 and the summer of 2003 and required startup and 

acclimation prior to technology evaluation activities. 

Mobilization activities described below were based on weekly 

oversight visits under a separate contract and on information 

provided by UNR. Mobilization activities after initial system 

construction, including bioreactor acclimation, typically 

require a two to three month period and include the following: 

• Delivery, positioning, and assembly of reagent 

storage tanks, reagent day tanks, reagent delivery 

pumps, reagent metering devices, and distribution 

lines 

• Reagent delivery and storage 

• Installation of solar panel and storage battery, layout 

of power lines for reagent delivery pumps (gravity 

flow operations) 

• Initial filling of the bioreactors and one settling pond 

• Monitoring of system influent, whole bioreactor 

influent and effluent, individual bioreactor effluent 

loops, and settling pond effluent for biological 

activity, sulfide generation, metals removal 

• Adjustment of ethanol and sodium hydroxide dosage 

along with gradual increase in influent flow as 

biological activity increases 

• Pipe and pump lay out and assembly for recirculation 

operations (recirculation flow operations) 

• Fuel storage tank and secondary containment system 

delivery, setup, and fuel delivery (recirculation flow 

operations) 

• Generator delivery and setup, layout of power lines 

for recirculation pumps (recirculation flow 

operations) 

2.4.2 Operation and Maintenance Activities 

The following section discusses O&M activities documented 

during the evaluation of each mode of bioreactor treatment 

operation. The discussion includes a summary of system 

operational dates, treatment and discharge rates, problems 

encountered, quantity of waste treated, reagents consumed, 

process waste generated, and percentage of time the system 

was operational. 

The bioreactor treatment system was operated in gravity flow 

mode from November 2003 through mid-May 2004, and in 

recirculation mode from mid-May 2004 through July 2005. A 

description of system O&M activities for each mode of 

operation is presented below. 

16
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Gravity Flow Operations. Bioreactor No.1 began receiving 

ARD during the first week on March 2003. On April 21, 2003 

12 L/min of neutralized ARD (pH 8) and 700 mg/L ethanol 

was diverted into Bioreactor No.1 to begin the acclimation 

process. On May 30, 2003, the flow of neutralized ARD (pH 

6 to 7) was reduced to 4 to 6 L/min. On June 24, 2003 

effluent from Bioreactor No.1 was allowed to discharge to and 

begin acclimation of Bioreactor No.2. Between August 12 

and October 22, 2003 influent ARD flow was slowly 

increased until the entire flow of Aspen Seep was being 

treated. Acclimation of the bioreactors was completed on 

November 12, 2003 at which point discharge from the 

treatment system was initiated. Following acclimation, 

treatment system discharge rates ranged from 25 to 47 L/min. 

On November 13, 2003, the sodium hydroxide supply was 

consumed and base addition at the influent weir was 

suspended for one day pending delivery of sodium hydroxide. 

Influent pH to the bioreactor was not adjusted; however, given 

the long bioreactor HRT no impact was observed. 

From November 25 through December 8, 2003, sodium 

hydroxide addition to system ARD influent was deliberately 

stopped to determine whether the bioreactors could treat the 

ARD without an initial pH adjustment. Starting on December 

8, 2003 sodium hydroxide was added to the effluent from 

Bioreactor No.2 to raise the pH to near neutral in order to 

promote the precipitation of iron sulfide in the settling pond. 

During the week of December 22, 2003 the solar system 

controller failure leading to a lack of base addition for up to 

three days. The cessation of sodium hydroxide addition 

reduced the pH in the pretreatment pond and Bioreactor No.1. 

Treatment of ARD from Aspen Seep under gravity flow 

conditions was completed on May 11, 2004. During gravity 

flow operations from November 12, 2003 through May 11, 

2004, the system treated 9.24 million liters of ARD using 

9,235 L of 25 percent sodium hydroxide (average dosage of 

317 mg/L) and 4,466 L of ethanol (average dosage of 381 

mg/L) and generated about 4.2 dry tons (3,800 kg) of nonhazardous solids. The system was operational approximately 

98 percent of the time during gravity flow operations. The 

system operated 24 hours per day and was maintained 1 to 2 

days per week by an operator. 

Recirculation Flow Operations. Treatment of ARD from 

Aspen Seep under recirculation flow conditions was initiated 

on May 12, 2004 and continued through the end of the 

technology evaluation period on July 13, 2005. Treatment 

rates ranged from 25 to 91 L/min. Recirculation rates from 

the settling pond to the head of Bioreactor No.1 ranged from 

114 to 227 L/min. On average, approximately five parts 

sulfide-rich bioreactor effluent were mixed with one part 

influent ARD in the settling pond. 

Twice during the week of July 12, 2004 the generator supply 

power for the recirculation pumps failed. Recirculation 

stopped and sulfide-rich water was not longer discharging 

from the bioreactors for up to two days. Influent ARD was 

treated by residual sulfide in the settling pond and the flushing 

pond. 

On August 19, 2004, UNR reversed the flow direction in 

Bioreactor No.1 to minimize development of preferential flow 

paths. Influent enters the north end of the bioreactor and 

effluent discharges from the south end of the bioreactor. 

Effluent is piped around the bioreactor and enters Bioreactor 

No.2 in the typical south to north flow regime. 

During the weeks of September 27 and October 4, 2004 sludge 

was transferred from Pond 3 to Pond 4 to provide the 

necessary sludge storage capacity in Pond 3 for winter 

operations. 

Twice during the week of November 8, 2004 the generator 

supply power for the recirculation pumps failed due to water 

in the diesel fuel tank. Recirculation stopped and sulfide-rich 

water was not longer discharging from the bioreactors for up 

to two days. The solar panel battery also failed, which 

stopped the addition of sodium hydroxide to the settling pond 

for up to three days. The cessation of sodium hydroxide 

addition reduced the pH in the settling and flushing ponds. 

Influent ARD was being treated by residual sulfide in the 

settling pond and the flushing pond. 

On November 25, 2004, the single large capacity recirculation 

pump was replaced with three smaller capacity pumps to 

provide redundancy in the event of a single pump failure. On 

December 3, 2004 the intakes on the three recirculation pumps 

were raised to reduce the intake of settled sludge from the 

settling pond and transfer of solids to the head of Bioreactor 

No.1. On February 3, 2005 the three smaller capacity pumps 

were replaced with a single large capacity recirculation pump 

due to reliability problems with the pump controller. 

On March 17, 2005 the generator supply power for the 

recirculation pump failed. Recirculation stopped and sulfiderich water was not longer discharging from the bioreactors for 

up to two days. Influent ARD was being treated by residual 

sulfide in the settling pond and the flushing pond. 

During the week of June 28, 2005 settled solids were 

transferred from the settling pond to the flushing pond. 

On July 13, 2005 the generator supply power for the 

recirculation pump failed. Recirculation stopped and sulfiderich water was not longer discharging from the bioreactors for 

a one day period. Influent ARD was being treated by residual 

sulfide in the settling pond and the flushing pond. 

17
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On July 13, 2005 two solar powered recirculation pumps were 

installed at the settling pond. The combined flow of the two 

pumps was about 45 L/min, handling approximately onequarter of the flow necessary for recirculation operations. 

On August 30, 2005 the generator supply power for the 

recirculation pump failed. Recirculation stopped and sulfiderich water was not longer discharging from the bioreactors for 

three days. Influent ARD was being treated by residual 

sulfide in the settling pond and the flushing pond. 

From mid-August through mid-November 2005, 

approximately 200,000 L of sludge from the settling pond was 

dewatered using seven bag filters. Each bag required one day 

to build up a sufficient layer of cake to adequately concentrate 

solids within the bag. Approximately 4.3 dry tons (3,900 kg) 

of non-hazardous bag filter solids were generated and 

disposed of off-site. Approximately 10 dry tons (9,100 kg) of 

non-hazardous solids remain in the settling and flushing 

ponds. 

During recirculation flow operations, the system treated 22.1 

million liters of ARD using 22,029 L of 25 percent sodium 

hydroxide (average dosage of 316 mg/L) and 10,617 L of 

ethanol (average dosage of 379 mg/L) and generated about 10 

dry tons (9,100 kg) of non-hazardous solids. The system was 

operational approximately 98 percent of the time during 

recirculation operations. The system operated 24 hours per 

day and was maintained 1 to 2 days per week by an operator. 

2.4.3 Process Modifications 

A number of modifications were made to the bioreactor 

treatment system to improve bioreactor performance, solids 

handling, and the type and rate of reagent consumption. The 

primary modification involved recirculation as an alternate 

mode of contact between ARD and sulfide-rich water and 

location for collection of metal sulfide precipitates. 

• An alternate method and location of contact between 

the ARD and sulfide-rich bioreactor effluent was 

implemented. Influent ARD was combined with 

bioreactor effluent at the head of the settling pond to 

promote precipitation and settling of metal sulfides in 

the pond rather than in the individual bioreactors. A 

portion of the sulfate-rich and metal-poor effluent 

from the settling pond was recirculated to the head of 

the two bioreactors for generation of additional 

sulfide. The new configuration places less stress on 

the sulfate-reducing bacteria through reduced metals 

toxicity, higher influent pH, a more stable flow, and 

greatly reduces the need to flush solids from the 

bioreactors. 

• Operation of the treatment system in the recirculation 

configuration eliminated the need for the 

pretreatment pond for initial pH adjustment and the 

long term requirement to periodically flush solids 

from the pond. 

• Sodium hydroxide was demonstrated during 

operation of the pilot-scale treatment system as the 

preferred method of base addition. During the 

evaluation of the full-scale treatment system, 

alternative sources for addition of base were 

evaluated. Sodium carbonate, sodium acetate, 

potassium acetate, and syn-rock were evaluated and 

were found to provide inadequate base delivery due 

to large dose required, poor solubility, freezing, or 

sealing of the reagent surface. 

• During the evaluation of the full-scale treatment 

system, alternative locations for addition of base 

were evaluated. Adjustment of influent pH to 

approximately 4.0 was found to be necessary prior to 

bioreactor treatment to reduce stress on the sulfatereducing bacteria. Addition of base prior to the 

settling pond to a neutral pH showed an improvement 

in metals removal. 

• In order to provide an opportunity for extended 

contact of sulfides and metals and extended settling 

of metal sulfides, the flushing pond was brought on 

line to receive effluent from the settling pond, 

effectively doubling settling time. 

• Rather than setup and periodically pump settled 

solids through bag filters for dewatering, settled 

solids from the pretreatment pond and settling pond 

were discharged to the flushing pond. Settled solids 

were allowed to accumulate in the flushing pond 

prior to bag filtration in the fall. 

2.4.4 Evaluation Monitoring Activities 

This section discusses monitoring activities conducted during 

the evaluation of each mode of treatment technology 

operation. The discussion includes a summary of sampling 

dates and locations for system performance, unit operations, 

solids handling, and solids disposal samples outlined in the 

sampling program (see Section 2.3.2). Summary tables 

documenting the water, sludge, and solids samples collected 

and the analyses performed for each mode of treatment system 

operation are presented in Appendix A. 

The bioreactor treatment system was operated in the gravity 

flow mode from November 2003 through mid-May 2004, and 

in recirculation mode from mid-May 2004 through July 2005. 

A description of evaluation monitoring activities for each 

mode of operation is presented below. 

Gravity Flow Evaluation Monitoring Activities. Both 

system performance and unit operations sampling was 

performed in 2003 and 2004. System performance and unit 

operations samples were collected from the system influent 

18
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and effluent on November 14 and 25, 2003; and January 29, 

February 19, March 24, and April 29, 2004. No solids 

samples were collected during gravity flow monitoring 

activities as the settling ponds were just beginning to fill with 

metal sulfide precipitates. 

Recirculation Evaluation Monitoring Activities. Both 

system performance and unit operations sampling was 

performed in 2004 and 2005. System performance and unit 

operations samples were collected from the system influent 

and effluent on June 16, August 19, and December 3, 2004; 

and February 3, March 17, April 27, and June 2, 2005. 

A settling pond sample was collected on June 14, 2004. 

Pretreatment pond, settling pond, flushing pond, and aeration 

channel sludge samples were collected on July 13, 2005. A 

composite sample of dewatered bag filter solids was collected 

on September 29, 2005 for waste characterization. 

2.4.5 Demobilization Activities 

The bioreactor treatment system has been permanently 

constructed at Leviathan Mine and operates on a year round 

basis. Therefore, no demobilization activities were observed. 

However, activities associated with preparation for winter 

conditions were observed and documented. 

Winterization activities observed for the bioreactor treatment 

system include: 

• Filling reagent and fuel tanks prior to build up of 

snow pack 

• Inspect and replace reagent delivery lines as 

necessary 

• Perform solar cell and battery maintenance 

• Perform generator maintenance (replacement or 

overhaul) 

• Remove solids from settling ponds to provide 

sufficient pond capacity for the winter 

• Ship accumulated bag filter solids to an off-site nonhazardous waste landfill or dispose of on-site. 

• Lower level on pond decant structures to allow extra 

precipitation capacity in settling/flushing ponds 

• Clear decant structures of debris 

• Remove portable toilets 

2.4.6 Lessons Learned 

This section discusses the lessons learned during the technical 

evaluation of the bioreactor treatment system. The discussion 

includes observations, recommendations, and ideas to be 

implemented during future operations and for similar 

treatment systems. 

Lessons learned during the operation of bioreactor treatment 

system include: 

• Gravity flow operation of the bioreactor treatment 

system allows precipitation and accumulation of 

metal sulfides within the bioreactor. The 

recirculation mode of operation evaluated at 

Leviathan Mine promoted the generation of sulfide in 

the bioreactors and the majority of metal sulfide 

precipitation in the settling pond rather than in the 

individual bioreactors. In addition, less stress was 

placed on the sulfate-reducing bacteria by reducing 

metals loading, operating at a higher influent pH, and 

reducing frequency of solids flushing from the 

bioreactors. 

• Adjustment of influent pH to approximately 4.0 was 

found to be necessary prior to bioreactor treatment to 

reduce stress on the sulfate-reducing bacteria. 

Addition of base prior to the settling pond to a neutral 

pH showed an improvement in metals removal. 

• Sodium hydroxide was demonstrated during 

operation of the pilot-scale and full-scale treatment 

system as the preferred method of base addition. 

Other source materials were found to be inadequate 

due to large dose required, poor solubility, freezing, 

or sealing of the reagent surface. 

• Health and safety issues observed during the 

technology evaluation include skin and eye splash 

contact when working with sodium hydroxide; 

accumulation of hydrogen sulfide gas in depressions 

and valve vaults; and slip hazards around the 

perimeter of the settling and flushing ponds. 

Mitigation of hazards associated with sodium 

hydroxide includes arm length chemical gloves, 

chemical apron, eye protection, and a face shield. 

Mitigation of hazards associated with hydrogen 

sulfide gas includes the use of gas detection meters 

and blowers. Mitigation of slips hazards around the 

settling and flushing ponds should include perimeter 

fencing, barriers around open ponds, and a safety 

rope when working inside the fenced area. 

• During periods of high flow, base delivery upsets, 

recirculation upsets, and extra pond capacity may be 

required to provide sufficient HRT for precipitate 

settling due to formation of smaller particles. At 

Leviathan Mine, the flushing pond was brought on 

line to receive effluent from the settling pond, 

effectively doubling settling time. 

• Sludge should be periodically transferred to the 

flushing pond to provide adequate settling capacity in 

the pretreatment and settling ponds. 

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• Rather than setup and continuously pump settled 

solids through bag filters for dewatering, settled 

solids should be allowed to accumulate in the 

flushing pond prior to periodic bag filtration. 

• Bag filters may limit operations during freezing 

temperatures in due to icing of the filter fabric, which 

will create backpressure within the system. 

Therefore, bag filtration of sludge should occur from 

late spring through early fall. 

2.5 Technology Evaluation Results 

This section summarizes the evaluation of the metals data 

collected during the SITE demonstration with respect to 

meeting project objectives. Attainment of project primary 

objectives is described in Sections 2.5.1 and 2.5.2, while 

secondary objectives are provided in Section 2.5.3. Solids 

handling and disposal for is discussed in Section 2.5.4. 

Preliminary evaluation of the influent, effluent, and 4-day 

average effluent metals data included an assessment of data 

characteristics through quantitative and graphical analysis. 

Influent, effluent, and 4-day average effluent concentrations 

for the 10 metals of interest for each mode of treatment system 

operation are presented in Tables B-1 through B-2 of 

Appendix B. Summary statistics calculated for these data sets 

include: mean, median, standard deviation, and coefficient of 

variation, which are presented in Tables B-3 through B-4 of 

Appendix B. Minimum and maximum concentrations are also 

presented. 

Summary statistics for influent, effluent, and 4-day average 

effluent data were determined using Analyze-It Excel 

(Analyze-It 2004) and ProUCL (EPA 2004) statistical 

software. In addition, frequency, box-and-whisker, and 

probability plots were prepared to identify data characteristics 

and relationships, evaluate data fit to a distribution (for 

example, normal or lognormal), and to identify anomalous 

data points or outliers for the 10 target metals for each of 

treatment system operation. The results of statistical plotting 

showed only one significant outlier in the effluent dataset for 

iron. The iron effluent outlier was the result of inadequate 

sodium hydroxide addition prior to the settling pond. 

Summary statistics were prepared for the iron effluent data set 

both with and without the outlier for comparative purposes. 

No significant outliers were identified in the effluent data for 

the other target metals. No significant outliers were identified 

in the influent or 4-day average effluent datasets. No data 

were rejected from the data sets. The statistical plots also 

showed the metals influent and effluent concentrations to be 

normally distributed, with the exception of those samples at or 

near method detection limits. Statistical plots are documented 

in the Technology Evaluation Report Data Summary (Tetra 

Tech 2006). 

2.5.1 Primary Objective No.1: Evaluation of 

Metals Removal Efficiencies 

The evaluation of the bioreactor treatment system focused on 

two primary objectives. The first objective was to determine 

the removal efficiencies for the primary metals of concern and 

the secondary water quality indicator metals. To successfully 

calculate removal efficiencies for each metal, influent 

concentrations must be significantly different than effluent 

concentrations. Based on preliminary statistical plots 

described in Section 2.5, the influent and effluent metals data 

sets were found to be normally distributed; therefore a paired 

Student’s-t test (as described in EPA guidance [EPA 2000]) 

was used to determine if the influent and effluent 

concentrations were statistically different. For this statistical 

evaluation, if the P-value (test statistic) was less than the 0.05 

significance level (or 95 percent confidence level), then the 

two data sets were considered statistically different. Influent 

and effluent concentrations for up to 7 of the 10 metals from 

each bioreactor treatment system mode of operation were 

found to be statistically different (P-value was less than 0.05), 

and for these metals, removal efficiencies were calculated. 

Tables 2-2 through 2-3 present the average and range of 

removal efficiencies for filtered influent and effluent samples 

collected during each mode of treatment system operation 

during the SITE demonstration and also the P-value for the 

paired Student’s-t test analysis. The average influent and 

effluent metals concentrations for each treatment system are 

also presented. Where influent and effluent concentrations for 

a particular metal were not statistically different (P-value was 

greater than 0.05), removal efficiencies were not calculated for 

that metal, as indicated in the summary tables. In addition, 

where one or both concentrations for a metal were not 

detected in an individual influent/effluent data pair, those data 

points were not included in the determination of removal 

efficiencies. 

For the gravity flow mode of treatment system operation, the 

average removal efficiency for the primary target metals was 

94 percent over 6 sampling events. For the recirculation mode 

of treatment system operation, the average removal efficiency 

for the primary target metals was 96 percent over 7 sampling 

events. Removal efficiencies for arsenic were not calculated 

because the influent and effluent metals concentrations were 

not statistically different. In addition, the concentration of 

arsenic in system influent was well below discharge standards. 

Average removal efficiencies for secondary target metals 

ranged from 41 to 99 percent in both modes of operation; 

however, removal efficiencies were not calculated for 

chromium, lead, and selenium during gravity flow operations 

as the influent and effluent concentrations were not 

statistically different. Similarly, removal efficiencies were not 

calculated for cadmium and selenium during recirculation 

operations. In the case of arsenic, cadmium, chromium, and 

lead in the ARD, concentrations were near or below the EPA 

20
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Table 2-2. Removal Efficiencies for the Bioreactor Treatment System – Gravity Flow Operation 

Target Metal 

Number of 

Sampling 

Events 

Average 

Filtered Influent 

Concentration 

(μg/L) 

Average Filtered 

Effluent 

Concentration 

(μg/L) 

Paired 

Student’s-t test 

P-value1 

Average 

Removal 

Efficiency (2) 

(%) 

Range of Removal 

Efficiencies (%) 

Primary Target Metals 

Aluminum 6 37,467 103 <0.05 99.7 99.5 to 99.9 

Arsenic 6 2.1 4.7 0.192 NC NC 

Copper 6 691 4.8 <0.05 99.3 99.1 to 99.7 

Iron 6 117,167 4,885 <0.05 95.8 65.6 to 99.9 

Nickel 6 487 65.5 <0.05 86.6 72.1 to 92.6 

Secondary Water Quality Indicator Metals 

Cadmium 6 0.61 <0.21 0.009 65.3 42.5 to 79 

Chromium 6 12.2 7.8 0.126 NC NC 

Lead 6 3.6 4.7 0.386 NC NC 

Selenium 6 13.9 11.2 0.149 NC NC 

Zinc 6 715 15.8 <0.05 97.8 95.9 to 98.6 

(1) A P-value less than 0.05 indicates that influent and effluent data are statistically different 

(2) Average removal efficiency calculated using the average influent and average effluent concentration data 

μg/L = Microgram per liter 

% = Percent 

NC = Not calculated as influent and effluent concentrations were not statistically different 

Table 2-3. Removal Efficiencies for the Bioreactor Treatment System – Recirculation Operation 

Target Metal 

Number of 

Sampling 

Events 

Average 

Filtered Influent 

Concentration 

(μg/L) 

Average Filtered 

Effluent 

Concentration 

(μg/L) 

Paired 

Student’s-t test 

P-value1 

Average 

Removal 

Efficiency (2) 

(%) 

Range of Removal 

Efficiencies (%) 

Primary Target Metals 

Aluminum 7 40,029 52.7 <0.05 99.9 99.7 to 99.9 

Arsenic 7 7.4 6.5 0.785 NC NC 

Copper 7 795 4.6 <0.05 99.4 98.8 to 99.8 

Iron 7 115,785 2,704 <0.05 97.7 92.8 to 99.7 

Nickel 7 529 69.7 <0.05 86.8 71.0 to 96.4 

Secondary Water Quality Indicator Metals 

Cadmium 7 0.60 <0.20 0.083 NC NC 

Chromium 7 11.1 6.4 0.002 42.5 21.2 to 84.8 

Lead 7 4.2 2.5 0.003 41.3 22.0 to 57.1 

Selenium 7 11.5 8.5 0.057 NC NC 

Zinc 7 776 8.9 <0.05 98.9 97.7 to 99.8 

(1) A P-value less than 0.05 indicates that influent and effluent data are statistically different 

(2) Average removal efficiency calculated using the average influent and average effluent concentration data 

μg/L = micrograms per liter 

% = Percent 

NC = Not calculated as influent and effluent concentrations were not statistically different 

21
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interim discharge standards in the influent; therefore, the 

treatment system was not optimized for removal of these 

metals resulting in lower removal efficiencies. Removal 

efficiencies for sulfate ranged from 8 to 35 percent with an 

average reduction in sulfate of 17 percent. There was on 

average a 9 percent increase in sulfate removal during the 

recirculation mode of treatment system operation. 

2.5.2 Primary Objective No.2: Comparison of 

Effluent Data to Discharge Standards 

The second primary objective was to determine whether the 

concentrations of the primary metals of concern in the effluent 

from the two modes of bioreactor treatment system operation 

were below EPA interim (pre-risk assessment and record of 

decision) discharge standards, as presented in Table 2-4. The 

4-day average discharge standard was originally intended for 

comparison to the average of four-consecutive-day sampling 

data. Instead, the average concentrations from four 

consecutive sampling events were compared against the fourday discharge standards. In addition, the attainment of 

discharge standards for the secondary water quality parameters 

was evaluated. Direct comparisons of the effluent data to the 

maximum and 4-day average discharge standards show that 

iron concentrations exceeded both sets of discharge standards, 

and that lead and selenium exceeded their respective 4-day 

average discharge standards. Additional statistical tests were 

used to evaluate whether any other metals concentrations in 

the effluent streams were statistically different from either set 

of discharge standards. 

Based on statistical plots described in Section 2.5, the metals 

effluent and 4-day average effluent concentrations were shown 

to be normally distributed; therefore, the one-sample 

parametric Student’s-t test (as described in EPA guidance 

[EPA 2000]) was used in the comparison of the metals 

concentrations to the discharge standards. The one- sample 

parametric Student’s-t test was used to determine if metals 

effluent and 4-day average effluent concentrations were 

significantly greater than the discharge standards (alternative 

or Ha hypothesis). The maximum daily discharge standards, 

maximum detected effluent concentrations, and average 

effluent concentrations are summarized in Table 2-5 and the 4­

day average discharge standards and 4-day average effluent 

concentrations are summarized in Table 2-6. 

Based on preliminary statistical plots described in Section 2.5, 

the metals effluent and 4-day average effluent concentrations 

were shown to be normally distributed; therefore, the onesample parametric Student’s-t test (as described in EPA 

guidance [EPA 2000]) was used in the comparison of the 

metals concentrations to the discharge standards. The onesample parametric Student’s-t test was used to determine if 

metals effluent and 4-day average effluent concentrations were 

significantly greater than the discharge standards (alternative 

or Ha hypothesis). The maximum daily discharge standards, 

maximum detected effluent concentrations, and average 

effluent concentrations are summarized in Table 2-5 and the 4­

day average discharge standards and 4-day average effluent 

concentrations are summarized in Table 2-6. 

Table 2-4. EPA Interim Discharge Standards 

Target Metals 

Maximum (a) 

(μg/L) 

Average (b) 

(μg/L) 

Primary Target Metals 

Aluminum 4,000 2,000 

Arsenic 340 150 

Copper 26 16 

Iron 2,000 1,000 

Nickel 840 94 

Secondary Water Quality Indicator Metals 

Cadmium 9.0 4.0 

Chromium 970 310 

Lead 136 5.0 

Selenium No Standard 5.0 

Zinc 210 210 

(a) Based on a daily composite of three grab samples 

(b) Based on the average of four consecutive daily composite samples 

μg/L = micrograms per liter 

For the metals data sets that could be analyzed, the 1-tailed Pvalues (test statistic) for all of the tests were above the 0.95 

significance level (or 95 percent confidence level) required for 

acceptance of the alternative hypothesis with the exception of 

iron, lead, and selenium. Iron and selenium concentrations 

were consistently above discharge standards, while only one 

lead effluent sample was above discharge standards and 

contributed to an elevated 4-day average concentration. There 

is no maximum daily discharge standard for selenium; 

therefore, there are no statistical results for selenium in Table 

2-5. In addition, cadmium was not detected in any of the 

effluent samples collected during either mode of treatment 

system operation; therefore, there are no statistical results for 

cadmium in either Table 2-5 or 2-6. 

The compost-free bioreactor treatment system was shown to 

be extremely effective at neutralizing acidity and reducing the 

concentrations of the 4 of the 5 target metals to below EPA 

interim discharge standards. Internal trials run to refine base 

addition requirements and to evaluate various sources of base 

addition lead to significant excursions of effluent iron 

concentrations above the EPA interim discharge standards 

during a portion of the evaluation period. However, after base 

optimization during gravity flow operations effluent iron 

concentrations met discharge standards. Iron also exceeded 

discharge standards during recirculation operations when base 

addition was stopped due to equipment failure or lack of 

adequate base supply. Although the influent concentrations 

22
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Table 2-5. Results of the Student’s-t Test Statistical Analysis for Maximum Daily Effluent Data 

Analyte 

Maximum Daily 

Discharge Limit 

(μg/L) 

Maximum Detected 

Concentration in 

Effluent Stream 

(μg/L) 

Average 

Concentration in 

Effluent Stream 

(μg/L) 

1-Tailed P-value 

(Effluent Data > 

Maximum Daily 

Discharge Limit) 

Effluent Concentration 

Significantly Greater 

than Maximum Daily 

Discharge Limit? 

(μg/L) 

Bioreactor Treatment System- Gravity Flow Mode Student’s-t test Comparisons 

Aluminum 4,000 160 103 1.0 No 

Arsenic 340 12.5 4.7 1.0 No 

Cadmium 9 <0.32 <0.21 NC No 

Chromium 970 16.3 7.8 1.0 No 

Copper 26 6.5 4.8 1.0 No 

Iron 2,000 39,200 4,597 0.107 Yes 

Lead 136 9.8 4.7 1.0 No 

Nickel 840 125 65.5 1.0 No 

Selenium No Standard 13.9 11.2 Not Tested Not Tested 

Zinc 210 29 15.8 1.0 No 

Bioreactor Treatment System- Recirculation Mode Student’s-t test Comparisons 

Aluminum 4,000 105 52.7 1.0 No 

Arsenic 340 11.2 6.51 1.0 No 

Cadmium 9 <0.3 <0.20 NC No 

Chromium 970 14.1 6.4 1.0 No 

Copper 26 9.5 4.6 1.0 No 

Iron 2,000 9,060 2,704 0.279 Yes 

Lead 136 4.6 2.5 1.0 No 

Nickel 840 154 69.7 1.0 No 

Selenium No Standard 12.3 8.5 Not Tested Not Tested 

Zinc 210 18.8 8.9 1.0 No 

μg/L = micrograms per liter 

A P-value greater than 0.95 indicates that effluent data are not greater than the discharge standard 

NC = Not calculated as sample results indicate metal was not detected 

for the primary target metals were up to 580 fold above the 

EPA interim discharge standards, the treatment system was 

successful in reducing the concentrations of the primary target 

metals in the ARD to between 1 and 43 fold below the 

discharge standards. In addition, the concentrations of the 

secondary target metals, with the exception of selenium, were 

reduced to below the discharge standards. 

2.5.3 Secondary Objectives for Evaluation of 

Bioreactor Treatment System Unit 

Operations 

The evaluation of the bioreactor treatment system at Leviathan 

Mine also included evaluation of four secondary objectives. 

These secondary objectives included: 

• Documentation of operating parameters and 

assessment of critical operating conditions necessary 

to optimize system performance. 

• Monitoring the general chemical characteristics of 

the ARD water as it passes through the treatment 

system. 

• Evaluating operational performance and efficiency of 

solids separation systems. 

• Documenting solids transfer, dewatering, and 

disposal operations. 

• Documentation of winter operating procedures and 

effectiveness 

• Determining the volume and type of metal precipitate 

generated in the bioreactors and the optimal 

frequency and duration of bioreactor flushing 

Documentation of year round operating conditions, discussion 

of reaction chemistry, evaluation of year round metals removal 

by unit operation, and evaluation of solids flushing and 

separation are presented in the following sections. The data 

presented were compiled from observations during the 

demonstration as well as data summarized in the Data 

Summary Report for Bioreactors at the Leviathan Mine Aspen 

Seep 2003 (Tsukamoto 2004), and the Data Summary Report 

for Bioreactors at the Leviathan Mine Aspen Seep 2004 

(Tsukamoto 2005a). Solids characterization and handling is 

documented in Section 2.5.4. 

23
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Table 2-6. Results of the Student’s-t Test Statistical Analysis for 4-Day Average Effluent Data 

Analyte 

4-Day Average 

Discharge Limit 

(μg/L) 

Maximum 

4-Day Average (1) 

Concentration in 

Effluent Stream 

(μg/L) 

Average 

4-Day Average (1) 

Concentration in 

Effluent Stream 

(μg/L) 

1-Tailed P-value 

(Effluent Data > 

Maximum Daily 

Discharge Limit) 

Effluent Concentration 

Significantly Greater 

than Maximum Daily 

Discharge Limit? 

(μg/L) 

Bioreactor Treatment System- Gravity Flow Mode Student’s-t test Comparisons 

Aluminum 2,000 128 108 1.0 No 

Arsenic 150 5.2 3.6 1.0 No 

Cadmium 4 <0.22 <0.21 NC No 

Chromium 310 6.8 5.8 1.0 No 

Copper 16 5.6 4.8 1.0 No 

Iron 1,000 15,783 14,118 0.005 Yes 

Lead 5 5.8 5.5 0.096 Yes 

Nickel 94 78.7 68.1 0.980 No 

Selenium 5 11.2 10.7 0.002 Yes 

Zinc 210 18.2 14.9 1.0 No 

Bioreactor Treatment System- Recirculation Mode Student’s-t test Comparisons 

Aluminum 2,000 58.3 52.1 1.0 No 

Arsenic 150 7.6 5.3 1.0 No 

Cadmium 4 <0.21 <0.18 NC No 

Chromium 310 7.4 5.0 1.0 No 

Copper 16 5.1 3.9 1.0 No 

Iron 1,000 3,760 2,951 0.012 Yes 

Lead 5 2.4 2 1.0 No 

Nickel 94 85.8 73 0.991 No 

Selenium 5 9.8 8.4 0.004 Yes 

Zinc 210 8.0 7.4 1.0 No 

(1) The data from four consecutive sampling events were used in the calculation of the average instead of four consecutive days 

μg/L = micrograms per liter 

A P-value greater than 0.95 indicates that effluent data are not greater than the discharge standard 

NC = Not calculated as sample results indicate metal was not detected 

2.5.3.1 Operating Conditions 

Operating conditions for the bioreactor treatment system in 

gravity flow and recirculation modes of operation are 

described below. 

Gravity Flow Operations. Operation of the treatment system 

in gravity flow mode (Figure 1-2) involved the collection of 

ARD from Aspen Seep in a rock-filled basin that was covered 

with soil to limit entrainment of oxygen. Minimization of 

dissolved oxygen in the influent ARD maximizes the 

efficiency of sulfate-reducing bacteria within the bioreactors. 

ARD discharges from the collection basin through a flow 

measurement weir at an average flow rate of 31.8 L/min. 

After passing through the weir, influent ARD discharges into a 

flow distribution box where 25 percent sodium hydroxide is 

dripped into the flow at an average dosage rate of 8.3 ml/min 

(83 mg/L) to reduce acidity and raise the pH of the ARD to 

approximately 4.0 which reduces the stress on the sulfatereducing bacteria in the downstream bioreactors. Ethanol is 

also dripped into the flow at an average dosage rate of 13.7 

ml/min (340 mg/L) to provide a carbon source for the sulfatereducing bacteria in the downstream bioreactors. The sodium 

hydroxide and ethanol are mixed into the ARD by turbulent 

discharge from the distribution box to a pretreatment pond. A 

small quantity of iron is typically precipitated out of solution 

and is retained in the pretreatment pond. However, the 

primary purpose of the pretreatment pond is to provide a flow 

equalization buffer for influent to the bioreactors. The 

average HRT of the pretreatment pond is 14.7 hours. Solids 

are flushed from the pretreatment pond approximately once a 

month, transferring from 2,000 to 7,000L of solids slurry to 

the flushing pond during warm weather conditions. More 

frequent flushing in winter is necessary due to limited 

operational volume when the pond ices over. A summary of 

the system operational parameters is presented in Table 2-7. 

The ARD then flows by gravity into the first bioreactor. 

Influent flow to both bioreactors is controlled through the use 

of standpipes, rather than valves. The standpipes control flow 

by manipulation of the energy grade line across each 

bioreactor. Influent flow can be added to either end of each 

bioreactor and can be targeted to the bottom, middle, or top of 

each bioreactor to minimize the development of preferential 

24
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Table 2-7. Gravity Flow Unit Operations Parameters 

Parameter Units Range Average 

System Influent Flow Rate (L/min) 25 to 47 31.8 

Influent Ethanol Dosage Rate (ml/min) 10.8 to 20.2 13.7 

Influent NaOH Dosage Rate (ml/min) 6.5 to 12.2 8.3 

Pretreatment Pond Settling Time (hr) 9.9 to 18.7 14.7 

Bioreactor No.1 Reaction Time (hr) 53.2 to 100 78.6 

Bioreactor No.2 Reaction Time (hr) 30.1 to 56.7 44.6 

Pre-Settling Pond NaOH Dosage Rate (ml/min) 21.3 to 40 27 

Settling Pond Residence Time (hr) 165 to 310 244 

Flushing Pond Residence Time (hr) 181 to 340 267 

Aeration Channel Residence Time (min) 29.8 to 56 44 

System Effluent Flow Rate (L/min) 25 to 47 31.8 

System Hydraulic Residence Time (hr) 440 to 826 650 

hr = hour min = Minute 

L/min = Liter per minute ml/min = Milliliter per minute 

flow paths. After sulfate reduction and precipitation of a 

moderate quantity of metal sulfide solids in the first bioreactor 

and generation of alkalinity through biological processes, 

effluent discharges to the second bioreactor for reduction of 

residual sulfate to sulfide and generation of additional 

alkalinity. Similar to influent flow, effluent flow from each 

bioreactor can be drawn from either end of each bioreactor 

and can be removed from the bottom, middle, or top of each 

bioreactor to minimize the development of preferential flow 

paths. Buildup of excess metal sulfide solids within either 

bioreactor can be drawn downward into flushing loops at the 

bottom of each bioreactor. The flushing loops are controlled 

by valves on a large flushing line that passes under the entire 

length of the treatment system and discharges to a flushing 

pond downstream of the pretreatment pond, the bioreactors, 

and the settling pond. The bioreactors were flushed about 

every two months during gravity flow operations, transferring 

an estimated 15,000 L of solids slurry to the flushing pond. 

The HRT of Bioreactor No.1 averages 78.6 hours, while the 

HRT of Bioreactor No.2 averages 44.6 hours at an average 

influent flow rate of 31.8 L/min. 

After passing through the two bioreactors, partially treated 

ARD is dosed with sodium hydroxide and discharges to a 

settling pond to allow extended time (244 hour average HRT) 

for metal precipitation and settling. Twenty-five percent 

sodium hydroxide solution is added to the settling pond 

influent line at an average dosage rate of 27 ml/min (270 

mg/L) to neutralize remaining acidity and raise the pH from 

about pH 5 to a near neutral condition (pH 7) necessary for 

precipitation of iron sulfide. The long HRT also allows 

settling of metal precipitates and degassing of carbon dioxide 

and hydrogen sulfide from solution, which reduces acidity and 

raises solution pH. Effluent from the settling pond can be 

discharged to a rock-lined aeration channel or to the flushing 

pond for additional extended precipitate settling time. In 

practice, effluent from the settling pond was always 

discharged to the flushing pond for additional settling (267 

hour average HRT) due to elevated particulate iron 

concentrations. Effluent from the flushing pond discharges to 

the rock-lined aeration channel to promote gas exchange and 

raise the ORP of the effluent. The aeration process promotes 

precipitation of additional metals that react with excess 

oxygen in solution. The average HRT for the system operated 

in gravity flow mode is 650 hours at an average flow rate of 

31.8 L/min. System HRT is extended to 827 hours in winter 

when influent flows from Aspen Seep drop to 25 L/min. The 

extended HRT provides adequate treatment during periods of 

decreased biological activity, even at water temperatures of 

1°C (degree Celsius). However, during the winter adequate 

base addition is necessary to convert all of the bisulfide 

generated in the bioreactors to sulfide necessary for iron 

sulfide precipitation. Lack of or inadequate base addition 

during the winter often leads to inability to meet iron 

discharge standards. 

Approximately 32,000 L of solids slurry is transferred from 

the settling pond to the flushing pond prior to the onset of 

winter. Periodically, metal sulfide sludge is pumped out of the 

settling and flushing ponds and into bag filters for passive 

dewatering prior to disposal as a nonhazardous solid. The 

filtration process involves the filling of a bag filter with sludge 

and gravity drainage of water through the filter fabric. Free 

water is allowed to drain back into the flushing pond 

following filtration. The process is repeated using a new bag 

filter placed on top of an older bag. Additional solids 

dewatering occurs in the bags on the bottom of the stack due 

to compression. The process generated approximately 3,900 

kilogram (kg) of dry solids over 100 days. The bag filtration 

process is limited to summer and early fall when temperatures 

are warm enough to prevent freezing of the filter membrane. 

Recirculation Operations. The treatment system operated in 

recirculation mode (Figure 1-3) utilizes the same processes as 

the system operated in gravity flow mode; however, the metalrich ARD influent bypasses the pretreatment pond and the two 

bioreactors and is combined with sulfide-rich bioreactor 

effluent and sodium hydroxide and introduced to the settling 

pond for metal sulfide precipitation. The key to recirculation 

is the precipitation of metal sulfides in the settling pond rather 

than in the two bioreactors, which reduces the need for and 

frequency of bioreactor flushing and provides a stable sulfatereducing bacteria population within the bioreactors. 

A portion of the sulfate-rich settling pond effluent containing 

residual concentrations of metals is recirculated at an average 

flow rate of 210 L/min to the head of Bioreactor No.1 and 

combined with ethanol to promote the generation of additional 

sulfide. Ethanol is dripped into recirculated flow at the head 

of Bioreactor No.1 at an average dosage rate of 105 ml/min 

(394 mg/L) to provide a carbon source for the sulfate-reducing 

bacteria in the downstream bioreactors. The recirculated 

settling pond effluent then flows by gravity through the two 

bioreactors. After sulfate reduction, precipitation of metal 

sulfides, and generation of alkalinity through biological 

processes in both bioreactors, effluent is combined with ARD 

influent at an average flow rate of 34.2 L/min and 25 percent 

25
______________________________________________________________________________________ 

sodium hydroxide solution at an average dosage rate of 17.1 

ml/min (159 mg/L) and discharges to the settling pond. The 

sodium hydroxide along with excess alkalinity in the 

bioreactor effluent neutralizes acidity and raises the ARD 

influent pH from about pH 3 to a near neutral condition (pH 7) 

necessary for precipitation of iron sulfide. The bioreactors 

were flushed every three to four months during recirculation 

operations, transferring an estimated 15,000 L of solids to the 

flushing pond. The HRT of Bioreactor No.1 averages 11.9 

hours, while the HRT of Bioreactor No.2 averages 6.8 hours at 

an average recirculation flow rate of 210 L/min. A summary 

of the system operational parameters is presented in Table 2-8. 

Table 2-8. Recirculation Unit Operations Parameters 

Parameter Units Range Average 

System Influent Flow Rate (L/min) 25 to 91 34.2 

Bypass to Settling Pond (L/min) 25 to 91 34.2 

Recirculation from Settling Pond to 

Bioreactor No.1 

(L/min) 189 to 227 210 

Influent Ethanol Dosage Rate (ml/min) 94.5 to 113.5 105 

Bioreactor No.1 Reaction Time (hr) 11 to 13.2 11.9 

Bioreactor No.2 Reaction Time (hr) 6.3 to 7.5 6.8 

Pre-Settling Pond NaOH Dosage Rate (ml/min) 12.5 to 45.5 17.1 

Settling Pond Residence Time (hr) 28.5 to 30.8 29.7 

Settling Pond Discharge Rate (L/min) 25 to 91 34.1 

Flushing Pond Residence Time (hr) 103 to 354 249 

Aeration Channel Residence Time (min) 17 to 56 41 

System Effluent Flow Rate (L/min) 25 to 91 34.1 

System Hydraulic Residence Time (hr) 149 to 407 298 

hr = hour min = Minute 

L/min = Liter per minute ml/min = Milliliter per minute 

The settling pond allows extended time (29.7 hour average 

HRT empty) for metal sulfide precipitation and settling. The 

settling pond does not completely freeze over during winter 

due to the circulation of water within the pond. Effluent (34.2 

L/min) from the settling pond was always discharged to the 

flushing pond for additional settling (249 hour average HRT) 

due to elevated residual iron concentrations. The long HRT 

also allows settling of metal precipitates and degassing of 

carbon dioxide and hydrogen sulfide from solution, which 

reduces acidity and raises solution pH. During recirculation 

upsets the ORP increases and metal hydroxides precipitate, 

which results in a pH decrease in the settling pond. 

Approximately 48,000 L of solids slurry is transferred from 

the settling pond to the flushing pond prior to the onset of 

winter. Periodically, metal sulfide sludge is pumped out of the 

settling and flushing ponds and into a bag filter for passive 

dewatering prior to disposal as a nonhazardous solid. 

Effluent from the flushing pond is discharged to the rock-lined 

aeration channel to promote gas exchange, raise solution ORP, 

and precipitate residual metals from solution. The average 

HRT for the system operated in recirculation mode is 298 

hours at an average flow rate of 34.2 L/min. System HRT is 

extended to 408 hours in winter when influent flows from 

Aspen Seep drop to 25 L/min. Adequate treatment is provided 

during winter, even at relatively short bioreactor HRT and 

very low water temperatures, due to the limited stress (neutral 

pH and low metals concentrations) placed on the bioreactors. 

However, adequate base addition is necessary to convert all of 

the bisulfide generated in the bioreactors to sulfide for iron 

sulfide precipitation in the settling pond. Lack of or 

inadequate base addition during the winter can stress the 

bioreactors resulting in reduce sulfide generation and an 

overall inability to meet iron discharge standards. 

2.5.3.2 Reaction Chemistry 

The reaction chemistry for the bioreactor treatment system is 

described below for both the gravity flow and recirculation 

modes of operation. A warm weather date for the gravity flow 

mode of operation was not available as the system was 

converted to recirculation operations in May 2004. Instead, a 

cold weather date (March 24, 2004) was selected for gravity 

flow mode of operation and a warm weather date (August 19, 

2004) was selected for recirculation mode to evaluate potential 

impact of cold weather on system effectiveness. 

Gravity Flow Reaction Chemistry. Changes in ARD 

chemistry within the pretreatment pond are driven by the 

addition of sodium hydroxide to the influent ARD at the 

influent weir box. Sodium hydroxide addition consumes 

mineral acidity, raises solution pH, increases the kinetics of 

iron oxidation, and provides a source of hydroxide ion for 

ferric hydroxide formation. A small quantity of iron 

precipitate formed, a portion of which is deposited in the 

pond. 

During the pretreatment process, solution pH increased from 

3.1 to 3.6 after sodium hydroxide addition and target metals 

decreased 28 percent (primarily aluminum at 7 percent, iron at 

35 percent) in response to excess hydroxide ion. The data also 

indicate that mineral acidity was reduced as evidenced by an 

increase in pH and a decrease in solution ORP. Field and 

analytical laboratory chemical parameters documenting 

reaction chemistry on March 24, 2004 are provided in Table 

2-9. 

Supernatant from the pretreatment pond discharges to the head 

of Bioreactor No.1, where it is combined with ethanol to 

provide a carbon substrate for the sulfate-reducing bacteria. 

Observed changes in ARD chemistry in the effluent from the 

two bioreactors were primarily due to the reduction of sulfate 

to sulfide by sulfate-reducing bacteria and the generation of 

acetate associated with incomplete oxidation of ethanol and 

alkalinity during the complete oxidation of ethanol to carbon 

dioxide. Sulfide combines with excess metals to form metal 

sulfide precipitates. Alkalinity raises the pH of ARD in the 

bioreactors and facilitates precipitation reactions. However, 

the pH is not high enough to convert bisulfide to sulfide and 

precipitate the majority of the iron as iron sulfide; therefore 

the majority of the iron and bisulfide pass out of the two 

bioreactors. 

26
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Table 2-9. Gravity Flow Unit Operation Reaction Chemistry 

Pretreatment Pond Bioreactor No.1 Bioreactor No.2 

Parameter Unit Influent Effluent Change Influent Effluent Change Influent Effluent Change 

pH (SU) 3.1 3.6 0.5 3.6 4.7 1.1 4.7 4.8 0.1 

Oxidation Reduction Potential (mV) 425 324 -101 324 -117 -441 -117 -122 -5 

Total Iron (dissolved) (mg/L) 113 73.1 -39.9 73.1 71.7 -1.4 71.7 63.7 -8 

Specific Conductance (μmhos/cm) 2,368 2,335 -33 2,335 2,166 -169 2,166 1,989 -177 

Dissolved Oxygen (mg/L) 3.3 6.8 3.6 6.8 6.1 -0.7 6.1 6.4 0.3 

Temperature (°C) 12.4 12.4 0 12.4 11.5 -0.9 11.5 11.3 -0.2 

Sulfate (mg/L) 1,510 1,520 10 1,520 1,480 -40 1,480 1,310 -170 

Sulfide (mg/L) 0 0 0 0 37 37 37 38 1 

Total Alkalinity (mg/L) <2 <2 0 <2 <2 0 <2 <2 0 

Total Dissolved Solids (mg/L) 2,200 2,240 40 2,240 2,380 140 2,380 2,090 -290 

μmhos/cm = Micromhos per centimeter mV = Millivolt NC = Not calculated 

°C = Degree Celsius mg/L = Milligram per liter SU = Standard unit 

Data collected on March 24, 2004 at a system influent and effluent flow rate of 45 L/min 

Settling and Flushing Ponds Aeration Channel 

Parameter Unit Influent Effluent Change Influent Effluent Change 

pH (SU) 4.8 7.5 2.7 7.5 7.7 0.2 

Oxidation Reduction Potential (mV) -122 91 213 91 40 -51 

Total Iron (dissolved) (mg/L) 63.7 0.19 -63.5 0.19 0.39 0.2 

Specific Conductance (μmhos/cm) 1,989 2,235 246 2,235 2,181 -54 

Dissolved Oxygen (mg/L) 6.4 8.6 2.2 8.6 8.8 0.2 

Temperature (°C) 11.3 12.6 1.3 12.6 12 -0.6 

Sulfate (mg/L) 1,310 1,170 -140 1,170 1,160 -10 

Sulfide (mg/L) 38 0 -38 0 0 0 

Total Alkalinity (mg/L) <2 113 113 113 110 -20 

Total Dissolved Solids (mg/L) 2,090 1,900 -190 1,900 1,720 -180 

μmhos/cm = Micromhos per centimeter mV = Millivolt SU = Standard unit 

°C = Degree Celsius mg/L = Milligram per liter 

Data collected on March 24, 2004 at a system influent and effluent flow rate of 45 L/min 

Bioreactor No.1 effluent pH increased from 3.6 to 4.7, ORP 

shifted from highly oxidizing (+324 mV [millivolt]) to 

moderately reducing (-117 mV), sulfate decreased from 

1,520 to 1,480 mg/L, and 37 mg/L of excess sulfide was 

generated. Target metals decreased 10 percent (primarily 

aluminum at 24 percent, copper at 99 percent, nickel at 22 

percent, and zinc at 95 percent). Divalent metals were 

removed primarily by sulfide precipitation, while aluminum 

was removed by hydroxide precipitation. The data also 

indicate that mineral acidity was reduced as evidenced by an 

increase in pH and a decrease in solution ORP. Bicarbonate 

alkalinity was generated as solution pH increased by over 

one standard unit, though excess alkalinity was not observed 

in bioreactor effluent. Biological generation of bicarbonate 

alkalinity reduces the sodium hydroxide dosage required. 

Bioreactor No.2 effluent pH increased from 4.7 to 4.8, ORP 

shifted to slightly more reducing (-117 to -122 mV), sulfate 

decreased from 1,480 to 1,310 mg/L, and excess sulfide 

generated increased slightly (37 to 38 mg/L). Target metals 

decreased 12 percent (primarily aluminum at 15 percent, 

iron at 11 percent, and nickel at 14 percent). Divalent 

metals were removed primarily by sulfide precipitation, 

while aluminum was removed by hydroxide precipitation. 

The data indicate that mineral acidity continued to be 

reduced. Bicarbonate alkalinity was generated as solution 

pH continued to increase, though excess alkalinity was not 

observed in bioreactor effluent. Organic analysis for 

residual ethanol or metabolites was not conducted as a part 

of the demonstration. However, the technology developer 

has indicated that approximately one-third of the ethanol is 

incompletely oxidized to acetate within the bioreactors 

(Tsukamoto 2005b). 

As a point of comparison, during cold weather conditions 

(water temperature 5°C) on February 19, 2004, sulfate 

decreased from 1,520 to 1,290 mg/L (15 percent) and total 

iron decreased from 70 to 67 mg/L (5 percent) across the 

bioreactors. A lack of adequate base addition was 

responsible for elevated iron concentrations, rather than 

insufficient sulfate reduction. Across the system as a whole, 

both low temperature and high flow suppresses sulfate 

reduction to sulfide and iron removal. The impact on 

temperature on sulfate reduction and iron removal is 

presented in Table 2-10. 

27
______________________________________________________________________________________ 

Table 2-10. Impact of Temperature on Sulfate Reduction 

and Iron Removal During Gravity Flow Operations 

Date 

Temp 

(°C) 

Sulfate 

Mass 

Removed 

(kg/day) 

Sulfate 

Removal 

Efficiency 

(%) 

Iron 

Mass 

Removed 

(kg/day) 

Iron 

Removal 

Efficiency 

(%) 

Flow 

(L/min) 

11/14/03 4.8 10.5 17.5 4.4 95.8 26 

11/25/03 4.5 11.2 18.1 4.3 89.6 26 

1/29/04 3.8 5.8 9.9 2.9 63.1 29 

2/19/04 5.2 11.3 17.4 4.2 93.7 29 

3/24/04 10.9 22.7 23.2 7.2 98.5 45 

4/29/04 10.1 11.2 13.4 6.6 99.7 39 

% = Percent kg/day = Kilogram per day 

°C = Degree Celsius L/min = Liter per minute 

After partially-treated ARD passes out of Bioreactor No.2, the 

effluent is combined with sodium hydroxide and discharged to 

the settling pond. Sodium hydroxide addition consumes the 

remaining mineral acidity, and converts a portion of the 

bisulfide to sulfide, which is necessary to precipitate the 

remaining iron as iron sulfide in the settling pond. Sodium 

hydroxide also provides a source of hydroxide ion for metals 

that do not form precipitates with sulfide. Excess sulfide from 

bioreactor No.2 is generally completely consumed by metals 

or is oxidized to sulfate during the extended settling pond 

HRT. 

The effluent pH from the flushing pond increased from 4.8 to 

7.5, ORP shifted from moderately reducing (-122 mV) to 

moderately oxidizing (+91 mV), and sulfate decreased from 

1,310 to 1,170 mg/L. No excess sulfide was observed in the 

flushing pond effluent, though sulfide may have been 

generated by sulfate-reducing bacteria in the settling pond and 

consumed in the flushing pond given the substantial decrease 

in sulfate concentrations across the two ponds. Target metals 

decreased 99.7 percent (primarily aluminum at 99.9 percent, 

iron at 99.7 percent, nickel at 84 percent, and zinc at 87 

percent). Divalent metals were removed primarily by sulfide 

precipitation in the settling pond, while aluminum was 

removed by metal hydroxide and oxyhydroxide precipitation 

at a neutral pH condition. Additional metals removal in the 

flushing pond was likely related to agglomeration of colloidal 

metals and particle settling. The remaining mineral acidity 

was completely consumed by excess sodium hydroxide in 

solution, yielding a bicarbonate alkalinity of 113 mg/L. 

After settling, treated ARD passes out of the flushing pond to 

an aeration channel to introduce oxygen, off-gas carbon 

dioxide, and precipitate residual metals from solution as metal 

hydroxides. Effluent dissolved oxygen was 8.8 mg/L. The 

effluent pH from the aeration channel increased from 7.5 to 

7.7, ORP decreased from +91 to +40 mV, and sulfate 

decreased slightly from 1,170 to 1,160 mg/L. No excess 

sulfide was observed. All of the target metals except for 

soluble chromium increased slightly. Excess alkalinity 

decreased slightly, likely in response to residual metals 

precipitating as metal hydroxides. 

Recirculation Reaction Chemistry. Influent ARD is 

combined with the effluent from Bioreactor No.2 and sodium 

hydroxide to form precipitates in the settling pond. Settling 

pond supernatant is at a near neutral pH and is slightly 

reducing, containing residual metals, excess sulfate, and 

excess bicarbonate alkalinity. A portion of the settling pond 

supernatant is recirculated to the head of Bioreactor No.1, 

where it is combined with ethanol to provide a carbon 

substrate for the sulfate-reducing bacteria. 

Observed changes in ARD chemistry in the effluent from the 

two bioreactors were primarily due to the reduction of sulfate 

to sulfide by sulfate-reducing bacteria and the generation of 

acetate associated with incomplete oxidation of ethanol and 

alkalinity during the complete oxidation of ethanol to carbon 

dioxide. Sulfide combines with excess metals to form metal 

sulfide precipitates. Because the partially-treated ARD in the 

bioreactors is at a neutral pH condition, residual metals 

actively precipitate in the bioreactors, while excess sulfides 

pass out of the two bioreactors to the settling pond. 

System influent ARD and the effluent from Bioreactor No.2 

are combined at the head of the settling pond. On August 19, 

2004, after combining the two ARD streams (8:1 dilution), pH 

increased from 3 to 6.8, ORP decreased from 510 to -114 mV, 

sulfate decreased from 1,630 to 1,156 mg/L, and sulfide 

increased from 0 to 44 mg/L, and target metals decreased from 

142 mg/L to 18 mg/L. Field and analytical laboratory 

chemical parameters documenting reaction chemistry are 

provided in Table 2-11. 

After the two ARD streams are combined, chemistry is driven 

by the addition of sodium hydroxide. Sodium hydroxide 

addition consumes mineral acidity, and converts bisulfide to 

sulfide, which is necessary to precipitate iron as iron sulfide. 

Sodium hydroxide also provides a source of hydroxide ion for 

ferric hydroxide precipitation, which occurs if the 

recirculation system is nonfunctional. 

During the contact of metal-rich influent ARD and sulfide-rich 

Bioreactor No.2 effluent in the settling pond, combined 

solution pH increased from 6.8 to 7.2 in the pond supernatant, 

ORP shifted from moderately to slightly reducing (-117 to -27 

mV), sulfate increased from 1,156 to 1,190 mg/L, and all of 

the excess sulfide (44 mg/L) from the bioreactors was 

oxidized or consumed. The data also indicate that mineral 

acidity was reduced as evidenced by an increase in pH and a 

decrease in solution ORP. Bicarbonate alkalinity decreased 

from 233 to 210 mg/L after addition of acidic influent ARD. 

Target metals decreased 71 percent across the settling pond 

(primarily aluminum at 97 percent, copper at 92 percent, iron 

at 61 percent, and zinc at 83 percent). Divalent metals were 

removed primarily by sulfide precipitation, while aluminum 

was removed by metal hydroxide and oxyhydroxide 

precipitation at a neutral pH condition. Insufficient sulfide 

was present in the settling pond to precipitate all of the metals 

28
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Table 2-11. Recirculation Unit Operation Reaction Chemistry 

Bioreactor No.1 Bioreactor No.2 

Parameter Unit Influent Effluent Change Influent Effluent Change System 

Influent 

Combined 

Influent 

pH (SU) 7.2 7.2 0 7.2 7.3 0.1 3 6.8 

Oxidation Reduction Potential (mV) -27 -174 -147 -174 -202 -28 510 -114 

Total Iron (dissolved) (mg/L) 4.9 0.26 -4.6 0.26 0.25 -0.01 99.5 12.5 

Specific Conductance (μmhos/cm) 2,595 2,569 -26 2,569 2,555 -14 2,572 2,557 

Dissolved Oxygen (mg/L) 1.9 0.3 -1.6 0.3 1.4 1.1 1.6 1.4 

Temperature (°C) 19.4 20.1 0.7 20.1 20.1 0 16.7 19.7 

Sulfate (mg/L) 1,190 1,160 -30 1,160 1,090 -70 1,630 1,156 

Sulfide (mg/L) 0 27 27 27 50 23 0 43.8 

Total Alkalinity (mg/L) 210 209 -1 209 266 57 <2 233 

Total Dissolved Solids (mg/L) 2,090 2,060 -30 2,060 2,150 90 3,040 2,260 

μmhos/cm = Micromhos per centimeter mV = Millivolt SU = Standard unit 

°C = Degree Celsius mg/L = Milligram per liter 

Data collected on August 19, 2004 at a system influent flow rate of 32 L/min, a recirculation rate of 227 L/min, and a system effluent rate 

of 28 L/min 

Settling Pond Flushing Pond Aeration Channel 

Parameter Unit 

Combined 

Influent Effluent Change Influent Effluent Change Influent Effluent Change 

pH (SU) 6.8 7.2 0.4 7.2 7.6 0.4 7.6 7.6 0 

Oxidation Reduction Potential (mV) -114 -27 87 -27 103 130 103 10 -93 

Total Iron (dissolved) (mg/L) 12.5 4.9 -7.6 4.9 0.1 -4.8 0.1 0.27 0.17 

Specific Conductance (μmhos/cm) 2,557 2,595 38 2,595 2,674 79 2,674 2,660 -14 

Dissolved Oxygen (mg/L) 1.4 1.9 0.48 1.9 4.1 2.2 4.1 2.1 -2 

Temperature (°C) 19.7 19.4 -0.3 19.4 21 1.6 21 21.3 0.3 

Sulfate (mg/L) 1,156 1,190 34 1,190 1,260 70 1,260 1,200 -60 

Sulfide (mg/L) 44 0 -44 0 0 0 0 0 0 

Total Alkalinity (mg/L) 233 210 -23 210 208 -2 208 202 -6 

Total Dissolved Solids (mg/L) 2,260 2,090 -170 2,090 2,160 70 2,160 2,140 -20 

μmhos/cm = Micromhos per centimeter mV = Millivolt NC = Not calculated 

°C = Degree Celsius mg/L = Milligram per liter SU = Standard unit 

Data collected on August 19, 2004 at a system influent flow rate of 32 L/min, a recirculation rate of 227 L/min, 

and a system effluent rate of 28 L/min 

out of solution. Recirculation of a portion of the settling pond 

supernatant to the head of Bioreactor No.1 provides an 

opportunity to generate additional sulfide necessary to remove 

residual metals (primarily iron) from solution. 

After recirculation of a portion of the settling pond supernatant 

to Bioreactor No.1, the bioreactor effluent pH remained at 7.2, 

ORP shifted from slightly to moderately reducing (-27 to -174 

mV), sulfate decreased from 1,190 to 1,160 mg/L, and 27 

mg/L of excess sulfide was generated. Target metals 

decreased 92 percent across bioreactor No.1 (primarily 

aluminum at 33, iron at 95 percent, and nickel at 84 percent). 

Divalent metals were removed primarily by sulfide 

precipitation. All soluble metals concentrations were below 

discharge standards. Bicarbonate alkalinity essentially 

remained unchanged. 

Bioreactor No.2 effluent pH increased slightly from 7.2 to 7.3, 

ORP shifted to slightly more reducing (-174 to -202 mV), 

sulfate decreased from 1,160 to 1,090 mg/L, and excess 

sulfide generated doubled (27 to 50 mg/L). Target metals 

concentrations remained essentially unchanged. Excess 

sulfide generated in the bioreactor is combined with system 

influent ARD as described above to precipitate metal sulfides 

in the settling pond. Bicarbonate alkalinity increased from 

209 to 266 mg/L due to biological oxidation of ethanol. 

Organic analysis for residual ethanol or metabolites was not 

conducted as a part of the demonstration. However, the 

technology developer has indicated that approximately onethird of the ethanol is incompletely oxidized to acetate within 

the bioreactors (Tsukamoto 2005b). 

As a point of comparison, during cold weather conditions 

(water temperature 3°C) on December 3, 2004, sulfate 

decreased from 1,310 to 1,300 mg/L (0.8 percent) and total 

iron decreased from 10.1 to 7.0 mg/L (30.7 percent) across the 

two bioreactors. Colder water temperature (3°C versus 20°C) 

appears to slow sulfate reduction (0.8 versus 8 percent) as well 

29
______________________________________________________________________________________ 

as iron removal (30.7 versus 95 percent). A larger amount of 

residual iron was recirculated from the settling pond to the 

head of the bioreactors in response to less available sulfide 

necessary for iron sulfide precipitation. Across the system as 

a whole, both low temperature and high influent and 

recirculation flows suppress sulfate reduction to sulfide and 

iron removal. The impact on temperature on sulfate reduction 

and iron removal is presented in Table 2-12. 

Table 2-12. Impact of Temperature on Sulfate Reduction 

and Iron Removal During Recirculation Operations 

Date 

Temp 

(°C) 

Sulfate 

Mass 

Removed 

(kg/day) 

Sulfate 

Removal 

Efficiency 

(%) 

Iron 

Mass 

Removed 

(kg/day) 

Iron 

Removal 

Efficiency 

(%) 

Flow 

(L/min) 

6/14/04 13.7 7.3 7.6 6 96.6 42 

8/19/04 14.7 19.8 26.4 4.5 99.5 32 

12/3/04 3.1 7.9 12.5 4.8 91.7 29 

2/3/05 6.3 10.8 19.7 4.3 97.3 25 

3/17/05 5.5 21.9 35.3 4.5 99.4 28 

4/24/05 8.6 33.5 18.5 13.3 98.3 83 

6/2/05 13.7 15.6 8 13.5 97.8 72 

% = Percent kg/day = Kilogram per day 

°C = Degree Celsius L/min = Liter per minute 

A portion of the settling pond supernatant also discharges to 

the flushing pond for extended settling. The effluent pH from 

the flushing pond increased from 7.2 to 7.6, ORP shifted from 

slightly reducing (-27 mV) to moderately oxidizing (+103 

mV), and sulfate increased from 1,190 to 1,260 mg/L. The 

increase in sulfate may be the result of the dissolution of 

suspended colloidal material and oxidation of sulfide. Soluble 

iron decreased by 98 percent from 4.9 to 0.1 mg/L likely in 

response to agglomeration of colloidal iron and particle 

settling. All other target metal concentrations, with the 

exception of aluminum, nickel, and zinc increased slightly. 

Bicarbonate alkalinity remained essentially unchanged at 208 

mg/L. 

After extended settling, treated ARD passes out of the flushing 

pond to an aeration channel off-gas carbon dioxide, introduce 

oxygen to the water, and precipitate residual metals from 

solution. Effluent dissolved oxygen was 2.1 mg/L, which is 

lower than observed during gravity flow operations. Low 

dissolved oxygen was observed for about 3 months following 

conversion to recirculation operations then increased to levels 

observed during gravity flow operations. The effluent pH 

from the aeration channel remained at about 7.6, ORP 

decreased from +103 to +10 mV, and sulfate decreased from 

1,260 to 1,200 mg/L. No excess sulfide was observed. 

Soluble aluminum, iron, and arsenic increased slightly, while 

all other target metals decreased slightly in response to metal 

hydroxide precipitation at a neutral pH condition. Excess 

alkalinity decreased slightly, likely in response to residual 

metals precipitating as metal hydroxides. 

2.5.3.3 Metals Removal by Unit Operation 

Metals removal by each bioreactor unit operation is described 

below for both the gravity flow mode (March 24, 2004) and 

recirculation mode (August 19, 2004) of operation. 

Gravity Flow Operations. Aluminum, copper, iron, lead, 

nickel, selenium, and zinc are the metals of concern in the 

ARD from Aspen Seep. All of the dissolved metals of 

concern exceeded their discharge standards after sodium 

hydroxide addition and initial settling in the pretreatment 

pond. Pretreatment pond dissolved metals removal 

efficiencies ranged from -48 to 35 percent, with the majority 

of the mass removal associated with aluminum and iron oxides 

and oxyhydroxides. No sulfate reduction occurred in the 

pretreatment pond. A summary of unit operations 

concentration and removal efficiency data for the dissolved 

metals of concern is presented in Table 2-13 for gravity flow 

unit operations on March 24, 2004. 

Following about a 3 percent reduction in sulfate concentration 

(40 mg/L) within Bioreactor No.1, the majority of the 

dissolved metals of concern continued to exceed their 

discharge standards, with the exception of copper and zinc, 

which appear to have precipitated as metal sulfides from 

solution. The concentration of aluminum and iron also 

decreased substantially, but precipitation was limited by too 

low of a pH in the bioreactor. Bioreactor No.1 dissolved 

metals removal efficiencies ranged from 2 to 99.1 percent, 

with the majority of the mass removal associated with 

aluminum, copper, iron, and zinc. Following an 12 percent 

reduction in sulfate concentration (170 mg/L) within 

Bioreactor No.2, the majority of dissolved metals of concern 

continued to exceed their discharge standards, with the 

exception of copper, lead, and zinc, which appear to have 

continued to precipitate as metal sulfides from solution. The 

concentration of aluminum and iron also continued to decrease 

substantially. Bioreactor No.2 dissolved metals removal 

efficiencies ranged from 10 to 15 percent, with the majority of 

the mass removal associated with aluminum and iron. 

Following sodium hydroxide addition to bioreactor effluent, 

which raised the pH to near neutral condition, and additional 

sulfide generation, metal sulfide precipitation, and solids 

settling in the settling and flushing ponds, only selenium 

exceeded its discharge standard, though not at a concentration 

that was statistically significant. Settling and flushing pond 

dissolved metals removal efficiencies ranged from 25 to 99.9 

percent, with the majority of the mass removal associated with 

aluminum and iron. Precipitation of aluminum and iron 

required a near neutral pH condition. 

All of the metals of concern, with the exception of selenium, 

met discharge standards at the toe of the rock lined aeration 

channel after hydrogen sulfide off-gassing and oxygen 

30
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Table 2-13. Gravity Flow Unit Operation Dissolved Metals Removal Efficiencies 

Pretreatment Pond Bioreactor No.1 Bioreactor No.2 

Settling and 

Flushing Ponds Aeration Channel System 

Parameter 

Influent 

(μg/L) 

Effluent 

(μg/L) 

Removal 

Efficiency 

(%) 

Effluent 

(μg/L) 

Removal 

Efficiency 

(%) 

Effluent 

(μg/L) 

Removal 

Efficiency 

(%) 

Effluent 

(μg/L) 

Removal 

Efficiency 

(%) 

Effluent 

(μg/L) 

Removal 

Efficiency 

(%) 

Removal 

Efficiency 

(%) 

Aluminum 36,900 34,200 7.3 26,100 23.7 22,200 14.9 31.7 99.9 144 -354 99.6 

Arsenic 2.8 <2.3 NC 3 NC <2.3 NC <2.3 NC 2.4 NC 14.3 

Cadmium 0.4 <0.23 NC <0.23 NC <0.23 NC <0.23 NC <0.23 NC 42.5 

Chromium 17.2 13.9 19.2 13.3 4.3 14.3 NC 6.9 51.8 6.4 7.3 62.8 

Copper 656 614 6.4 5.7 99.1 6.1 NC 4.3 29.5 5.6 NC 99.1 

Iron 113,000 73,100 35.3 71,700 1.9 63,700 11.2 186 99.7 389 -109 99.7 

Lead 5.3 5.8 NC 5.8 NC 5 NC 2.9 42.0 3.4 NC 35.8 

Nickel 481 449 6.7 350 22.1 300 14.3 49.2 83.6 53.1 -7.9 89 

Selenium 9.6 14.2 -47.9 10.8 23.9 10.6 NC 7.9 25.5 8.7 NC 9.4 

Zinc 702 661 5.8 32 95.2 28.8 10.0 3.7 87.2 10.3 -178 98.5 

% = Percent NC = Not calculated as influent and effluent concentrations were not statistically different 

μg/L = Microgram per liter Data collected on March 24, 2004 at a flow rate of 45 L/min 

Table 2-14. Gravity Flow Unit Operation Metals and Sulfate Load Reduction 

Pretreatment Pond Bioreactor No.1 Bioreactor No.2 

Settling and 

Flushing Ponds Aeration Channel 

Parameter 

Influent 

(g/day) 

Effluent 

(g/day) 

Mass 

Change 

(g/day) 

Effluent 

(g/day) 

Mass 

Change 

(g/day) 

Effluent 

(g/day) 

Mass 

Change 

(g/day) 

Effluent 

(g/day) 

Mass 

Change 

(g/day) 

Effluent 

(g/day) 

Mass 

Change 

(g/day) 

Aluminum 2,391 2,341 -50 1,834 -508 1,471 -363 7.9 -1,463 30.3 22.4 

Arsenic 0 0.23 0.23 0 -0.23 0.22 0.22 0 -0.22 0.29 0.29 

Cadmium 0.027 0.027 0 0 -0.03 0 0 0 0 0 0 

Chromium 1.06 0.95 -0.11 0.90 -0.05 0.83 -0.07 1.5 0.67 0.52 -0.98 

Copper 41.9 42.1 0..2 4.4 -37.3 3.5 -0.90 0.28 -3.2 0.51 0.23 

Iron 7,322 5,612 -1,710 5,035 -577 4,128 -907 103.7 -4,204 108 3.9 

Lead 0.32 0.38 0.06 0.356 -0.02 0.29 -0.07 0.13 -0.16 0.19 0.06 

Nickel 31.0 30.6 -0.34 24.0 -6.7 19.4 -4.5 4.0 -15.4 4.6 0.59 

Selenium 0.79 0.90 0.11 0.804 -0.10 0.64 -0.16 0.58 -0.06 0.34 -0.24 

Zinc 44.8 46.1 1.21 8.1 -37.9 6.0 -2.1 0.38 -5.6 0.95 0.57 

Target Metals 9,801 8,074 -1,759 6,907 -1,166 5,630 -1,278 119 -5,511 145 26.8 

Total Metals (1) 38,350 36,690 -1,660 36,290 -400 31,085 -5,205 24,200 -6,885 23,120 -1,080 

Sulfate 97,850 98,500 650 95,900 -2,600 84,890 -11,010 75,820 -9,070 75,170 -650 

Sulfide 0 0 0 870 870 3,670 2,800 0 -3,670 0 0 

(1) Total metals excluding added sodium from sodium hydroxide addition Data collected on March 24, 2004 at a flow rate of 45 L/min 

g/day = gram per day 

entrainment. Selenium exceeded its discharge standard, 

though not at a concentration that was statistically significant. 

Removal efficiencies for almost all of the dissolved metals 

were negative, indicating that either suspended solids 

discharged from the flushing pond were dissolving into 

solution or that solids were being flushed out of the aeration 

channel. Review of unfiltered channel influent and effluent 

data indicate that solids were being actively flushed from the 

channel during the sampling event. Treatment system removal 

efficiencies for the dissolved metals of concern ranged from 9 

percent for selenium to 99.7 percent for iron at a concurrent 

sulfate removal efficiency of 23 percent. 

An evaluation of target metals load reduction, sulfate load 

reduction, and sulfide generation was prepared for gravity 

flow operations based on unit operations data collected on 

March 24, 2004 and is presented in Table 2-14. A total metals 

load of 38.3 kg and a sulfate load of 97.9 kg entered the 

bioreactor treatment system at 45 L/min. A total of 1.7 kg of 

metals was precipitated out of solution, following the addition 

of 4.1 kg of sodium hydroxide to the ARD in the pretreatment 

pond, leaving 36.7 kg of metals (excluding sodium addition) 

and 98.5 kg of sulfate in pretreatment pond effluent. 

Sulfate-reducing bacteria in Bioreactor No.1 removed 2.6 kg 

of sulfate (generating 0.9 kg sulfide) and 0.4 kg of metals from 

solution as a metal sulfide precipitate, leaving 36.3 kg of 

metals (excluding sodium addition) and 95.9 kg of sulfate in 

Bioreactor No.1 effluent for further treatment in Bioreactor 

No.2. An additional 5.2 kg of metals and 11 kg of sulfate 

(generating 3.7 kg sulfide) were removed from solution as a 

metal sulfide precipitate in Bioreactor No.2. 

31
______________________________________________________________________________________ 

A total of 31 kg of metals (excluding sodium addition) and 

84.9 kg of sulfate were discharged from Bioreactor No.2 to the 

settling and flushing ponds in conjunction with 11.9 kg of 

sodium hydroxide for extended metal sulfide and metal oxide 

and oxyhydroxide contact, precipitation, and settling, 

removing 6.9 kg of metals and 9.1 kg of sulfate from solution. 

A total of 24.2 kg of metals (excluding sodium addition) and 

75.8 kg of sulfate were discharged from the settling and 

flushing ponds to the rock lined aeration channel to entrain 

oxygen and remove additional metals from solution as metal 

hydroxides and oxyhydroxides. A total of 1.1 kg of metals 

and 0.7 kg of sulfate were removed from solution along the 

aeration channel. Overall, a total of 16 kg of sodium 

hydroxide and 4.5 kg of sulfide were required to neutralize 

acidity and precipitate 15.2 kg of total metals (9.7 kg of target 

metals) from ARD. 

Recirculation Operations. Aluminum, copper, iron, lead, 

nickel, selenium, and zinc are the metals of concern in the 

ARD from Aspen Seep. Iron and selenium were the only 

dissolved metals of concern that exceeded their discharge 

standards in the settling pond effluent after combining the 

influent ARD, Bioreactor No.2 effluent, and sodium 

hydroxide in the settling pond. Settling pond metals removal 

efficiencies ranged from 3 to 97 percent, with the majority of 

the mass removal associated with aluminum, copper, iron, and 

zinc. No sulfate reduction occurred in the settling pond likely 

due to the short HRT and biologically stressful pond 

conditions. A summary of unit operations concentration and 

removal efficiency data for the metals of concern is presented 

in Table 2-15 for recirculation unit operations. 

Following recirculation of a portion of the settling pond 

effluent to the head of Bioreactor No.1, the sulfate-reducing 

bacteria removed an additional 3 percent reduction of sulfate 

from solution (30 mg/L). All of the dissolved metals of 

concern were below their discharge standards, with the 

exception of selenium. Bioreactor No.1 metals removal 

efficiencies ranged from -52 to 95 percent, with the majority 

of the mass removal associated with aluminum, iron, and 

nickel as the pH within the bioreactor was near neutral 

condition. Following a 6 percent reduction in sulfate 

concentration (70 mg/L) within Bioreactor No.2, all of the 

dissolved metals of concern were below their discharge 

standards, with the exception of selenium. Bioreactor No.2 

metals removal efficiencies ranged from –65 to 13 percent. 

There was no significant reduction in metals mass within 

Bioreactor No.2. Instead, biological activity generated excess 

sulfide in the bioreactor effluent for downstream blending 

with ARD influent in the settling pond. Comparison of the 

amount of sulfate reduced between the two modes of operation 

is difficult because the flow rate through the bioreactors is up 

to 8 times higher with recirculation. In fact, if the 

recirculation rate was decreased slightly sulfate reduction 

would exceed that of the gravity flow system due to the more 

favorable environmental conditions (neutral pH and low 

metals concentrations). 

After initial precipitation in the settling pond, effluent was 

held in the flushing pond to allow extended time for metal 

sulfide precipitation and settling. Only selenium exceeded its 

discharge standard, though not at a concentration that was 

statistically significant. Sulfate-reducing bacteria did not 

appear to be active in the flushing pond. Flushing pond metals 

removal efficiencies ranged from -60 to 98 percent, with the 

majority of the mass removal associated with aluminum, iron, 

and nickel. 

All of the metals of concern, with the exception of selenium, 

met discharge standards at the toe of the rock lined aeration 

channel following gas exchange. Selenium exceeded its 

discharge standard, though not at a concentration that was 

statistically significant. Removal efficiencies for aluminum, 

arsenic, and iron were negative, indicating that suspended 

solids or colloids discharged from the flushing pond were 

dissolving into solution. The system as a whole removed from 

40 to 99.7 percent of the target metals from solution. 

Treatment system removal efficiencies for the metals of 

concern ranged from 41 percent for arsenic to 99.7 percent for 

iron at a concurrent sulfate removal efficiency of 26 percent. 

An evaluation of target metals load reduction, sulfate load 

reduction, and sulfide generation was prepared for 

recirculation operations based on unit operations data 

collected on August 19, 2004 and is presented in Table 2-16. 

A total metals load of 28.2 kg and a sulfate load of 75.1 kg 

entered the bioreactor treatment system at 32 L/min. The 

influent ARD was blended with 152 kg of metals and 356 kg 

of sulfate discharging from Bioreactor No.2 at 227 L/min. 

The combined influent metals load of 180 kg and sulfate load 

of 431 kg was blended with 5.8 kg of sodium hydroxide and 

discharged to the settling pond at 259 L/min. A total of 4.1 kg 

of metals was removed from solution and 12.4 kg of sulfate 

entered solution (sulfide oxidation) in the settling pond, 

leaving 176 kg of metals (excluding sodium addition) and 443 

kg of sulfate in settling pond supernatant, a portion of which 

was recirculated to the head of Bioreactor No.1 at 227 L/min. 

Sulfate-reducing bacteria in Bioreactor No.1 removed 9.8 kg 

of sulfate (generating 3.3 kg sulfide), leaving 379 kg of sulfate 

in solution for further treatment in Bioreactor No.2. 

Approximately 1.2 kg of metals was deposited in Bioreactor 

No.1. An additional 1.2 kg of metals and 22.9 kg of sulfate 

(generating 4.4 kg sulfide) were removed from solution as a 

metal sulfide precipitate in Bioreactor No.2. 

A portion of the settling pond supernatant containing 21.8 kg 

of metals and 54.8 kg of sulfate was also discharged (32 

L/min) to the flushing pond for extended metal sulfide 

precipitation and settling, removing 2.3 kg of metals and 4 kg 

of sulfate from solution. A total of 19.5 kg of metals 

(excluding sodium addition) and 50.8 kg of sulfate were 

discharged from the flushing pond to the rock lined aeration 

channel to entrain oxygen and remove additional metals from 

32
______________________________________________________________________________________ 

Table 2-15. Recirculation Unit Operation Dissolved Metals Removal Efficiencies 

Bioreactor No.1 Bioreactor No.2 Settling Pond Flushing Pond Aeration Channel System 

Parameter 

Effluent 

(μg/L) 

Removal 

Efficiency 

(%) 

Effluent 

(μg/L) 

Removal 

Efficiency 

(%) 

System 

Influent 

(μg/L) 

Combined 

Influent 

(μg/L) 

Effluent 

(μg/L) 

Removal 

Efficiency 

(%) 

Effluent 

(μg/L) 

Removal 

Efficiency 

(%) 

Effluent 

(μg/L) 

Removal 

Efficiency 

(%) 

Removal 

Efficiency 

(%) 

Aluminum 104 32.9 108 NC 40,400 5,086 155 97.0 94.7 57.4 105 -10.9 99.7 

Arsenic 5.9 NC 5 NC <2.1 4.64 4.4 NC 3.7 15.9 14.7 -297 -600 

Cadmium 0.21 40.0 0.41 NC 0.94 0.48 0.35 26.4 0.39 NC <0.16 59.0 83.0 

Chromium 11.8 NC 12 NC 19.3 12.9 12.2 5.4 12.2 NC 11.6 4.9 39.9 

Copper 7.1 14.5 7.6 NC 766 101.3 8.3 91.8 10 -20.5 9.5 NC 98.8 

Iron 266 94.6 247 7.1 99,500 12,510 4,900 60.8 109 97.8 269 -147 99.7 

Lead 4.2 NC 4 NC 5.9 4.23 4.2 NC 6.7 -59.5 3.1 53.7 47.5 

Nickel 11.7 83.9 10.2 12.8 531 74.6 72.6 2.6 54.8 24.5 18.9 65.5 96.4 

Selenium 11.4 -52.0 11.6 NC 14.4 11.95 7.5 37.2 11.1 -48.0 7.8 29.7 45.8 

Zinc 6.3 63.4 10.4 -65.1 755 102.4 17.2 83.2 10.2 40.7 4.5 55.9 99.4 

% = Percent NC = Not calculated as influent and effluent concentrations were not statistically different 

μg/L = Microgram per liter Data collected on August 19, 2004 at a system influent flow rate of 32 L/min, a recirculation rate of

 227 L/min, and a system effluent rate of 28 L/min 

Table 2-16. Recirculation Unit Operation Metals and Sulfate Load Reduction 

Bioreactor No.1 Bioreactor No.2 Settling Pond Flushing Pond Aeration Channel 

Parameter 

Effluent 

(g/day) 

Mass 

Change 

(g/day) 

Effluent 

(g/day) 

Mass 

Change 

(g/day) 

System 

Influent 

(g/day) 

Combined 

Influent 

(g/day) 

Pond (2) 

Effluent 

(g/day) 

Mass 

Change 

(g/day) 

Influent 

(g/day) 

Effluent 

(g/day) 

Mass 

Change 

(g/day) 

Effluent 

(g/day) 

Mass 

Change 

(g/day) 

Aluminum 127 -255 109 -18 1,862 1,971 436 -1,535 53.9 6.9 -47 4.8 -2.1 

Arsenic 0 0 0.85 0.85 0 0.85 0 -0.85 0 0 0 0.6 0.6 

Cadmium 0 -0.08 0.08 0.08 0.05 0.14 0.09 -0.05 0.01 0 -0.01 0 0 

Chromium 3.92 0 3.82 -0.10 0.91 4.74 4.47 -0.27 0.55 0.48 -0.07 0.53 0.05 

Copper 3.5 -4.45 3.73 0.23 34.9 38.61 9.06 -29.6 1.12 0.47 -0.65 0.32 -0.15 

Iron 1,026 -1,566 879 -147 4,567 5,446 2,958 -2,488 365 41.5 -324 21.5 -20.1 

Lead 1.54 0.13 1.24 -0.29 0.33 1.57 1.6 0.03 0.2 0.16 -0.04 0.26 0.1 

Nickel 10.9 -13.1 9.35 -1.57 24.4 33.7 27.4 -6.3 3.38 2.15 -1.23 0.9 -1.25 

Selenium 3.37 -0.69 2.91 -0.46 0.92 3.83 4.62 0.79 0.57 0.38 -0.19 0.44 0.06 

Zinc 4.48 -4.67 4.77 0.29 34.9 39.7 10.5 -29.2 1.29 1.25 -0.04 0.43 -0.82 

Sum of Target 

Metals 

1,181 -1,844 1,015 -166 6,525 7,540 3,452 -4,088 426.5 53.4 -373 29.8 -23.6 

Total Metals (1) 153,350 1,160 152,140 -1,210 28,200 180,350 176,300 -4,050 21,780 19,450 -2,330 20,150 700 

Sulfate 379,200 -9,800 356,300 -22,900 75,110 431,400 443,820 12,420 54,840 50,800 -4,040 48,380 -2,420 

Sulfide 3,270 3,270 7,640 4,370 0 7,640 0 -7,640 0 0 0 0 0 

(1) Total metals excluding added sodium from sodium hydroxide addition g/day = gram per day Recirc = Recirculation 

(2) Settling pond effluent loads are split between recirculation and flushing pond influent 

Data collected on August 19, 2004 at a system influent flow rate of 32 L/min, a recirculation rate of 227 L/min, and a system effluent rate of 28 L/min 

solution as metal hydroxides and oxyhydroxides. A total of 

2.4 kg of sulfate was removed from solution along the aeration 

channel, while total metals mass increased by 0.7 kg due to 

entrainment of metals along the aeration channel. Overall, a 

total of 5.8 kg of sodium hydroxide and 7.6 kg of sulfide were 

required to neutralize acidity and precipitate 8 kg of total 

metals (6.5 kg of target metals) from ARD. 

Operation of the treatment system in recirculation mode 

required 49 percent less sodium hydroxide and reduced 41 

percent more sulfate to sulfide than the treatment system 

operated in gravity flow mode. Metals removal in each mode 

of operation was similar. 

2.5.3.4 Solids Separation 

Solids separation techniques used during both the gravity flow 

mode (March 24, 2004) and recirculation mode (August 19, 

2004) of operation are described below. 

Gravity Flow Operations. Precipitate generated during 

operation of the bioreactor treatment system in gravity flow 

mode is separated from ARD using a pretreatment pond, 

bioreactor pore space, a settling pond, and a flushing pond. 

Sodium hydroxide is used during the pretreatment process to 

raise the influent pH to Bioreactor No.1 to approximately 

33
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Table 2-17. Gravity Flow Operation Solids Separation Efficiencies 

Pretreatment Pond Bioreactor No.1 Bioreactor No.2 

Parameter 

Unfiltered 

Influent 

(μg/L) 

Unfiltered 

Effluent 

(μg/L) 

Percent 

Removal 

(%) 

Unfiltered 

Influent 

(μg/L) 

Unfiltered 

Effluent 

(μg/L) 

Percent 

Removal 

(%) 

Unfiltered 

Influent 

(μg/L) 

Unfiltered 

Effluent 

(μg/L) 

Percent 

Removal 

(%) 

Aluminum 36,400 36,300 0.3 36,300 28,300 22 28,300 22,700 19.8 

Arsenic 4.2 <2.2 47.6 <2.2 <2.3 -4.6 <2.3 3.4 -47.8 

Cadmium 0.41 0.42 -2.4 0.42 <0.23 45.2 <0.23 <0.23 0 

Chromium 16.4 14.7 10.4 14.7 13.9 5.4 13.9 12.8 7.9 

Copper 647 653 -0.9 653 67.6 89.7 67.6 53.7 20.6 

Iron 113,000 87,000 23 87,000 77,700 10.7 77,700 63,700 18 

Lead 4.9 5.9 -20.4 5.9 5.5 6.8 5.5 4.4 20 

Nickel 478 475 0.6 475 370 22.1 370 300 18.9 

Selenium 12.2 14 -14.8 14 12.4 11.4 12.4 9.9 20.2 

Zinc 692 714 -3.2 714 125 82.5 125 92.7 25.8 

TSS 36,000 87,000 -142 87,000 9,000 89.7 9,000 16,000 -77.8 

% = Percent Data collected on March 24, 2004 at a flow rate of 45 L/min 

μg/L = Microgram per liter 

Settling and Flushing Ponds Aeration Channel Cumulative 

Parameter 

Unfiltered 

Influent 

(μg/L) 

Unfiltered 

Effluent 

(μg/L) 

Percent 

Removal 

(%) 

Unfiltered 

Influent 

(μg/L) 

Unfiltered 

Effluent 

(μg/L) 

Percent 

Removal 

(%) 

Percent 

Removal 

(%) 

Aluminum 22,700 122 99.5 122 468 -284 98.7 

Arsenic 3.4 <2.3 32.4 <2.3 <2.2 4.4 47.6 

Cadmium <0.23 <0.23 0 <0.23 <0.23 0 43.9 

Chromium 12.8 23.2 -81.3 23.2 8 65.5 51.2 

Copper 53.7 4.3 92 4.3 7.8 -81.4 98.8 

Iron 63,700 1,600 97.5 1,600 1,660 -3.8 98.5 

Lead 4.4 2 54.6 2 2.9 -45 40.8 

Nickel 300 62.4 79.2 62.4 71.5 -14.6 85 

Selenium 9.9 8.9 10.1 8.9 5.2 41.6 57.4 

Zinc 92.7 5.9 93.6 5.9 14.7 -149 97.9 

TSS 16,000 6,000 62.5 6,000 6,000 0 83.3 

% = Percent Data collected on March 24, 2004 at a flow rate of 45 L/min 

μg/L = Microgram per liter 

pH 4. Metal hydroxide and oxyhydroxide precipitate is 

formed during the process, a portion of which settles within 

the 10.3 hour pond HRT at a flow rate of 45 L/min. 

Approximately 23 percent of the iron in the influent ARD 

precipitated and settled in the pretreatment pond during this 

process. An increase in TSS concentration in the pond 

effluent indicates that an additional 11 percent of the iron 

precipitate that was formed in the pretreatment pond was 

passed out of the pond and into bioreactor No.1. On average, 

approximately 3.9 kg of settled solids are generated in the 

pretreatment pond each day. From 2,000 to 7,000L of solids 

are flushed out of the pretreatment pond to the flushing pond 

approximately once a month. Settled solids are determined by 

calculating the differences between influent and effluent 

metals and anion concentrations for each unit operation, 

identifying likely metal-anion pairs, and summing the masses 

of metal-anion pairs that likely formed precipitates. Total 

metals removal efficiencies for each unit operation are 

provided in Table 2-17. 

Metal sulfide precipitate is formed within the two bioreactors 

as sulfate is converted to sulfide by sulfate-reducing bacteria. 

Precipitate formation and settling within Bioreactor No.1 

occurred over a 55.6 hour HRT. Metal sulfide precipitation 

and settling in Bioreactor No.1 provided an additional 5 to 90 

percent removal of influent metals (primarily aluminum, 

copper, iron, nickel, and zinc) from solution. An additional 2 

percent of the aluminum, 10 percent of the copper, and 13 

percent of the zinc precipitates that were formed in bioreactor 

No.1 were passed out of the bioreactor to bioreactor No.2. 

However, the decrease in TSS concentration in the bioreactor 

effluent, primarily related to iron precipitate, confirmed that 

the majority of the solids were retained in the bioreactor. 

Precipitate formation and settling within Bioreactor No.2 

occurred over a 31.5 hour HRT. Metal sulfide precipitation 

and settling in Bioreactor No.2 provided an additional 8 to 26 

percent removal of influent metals (primarily aluminum, 

copper, iron, nickel, and zinc) from solution. An additional 2 

percent of the aluminum, 70 percent of the copper, and 66 

34
______________________________________________________________________________________ 

percent of the zinc precipitates that were formed in bioreactor 

No.2 passed out of the bioreactor to the settling pond. The 

slight increase in TSS concentration in the bioreactor effluent 

confirmed that the majority of the solids were passed out of 

the bioreactor. On average, approximately 1 kg of settled 

solids are generated in Bioreactor No.1 and 12 kg of settled 

solids in Bioreactor No.2 each day. Every 2 months 

approximately 15,000 L of solids are flushed out of the two 

bioreactors to the flushing pond. Formation of sulfide 

precipitates is limited by low solution pH (4 to 5.5); therefore, 

the bulk of metal sulfide precipitate formation and settling 

occurs downstream of the bioreactors in the settling pond, 

after adjustment of effluent pH to a near neutral condition. 

Maintaining a low pH in the bioreactors reduces the volume of 

settled solids and the need for bioreactor flushing, which 

places a stress on the sulfate-reducing bacteria. 

Metals and sulfides in the Bioreactor No.2 effluent were 

combined with sodium hydroxide to raise the pH to a neutral 

condition, and discharged to the settling pond for the bulk of 

precipitate formation and solids settling. Effluent from the 

settling pond was discharged to the flushing pond for extended 

settling. Metal sulfide, metal hydroxide, and metal 

oxyhydroxide precipitate is formed during the process, which 

is allowed to settle within the 172 hour settling pond HRT and 

188.9 hour flushing pond HRT. Precipitate formation and 

settling within the two ponds provided an additional 25.5 to 

99.9 percent removal of influent metals (primarily aluminum, 

copper, iron, nickel, and zinc) from solution. An additional 

0.4 percent of the aluminum, 2.2 percent of the iron, and 4.4 

percent of the nickel precipitates that were formed in the 

flushing pond were passed out of the pond to the aeration 

channel. The decrease in TSS concentration in the effluent 

confirmed that solids were retained in the settling and flushing 

ponds. Depth of accumulated solids within the two ponds 

suggests that approximately 95 percent of the solids are 

retained in the settling pond, with the other 5 percent of solids 

retained in the flushing pond. On average, approximately 15.5 

kg of settled solids are generated each day in the settling pond 

and 0.8 kg of settled solids in the flushing pond. Prior to the 

onset of winter, approximately 32,000 L of solids are 

transferred out of the settling pond to the flushing pond to 

maintain an adequate HRT necessary for solids settling. 

The concentration of aluminum, copper, iron, lead, nickel, and 

zinc increased slightly in aeration channel effluent. However, 

TSS concentrations did not increase and effluent from the 

aeration channel met EPA discharge criteria. On average, 

approximately 2.5 kg of solids settle in the aeration channel 

each day. Collectively, the treatment system generated 33.2 

kg of solids each day. Settled solids are pumped out of the 

flushing pond and settling pond and passed through bag filters 

for dewatering each fall to provide adequate solids storage 

capacity over the following winter. During the fall of 2005, a 

bag filtration process was used to dewater settled solids 

pumped out of the settling and flushing ponds prior to disposal 

as a nonhazardous solid. The settled solids were generated by 

both gravity flow and recirculation modes of operation. The 

bag filtration process involved the filling of a bag filter with 

settled solids, followed by gravity drainage of water through 

the filter fabric for up to two weeks. Free water was allowed 

to drain back into the flushing pond following filtration. The 

process was repeated using a new bag filter placed on top of 

an older bag. Additional solids dewatering occurred in the 

bags on the bottom of the stack due to compression. 

Approximately 200,000 L of settled solids from both modes of 

operation were discharged to seven bag filters over 100 days 

of solids dewatering, generating approximately 3,900 kg (4.3 

dry tons) of solids in the fall of 2005. The bag filters removed 

10 percent of the water from the settled solids and 

concentrated metals by 120 percent. The bag filters remain on 

site and are being allowed to air dry to further reduce moisture 

content prior to disposal. The bag filtration process is limited 

to summer and early fall when temperatures are warm enough 

to prevent freezing of the filter membrane. 

Recirculation Operations. Precipitate generated during 

operation of the bioreactor treatment system in recirculation 

mode is separated from ARD using a settling pond, bioreactor 

pore space, and a flushing pond. Residual metals and excess 

sulfide in Bioreactor No.2 effluent were combined with 

influent ARD and sodium hydroxide to raise the pH to a 

neutral condition, and discharged to the settling pond for the 

bulk of precipitate formation and solids settling. A small 

portion of the settling pond effluent was discharged to the 

flushing pond, while the majority was recirculated to the head 

of Bioreactor No.1 for additional sulfide generation. Metal 

sulfide, metal hydroxide, and metal oxyhydroxide precipitate 

is formed in the pond, which is allowed to settle within the 

29.9 hour settling pond HRT at a combined flow rate of 259 

L/min. Precipitate formation and settling provided 6 to 78 

percent removal of combined influent metals and 38 to 97 

percent removal of system influent metals (primarily 

aluminum, copper, iron, nickel, and zinc) from solution. An 

additional 19.1 percent of the aluminum, 15.2 percent of the 

copper, 15.1 percent of the iron, and 9.6 percent of the zinc 

precipitates that were formed in the settling pond were passed 

out of the pond to both the head of Bioreactor No.1 and the 

flushing pond for extended settling. The TSS concentration 

increased in settling pond effluent, indicating that the HRT of 

the pond was too short to allow adequate solids settling. On 

average, approximately 9.9 kg of settled solids are generated 

each day in the settling pond. Prior to the onset of winter, 

approximately 48,000 L of solids are transferred out of the 

settling pond to the flushing pond to maintain an adequate 

HRT necessary for solids settling. Settled solids are 

determined by calculating the differences between influent and 

effluent metals and anion concentrations for each unit 

operation, identifying likely metal-anion pairs, and summing 

the masses of metal-anion pairs that likely formed precipitates. 

Total metals removal efficiencies for each unit operation are 

provided in Table 2-18. 

35
______________________________________________________________________________________ 

Table 2-18. Recirculation Operation Solids Separation Efficiencies 

Bioreactor No.1 Bioreactor No.2 Settling Pond 

Parameter 

Unfiltered 

Influent 

(μg/L) 

Unfiltered 

Effluent 

(μg/L) 

Percent 

Removal 

(%) 

Unfiltered 

Influent 

(μg/L) 

Unfiltered 

Effluent 

(μg/L) 

Percent 

Removal 

(%) 

System 

Unfiltered 

Influent 

(μg/L) 

Combined 

Unfiltered 

Influent 

(μg/L) 

Unfiltered 

Effluent 

(μg/L) 

Percent 

Removal 

(%) 

Aluminum 1,170 389 66.8 389 334 14.1 40,400 5,284 1,170 77.9 

Arsenic <2.1 <2.1 0 <2.1 2.6 -23.8 <2.1 2.3 <2.1 8.7 

Cadmium 0.23 <0.16 30.4 <0.16 0.26 -62.5 1.1 0.36 0.23 36.1 

Chromium 12 12 0 12 11.7 2.5 19.8 12.7 12 5.8 

Copper 24.3 10.7 56 10.7 11.4 -6.5 757 104 24.3 76.6 

Iron 7,930 3,140 60.4 3,140 2,690 14.3 99,100 14,602 7,930 45.7 

Lead 4.3 4.7 -9.3 4.7 3.8 19.2 7.2 4.2 4.3 -2.4 

Nickel 73.4 33.4 54.5 33.4 28.6 14.4 529 90.4 73.4 18.8 

Selenium 12.4 10.3 16.9 10.3 8.9 13.6 19.9 10.3 12.4 -20.4 

Zinc 28 13.7 51.1 13.7 14.6 -6.6 757 106 28 73.6 

TSS 27,000 42,000 -55.6 42,000 7,000 83.3 <10,000 7,000 27,000 -286 

% = Percent Data collected on August 19, 2004 at a system influent flow rate of 32 L/min, 

μg/L = Microgram per liter a recirculation rate of 227 L/min, and a system effluent rate of 28 L/min.

 Combined influent to the settling pond takes into account the mass of metals in the 

 influent ARD as well as the mass of metals in the effluent from bioreactor No.2. 

Flushing Pond Aeration Channel Cumulative 

Parameter 

Unfiltered 

Influent 

(μg/L) 

Unfiltered 

Effluent 

(μg/L) 

Percent 

Removal 

(%) 

Unfiltered 

Influent 

(μg/L) 

Unfiltered 

Effluent 

(μg/L) 

Percent 

Removal 

(%) 

System 

Percent 

Removal 

(%) 

Aluminum 1,170 172 85.3 172 120 30.2 99.7 

Arsenic <2.1 <2.1 0 <2.1 14.9 -609 -548 

Cadmium 0.23 <0.16 30.4 <0.16 <0.16 0 85.5 

Chromium 12 11.9 0.8 11.9 13.2 -10.9 33.3 

Copper 24.3 11.7 51.9 11.7 7.9 32.5 99 

Iron 7,930 1,030 87 1,030 532 48.4 99.5 

Lead 4.3 4 7 4 6.5 -62.5 9.7 

Nickel 73.4 53.3 27.4 53.3 22.4 58 95.8 

Selenium 12.4 9.4 24.2 9.4 10.8 -14.9 45.7 

Zinc 28 31 -10.7 31 10.6 65.8 98.6 

TSS 27,000 <10,000 63 <10,000 <10,000 0 0 

% = Percent 

μg/L = Microgram per liter 

Data collected on August 19, 2004 at a system influent flow 

rate of 32 L/min, a recirculation rate of 227 L/min, and a

 system effluent rate of 28 L/min 

A moderate quantity of metal sulfide precipitate is formed 

within the two bioreactors as sulfate is converted to sulfide by 

sulfate-reducing bacteria. Precipitate formation and settling 

within Bioreactor No.1 occurs over an 11.0 hour HRT at a 

recirculation rate of 227 L/min. Metal sulfide precipitation 

and settling in Bioreactor No.1 provided an additional 17 to 67 

percent removal of influent metals (primarily aluminum, 

copper, iron, nickel, and zinc) from recirculated solution. An 

additional 34.2 percent of the iron, 29.4 percent of the nickel, 

and 12.3 percent of the zinc precipitates that were formed in 

bioreactor No.1 were passed out of the bioreactor No.1 to 

bioreactor No.2. The increase in TSS concentration in the 

bioreactor effluent confirmed that solids were being passed 

out of the bioreactor. On average, approximately 2.7 kg of 

solids settled in Bioreactor No.1 each day. 

Precipitate formation and settling within Bioreactor No.2 

occurs over a 6.2 hour HRT. Metal sulfide precipitation and 

settling in Bioreactor No.2 provided an additional 3 to 19 

percent removal of influent metals (primarily aluminum, iron, 

and nickel) from recirculated solution. None of the aluminum, 

iron, or nickel precipitates were passed out of the bioreactor. 

The decrease in TSS concentration in the bioreactor effluent 

confirmed that solids were retained in the bioreactor. On 

average, approximately 2.7 kg of solids settled in Bioreactor 

No.2 each day. Every 3 to 4 months approximately 15,000 L 

of solids are flushed out of the two bioreactors to the flushing 

pond. Because recirculated ARD within the two bioreactors is 

near a neutral pH condition, formation and settling of 

precipitate can readily occur within the bioreactors. However, 

the majority of precipitate formation and settling occurs in the 

settling pond and only residual concentrations of metals enter 

36
______________________________________________________________________________________ 

the bioreactors. Careful control of solids settling and depth of 

accumulation within the settling pond is required to prevent 

entrainment of settled solids during recirculation and 

deposition of solids in the two bioreactors. 

Residual metals and sulfide in settling pond effluent are 

discharged to the flushing pond for extended metals and 

sulfide contact, precipitate formation, and settling. Metal 

sulfide, metal hydroxide, and metal oxyhydroxide precipitate 

is formed and allowed to settle within the 304 hour flushing 

pond HRT at 28 L/min. Extended settling provided an 

additional 0.8 to 85 percent removal of influent metals 

(primarily aluminum, copper, iron, and nickel) from solution. 

An additional 10.8 percent of the iron precipitate that was 

formed in the flushing pond was passed out of the pond to the 

aeration channel. The decrease in TSS concentration in the 

effluent confirmed that solids were retained in the flushing 

pond. On average, approximately 5.3 kg of settled solids are 

generated each day in the in the flushing pond. 

Aeration promoted removal of 30 to 66 percent removal of the 

remaining aluminum, copper, iron, nickel, and zinc from 

solution. On average, approximately 0.1 kg of solids settled in 

the aeration channel each day when considering only target 

metals. However, calcium and magnesium concentrations also 

increased in system effluent, resulting in a net loss of 

approximately 1.6 kg of precipitate from the aeration channel 

each day. TSS concentrations did not increase and the 

system effluent from the aeration channel met EPA discharge 

criteria. Metals dissolution and suspended solids carryover to 

the aeration channel could be minimized by more frequent 

removal and dewatering of settled solids from the flushing 

pond. As a whole, the treatment system reduced metals 

concentrations from 9.7 to 99.7 percent, with many of the 

target metals exceeding 85 percent removal efficiency. 

Collectively, the treatment system generated a net mass of 19 

kg of solids each day. Settled solids are pumped out of the 

flushing pond and settling pond and passed through bag filters 

for dewatering each fall to provide adequate solids storage 

capacity over the following winter. Bag filtration is discussed 

under gravity flow operations above. 

2.5.4 Evaluation of Solids Handling and 

Disposal 

This section describes solids handling activities conducted 

during the operation of the bioreactor treatment system. The 

discussion includes a summary of waste characterization and 

handling requirements, identifies the sources and quantity of 

solids from the treatment system, identifies the characteristics 

of each solid waste stream, and identifies the method of 

disposal for each solids waste stream. 

2.5.4.1 Waste Characterization and Handling 

Requirements 

Bioreactor treatment of ARD generates a metal sulfide, metal 

hydroxide, metal oxyhydroxide, and calcium carbonate solid 

waste stream. The solid waste residuals produced by the 

treatment system were analyzed for hazardous waste 

characteristics. Determination of waste characteristics is 

necessary to determine appropriate handling and disposal 

requirements. Therefore, total and leachable metals analyses 

were performed on the solid waste streams for comparison to 

state of California and Federal hazardous waste classification 

criteria. To determine if the solid waste streams are a Federal 

Resource Conservation and Recovery Act (RCRA) waste, 

TCLP results were compared to TCLP limits. To determine 

whether the solid waste streams are a California hazardous 

waste, total metals results (wet weight) were compared to 

California total threshold limit concentration (TTLC) criteria. 

If a solid waste stream exceeds either Federal TCLP criteria or 

California TTLC criteria, then the waste is considered to be 

hazardous and must be disposed of in a permitted treatment, 

storage, and disposal (TSD) facility. 

If a solid waste stream is found to be non-hazardous, then the 

potential to impact water quality must be evaluated. The 

leachability of metals from a solid waste stream must be 

determined using the California WET procedure if disposed of 

in California or another accepted leaching procedure if 

disposed of in other states. Deionized water (DI) was used as 

the WET leaching solution. To determine whether a nonhazardous solid waste stream poses a threat to water quality in 

California, metals concentrations in WET leachate samples 

were compared to California soluble threshold limit 

concentration (STLC) criteria. Solid waste stream samples 

were also subject to the SPLP, a commonly accepted leaching 

procedure in other states. If a solid waste stream exceeds the 

California STLC criteria, then the waste is considered to be a 

threat to water quality and the waste must be disposed of in a 

permitted TSD facility or engineering controls implemented to 

protect water quality. Interpretation of SPLP data are statespecific and are beyond the scope of this discussion. 

Evaluation of the quantity, characteristics, and disposal of 

solid waste streams generated by the bioreactor treatment 

system is presented in Section 2.5.4.2. 

2.5.4.2 Bioreactor Treatment System Solids 

Operation of the bioreactor treatment system between 

November 2003 and July 2005 produced about 14.2 dry tons 

(12,900 kg) of sludge (86 to 99.6 percent moisture), which 

equals about 0.45 dry ton (410 kg) of sludge per million liters 

of ARD treated. The estimate of solids generated includes 

approximately 4.3 dry tons (3,900 kg) of bag filter solids, 

37
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10 dry tons (9,100 kg) of settling pond sludge, and 4.3 dry treatment system operation are presented in Table 2-19. None 

tons (3,900 kg) of flushing pond sludge. The sludge consists of the various sources of sludge were determined to be a 

mainly of metal sulfides and hydroxides that are high in RCRA or California hazardous waste and did not pose a threat 

aluminum, copper, iron, nickel, and zinc. No other waste to water quality. Bag filter solids were shipped off-site to a 

streams were generated the treatment system. The municipal landfill for disposal pending designation of an oncharacteristics of the solid waste streams generated during site disposal area. 

38
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Table 2-19. Bioreactor Treatment System Waste Characterization 

Parameter 

Total Metals1 

(mg/kg) 

Total Metals2 

(mg/kg) 

Exceed 

TTLC? 

DI WET Metals 

(mg/L) 

Exceed 

STLC? 

TCLP 

(mg/L) 

Exceed 

TCLP? 

SPLP Metals 

(mg/L) 

Pretreatment Pond Sludge 

Antimony <4.7 <0.21 No <0.015 No <0.0058 NA 0.0082 

Arsenic 15.1 0.664 No 0.321 No <0.0052 No 0.0903 

Barium 13.5 0.059 No 0.19 No 0.0677 No 0.105 

Beryllium 5.2 0.229 No 0.0995 No 0.003 NA 0.0462 

Cadmium <0.31 <0.014 No <0.0014 No <0.00054 No <0.00027 

Chromium 11.1 0.488 No 0.13 No <0.00084 No 0.0725 

Cobalt 97.9 4.31 No 1.11 No 0.166 NA 0.174 

Copper 487 21.4 No 4.61 No 0.0258 NA 0.614 

Lead <2.5 <0.11 No 0.0493 No 0.0107 No 0.0046 

Mercury 1.3 0.057 No 0.00087 No 0.00037 No 0.00031 

Molybdenum <0.99 <0.044 No <0.0034 No <0.0013 NA <0.00067 

Nickel 111 4.88 No 1.54 No 0.312 NA 0.373 

Selenium <6.1 <0.268 No 0.293 No 0.0247 No 0.0875 

Silver <0.7 <0.031 No <0.0023 No <0.00092 No <0.00046 

Thallium 12.9 0.568 No 0.0398 No 0.0036 NA 0.0194 

Vanadium 7 0.308 No 0.165 No <0.00088 NA 0.0712 

Zinc 320 14.1 No 4.6 No 0.795 NA 1.2

 Settling Pond Sludge 

Antimony <4.9 <0.211 No <0.015 No <0.0058 NA <0.0029 

Arsenic 98.4 4.23 No 0.45 No <0.0052 No <0.0026 

Barium 83 3.569 No 0.323 No 0.0949 No 0.016 

Beryllium 18.3 0.7869 No 0.105 No 0.003 NA 0.0002 

Cadmium 1.5 0.0645 No 0.004 No 0.00076 No <0.00027 

Chromium 17.6 0.7568 No 0.0281 No 0.0035 No 0.0017 

Cobalt 378 16.254 No 1.65 No 0.208 NA 0.0045 

Copper 757 32.551 No 2.42 No 0.0165 NA 0.0078 

Lead 6 0.258 No 0.0307 No 0.0062 No <0.0013 

Mercury 7.9 0.3397 No 0.0012 No 0.00049 No 0.00034 

Molybdenum <1 <0.043 No <0.0034 No <0.0013 NA 0.0012 

Nickel 484 20.812 No 2.4 No 0.407 NA 0.01 

Selenium <6.3 <2.71 No 0.138 No 0.015 No <0.0042 

Silver 0.82 0.03526 No <0.0023 No 0.0025 No 0.00099 

Thallium 18 0.774 No 0.0737 No 0.0191 NA 0.0074 

Vanadium 25.8 1.1094 No 0.122 No <0.00088 NA <0.00044 

Zinc 728 31.304 No 3.57 No 0.586 NA 0.0135 

Flushing Pond Sludge 

Antimony <49 <0.196 No <0.015 No <0.0058 NA <0.0029 

Arsenic 172 0.688 No 0.016 No <0.0052 No <0.0026 

Barium 135 0.54 No 0.076 No 0.0366 No 0.0401 

Beryllium 11.6 0.0464 No 0.0041 No <0.00022 NA <0.00011 

Cadmium 4.5 0.018 No <0.0014 No <0.00054 No <0.00027 

Chromium 27.7 0.1108 No 0.0022 No <0.00084 No <0.00042 

Cobalt 409 1.636 No 0.0224 No 0.0031 NA 0.0035 

Copper 707 2.828 No 0.0346 No 0.0085 NA 0.0063 

Lead <26 <0.104 No <0.0065 No <0.0026 No 0.0018 

Mercury 47 0.188 No 0.00098 No 0.00027 No 0.00067 

Molybdenum <10 <0.04 No 0.0059 No 0.0045 NA 0.002 

Nickel 627 2.508 No 0.104 No 0.027 NA 0.0384 

Selenium <63 <0.252 No <0.021 No 0.0189 No 0.0045 

Silver <7.2 <0.288 No 0.0032 No <0.00092 No 0.00092 

Thallium <35 <0.14 No <0.0085 No <0.0034 NA <0.0017 

Vanadium 13.5 0.054 No 0.0046 No <0.00088 NA 0.0012 

Zinc 850 3.4 No 0.0546 No 0.0163 NA 0.0086 

1

 Metals data reported as dry weight 

DI WET = Waste extraction test using deionized water

mg/kg = Milligram per kilogram 

mg/L = Milligram per liter 

NA = Not applicable 

2 Metals data reported as wet weight for comparison to TTLC 

 SPLP = Synthetic precipitation leaching procedure 

STLC = Soluble threshold limit concentration 

TCLP = Toxicity characteristic leaching procedure 

TTLC = Total threshold limit concentration 

39
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Table 2-19. Bioreactor Treatment System Waste Characterization (continued) 

Parameter 

Total Metals1 

(mg/kg) 

Total Metals2 

(mg/kg) 

Exceed 

TTLC? 

DI WET Metals 

(mg/L) 

Exceed 

STLC? 

TCLP 

(mg/L) 

Exceed 

TCLP? 

SPLP Metals 

(mg/L) 

Aeration Channel Sludge 

Antimony <21 <0.21 No 0.0474 No <0.0058 NA 0.0205 

Arsenic 163 1.63 No 1.93 No 0.0466 No 0.821 

Barium 419 4.19 No 3.55 No 0.303 No 1.68 

Beryllium 1 0.01 No 0.0145 No 0.00075 NA 0.0086 

Cadmium 2.4 0.024 No 0.0064 No <0.00054 No 0.0042 

Chromium 23.7 0.237 No 0.123 No 0.002 No 0.0553 

Cobalt 349 3.49 No 4.39 No 0.785 NA 0.941 

Copper 110 1.1 No 1.34 No 0.0204 NA 0.225 

Lead 22.2 0.222 No 0.188 No <0.0026 No 0.0456 

Mercury 21.9 0.219 No 0.0202 No 0.00046 No 0.0044 

Molybdenum <4.4 <0.044 No <0.0034 No 0.0021 NA <0.00067 

Nickel 502 5.02 No 7.22 No 2.43 NA 3.27 

Selenium <27 <0.27 No 0.123 No 0.0098 No 0.0857 

Silver <3.1 <0.031 No <0.0023 No <0.00092 No <0.00046 

Thallium <15 <0.15 No 0.0984 No 0.0186 NA 0.0321 

Vanadium 37.4 0.374 No 0.448 No <0.00088 NA 0.3 

Zinc 431 4.31 No 4.15 No 0.713 NA 0.924 

Bag Filter Solids 

Antimony 5.9 0.82 No <0.0047 No <0.0094 NA <0.0047 

Arsenic 14.3 2.0 No <0.0037 No <0.0074 No <0.0037 

Barium 10.3 1.4 No 0.125 No 0.013 No 0.0045 

Beryllium 19.1 2.6 No 0.246 No 0.00023 NA <0.000066 

Cadmium 3.8 0.53 No <0.00046 No <0.00092 No <0.00046 

Chromium 15.1 2.1 No 0.184 No 0.0373 No 0.007 

Cobalt 416 57.6 No 0.169 No 0.0437 NA <0.00064 

Copper 2,030 281 No 0.0208 No 0.0145 NA 0.0082 

Lead 8.9 1.2 No 0.0572 No 0.0126 No 0.0025 

Mercury 0.18 0.026 No 0.00012 No 0.0022 No 0.0024 

Molybdenum <0.5 <0.2 No <0.0014 No <0.0028 NA <0.0014 

Nickel 561 77.6 No 2.91 No 0.278 NA 0.0025 

Selenium <1.3 <0.5 No 0.121 No 0.0381 No 0.0091 

Silver <0.4 <0.5 No <0.00099 No 0.0036 No 0.0027 

Thallium 30.1 4.2 No 0.111 No 0.0365 NA <0.0028 

Vanadium 6 0.83 No 0.0807 No <0.0014 NA <0.00068 

Zinc 1,400 194 No 0.58 No 0.137 NA 0.0071 

1

 Metals data reported as dry weight 

DI WET = Waste extraction test using deionized water

mg/kg = Milligram per kilogram 

mg/L = Milligram per liter 

NA = Not applicable 

2 Metals data reported as wet weight for comparison to TTLC 

 SPLP = Synthetic precipitation leaching procedure 

STLC = Soluble threshold limit concentration 

TCLP = Toxicity characteristic leaching procedure 

TTLC = Total threshold limit concentration 

40
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SECTION 3 

TECHNOLOGY APPLICATIONS ANALYSIS 

This section of the ITER describes the general applicability of 

the compost-free bioreactor treatment technology to reduce 

acidity and toxic levels of metals in water at ARDcontaminated mine sites. The analysis is based on the results 

from and observations made during the SITE demonstration. 

3.1 Key Features 

Oxidation of sulfur and sulfide minerals within the mine 

workings and waste rock forms sulfuric acid (H2SO4), which 

liberates toxic metals from the mine wastes creating ARD. 

Biological treatment of ARD reverses this process and relies 

on the biologically mediated reduction of sulfate to sulfide 

followed by metal sulfide precipitation. Biologically 

promoted sulfate-reduction has been attributed primarily to a 

consortium of sulfate-reducing bacteria, which utilize a variety 

of carbon substrates to reduce sulfate to sulfide. This process 

generates hydrogen sulfide, elevates pH to about 7, and 

precipitates divalent metals as metal sulfides. The following 

general equations describe the sulfate-reduction and metal 

sulfide precipitation processes. 

- 2CH3CH2OH + 3SO42- → 3HS- + 3HCO3 + 3H2O (1) 

2CH3CH2OH + SO4

2- → 2 CH3COO- + HS-

 + H2O (2) 

HS- + M2+→ MS + 2H+ (3) 

Here ethanol is the carbon source and SO4

2- is the terminal 

electron acceptor in the electron transport chain of sulfatereducing bacteria. Reaction No.1 causes an increase in 

alkalinity and a rise in pH, while reaction No.2 results in the 

generation of acetate rather than complete oxidation to 

carbonate. HS- then reacts with a variety of divalent metals 

(M2+), resulting in a metal sulfide (MS) precipitate. 

At Leviathan Mine, biological treatment is conducted in two 

compost-free gravity-flow bioreactors, two settling ponds, and 

an aeration channel. The bioreactors are filled with river rock 

because of the ease at which precipitates can be flushed 

through the matrix and the stability (little compaction) of the 

matrix. Operated in gravity flow mode, ARD is introduced to 

the pretreatment pond, where sodium hydroxide is added to 

adjust the influent pH of 3.1 up to 4 to maintain a favorable 

environment for sulfate-reducing bacteria and ethanol is added 

as a carbon source. Minimal chemically-mediated metals 

precipitation occurs in the pretreatment pond. ARD from the 

pre-treatment pond then flows through the first bioreactor to 

biologically reduce sulfate to sulfide. Excess sulfide 

generated in the first bioreactor is passed, along with partially 

treated ARD water, through to the second bioreactor for 

additional metals removal. Precipitates in effluent from the 

second bioreactor are settled in a continuous flow settling 

pond. 

Operated in recirculation mode, metal-rich influent ARD is 

combined with sodium hydroxide and sulfide-rich water 

discharged from the second bioreactor to precipitate metals in 

the settling pond rather than in the bioreactors. Precipitation 

of metal sulfides downstream of the two bioreactors greatly 

reduces the need for flushing and the associated stress on 

bacteria in the two bioreactors. A portion of the pond 

supernatant containing minimal residual metals and excess 

sulfate is pumped to the first bioreactor and combined with 

alcohol feed stock to promote additional sulfate reduction to 

sulfide in the two bioreactors. The pH of the supernatant 

recirculated through the bioreactors is near neutral, providing 

optimal conditions for sulfate-reducing bacteria growth. 

During both modes of operation, the effluent from the 

continuous flow settling pond flows through a rock lined 

aeration channel to promote gas exchange prior to effluent 

discharge. Precipitate slurry is periodically flushed from the 

bioreactors to prevent plugging of the river rock matrix and 

provide adequate volume in the settling pond, and settled in a 

flushing pond. Settled solids from the flushing pond are 

periodically dewatered using bag filters. 

41
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3.2 Applicable Wastes 

Conventional methods of treating ARD involve the capture, 

storage, and batch or continuous treatment of water using a 

large quantity of added lime, which neutralizes acidity and 

precipitates a large volume of metal hydroxide sludge. 

Biological treatment using sulfate-reducing bacteria is 

applicable to any waste stream containing metals and sulfate 

ion, requires a small quantity of base addition and a liquid 

carbon source, and generates a relatively small volume of 

metal sulfide sludge. Metals typically treated include 

aluminum, arsenic, cadmium, chromium, copper, iron, lead, 

nickel, and zinc. Biological treatment is also passive, 

requiring less labor for system O&M. 

The compost-free bioreactor treatment system in operation at 

the Leviathan Mine site is an improvement to the current 

wood chip, compost, and manure biological treatment systems 

in place or being evaluated at many facilities today. The 

compost-free bioreactor technology removes the uncertainties 

related to carbon availability and sulfate reduction efficiency 

through the use of a liquid carbon substrate (ethanol). The 

compost-free bioreactor technology also eliminates the 

problems associated with matrix compaction and short 

circuiting through the use of river rock, which allows rapid 

flushing of solids in comparison to compost and wood chip 

matrices. 

3.3 Factors Affecting Performance 

Several factors can influence the performance of the 

bioreactor treatment system demonstrated at Leviathan Mine. 

These factors can be grouped into three categories: (1) mine 

drainage characteristics, (2) operating parameters, and (3) 

system design. The bioreactor treatment system is capable of 

treating a broad range of metals in ARD. The level of acidity, 

metals concentration, and metals composition directly impact 

the quantity of sulfide ion that must be generated, and the 

subsequent sodium hydroxide and ethanol dosages required to 

neutralize acidity and in conjunction with sulfate-reducing 

bacteria, generate the sulfide necessary to precipitate target 

metals. 

Operating parameters for the bioreactors also directly impact 

system performance. Optimizing and limiting fluctuations in 

reagent dosages, bioreactor HRT, bioreactor temperature, 

gravity and recirculation flow rates, and settling pond HRT all 

impact the activity of sulfate-reducing bacteria, generation of 

sulfides, and removal of target metals. The system should be 

designed and operated to limit stress placed on the sulfatereducing bacteria in the bioreactors. The system should be 

operated to allow as near neutral a pH in the bioreactors as 

possible and maintain a consistent ethanol dosage rate. 

In order to minimize fluctuations in pH and maintain a near 

neutral pH, operation of the system in recirculation mode was 

found to be optimal. Sodium hydroxide is added to the 

settling pond along with sulfide rich water to precipitate metal 

sulfides from solution. The pond supernatant, at a near neutral 

pH and with low metals concentrations, is recirculated through 

the bioreactors, which favors sulfate-reducing bacteria and 

minimizes metal toxicity. Settling of metal sulfides in the 

pond rather than the bioreactors also minimizes the need for 

bioreactor flushing and associated biological stress. In the 

absence of a recirculation pump, the system design should 

include a pretreatment pond upstream of the treatment system 

to reduce fluctuations in acidity and metals concentration in 

influent ARD and allow extended mixing time for sodium 

hydroxide and ethanol reagents added to solution, all of which 

will promote a tighter control of reaction chemistry enter the 

bioreactors. 

In locations where extremely cold winter conditions persist 

over several months, consideration should be given to 

ensuring that the bioreactor and settling ponds are of sufficient 

depth to prevent deep freezing and insulate the active portion 

of the bioreactor from extreme cold. The bioreactors at 

Leviathan Mine are 3 meters deep and were not impact by 

extreme cold below a depth of approximately 0.6 meter. In 

addition, the settling ponds did not freeze below about 0.6 

meter. 

The rock substrate within the bioreactors is essentially noncompactable over time in comparison to traditional wood chip, 

compost, and manure substrate-based bioreactors. A stable 

substrate minimizes dead zones and preferential pathways 

within a bioreactor over time. The use of ethanol as a carbon 

substrate rather than traditional wood- or manure-based 

carbon sources provides a stable carbon supply and is a more 

efficient source of reducing equivalents for sulfate-reducing 

bacteria. Together, a rock matrix and a liquid carbon substrate 

allow long-term operation of a treatment system that 

traditionally requires excavation and replace of the wood or 

manure substrate every five years, depending on the initial 

quantity of wood or manure used. 

Finally, the method and duration of precipitate settling and 

separation also impacts system performance. The treatment 

system relies on sodium hydroxide addition to generate 

settleable solids, a large settling pond to allow extended 

settling of pin floc, and bag filters to dewater sludge pumped 

out of the settling pond. A second settling pond should also 

be considered during system design to provide the system 

operator some room for error during system upsets. If sodium 

hydroxide addition to the settling pond is not controlled above 

a pH of 8, target metals may dissolve back into solution. 

3.4 Technology Limitations 

In general, the limitations of the bioreactor treatment system 

implemented at Leviathan Mine were not related to the 

applicability of the technology, but rather to operational issues 

42
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due to weather conditions, maintenance problems, and the 

remoteness of the site. The technology is not limited by the 

sub-freezing temperatures encountered in the high Sierra 

Nevada during the winter months. However, biological 

activity did slow resulting in decreased sulfate reduction to 

sulfide. Effluent discharge standards were met as the flow of 

ARD entering the bioreactor treatment system also decreased 

during the winter. When designing systems for extremely 

cold winters, consideration should be given to constructing 

bioreactors of sufficient size to meet winter HRT requirements 

and depth to buffer freezing temperatures near the ground 

surface. In addition, adjustable standpipes in below grade 

vaults should be used to control the flow of water rather than 

mechanical valves, which are subject to freezing during the 

winter. 

During extended operation of the bioreactor treatment system, 

reagent metering and water recirculation pumps and the 

generator that provided power to these pumps were 

susceptible to failure. In addition, aboveground influent ARD 

transfer and partially treated recirculation pipelines were 

susceptible to breakage. These limitations are currently being 

mitigated by 1) developing wind, solar, and hydroelectric 

power sources, 2) installing redundant pumps, and 3) placing 

transfer lines below grade. Overall, the bioreactor treatment 

system required minimal maintenance (1 to 2 days a week). 

The remoteness of the site also created logistical challenges in 

maintaining operation of the bioreactor treatment system. A 

winter snow pack from November through May prevents site 

access to all delivery vehicles except for snowmobiles. 

Consumable materials, such as sodium hydroxide, ethanol, 

and diesel fuel (to power a generator) must be transported to 

and stored in bulk at the site during the summer. Sludge 

transfer from the settling ponds, dewatering, and on- or offsite disposal must also be performed during the summer 

months to provide sufficient settling pond capacity during the 

following winter months. Careful planning is essential to 

maintain supplies of consumable materials and replacement 

equipment at a remote site such as Leviathan Mine. 

3.5 Range of Suitable Site Characteristics 

This section describes the site characteristics necessary for 

successful application of the bioreactor treatment technology. 

Staging Area and Support Facilities: For full-scale 

bioreactor treatment systems such as those in operation at 

Leviathan Mine, minimal staging areas and support facilities 

are necessary for continuous operation of the treatment 

system. A small staging area is needed for storage of 

consumable materials, and supplies; loading and unloading 

equipment; and for placement of a Connex, which is used for 

storage of spare parts and equipment that are not weather 

resistant. Additional space is necessary for placement of a 

health and safety eyewash and shower; a portable toilet; and 

power generating equipment. The staging and storage areas 

required for a treatment system should range from 300 and 

500 square meters and are usually located adjacent to the 

treatment system. A reagent storage area of about 50 square 

meters for bulk quantities of ethanol and sodium hydroxide is 

also required up gradient of or at the head of the treatment 

system. 

Treatment System Space Requirements: To conduct fullscale bioreactor treatment of ARD, the main site requirement 

at the Leviathan Mine site was developing adequate space for 

the treatment system, staging areas, and support facilities. 

Space is needed for reagent storage tanks, a pretreatment 

pond, bioreactor ponds, settling ponds, an aeration channel, 

and bag filters. Additional space was required adjacent to the 

treatment system for storage of spare parts and equipment, for 

loading and unloading equipment, supplies, and reagents, and 

for placement of operating facilities such eye wash stations, 

fuel storage tank, and power generating equipment. Overall, 

the space requirement for the bioreactor treatment of ARD at a 

flow rate of 114 L/min at Leviathan Mine is about 3,000 

square meters. 

Climate: Operation of the bioreactor treatment system is 

slightly affected by freezing temperatures. In areas where 

freezing temperatures are normal throughout the winter 

months, such as at the Leviathan Mine site, biological activity 

does slow resulting in decreased sulfate reduction to sulfide. 

At Leviathan Mine, effluent discharge standards were 

generally met as the flow of ARD entering the bioreactor 

treatment system also decreased during the winter. When 

designing systems for extremely cold winters, consideration 

should be given to constructing bioreactors of sufficient size 

to meet winter HRT requirements and depth to buffer freezing 

temperatures near the ground surface. In addition, adjustable 

standpipes in below grade vaults should be used to control the 

flow of water rather than mechanical valves, which are subject 

freezing during the winter. 

The remoteness of the site also created logistical challenges in 

maintaining operation of the bioreactor treatment system. A 

winter snow pack from November through May prevents site 

access to all delivery vehicles except for snowmobiles. 

Consumable materials, such as sodium hydroxide, ethanol, 

and diesel fuel (to power a generator) must be transported to 

and stored in bulk at the site during the summer. Sludge 

transfer from the settling ponds, dewatering, and on- or offsite disposal must also be performed during the summer 

months to provide sufficient settling pond capacity during the 

following winter months. Careful planning is essential to 

maintain supplies of consumable materials and replacement 

equipment at a remote site such as Leviathan Mine. 

Utilities: The main utility requirement for the bioreactor 

treatment system is electricity, which is used to operate 

reagent delivery pumps, water recirculation pump, sludge 

transfer pumps, and site work lighting. The bioreactor 

43
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treatment system, operated in recirculation mode, requires less 

than 0.6 kilowatt (KW) hour of electricity for continuous 

operation. Power for recirculation mode is provided by a 6 

KW-hour diesel generator. Diesel fuel for the generator is 

stored in a 3,785 L above ground tank. The bioreactor 

treatment system, operated in gravity flow mode, requires less 

than 0.1 KW hour of electricity for continuous operation as a 

recirculation pump is not required. Power for the gravity flow 

mode of operation is provided by a solar panel and storage 

batteries. A wind or water turbine and storage battery may 

also be used to provide power. Satellite phone service is also 

required due to the remoteness of the site. 

Supervisory Control and Data Acquisition (SCADA) service 

through a satellite uplink may also be used to monitor water 

chemistry and control dosing of ethanol and sodium hydroxide 

to the bioreactor treatment system. 

3.6 Personnel Requirements 

Personnel requirements for operation of the treatment system 

following initial design and construction can be broken down 

into the following activities: startup and acclimation, and 

O&M. System start-up and acclimation includes the labor to 

setup pumps and pipes, fill and recirculate ARD within the 

system, adjust system hydraulics and reagent dosages, and 

optimize the operational HRT to meet discharge standards. 

System startup and acclimation occurs once after initial 

system construction as the system is design to operate year 

round, even in extremely cold weather. System start up of the 

treatment system will take a two-person crew two weeks to 

complete. After system construction and start up, an 

acclimation period is necessary to allow for the acclimation of 

sulfate-reducing bacteria to the source water, optimization of 

carbon substrate dosage and pH within the bioreactors, and the 

slow ramp up of ARD flow to attain discharge standards. 

System acclimation will require only one person visiting the 

system 3 days a week over a 10 week period. 

Field personnel are necessary to operate the treatment system, 

perform weekly maintenance, collect weekly discharge 

monitoring samples, monitor unit operation chemistry and 

flow rates, and to adjust ethanol and sodium hydroxide 

dosages, adjust unit operation HRT, and adjust recirculation 

rates. Due to the passive nature of the treatment system, 

minimal O&M labor is necessary in comparison to an active 

treatment system. Long-term O&M of the treatment system 

will require only one person visiting the system 1 day a week 

over the course of a year. 

In addition to field personnel, support staff is required for 

project management and administrative support functions. 

The level of effort required for support staff is approximately 

15 percent of the total project level of effort. 

3.7 Materials Handling Requirements 

There is one process residual associated with bioreactor 

treatment of ARD. The process produces a relatively small 

quantity of sludge containing metal sulfides, oxides, and 

oxyhydroxides. During operation from November 2003 

through July 2005, the bioreactor generated about 14.2 dry 

tons (12,900 kg) of sludge consisting mainly of iron sulfide. 

This equals 1.7 dry tons (1,550 kg) of sludge per million 

gallons (0.45 dry ton [410 kg] per million liters) of ARD 

treated. 

The solid waste residuals produced by the treatment system 

were analyzed for hazardous waste characteristics. Total 

metals and leachable metals analyses were performed on the 

solid wastes for comparison to California and Federal 

hazardous waste classification criteria. To determine whether 

the residuals are California hazardous waste, total metals 

results were compared to TTLC criteria. To determine 

whether metals concentrations in the solid waste residuals 

pose a threat to water quality, DI WET leachate results were 

compared to STLC criteria. To determine if the residuals are a 

RCRA waste, TCLP leachate results were compared to TCLP 

limits. The hazardous waste characteristics determined for the 

solid waste stream are presented in Table 3-1. None of the 

solid wastes were found to be hazardous or a threat to water 

quality; however, the solids were disposed of off site pending 

designation of an on-site disposal area. 

3.8 Permit Requirements 

Actions taken on-site during a CERCLA cleanup action must 

comply only with the substantive portion of a given 

regulation. On-site activities need not comply with 

administrative requirements such as obtaining a permit, record 

keeping, or reporting. Actions taken off-site must comply 

with both the substantive and administrative requirements of 

applicable laws and regulations. All actions taken at the 

Leviathan Mine Superfund site were on-site; therefore permits 

were not obtained. 

Permits that may be required for off-site actions or actions at 

non-CERCLA sites include: a permit to operate a hazardous 

waste treatment system, an National Pollutant Discharge and 

Elimination System (NPDES) permit for effluent discharge, an 

NPDES permit for discharge of storm water during 

construction activities, and an operations permit from a local 

air quality management district (AQMD) for activities 

generating particulate emissions. Permits from local agencies 

may also be required for grading, construction, and 

operational activities; transport of oversized equipment on 

local roads; and transport of hazardous materials on local 

roads. 

44
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Table 3-1. Determination of Hazardous Waste Characteristics for Bioreactor Solid Waste Streams 

TTLC STLC TCLP 

Treatment 

System Solid Waste Stream 

Total Solid 

Waste Generated 

Pass or 

Fail 

Pass or 

Fail 

Pass or 

Fail Waste Handling Status 

Bioreactor 

Treatment 

System 

Dewatered Sludge 4.3 dry tons P P P Off-site Disposal 

Pretreatment Pond Moved into Flushing Pond P P P Moved into Flushing Pond 

Settling Pond 10 dry tons (estimated) P P P Pending Filtration 

Flushing Pond 4.3 dry tons (estimated) P P P Pending Filtration 

STLC = Soluble limit threshold concentration TTLC = Total threshold limit concentration 

TCLP = Toxicity characteristic leaching procedure 1 dry ton = 907 kilogram 

3.9 Community Acceptance 

Community acceptance for the compost-free bioreactor 

treatment system operated at Leviathan Mine is positive. The 

diversion and treatment of ARD at the mine site is seen as a 

necessary and positive step towards reestablishing a quality 

watershed within the Sierra Nevada mountain range. The 

treatment system is able to meet discharge standards and 

operates on a year round basis, promoting improved watershed 

and fishery health. Continued community involvement and 

regulatory agency support will be necessary for long term 

treatment and monitoring at a mine site such as Leviathan 

Mine. 

Operation of the bioreactor treatment system presents minimal 

to no risk to the public since all system components and 

treatment operations occur within a contained site. Solids 

generated during the treatment process are nonhazardous. 

Hazardous chemicals used in the treatment system include 

ethanol, sodium hydroxide, and diesel fuel for generator 

power. These chemicals pose the highest risk to the public 

during transportation to the site by truck and trailer. 

Appropriate Department of Transportation (DOT) regulations 

are followed during shipment of these chemicals to minimize 

potential impacts to the public. During operation, the diesel 

generator used to power the treatment system creates the most 

noise and air emissions at the site. Hydrogen sulfide gas is 

also generated by the treatment process, but is only of concern 

within the treatment system valve vaults. Because of the 

remoteness of the Leviathan Mine site, the public is not 

impacted by these issues. Alternative power sources are 

currently being evaluated, including wind and water turbines, 

which will replace or augment the diesel-powered generator. 

3.10 Availability, Adaptability, and 

Transportability of Equipment 

The components of the compost-free bioreactor treatment 

system are generally available and not proprietary. System 

process components include (1) distribution piping and 

valving, pond liners, rock substrate, recirculation pumps, and 

reagent storage tanks; (2) control equipment such as a 

SCADA system, a pH monitoring system, a recirculation 

pump controller, and ethanol and sodium hydroxide dosage 

and feed systems; and (3) solids handling equipment such as 

sludge pumps, bag filters, and roll-off bins. This equipment is 

available from numerous suppliers throughout the country and 

may be ordered in multiple sizes to meet flow requirements 

and treatment area accessibility. An integrated design is 

recommended to properly size and assemble individual 

components for proper system operation. 

Transport of earth moving equipment, piping, stairs, 

bioreactor rock substrate, and reagent storage tanks to a site 

may require handling as oversize or wide loads. Additional 

consideration should be given to the stability of mine access 

roads, bridge clearances, and load limits for large shipments. 

Process reagents and consumables, such as ethanol, sodium 

hydroxide, and generator fuel, are considered hazardous 

materials and will require stable site access roads for delivery. 

3.11 Ability to Attain ARARs 

Under CERCLA, remedial actions conducted at Superfund 

sites must comply with Federal and state (if more stringent) 

environmental laws that are determined to be applicable or 

relevant and appropriate. Applicable or relevant and 

appropriate requirements (ARAR) are determined on a sitespecific basis by the EPA remedial project manager. They are 

used as a tool to guide the remedial project manager toward 

the most environmentally safe way to manage remediation 

activities. The remedial project manager reviews each Federal 

environmental law and determines if it is applicable. If the 

law is not applicable, then the determination must be made 

whether the law is relevant and appropriate. Actions taken onsite during a CERCLA cleanup action must comply only with 

the substantive portion of a given ARAR. On-site activities 

need not comply with administrative requirements such as 

obtaining a permit, record keeping, or reporting. Actions 

conducted off-site must comply with both the substantive and 

administrative requirements of applicable laws and 

regulations. 

On-site remedial actions, such as the compost-free bioreactor 

treatment system in operation at the Leviathan Mine site, must 

comply with Federal and more stringent state ARARs, 

however, ARARs may be waived under six conditions: (1) the 

45
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action is an interim measure, and the ARAR will be met at 

completion; (2) compliance with the ARAR would pose a 

greater risk to human health and the environment than 

noncompliance; (3) it is technically impracticable to meet the 

ARAR; (4) the standard of performance of an ARAR can be 

met by an equivalent method; (5) a state ARAR has not been 

consistently applied elsewhere; and (6) ARAR compliance 

would not provide a balance between the protection achieved 

at a particular site and demands on the Superfund for other 

sites. These waiver options apply only to Superfund actions 

taken on-site, and justification for the waiver must be clearly 

demonstrated. 

The following sections discuss and analyze specific 

environmental regulations pertinent to operation of the 

bioreactor treatment system, including handling, transport, and 

disposal of both hazardous and non-hazardous treatment 

residuals. ARARs identified include: (1) CERCLA; (2) 

RCRA; (3) the Clean Air Act (CAA); (4) the Clean Water Act 

(CWA); (5) Safe Drinking Water Act (SDWA); and (6) 

Occupational Safety and Health Administration (OSHA) 

regulations. These six general ARARs, along with additional 

state and local regulatory requirements (which may be more 

stringent than Federal requirements) are discussed below. 

Specific ARARs that may be applicable to the bioreactor 

treatment system are identified in Table 3-2. 

3.11.1 Comprehensive Environmental Response, 

Compensation, and Liability Act 

CERCLA of 1980 authorizes the Federal government to 

respond to releases or potential releases of any hazardous 

substance into the environment, as well as to releases of 

pollutants or contaminants that may present an imminent or 

significant danger to public health and welfare or to the 

environment. As part of the requirements of CERCLA, EPA 

has prepared the National Oil and Hazardous Substances 

Pollution Contingency Plan (NCP) for hazardous substance 

response. The NCP, codified in Title 40 Code of Federal 

Regulations (CFR) Part 300, delineates methods and criteria 

used to determine the appropriate extent of removal and 

cleanup for hazardous waste contamination. 

The 1986 SARA amendment to CERCLA directed EPA to: 

• Use remedial alternatives that permanently and 

significantly reduce the volume, toxicity, or mobility 

of hazardous substances, pollutants, or contaminants. 

• Select remedial actions that protect human health and 

the environment, are cost-effective, and involve 

permanent solutions and alternative treatment or 

resource recovery technologies to the maximum 

extent possible. 

• Avoid off-site transport and disposal of untreated 

hazardous substances or contaminated materials 

when practicable treatment technologies exist 

(Section 121[b]). 

In general, two types of responses are possible under 

CERCLA: removal and remedial actions. Removal actions 

are quick actions conducted in response to an immediate threat 

caused by release of a hazardous substance. Remedial actions 

involve the permanent reduction of toxicity, mobility, and 

volume of hazardous substances or pollutants. The bioreactor 

treatment technology implemented at the Leviathan Mine 

Superfund site fall under the purview of CERCLA and SARA; 

the treatment system is operated on site and reduces the 

mobility of toxic metals through metal sulfide precipitation 

and volume through metal concentration in sludge and bag 

filter solids. The technologies are protective of human health 

and the environment, cost effective, and permanent. 

The bioreactor treatment technology can be applied at sites 

such as Leviathan Mine and operated as long-term CERCLA 

remedial actions; however, it may also be designed and 

operated for short term operation at a site in support of a 

CERCLA removal action, where immediate removal of toxic 

metals from a waste stream is necessary. 

3.11.2 Resource Conservation and Recovery Act 

RCRA, an amendment to the Solid Waste Disposal Act, was 

enacted in 1976 to address the problem of safe disposal of the 

enormous volume of municipal and industrial solid waste 

generated annually. The Hazardous and Solid Waste 

Amendments of 1984 greatly expanded the scope and 

requirements of RCRA. Regulations in RCRA specifically 

address the identification and management of hazardous 

wastes. Subtitle C of RCRA contains requirements for 

generation, transport, treatment, storage, and disposal of 

hazardous waste, most of which are applicable to CERCLA 

actions. In order to generate and dispose of a hazardous 

waste, the site responsible party must obtain an EPA 

identification number. However, mining wastes are generally 

not subject to regulation under RCRA (see the Bevill 

Amendment at Section 3001(a)(3)(A)(ii)), unless the waste is 

disposed of off-site. For treatment residuals determined to be 

RCRA hazardous, substantive and administrative RCRA 

requirements must be addressed if the wastes are shipped off 

site for disposal. If treatment residuals remain on-site, the 

substantive requirements of state disposal and siting laws and 

the Toxic Pits Control Act may be relevant and appropriate. 

Criteria for identifying RCRA characteristic and listed 

hazardous wastes are included in 40 CFR Part 261 Subparts C 

and D. Other applicable RCRA requirements include 

hazardous waste manifesting for off-site disposal and time 

limits on accumulating wastes. 

46
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Table 3-2. Federal Applicable or Relevant and Appropriate Requirements for the Bioreactor Treatment System 

Regulated Activity ARAR Description ApplicCharacterization of untreated AMD and ARD 

RCRA: 40 CFR Part 261 or state equivalent 

Standards that apply to identification and characterization of wastes. 

Not applicable as 

mine wastes are not su

A

mend

ment. 

Construction of Treat

ment System 

OSHA: 29 CFR 1910.120 Protection of workers from toxic 

metals during earth 

moving 

activities and syste

m construction. 

Applicable. Provide air 

monitoring and 

equip

ment. 

CAA: 40 CFR Part 50 or state equivalent 

Standards that apply to the e

mission of particulates and toxic 

pollutants. 

Relevant and appropriate. Control emissengineering controls. May require air m

CWA: 40 CFR Part 122 

Standards for discharge of storm water generated during 

construction activities. Requires compliance with best management practices and discharge standards in nation

wide 

storm water discharge per

mit for construction activities. 

Not applicable to a CERCLA action; howrelevant and appropriate. 

Best managem

meet discharge standards. 

Treat

ment System 

Operation 

OSHA: 29 CFR 1910.120 

Protection of workers from toxic 

metals and hydrogen sulfide gas 

during system operation, splashes during sodium hydroxide handling, and dust emissions during treatment residual handling. 

Applicable. Provide appropriate personnmonitoring, and if necessary supplied air 

RCRA: 40 CFR Part 264 or state equivalent Standards apply to treat

ment of wastes in a treat

ment facility. 

Not applicable as 

mine wastes are not su

Amend

ment. However, may be relevant 

and contingency planning as well as reco

CAA: 40 CFR Part 50 or state equivalent 

Standards that apply to the e

mission of particulates and toxic 

pollutants. 

Relevant and appropriate. Control emissusing engineering controls. May require 

Deter

mination of Cleanup 

Standards 

SARA: Section 121(d)(2)(A)(ii) SDWA: 40 CFR Part 141 

Standards that apply to pollutants in waters that 

may be used as a 

source of drinking water. 

Not applicable for re

moval actions. 

Efflu

standards specified in the action 

memora

Effluent 

must obtain MCL and to the ext

Waste Disposal 

RCRA: 40 CFR Part 261 or state equivalent 

Standards that apply to identification and characterization of wastes. 

Applicable only when treat

ment residual

relevant and appropriate for deter

minatio

appropriate on-site disposal requirements

RCRA: 40 CFR Part 262 and 263 Standards that apply to generators of hazardous waste. Applicable for off-site disposal of hazard

identification of the generator and dispos

CWA: 40 CFR Part 125 Standards for discharge of effluent to a navigable water

way. 

Requires a NPDES permit for discharge to a navigable water

way. 

Not applicable to a CERCLA action; howrelevant and appropriate. Discharge stanMCLs or MCLGs due to potential enviro

AMD = Acid 

mine drainage MCL = Maximum contaminant level 

ARAR = Applicable or relevant and appropriate require

ment MCLG = Maximum contaminant level goal 

ARD = Acid rock drainage NPDES = National Pollutant Discharge Eli

mination System 

CAA = Clean Air Act OSHA = Occupational Safety and Health Ad

ministration 

CERCLA = Co

mprehensive Environmental Response, Co

mpensation, and Liability Act RCRA = Resource Conservation and Recovery Act 

CFR = Code of Federal Regulation SARA = Superfund Amend

ments and Reauthorization Act 

C

WA = Clean Water Act S

D

WA = Safe Drinking Water Act 

47
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At Leviathan Mine, treatment residuals generated from the 

bioreactor treatment system have been determined to be nonhazardous wastes. Non-hazardous waste residuals are either 

stored or disposed of on site. 

3.11.3 Clean Air Act 

The CAA establishes national primary and secondary ambient 

air quality standards for sulfur oxides, particulate matter, 

carbon monoxide, ozone, nitrogen dioxide, and lead. It also 

limits the emission of 189 listed hazardous pollutants. States 

are responsible for enforcing the CAA. To assist in this, air 

quality control regions (ACQR) were established. Allowable 

emission limits are determined by the AQCR and AQMD 

subunits. The emission limits are established based on 

attainment of national ambient air quality standards. 

The CAA requires that TSD facilities comply with primary 

and secondary ambient air quality standards. Emissions 

resulting from solids handling during the construction and 

operation of the bioreactor treatment system may need to meet 

air quality standards. For example, dust generated during 

earthwork and residual solids handling may be regulated by a 

local AQMD. No air permits are required for the bioreactor 

treatment system operated at the Leviathan Mine Superfund 

site; however, dust emissions are limited through careful 

handling and maintaining soil moisture during construction 

and system operation. 

3.11.4 Clean Water Act 

The objective of the CWA is to restore and maintain the 

chemical, physical, and biological integrity of the nation’s 

waters by establishing Federal, State, and local discharge 

standards. If treated water is discharged to surface water 

bodies or publicly-owned treatment works (POTW), CWA 

regulations will apply. A facility discharging water to a 

navigable waterway must apply for a permit under the 

NPDES. NPDES discharge permits are designed as 

enforcement tools with the ultimate goal of achieving ambient 

water quality standards. Discharges to POTWs also must 

comply with general pretreatment regulations outlined in 40 

CFR Part 403, as well as other applicable state and local 

administrative and substantive requirements. 

Treated effluent from the bioreactor treatment system is 

discharged to Aspen Creek, if EPA interim discharge 

standards (pre-risk assessment and record of decision) are met. 

An NPDES permit is not required under CERCLA, although 

the substantive requirements of the CWA are met. 

3.11.5 Safe Drinking Water Act 

The SDWA of 1974 and the Safe Drinking Water 

Amendments of 1986 require EPA to establish regulations to 

protect human health from contaminants in drinking water. 

The law authorizes national drinking water standards and a 

joint Federal-State system for ensuring compliance with these 

standards. The National Primary Drinking Water Standards 

are found at 40 CFR Parts 141 through 149. These standards 

are expressed as maximum contaminant levels (MCL) and 

maximum contaminant level goals (MCLG). Under CERCLA 

(Section 121(d)(2)(A)(ii)), remedial actions are required to 

meet MCLs and MCLGs when relevant and appropriate. State 

drinking water requirements may also be more stringent than 

Federal standards. 

Effluent from the bioreactor treatment system discharges to 

Aspen Creek, a tributary to Leviathan Creek which is a 

potential source of drinking water. Effluent from the 

treatment system generally met the EPA interim (pre-risk 

assessment and record of decision) discharge standards; 

however, iron concentrations do not meet the Federal 

secondary MCL. Attainment of the secondary MCL for iron is 

fully achievable through addition of more sodium hydroxide 

or increased HRT; however, under the current EPA action 

memorandum, operation of the Leviathan Mine bioreactor 

treatment system to meet MCLs is not required. 

3.11.6 Occupational Safety and Health Act 

CERCLA remedial actions and RCRA corrective actions must 

be conducted in accordance with OSHA requirements detailed 

in 29 CFR Parts 1900 through 1926, in particular Part 

1910.120, which provides for health and safety of workers at 

hazardous waste sites. On-site construction at Superfund or 

RCRA corrective action sites must be conducted in 

accordance with 29 CFR Part 1926, which describes safety 

and health regulations for construction sites. State OSHA 

requirements, which may be significantly stricter than Federal 

standards, also must be met. Workers involved with the 

construction and operation of the bioreactor treatment system 

are required to have completed an OSHA training course and 

be familiar with OSHA requirements relevant to hazardous 

waste sites. Workers on hazardous waste sites must also be 

enrolled in a medical monitoring program. 

Minimum personal protective equipment (PPE) for workers at 

the Leviathan Mine site includes gloves, hard hat, steel-toe 

boots, and Tyvek® coveralls PPE, including respirators, eye 

protection, and skin protection is required when handling 

ARD and sodium hydroxide. Based on contaminants and 

chemicals used at the site, the use of air purifying respirators 

is not required. However, hydrogen sulfide gas generated by 

the bioreactors may accumulate in valve vaults. Therefore, the 

work area should be monitored for hydrogen sulfide gas and a 

blower or supplied air should be available to mitigate any 

hazards. Noise levels are generally not high, except during 

earthwork activities, which involve the operation of heavy 

equipment. During these activities, noise levels must be 

monitored to ensure that workers are not exposed to noise 

levels above a time-weighted average of 85 decibels over an 

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eight-hour day. If noise levels exceed this limit, workers are 

required to wear hearing protection. 

3.11.7 State Requirements 

State and local regulatory agencies may require permits prior 

to operation of a bioreactor treatment system. Most Federal 

permits will be issued by an authorized state agency. An air 

permit from the local AQMD may be required if air emissions 

in excess of regulatory standards are anticipated. State and 

local agencies will have direct regulatory responsibility for all 

environmental concerns. If a removal or remedial action 

occurs at a Superfund site, Federal agencies, primarily EPA, 

will provide regulatory oversight. If off-site disposal of 

contaminated waste is required, the waste must be taken to the 

disposal facility by a licensed transporter. 

3.12 Technology Applicability to Other Sites 

Bioreactor treatment of ARD at Leviathan Mine was evaluated 

for applicability to other mine sites based on the nine criteria 

used for decision making in the Superfund feasibility study 

process. The nine criteria and the results of the evaluation are 

summarized in Table 3-3. The bioreactor treatment system 

evaluated was specifically designed to treat ARD at the mine 

site to EPA interim discharge standards for aluminum, arsenic, 

copper, iron, and nickel. In addition to the five primary target 

metals of concern, EPA identified cadmium, chromium, lead, 

selenium, and zinc as secondary water quality indicator 

metals. The treatment system implemented at Leviathan Mine 

was also successful at reducing concentrations of these 

secondary metals in the ARD to below EPA interim discharge 

standards. The treatment system can be modified to treat 

wastes with varying metals concentrations and acidity. 

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Table 3-3. Feasibility Study Criteria Evaluation for the Bioreactor Treatment System at Leviathan Mine 

Criteria Technology Performance 

Overall Protection of 

Human Health and the 

Environment 

Bioreactor treatment has been proven to be extremely effective at reducing concentrations of aluminum, copper, iron, nickel, 

zinc, and other dissolved metals in ARD. The bioreactor treatment system evaluated at Leviathan Mine reduced the 

concentrations of toxic metals in ARD, which was historically released to Aspen and Leviathan Creeks, to below EPA interim 

discharge standards, which were established to protect water quality and the ecosystem in Aspen and Leviathan Creeks and 

down-stream receiving waters. Resulting metals-enriched solid wastes were determined to be non-hazardous based on State and 

Federal criteria and do not pose a threat to water quality. The solid waste can be used disposed of at an off-site non-hazardous 

waste repository or on-site as a soil amendment depending regulatory approval. 

Compliance with Applicable 

or Relevant and Appropriate 

Requirements (ARAR) 

The bioreactor treatment system is generally compliant with EPA interim (pre-risk assessment and record of decision) discharge 

standards for the Leviathan Mine site. However, the effluent from the treatment system did not always meet the EPA interim 

discharge standards for the site or the secondary maximum contaminant limit (MCL) for iron, which could easily be met with 

additional sodium hydroxide dosing. No hazardous process residuals are generated by the treatment system. 

Long-term Effectiveness 

and Performance 

A bioreactor treatment system has been in operation at Leviathan Mine since 1996. The current full-scale compost-free 

bioreactor treatment system has been in operation since the summer of 2003. By the fall of 2003, the entire ARD flow from 

Aspen Seep was being treated by the full-scale system. The treatment system has consistently met EPA interim discharge 

standards, with the exception of iron, since the fall of 2003. The treatment system operates year round; therefore, discharge of 

metals-laden ARD has not occurred from the mine site since initiation of treatment. The treatment system continues to be 

operated by UNR and ARCO. Long-term optimization of the treatment system will likely refine sodium hydroxide dosage 

necessary for iron polishing, evaluate alternate sources of base addition, optimize recirculation rates for sulfide generation, 

improve solids handling and dewatering processes, and demonstrate whether wind, solar, or a water turbine can meet the power 

required for chemical dosage and recirculation pumps. 

Reduction of Toxicity, 

Mobility, or Volume 

through Treatment 

Bioreactor treatment significantly reduces the mobility and volume of toxic metals from ARD at Leviathan Mine. The dissolved 

toxic metals are precipitated from solution, concentrated, and dewatered removing toxic levels of metals from the ARD. The 

bioreactor treatment does produce a solid waste; however, the waste generated has been determined to be non-hazardous and 

can be disposed of on site. 

Short-term Effectiveness The resulting effluent from the bioreactor treatment system does not pose any risks to human health. The sodium hydroxide 

solution, ethanol feedstock, and biologically-generated hydrogen sulfide gas, each having potentially hazardous chemical 

properties, may pose a risk to site workers during treatment system operation. Exposure to these hazardous chemicals must be 

mitigated through engineering controls and proper health and safety protocols. 

Implementability The bioreactor treatment technology relies on a relatively simple biologically-mediated sulfate reduction and metal sulfide 

precipitation process and can be constructed using readily available equipment and materials. The technology is not proprietary, 

nor does it require proprietary equipment or reagents. Once installed, the system can be optimized and maintained indefinitely. 

System startup and biological acclimation can take up to three months, depending on target metal concentrations and weather 

conditions. Routine maintenance is required, involving a weekly visit by an operator to ensure reagent and recirculation pumps 

are operational, replenish reagents as needed, and handle settled metal sulfides as needed. The remoteness of the site also 

necessitates organized, advanced planning for manpower, consumables, and replacement equipment and supplies. 

Cost Total first year cost for the construction and operation of the bioreactor treatment system operated in gravity flow mode was 

$941,248 and $962,471 operated in recirculation mode. The operation and maintenance costs associated with the treatment 

system ranged from $15.28 (recirculation) to $16.54 (gravity flow) per 1,000 gallons at an average ARD flow rate of 35.75 liters 

per minute. The operational costs were incurred during a research mode of operation. Once the system is optimized an 

operations mode will be implemented which will reduce operational labor and reagent costs. Costs for construction and O&M 

of the treatment system are dependent on local material, equipment, consumable, and labor costs, required discharge standards, 

and hazardous waste classification requirements and disposal costs (if necessary). 

Community Acceptance The bioreactor treatment technology presents minimal to no risk to the public since all system components are located at and 

treatment occurs on the Leviathan Mine site, which is a remote, secluded site. Hazardous chemicals used in the treatment system 

include sodium hydroxide, ethanol, and for the short term diesel fuel. These chemicals pose the highest risk to the public during 

transportation to the site by truck. The diesel generator creates the most noise and air emissions at the site; again, because of the 

remoteness of the site, the public is not impacted. Alternative sources of power are being pilot tested at the site to eliminate the 

need for the diesel powered generator. 

State Acceptance ARCO, in concurrence with the State of California, selected, constructed, and is currently operating a full-scale bioreactor 

treatment system at Leviathan Mine, which indicates the State’s acceptance of the technology to treat ARD. The bioreactor 

treatment system is the only technology operating year round at the mine site. All other treatment systems at the mine site 

shutdown for the winter, requiring long-term storage or discharge of ARD and AMD. 

AMD = Acid mine drainage EPA = U.S. Environmental Protection Agency 

ARD = Acid rock drainage TSD = Treatment, storage, and disposal 

ARCO = Atlantic Richfield Company 

50
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SECTION 4 

ECONOMIC ANALYSIS 

This section presents an economic analysis of the compostfree bioreactor treatment system used to treat ARD with 

chemistry, flow rates, and site logistical issues similar to 

those at the Leviathan Mine. 

4.1 Introduction 

The information presented in this section has been derived 

from (1) observations made and experiences gained during 

the technology evaluation, (2) data compiled from the 

Leviathan Mine Site Engineering Evaluation/Cost Analysis 

(EE/CA) (EMC2

 2004a), and (3) personal communications 

with Dr. Tim Tsukamoto (Tsukamoto 2005b). The costs 

associated with designing, constructing, and operating the 

bioreactor treatment system in a research mode have been 

broken down into the following 10 elements and are 

assumed to be appropriate for extrapolation to other mine 

sites with similar conditions. Because of the robust system 

design and a research mode of operation, a less robust 

system and reduced operational labor may be sufficient for 

long term operation. 

Each cost element is further broken down to document 

specific costs associated with each treatment system. 

Demobilization is not addressed as the system operates on a 

year round basis. 

1) Site Preparation 

2) Permitting and Regulatory Requirements 

3) Capital and Equipment 

4) System Startup and Acclimation 

5) Consumables and Rentals 

6) Labor 

7) Utilities 

8) Residual Waste Handling and Disposal 

9) Analytical Services 

10) Maintenance and Modifications 

This economic analysis is based primarily on data collected 

during the mid-November 2003 through mid-May 2004 

evaluation period for the bioreactor treatment system 

operated in gravity flow mode and the mid-May 2004 

through July 2005 evaluation period for the Bioreactor 

treatment system operated in recirculation mode. During 

the 2003-2004 evaluation period the bioreactor treatment 

system operated in gravity flow mode for twenty-six weeks 

(November 14, 2003 to May 11, 2004) and treated 9.24 

million liters of ARD from Aspen Seep at an average rate of 

31.8 L/min. The bioreactor treatment system also operated 

in recirculation mode for sixty-four weeks (May 12, 2004 to 

July 31, 2005), treating 22.1 million liters of ARD from 

Aspen Seep at an average rate of 34.2 L/min. Costs are 

presented for each mode of system operation over their 

respective periods of operation. The cost per 1,000 L of 

water treated is presented as well as the present worth of the 

cumulative variable costs over 5, 15, and 30 years of 

treatment. A comparison of treatment costs between the 

two modes of system operation will also be discussed. 

Section 4.2 presents a cost summary and identifies the major 

expenditures for each mode of treatment system operation 

(costs are presented in 2005 dollars). As with any cost 

analysis, caveats may be applied to specific cost values 

based on associated factors, issues and assumptions. The 

major factors that can affect estimated costs are discussed in 

Section 4.3. Assumptions used in the development of this 

economic analysis are identified in Section 4.4. Detailed 

analysis of each of the 10 individual cost elements for both 

modes of treatment system operation is presented in 

Section 4.5. 

4.2 Cost Summary 

The initial fixed costs to construct bioreactor treatment 

system are $836,617 for the treatment system operated in 

gravity flow mode, and $864,119 for the treatment system 

operated in recirculation mode. Fixed costs consist of site 

preparation, permitting, and capital and equipment costs. 

Site preparation includes system design, project and 

construction management, and preconstruction site work. 

Capital and equipment costs include all equipment, 

materials, delivery, earthwork, and initial system 

51
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construction. Equipment and materials include reagent 

storage tanks, pumps, piping, valves, pond liners, rock 

substrate, pH control equipment, automation equipment and 

satellite phone for reliable communication at a remote site. 

A breakdown of fixed costs for each system is presented in 

Section 4.5. 

Variable costs to operate the bioreactor treatment system are 

$82,155 in gravity flow mode and $75,877 in recirculation 

mode. Variable costs consist of system startup and 

acclimation, consumable and rentals, labor, utilities, waste 

handling and disposal, analytical services, and maintenance 

and system modifications. A breakdown of variable costs 

for each system is presented in Section 4.5. 

The total first year cost to design, construct, and operate the 

treatment system; yearly operational costs for each mode of 

treatment system operation; and the cumulative 5-year, 15­

year, and 30-year treatment costs for each mode of 

treatment system operation are summarized in Table 4-1. 

Table 4-1. Cost Summary for Each Mode of Operation 

Description 

Gravity 

Flow 

Recirculation 

Total First Year Cost $941,248 $962,472 

First Year Cost per 1,000 Gallons Treated $189.54 $193.81 

Total Variable Costs $82,155 $75,877 

Variable Costs per 1,000 Gallons Treated $16.54 $15.28 

Cumulative 5-Year Total Variable Cost 

(Present Worth at 7% Rate of Return) $343,834 $321,654 

Cumulative 15-Year Total Variable Cost 

(Present Worth at 7% Rate of Return) $764,950 $715,681 

Cumulative 30-Year Total Variable Cost 

(Present Worth at 7% Rate of Return) $1,045,005 $977,880 

4.3 Factors Affecting Cost Elements 

A number of factors can affect the cost of treating ARD 

with the bioreactor treatment system. These factors 

generally include flow rate, concentration of contaminants, 

discharge standards, physical site conditions, geographical 

site location, and type and quantity of residuals generated. 

Increases in flow rate due to spring melt will slightly raise 

operating costs of each system due to proportional increases 

in ethanol and sodium hydroxide consumption. Flow rate 

increases can also impact fixed costs (number and size of 

the bioreactors and settling ponds) when the minimum 

system or unit operation HRT is not sufficient to meet 

discharge standards. 

Operating costs may be slightly impacted by seasonal 

increases in contaminant concentration. Increases in metals 

concentrations generally require additional HRT to attain 

discharge standards. Higher contaminant concentrations 

may also change the classification of a residual waste from a 

non-hazardous to a hazardous waste, requiring increased 

disposal costs. Restrictive discharge standards impact both 

fixed and variable costs. System designers and operators 

may be forced to extend system and unit operation HRTs 

(number and size of bioreactors and settling ponds) and 

increase sodium hydroxide dosage to meet stricter discharge 

requirements. 

Physical site conditions may impact site preparation and 

construction costs associated with excavation and 

construction of the bioreactors and settling ponds. Cold 

climates may limit site access and decrease the activity of 

sulfate-reducing bacteria, requiring bioreactors with 

extended HRT. The characteristics of the residual solids 

produced during treatment may greatly affect disposal costs, 

where production of hazardous solids will require off site 

disposal at a permitted TSD facility. 

4.4 Issues and Assumptions 

The following assumptions have been used in the 

development of this economic analysis: 

• Standard sized tanks are used for ethanol and 

sodium hydroxide storage. 

• An appropriate staging area is available for 

equipment staging, setup and delivery. 

• Construction and maintenance of access roads is no 

required. 

• The treatment system will be operated year round. 

• The treatment system will be operated unmanned, 

with the exception of a weekly maintenance visit. 

• All site power is obtained from a water turbine and 

battery system, with a diesel generator as backup. 

• Utility water can be obtained on site. 

• Non-hazardous sludge will be disposed of at an 

off-site landfill or at an existing on-site repository. 

• The site is located within 400 kilometers of an offsite landfill. 

• Permitting for the treatment system is not required 

because of CERCLA status. 

• Treatment goals and discharge standards apply to 

those presented in Table 2-4. 

• Samples are collected and analyzed weekly to 

verify attainment of discharge standards. 

4.5 Cost Elements 

Each of the 10 cost elements identified in Section 4.1 has 

been defined and the associated costs for each treatment 

system element presented below. The cost elements for the 

each mode of bioreactor treatment system operation, at an 

average flow rate of 35.75 L/min, are summarized in Table 

4-2. Cost element details for each mode of treatment system 

operation are presented in Appendix C. 

52
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Table 4-2. Summary of Cost Elements 4.5.1 Site Preparation 

Description 

Gravity 

Flow Recirculation 

Site Preparation $288,185.95 $309,568.00 

Permitting and Regulatory 

Requirements $0.00 $0.00 

Compost-Free Bioreactor 

Treatment System $495,791.00 $501,911.00 

Equipment Mobilization/ 

Demobilization $73,550.00 $73,550.00 

Pond and Pipe Trench Earthwork $136,442.00 $136,442.00 

Installation of Pond Liners, Stairs, 

and Decant Structures $63,756.00 $63,756.00 

Installation of Distribution Piping 

and Valve Vaults $149,263.00 $149,263.00 

Placement of Bioreactor Substrate $47,173.00 $47,173.00 

Erosion Control and 

Revegetation/Reseeding $10,907.00 $10,907.00 

Recirculation Pump and Piping $0.00 $6,120.00 

Water Turbine and Storage Batteries $14,700.00 $14,700.00 

Reagent Storage and Distribution $35,200.00 $35,200.00 

Ethanol Storage Tank and 

Delivery System $13,400.00 $13,400.00 

Sodium Hydroxide Storage Tank 

and Delivery System $15,800.00 $15,800.00 

Make up Water Storage Tank and 

Delivery System $2,000.00 $2,000.00 

Reagent Storage Area Fencing $4,000.00 $4,000.00 

Automation $15,945.00 $15,945.00 

Remote Monitoring/Alarm System $9,742.50 $9,742.50 

pH Controller System $6,202.50 $6,202.50 

Communications $1,495.00 $1,495.00 

Total Capital and Equipment Cost $548,431.00 $554,551.00 

Total Fixed Cost $836,616.95 $864,119.00 

System Start-up and Acclimation $22,476.00 $22,476.00 

Consumables and Rentals $26,854.15 $25,046.35 

Labor $28,198.24 $28,198.24 

Utilities $8,348.00 $8,348.00 

Residual Waste Handling and 

Disposal $14,315.00 $9,844.00 

Analytical Services $4,440.00 $4,440.00 

Maintenance and Modifications $16,200.00 $21,200.00 

Total 1st Year Variable Costs $104,613.39 $98,352.59 

Recurring Variable Costs $82,155.39 $75,876.59 

Periodic Variable Costs $16,200.00 $21,200.00 

Total 1st Year Cost s $941,248.34 $962,471.59 

Total 1st Year Costs/1,000-gallons $189.54 $193.81 

Total Variable Costs/1,000-gallons $16.54 $15.28 

Cumulative 5-Year Total Variable 

Costs (Present Worth at 7 Percent 

Rate of Return) 

$343,834.00 $321,654.00 

Cumulative 15-Year Total Variable 

Costs (Present Worth at 7 Percent 

Rate of Return) 

$764,950.00 $715,681.00 

Cumulative 30-Year Total Variable 

Costs (Present Worth at 7 Percent 

Rate of Return) 

$1,045,005.00 $977,880.00 

Site preparation for the treatment system addresses system 

design, construction management, project management, and 

preconstruction site work. System design is estimated at 20 

percent of the capital and equipment cost for a treatment 

system. Construction management is estimated at 15 

percent and project management at 10 percent of the capital 

and equipment costs for a treatment system (US Army Corp 

of Engineers [USACE] 2000). Preconstruction site work 

includes clearing trees and vegetation, chipping cleared 

vegetation, debris removal, and topsoil removal and 

stockpiling for site restoration purposes. The total site 

preparation cost for the bioreactor treatment system 

operated in gravity flow mode is $288,186; while the total 

site preparation cost for the treatment system operated in 

recirculation mode is $309,568. The difference in the costs 

is attributed directly to the capital costs associated with the 

recirculation system as the majority of the site preparation 

costs are a percentage of the capital costs. 

4.5.2 Permitting and Regulatory Requirements 

Permitting and regulatory costs vary depending on whether 

treatment occurs at a CERCLA-lead or a state- or local 

authority-lead site. At CERCLA sites such as Leviathan 

Mine, removal and remedial actions must be consistent with 

environmental laws, ordinances, and regulations, including 

Federal, State, and local standards and criteria; however, 

permitting is not required. 

At a state- or local authority-lead site, a NPDES permit, an 

air permit, and a storm water permit will likely be required 

as well as additional monitoring, which can increase 

permitting and regulatory costs. National Environmental 

Policy Act or state equivalent documentation may also be 

required for system construction. For a treatment system 

similar to those described here, constructed at a state- or 

local authority-lead site, permitting and regulatory costs are 

estimated to be $50,000. 

4.5.3 Capital and Equipment 

Capital costs include earthwork and pond construction; 

delivery and installation of piping, pond liners, substrate; 

and delivery and installation of reagent storage tanks, 

pumps, and automation equipment. Equipment and 

materials include reagent storage tanks, pumps, piping, 

valves, pond liners, rock substrate, pH control equipment, 

automation equipment and satellite phone for reliable 

communication at a remote site. This analysis assumes that 

an area of at least 3,000 to 4,000 square meters is available 

for bioreactor and settling pond construction, reagent 

storage tanks, support equipment, and staging supplies. 

53
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Total capital expenditures for the bioreactor treatment 

system operated in gravity flow mode are $548,431 and 

$554,551 for the system operated in recirculation mode. 

System construction involves equipment mobilization/ 

demobilization ($73,550), pond and pipe trench excavation 

($136,442), installation of pond liners, stairs, and decant 

structures ($63,756), installation of distribution piping and 

valve vaults ($149,263), placement of bioreactor rock 

substrate ($47,173), erosion control/reseeding ($10,907), 

and installation of a water turbine and battery to supply 

power ($14,700). Ethanol and sodium hydroxide storage 

tanks, delivery systems, and containment are also required 

at a cost of $35,200. Automation components of the system 

include an automatic pH control system and a SCADA 

remote monitoring/alarm system at a cost of approximately 

$15,945, including installation. A satellite phone to provide 

reliable communication at a remote location is estimated at 

$1,495. The cost for construction of the treatment system 

operated in gravity flow mode is $495,791. An additional 

$6,120 is required for construction of the recirculation 

system and is associated with the installation of the 

recirculation pump and bypass and return pipelines. 

4.5.4 System Startup and Acclimation Costs 

System start-up and acclimation includes the labor to setup 

pumps and pipes, fill and recirculate ARD within the 

system, adjust system hydraulics and reagent dosages, and 

optimize the operational HRT to meet discharge standards. 

System startup and acclimation occurs once after initial 

system construction as the system is design to operate year 

round, even in extremely cold weather. 

The estimated start up cost for the bioreactor treatment 

system is $22,476. It is assumed that start up of the 

treatment system will take a two-person crew two weeks to 

complete; while acclimation will require only one person 

visiting the system 3 days a week over a 10 week period. 

Startup and acclimation costs for this system are less than 

the active treatment system due to the simplicity of system 

design. However, acclimation does require at least 2 

months before the system is able to meet discharge 

standards. 

4.5.5 Consumables and Supplies 

Consumables and rentals for the bioreactor treatment system 

consist of chemicals and supplies required to treat ARD, 

including ethanol and sodium hydroxide, health and safety 

equipment, air and water chemistry monitoring equipment, 

and storage Connex rental. Total consumable and rental 

costs for the bioreactor treatment system are $26,854 for 

gravity flow operations and $25,046 for operation in 

recirculation mode. 

The two largest consumable expenditures are ethanol and 

sodium hydroxide. During gravity flow operations, ethanol 

was consumed at a rate of approximately 0.43 ml/L of ARD 

treated at a cost of $5,655; while sodium hydroxide was 

consumed at a rate of approximately 1.1 ml/L of ARD 

treated at a cost of $4,963. During operation in recirculation 

mode, ethanol was consumed at a rate of approximately 0.5 

ml/L of ARD treated at a cost of $6,575; while sodium 

hydroxide was consumed at a rate of approximately 0.5 

ml/L of ARD treated at a cost of $2,235. 

The largest rental cost throughout the year is for a hydrogen 

sulfide gas meter and a water quality meter. The meters are 

necessary to safely access sampling locations and conduct 

internal system monitoring of pH, dissolved oxygen, ORP, 

temperature, and the specific conductance of water within 

the bioreactors and settling ponds. The annual cost for the 

meters, based of four site visits per month is $12,000. 

Equipment storage from year to year is also required at a 

cost of $3,900. A mobilization and set-up fee is included in 

the Connex rental. Purchase of air and water quality meters 

as well as a storage Connex should also be considered at a 

substantial long term cost savings. 

4.5.6 Labor 

Labor costs for the long-term O&M of the bioreactor 

treatment system include the field personnel necessary to 

operate the system, address day-to-day maintenance issues, 

collect weekly discharge monitoring samples, monitor unit 

operation chemistry and flow rates, adjust reagent dosages, 

adjust unit operation HRT, and adjust recirculation rates. 

Labor associated with system startup and acclimation is 

included in Section 4.5.4. 

Due to the passive nature of the treatment system, minimal 

O&M labor is necessary in comparison to an active 

treatment system. It is assumed that long-term O&M of the 

treatment system will require only one person visiting the 

system 1 day a week over the course of a year. The field 

technician labor cost for O&M of the bioreactor treatment 

system is $23,375. An additional labor cost of $4,823 is 

required for project management and administrative support. 

4.5.7 Utilities 

Due to the remote nature of the site, utilities are not 

available. A water turbine and storage battery may be used 

to provide power. Utility costs generally consist of the cost 

to lease a 3kW backup generator, generator fuel, seasonal 

portable toilet rental, and satellite phone service. Water is 

gravity fed to the treatment system from upper Aspen Creek 

via the water turbine outfall. SCADA service through a 

satellite uplink may also be used to monitor water chemistry 

and control dosing of ethanol and sodium hydroxide to the 

54
_______________________________________________________________________________________ 

bioreactor treatment system. Total utility costs to support 

operation of the treatment system in either mode are $8,348. 

4.5.8 Residual Waste Handling and 

Disposal 

The bioreactor treatment system produces metal sulfide 

sludge. Solids accumulation in the settling ponds occur at a 

slow enough rate to require removal once every two to three 

years; however, it is removed annually to allow extended 

HRT. Removal of sludge from the settling ponds and bag 

filtration is performed in late summer to allow time for 

profiling and disposal. The cost to dewater the sludge from 

the settling ponds, using eight to ten bag filters, is 

approximately $3,795. The bioreactor treatment system 

operated in gravity flow mode generates approximately 

8 dry tons (40 wet tons at 80 percent moisture content) of 

bag filter solids over the course of a year, while 

recirculation mode generates only 4.6 dry tons (23 wet tons 

at 80 percent moisture content) 

Bag filter solids were evaluated for hazardous waste 

characteristics. The bag filter solids were determined to be 

non-hazardous. The solids may be disposed of off-site in a 

non-hazardous waste repository at a total cost of $10,520 for 

gravity flow operations and $6,049 for recirculation 

operations. Non-hazardous solid waste may also be 

disposed of on site after a designated repository has been 

identified. 

4.5.9 Analytical Services 

Analytical services consist of weekly sampling of the 

bioreactor treatment system to verify compliance with 

discharge standards. One effluent grab sample is collected 

each week and analyzed for metals using EPA Methods 

6010B and 7470 to demonstrate compliance with discharge 

standards. The cost for weekly analytical services is $4,160 

for the bioreactor treatment system. 

A grab sample of bag filter solids is also collected to 

support waste characterization, profiling, and disposal. 

Each grab solid sample is analyzed for metals using EPA 

Methods 6010B and 7471 and leachable metals using the 

EPA Methods 1311, 6010B, and 7470 for comparison to 

Federal RCRA and TCLP criteria and California DI 

WET/EPA Method 6010B for comparison to State TTLC 

and STLC criteria. Analysis of one composite bag filter 

solids sample generated during solids filtration is required at 

a cost of $280. 

4.5.10 Maintenance and Modifications 

Maintenance and modifications costs include regular 

equipment replacement due to wear and tear. Equipment 

expected to require replacement includes reagent pumps and 

delivery lines, recirculation pump, water turbine, and 

storage batteries. 

Reagent pumps and delivery lines ($2,000) should be 

replaced every two years. The recirculation pump ($5,000) 

and water turbine storage battery ($5,200) may require 

replacement every five years. It is estimated that the water 

turbine ($9,000) may require replacement on a 20 year 

schedule. The annualized equipment replacement cost for 

the bioreactor treatment system operated in gravity flow and 

recirculation modes is approximately $2,490 and $3,490, 

respectively. 

55
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SECTION 5 

DATA QUALITY REVIEW

SITE demonstration samples were collected in accordance 

with the 2003 TEP/QAPP (Tetra Tech 2003). As part of the 

quality assurance/quality control (QA/QC) requirements 

specified in the TEP/QAPP, any deviations from the sampling 

plan, such as missed sampling events, changes in sampling 

locations, or changes in analytical methods, were documented 

throughout the duration of the demonstration and are 

presented in Section 5.1. Documentation of these deviations is 

important because of the potential effects they have on data 

quality and on the ability of the data to meet the project 

objectives. 

As part of the QA/QC data review, sample delivery groups 

(SDG) received from the laboratory underwent data validation 

through a third-party validator to ensure that the data 

generated is of a quality sufficient to meet project objectives. 

As specified in the TEP/QAPP, data packages underwent 10 

percent full validation in accordance with EPA validation 

guidance (EPA 1995). A summary of the data validation 

performed on the bioreactor treatment technology SITE 

demonstration data is presented in Section 5.2. 

5.1 Deviations from TEP/QAPP 

Due to various operating issues, several changes were required 

in the sampling of the bioreactor treatment system during the 

SITE demonstration. Deviations from the TEP/QAPP related 

to each mode of treatment system operation were documented 

throughout the duration of the SITE demonstration and are 

presented below. 

• The sample frequency was reduced from every two 

weeks to once a month, at the direction of the EPA 

task order manager (TOM), to extended the 

demonstration period over two successive winters of 

system operation. 

• Began analysis of samples collected from the influent 

(S3) and effluent (S4) of Bioreactor No.1 for sulfate, 

TSS, TDS, and alkalinity after system acclimation 

period. The data will be used to allow independent 

evaluation of each bioreactor, rather than a 

combination of the two bioreactors. 

• Began analysis of samples collected from the influent 

(S5) and effluent (S7) of the settling ponds for sulfate 

at the start of the demonstration to determine if 

additional sulfate reduction is occurring in the 

settling and flushing ponds. 

• Began analysis of samples collected from the influent 

(S5) and effluent (S7) of the settling ponds for 

alkalinity after system acclimation to evaluate the 

source of alkalinity observed in system effluent. 

• Collected an unsettled solids slurry sample from 

settling pond (S14) to evaluate changes in settling 

pond chemistry after reconfiguration of the system 

for recirculation operation. 

• Collected a solids composite sample (S15) from one 

of the bag filters used to dewater sludge from the 

settling pond to assess the content and leachability of 

metals in dewatered treatment system sludge. The 

solids sample was analyzed for total metals and 

metals after TCLP extraction, SPLP extraction, and 

California DI WET extraction. The solids sample 

was also analyzed for total solids and percent 

moisture in order to estimate the likely increase in 

metals concentration after drying. 

• Samples were not collected from the settling pond 

outfall (S6) due to lack of accessibility. The system 

operator discharged directly from the settling pond to 

the flushing pond to allow extended settling. 

Therefore, effluent from the flushing pond (S7) 

represents the treatment effectiveness of both ponds. 

• Aqueous samples were not collected from the 

flushing pond (S11) because the extended HRT of the 

pond limited changes in pond chemistry. In addition, 

the pond surface was frozen over for at least a onethird of the demonstration period. Instead, the pond 

effluent (S7) was used to represent changes in pond 

chemistry. 

56
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• A sample was not collected at the system point of 

discharge on February 3, 2005 due to lack of 

accessibility (iced over), instead the effluent from the 

flushing pond (S7) was used to represent the system 

effluent for the day. 

• Samples of flushed metal sulfide precipitate were not 

collected from the two bioreactors (S8 and S9) 

because not enough solids have built up in the 

bioreactors to require flushing. 

5.2 Summary of Data Validation and PARCC 

Criteria Evaluation 

The critical data quality parameters evaluated during data 

validation include precision, accuracy, representativeness, 

completeness, and comparability (PARCC). Evaluation of 

these critical parameters provides insight on the quality of the 

data and is essential in determining whether the data is of 

sufficient quality to meet project objectives. A summary of 

the data validation for the SITE demonstration data and an 

evaluation of the PARCC parameters for the primary target 

analytes are presented below. 

Based on data validation, no metals results were rejected in the 

samples analyzed. However, some metals data were qualified 

as estimated based on other QC issues. QC issues resulting in 

qualified data typically consisted of problems with calibration 

and method blank contamination, inductively coupled plasma 

(ICP) interference check sample analysis, percent recovery 

and relative percent difference (RPD) values outside of 

acceptable values, and ICP serial dilution problems. An 

evaluation of the PARCC parameters follows. 

Precision: Precision for the SITE demonstration data was 

evaluated through the analysis of matrix duplicates (MD) 

samples for metals. The precision goal for MD samples was 

established at less than or equal to 25 percent RPD. Over the 

duration of the SITE demonstration, a total of 13 aqueous 

samples and two sludge samples were collected from the 

treatment system and analyzed in duplicate. Where one or 

both metals results in a duplicate pair were below the practical 

quantitation limit (PQL) or not detected, the RPD was not 

calculated. Out of the five primary target metals and the five 

secondary water quality indicator metals, none of the metals 

exceeded the 25 percent RPD criteria. Corresponding metals 

data for associated samples within each SDG were qualified as 

estimated based on duplicate precision problems; however, no 

data was rejected. 

Accuracy: Accuracy for the SITE demonstration data was 

evaluated through the analysis of matrix spike (MS) samples 

for the metals analyses. The accuracy goal for MS samples 

was established at 75 to 125 percent for percent recovery. 

Over the duration of the SITE demonstration, a total of 13 

aqueous samples were collected from the treatment system 

and analyzed as MS samples. In addition, two sludge samples 

and six metals leachate samples were analyzed as MS 

samples. Potassium in one water sample and in one leachate 

sample was qualified based on MS recovery problems. 

Representativeness: Representativeness expresses the degree 

to which sample data accurately and precisely represent the 

characteristics of a population, parameter variations at a 

sampling point, or an environmental condition that they are 

intended to represent. Representativeness is a qualitative 

parameter; therefore, no specific criteria must be met. 

Representative data were obtained during the SITE 

demonstration through selection of proper sampling locations 

and analytical methods based on the project objectives and 

sampling program described in Section 2.3. As specified in 

the TEP/QAPP, proper collection and handling of samples 

avoided cross contamination and minimized analyte losses. 

The application of standardized laboratory procedures also 

facilitated generation of representative data. 

To aid in the evaluation of sample representativeness, 

laboratory-required method blank samples were analyzed and 

evaluated for the presence of contaminants. Sample data 

determined to be non-representative by comparison with 

method blank data was qualified, as described earlier in this 

section. The data collected during the SITE demonstration are 

deemed representative of the chemical concentrations, 

physical properties, and other non-analytical parameters that 

were being sampled or documented. No metals data were 

rejected. 

Completeness: Completeness is a measure of the percentage 

of project-specific data deemed valid. Valid data are obtained 

when samples are collected and analyzed in accordance with 

QC procedures outlined in the TEP/QAPP and when none of 

the QC criteria that affect data usability are significantly 

exceeded. Other factors not related to the validity of the data 

can also affect completeness, such as lost or broken samples, 

missed sampling events, or operational changes by the system 

operator. 

Due to the time required to acclimate the bioreactor treatment 

system in cold weather conditions, the original sampling 

frequency of twice a month during the acclimation period was 

not followed. Instead, a monthly sampling frequency was 

followed toward the end of the acclimation period. A monthly 

sampling frequency was followed for the duration of the 

demonstration, unless the site was inaccessible due to winter 

storms. A monthly sampling frequency was selected to 

provide a long-term evaluation of the treatment system over 

two winters. 

From November 2003 through mid-May 2004, the bioreactor 

treatment system was evaluated based on the original system 

configuration. In mid-May 2004, UNR and ARCO modified 

the operation of the system to include introduction of system 

influent to the settling pond, contact of ARD influent with 

57
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sulfide-rich bioreactor effluent in the settling pond, and 

recirculation of settling pond effluent to the head of Bioreactor 

No.1. The treatment system was operated in recirculation 

mode from mid-May 2004 through the end of the 

demonstration period in July 2005. 

Evaluation of the system during recirculation operation 

represented a significant departure from the TEP/QAPP. The 

original sample design was reviewed and retained and only 

modified where a sampling location was no longer valid or 

duplicative. The monthly evaluation of the treatment system 

in both modes of operation (gravity-flow and recirculation), 

though a modification in scope and frequency, was also fully 

achieved. 

As specified in the TEP/QAPP, the project completeness goal 

for the SITE demonstration was 90 percent. Based on an 

evaluation of the data that was collected and analyzed and 

other documentation, completeness for the project was greater 

than 99 percent. Deviations from the TEP/QAPP due to 

unplanned changes in system operation by the system operator 

did not impact the validity of the data. Instead, the unplanned 

changes provided an opportunity to evaluate different modes 

of system operation and system response to changes in flow 

rate and HRT. 

Comparability: The comparability objective determines 

whether analytical conditions are sufficiently uniform 

throughout the duration of the project to ensure that reported 

data are consistent. For the SITE demonstration, the 

generation of uniform data was ensured through adherence of 

the contracted laboratory to specified analytical methods, QC 

criteria, standardized units of measure, and standardized 

electronic deliverables in accordance with the TEP/QAPP. 

Comparability for the SITE demonstration data was also 

ensured through third party validation. As a result of these 

efforts, no data comparability issues were documented by the 

project team for this project. 

58
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SECTION 6 

TECHNOLOGY STATUS 

The technology associated with the compost-free bioreactor 

treatment system is not proprietary, nor are proprietary 

reagents or equipment required for system operation. The 

treatment system has been demonstrated at full-scale and is 

currently operational at Leviathan Mine. The treatment 

system is scalable, requiring an increase in the size or number 

of bioreactors and settling ponds to achieve the required unit 

operation and system HRT necessary for sulfide generation, 

metal-sulfide contact, and precipitate settling. The bioreactor 

treatment system at Leviathan Mine has been operated at 

flows ranging from 25 to 91 L/min. 

The treatment system is undergoing continuous refinement 

and optimization to reduce the quantity of ethanol and base 

required, evaluate alternate sources of base addition, reduce 

recirculation rates, improve attainment of discharge standards 

for iron and selenium, and improve solids handling and 

dewatering processes. The power required for recirculation of 

water to the head of the system is currently provided by a 

generator. In 2006, alternative methods of power generation 

will be investigated. Because of the success of compost-free 

bioreactor treatment system at Leviathan Mine, ARCO will 

continue to use this technology to treat ARD at the Aspen 

Seep and are also evaluating the potential effectiveness, 

implementability, and costs for treatment of other ARD 

sources at the mine site. 

Application of the technology to other ARD-impacted sites 

does not require a pilot-scale system because the uncertainties 

related to carbon availability and sulfate reduction efficiency, 

matrix compaction, and solids flushing associated with 

compost and wood chip matrices are essentially eliminated. A 

simple bench test can be used to optimize the ethanol dose 

necessary to reduce sulfate, to optimize the base type and dose 

required to neutralize acidity, and to determine the volume of 

metal sulfide precipitate that will be generated. 

59
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REFERENCES CITED 

Analyze-It. 2004. Analyze-It Statistical Software. 

Version 1.71. September. Available on-line: 

http://www.analyse-it.com/ 

California Regional Water Quality Control Board – Lahontan 

Region (RWQCB). 1995. “Leviathan Mine 5-year Work 

Plan.” July. 

EMC2

. 2004. “Engineering Evaluation/Cost Analysis for 

Leviathan Mine.” March 31, 2004. 

State of California. 2004. “Waste Extraction Test.” 

California Code of Regulations. Title 22, Division 4­

Environmental Health. July. 

Tetra Tech. 2003. “2003 Technology Evaluation Plan/ 

Quality Assurance Project Plan, Leviathan Mine 

Superfund Site.” Alpine County, California. August. 

Tetra Tech. 2006. “Draft Technology Evaluation Report Data 

Summary, Demonstration of Compost-Free Bioreactor 

Treatment Technology, Leviathan Mine Superfund Site.” 

Alpine County, California. January. 

Tsukamoto, Tim. 2004. “Data Summary Report for 

Bioreactors at the Leviathan Mine Aspen Seep 2003.” 

April. 

Tsukamoto, Tim. 2005a. “Data Summary Report for 

Bioreactors at the Leviathan Mine Aspen Seep 2004.” 

August. 

Tsukamoto, Tim. 2005b. Personal communications regarding 

bioreactor treatment system construction and operating 

costs. November. 

U.S. Army Corp of Engineers (USACE). 2000. A Guide to 

Developing and Documenting Cost Estimates during the 

Feasibility Study. July 2000. 

U.S. Environmental Protection Agency (EPA). 1995. “CLP 

SOW for Inorganics Analysis, Multi-Media, 

Multi-Concentration.” Document Number ILM04.0. 

EPA. 1997. Test Methods for Evaluating Solid 

Waste/Chemical Methods, Laboratory, Volume 1A 

through 1C, and Field Manual, Volume 2. SW-846, 

Third Edition (Revision III). Office of Solid Waste and 

Emergency Response. 

EPA. 2000. “Guidance for Data Quality Assessment: 

Practical Methods for Data Analysis.” EPA QA/G-9. 

EPA/600/R-96/084. 

EPA. 2002. “Remedial Action Memorandum: Request for 

Approval of Removal Action at the Leviathan Mine, 

Alpine County, CA.” From: Kevin Mayer, RPM, Site 

Cleanup Branch, EPA Region 9, To: Keith Takata, 

Director, Superfund Division, USEPA. July 18. 

EPA. 2004. ProUCL Version 3.0. EPA Statistical Program 

Package. April. Available on-line: 

http://www.epa.gov/nerlesd1/tsc/form.htm 

60
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APPENDIX A 

SAMPLE COLLECTION AND ANALYSIS TABLES 

61
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Table A-1. Sa

mple Register for the Co

mpost-Free Bioreactor Treat

ment Syste

m, Gravity Flow Operations 

Sa

mple ID Date Location Filtered? 

Project 

Objective 

Total 

Metals Sulfate Alkalinity 

3-AW-01-5-S01-

W-C 11/14/2003 Syste

m Influent at 

Weir No P1, P2, SG1, SG2, SG6 X X X 

3-AW-01-5-S01-

W-C-F 11/14/2003 Syste

m Influent at 

Weir Yes P1, P2 X 

3-AW-01-5-S02-

W-C 11/14/2003 System 

Effluent No P1, P2, SG1, SG2, SG3, SG6 X X X 

3-AW-01-5-S02-

W-C-F 11/14/2003 Syste

m Effluent Yes P1, P2 X 

3-AW-01-5-S03-W-C 11/14/2003 Bioreactor 1 Influent No SG1, SG6 X X 3-AW-01-5-S03-W-C-F 11/14/2003 Bioreactor 1 Influent Yes SG1, SG6 X 3-AW-01-5-S04-W-C 11/14/2003 Bioreactor 1 Effluent No SG1, SG6 X X 3-AW-01-5-S04-W-C-F 11/14/2003 Bioreactor 1 Effluent Yes SG1, SG6 X 3-AW-01-5-S05-W-C 11/14/2003 Bioreactor 2 Effluent No SG1, SG3, SG6 X X 3-AW-01-5-S05-W-C-F 11/14/2003 Bioreactor 2 Effluent Yes SG1, SG3, SG6 X 3-AW-01-5-S07-

W-C 11/14/2003 Pond 4 Effluent Pipe No SG1, SG3, SG6 X X 

3-AW-01-5-S07-

W-C-F 11/14/2003 Pond 4 Effluent Pipe Yes SG1, SG3, SG6 X 

3-AW-03-2-S01-

W-C 11/25/2003 Syste

m Influent at Weir No P1, P2, SG1, SG2, SG6 X X X 

3-AW-03-2-S01-

W-C-F 11/25/2003 Syste

m Influent at 

Weir Yes P1, P2 X 

3-AW-03-2-S02-

W-C 11/25/2003 System 

Effluent No P1, P2, SG1, SG2, SG3, SG6 X X X 

3-AW-03-2-S02-

W-C-F 11/25/2003 Syste

m Effluent Yes P1, P2 X 

3-AW-03-2-S03-W-C 11/25/2003 Bioreactor 1 Influent No SG1, SG6 X X 3-AW-03-2-S03-W-C-F 11/25/2003 Bioreactor 1 Influent Yes SG1, SG6 X 3-AW-03-2-S04-W-C 11/25/2003 Bioreactor 1 Effluent No SG1, SG6 X X 3-AW-03-2-S04-W-C-F 11/25/2003 Bioreactor 1 Effluent Yes SG1, SG6 X 3-AW-03-2-S05-W-C 11/25/2003 Bioreactor 2 Effluent No SG1, SG3, SG6 X X 3-AW-03-2-S05-W-C-F 11/25/2003 Bioreactor 2 Effluent Yes SG1, SG3, SG6 X 3-AW-03-2-S07-

W-C 11/25/2003 Pond 4 Effluent Pipe No SG1, SG3, SG6 X X X 

3-AW-03-2-S07-

W-C-F 11/25/2003 Pond 4 Effluent Pipe Yes SG1, SG3, SG6 X 

AW-1/29/04-S1-

W-C 1/29/2004 Syste

m Influent at 

Weir No P1, P2, SG1, SG2, SG6 X X X 

AW-1/29/04-S1-

W-C-F 1/29/2004 Syste

m Influent at 

Weir Yes P1, P2 X 

AW-1/29/04-S2-

W-C 1/29/2004 System 

Effluent No P1, P2, SG1, SG2, SG3, SG6 X X X 

AW-1/29/04-S2-

W-C-F 1/29/2004 Syste

m Effluent Yes P1, P2 X 

AW-1/29/04-S3-W-C 1/29/2004 Bioreactor 1 Influent No SG1, SG6 X AW-1/29/04-S3-W-C-F 1/29/2004 Bioreactor 1 Influent Yes SG1, SG6 X AW-1/29/04-S4-W-C 1/29/2004 Bioreactor 1 Effluent No SG1, SG6 X 

62
________________________________________________________________________________________

Table A-1. Sa

mple Register for the Co

mpost-Free Bioreactor Treatment Syste

m, Gravity Flow Operations (continued) 

Sa

mple ID Date Location Filtered? 

Project 

Objective 

Total 

Metals Sulfate Alkalinity 

AW-1/29/04-S4-W-C-F 1/29/2004 Bioreactor 1 Effluent Yes SG1, SG6 X AW-1/29/04-S5-W-C 1/29/2004 Bioreactor 2 Effluent No SG1, SG3, SG6 X X AW-1/29/04-S5-W-C-F 1/29/2004 Bioreactor 2 Effluent Yes SG1, SG3, SG6 X AW-1/29/04-S7-

W-C 1/29/2004 Pond 4 Effluent Pipe No SG1, SG3, SG6 X X 

AW-1/29/04-S7-

W-C-F 1/29/2004 Pond 4 Effluent Pipe Yes SG1, SG3, SG6 X 

4-AW-2/19/04-S1-

W-C 2/19/2004 Syste

m Influent at 

Weir No P1, P2, SG1, SG2, SG6 X X X 

4-AW-2/19/04-S1-

W-C-F 2/19/2004 Syste

m Influent at 

Weir Yes P1, P2 X 

4-AW-2/19/04-S2-

W-C 2/19/2004 System 

Effluent No P1, P2, SG1, SG2, SG3, SG6 X X X 

4-AW-2/19/04-S2-

W-C-F 2/19/2004 Syste

m Effluent Yes P1, P2 X 

4-AW-2/19/04-S3-W-C 2/19/2004 Bioreactor 1 Influent No SG1, SG6 X X X 4-AW-2/19/04-S3-W-C-F 2/19/2004 Bioreactor 1 Influent Yes SG1, SG6 X 4-AW-2/19/04-S4-W-C 2/19/2004 Bioreactor 1 Effluent No SG1, SG6 X X X 4-AW-2/19/04-S4-W-C-F 2/19/2004 Bioreactor 1 Effluent Yes SG1, SG6 X 4-AW-2/19/04-S5-W-C 2/19/2004 Bioreactor 2 Effluent No SG1, SG3, SG6 X X X 4-AW-2/19/04-S5-W-C-F 2/19/2004 Bioreactor 2 Effluent Yes SG1, SG3, SG6 X 4-AW-2/19/04-S7-

W-C 2/19/2004 Pond 4 Effluent Pipe No SG1, SG3, SG6 X X X 

4-AW-2/19/04-S7-

W-C-F 2/19/2004 Pond 4 Effluent Pipe Yes SG1, SG3, SG6 X 

4-AW-3/24/04-S1-

W-C 3/24/2004 Syste

m Influent at 

Weir No P1, P2, SG1, SG2, SG6 X X X 

4-AW-3/24/04-S1-

W-C-F 3/24/2004 Syste

m Influent at 

Weir Yes P1, P2 X 

4-AW-3/24/04-S2-

W-C 3/24/2004 System 

Effluent No P1, P2, SG1, SG2, SG3, SG6 X X X 

4-AW-3/24/04-S2-

W-C-F 3/24/2004 Syste

m Effluent Yes P1, P2 X 

4-AW-3/24/04-S3-W-C 3/24/2004 Bioreactor 1 Influent No SG1, SG6 X X X 4-AW-3/24/04-S3-W-C-F 3/24/2004 Bioreactor 1 Influent Yes SG1, SG6 X 4-AW-3/24/04-S4-W-C 3/24/2004 Bioreactor 1 Effluent No SG1, SG6 X X X 4-AW-3/24/04-S4-W-C-F 3/24/2004 Bioreactor 1 Effluent Yes SG1, SG6 X 4-AW-3/24/04-S5-W-C 3/24/2004 Bioreactor 2 Effluent No SG1, SG3, SG6 X X X 4-AW-3/24/04-S5-W-C-F 3/24/2004 Bioreactor 2 Effluent Yes SG1, SG3, SG6 X 4-AW-3/24/04-S7-

W-C 3/24/2004 Pond 4 Effluent Pipe No SG1, SG3, SG6 X X X 

4-AW-3/24/04-S7-

W-C-F 3/24/2004 Pond 4 Effluent Pipe Yes SG1, SG3, SG6 X 

4-AW-4/29/04-S1-

W-C 4/29/2004 Syste

m Influent at 

Weir No P1, P2, SG1, SG2, SG6 X X X 

4-AW-4/29/04-S1-

W-C-F 4/29/2004 Syste

m Influent at 

Weir Yes P1, P2 X 

63
________________________________________________________________________________________

Table A-1. Sa

mple Register for the Co

mpost-Free Bioreactor Treatment Syste

m, Gravity Flow Operations (continued) 

Sa

mple ID Date Location Filtered? 

Project 

Objective 

Total 

Metals Sulfate Alkalinity 

4-AW-4/29/04-S2-

W-C 4/29/2004 System 

Effluent No P1, P2, SG1, SG2, SG3, SG6 X X X 

4-AW-4/29/04-S2-

W-C-F 4/29/2004 Syste

m Effluent Yes P1, P2 X 

4-AW-4/29/04-S3-W-C 4/29/2004 Bioreactor 1 Influent No SG1, SG6 X X X 4-AW-4/29/04-S3-W-C-F 4/29/2004 Bioreactor 1 Influent Yes SG1, SG6 X 4-AW-4/29/04-S4-W-C 4/29/2004 Bioreactor 1 Effluent No SG1, SG6 X X X 4-AW-4/29/04-S4-W-C-F 4/29/2004 Bioreactor 1 Effluent Yes SG1, SG6 X 4-AW-4/29/04-S5-W-C 4/29/2004 Bioreactor 2 Effluent No SG1, SG3, SG6 X X X 4-AW-4/29/04-S5-W-C-F 4/29/2004 Bioreactor 2 Effluent Yes SG1, SG3, SG6 X 4-AW-4/29/04-S7-

W-C 4/29/2004 Pond 4 Effluent Pipe No SG1, SG3, SG6 X X X 

4-AW-4/29/04-S7-

W-C-F 4/29/2004 Pond 4 Effluent Pipe Yes SG1, SG3, SG6 X 

MS/MS

D=Matrix spike/

matrix duplicate TDS=Total dissolved solids TSS=Tot

64
________________________________________________________________________________________

Table A-2. Sa

mple Register for the Co

mpost-Free Bioreactor Treat

ment Syste

m, Recirculation Operations 

Sa

mple ID Date Location Filtered? 

Project 

Objective 

Total 

Metals Sulfate Alkalinity 

AW-6/14/04-S14-

W-G 6/16/2004 Pond 3 No SG2, SG3 X X X 

AW-6/14/04-S14-

W-G-F 6/16/2004 Pond 3 Yes SG2, SG3 X 

AW-6/14/04-S1-

W-C 6/16/2004 Syste

m Influent at 

Weir No P1, P2, SG1, SG2, SG6 X X X 

AW-6/14/04-S1-

W-C-F 6/16/2004 Syste

m Influent at 

Weir Yes P1, P2 X 

AW-6/14/04-S2-

W-C 6/16/2004 System 

Effluent No P1, P2, SG1, SG2, SG3, SG6 X X X 

AW-6/14/04-S2-

W-C-F 6/16/2004 Syste

m Effluent Yes P1, P2 X 

AW-6/14/04-S3-W-C 6/16/2004 Bioreactor 1 Influent No SG1, SG6 X X X AW-6/14/04-S3-W-C-F 6/16/2004 Bioreactor 1 Influent Yes SG1, SG6 X AW-6/14/04-S4-W-C 6/16/2004 Bioreactor 1 Effluent No SG1, SG6 X X X AW-6/14/04-S4-W-C-F 6/16/2004 Bioreactor 1 Effluent Yes SG1, SG6 X AW-6/14/04-S5-W-C 6/16/2004 Bioreactor 2 Effluent No SG1, SG3, SG6 X X X AW-6/14/04-S5-W-C-F 6/16/2004 Bioreactor 2 Effluent Yes SG1, SG3, SG6 X AW-6/14/04-S7-

W-C 6/16/2004 Pond 4 Effluent Pipe No SG1, SG3, SG6 X X X 

AW-6/14/04-S7-

W-C-F 6/16/2004 Pond 4 Effluent Pipe Yes SG1, SG3, SG6 X 

AW-8/19/04-S1-

W-C 8/19/2004 Syste

m Influent at 

Weir No P1, P2, SG1, SG2, SG6 X X X 

AW-8/19/04-S1-

W-C-F 8/19/2004 Syste

m Influent at 

Weir Yes P1, P2 X 

AW-8/19/04-S2-

W-C 8/19/2004 System 

Effluent No P1, P2, SG1, SG2, SG3, SG6 X X X 

AW-8/19/04-S2-

W-C-F 8/19/2004 Syste

m Effluent Yes P1, P2 X 

AW-8/19/04-S3-W-C 8/19/2004 Bioreactor 1 Influent No SG1, SG6 X X X AW-8/19/04-S3-W-C-F 8/19/2004 Bioreactor 1 Influent Yes SG1, SG6 X AW-8/19/04-S4-W-C 8/19/2004 Bioreactor 1 Effluent No SG1, SG6 X X X AW-8/19/04-S4-W-C-F 8/19/2004 Bioreactor 1 Effluent Yes SG1, SG6 X AW-8/19/04-S5-W-C 8/19/2004 Bioreactor 2 Effluent No SG1, SG3, SG6 X X X AW-8/19/04-S5-W-C-F 8/19/2004 Bioreactor 2 Effluent Yes SG1, SG3, SG6 X AW-8/19/04-S7-

W-C 8/19/2004 Pond 4 Effluent Pipe No SG1, SG3, SG6 X X X 

AW-8/19/04-S7-

W-C-F 8/19/2004 Pond 4 Effluent Pipe Yes SG1, SG3, SG6 X 

AW-12/3/04-S1-

W-C 12/3/2004 Syste

m Influent at 

Weir No P1, P2, SG1, SG2, SG6 X X X 

AW-12/3/04-S1-

W-C-F 12/3/2004 Syste

m Influent at 

Weir Yes P1, P2 X 

AW-12/3/04-S2-

W-C 12/3/2004 System 

Effluent No P1, P2, SG1, SG2, SG3, SG6 X X X 

AW-12/3/04-S2-

W-C-F 12/3/2004 Syste

m Effluent Yes P1, P2 X 

AW-12/3/04-S3-W-C 12/3/2004 Bioreactor 1 Influent No SG1, SG6 X X X 

65
________________________________________________________________________________________

Table A-2. Sa

mple Register for the Co

mpost-Free Bioreactor Treat

ment Syste

m, Recirculation Operations (continued) 

Sa

mple ID Date Location Filtered? 

Project 

Objective 

Total 

Metals Sulfate Alkalinity 

AW-12/3/04-S3-W-C-F 12/3/2004 Bioreactor 1 Influent Yes SG1, SG6 X AW-12/3/04-S4-W-C 12/3/2004 Bioreactor 1 Effluent No SG1, SG6 X X X AW-12/3/04-S4-W-C-F 12/3/2004 Bioreactor 1 Effluent Yes SG1, SG6 X AW-12/3/04-S5-W-C 12/3/2004 Bioreactor 2 Effluent No SG1, SG3, SG6 X X X AW-12/3/04-S5-W-C-F 12/3/2004 Bioreactor 2 Effluent Yes SG1, SG3, SG6 X AW-12/3/04-S7-

W-C 12/3/2004 Pond 4 Effluent Pipe No SG1, SG3, SG6 X X X 

AW-12/3/04-S7-

W-C-F 12/3/2004 Pond 4 Effluent Pipe Yes SG1, SG3, SG6 X 

AW-2/3/05-S1-

W-C 2/3/2005 Syste

m Influent at 

Weir No P1, P2, SG1, SG2, SG6 X X X 

AW-2/3/05-S1-

W-C-F 2/3/2005 Syste

m Influent at 

Weir Yes P1, P2 X 

AW-2/3/05-S3-WC 2/3/2005 Bioreactor 1 Influent No SG1, SG6 X X X AW-2/3/05-S3-WC-F 2/3/2005 Bioreactor 1 Influent Yes SG1, SG6 X AW-2/3/05-S4-WC 2/3/2005 Bioreactor 1 Effluent No SG1, SG6 X X X AW-2/3/05-S4-WC-F 2/3/2005 Bioreactor 1 Effluent Yes SG1, SG6 X AW-2/3/05-S5-WC 2/3/2005 Bioreactor 2 Effluent No SG1, SG3, SG6 X X X AW-2/3/05-S5-WC-F 2/3/2005 Bioreactor 2 Effluent Yes SG1, SG3, SG6 X AW-2/3/05-S7-

W-C 2/3/2005 Pond 4 Effluent Pipe No P1, P2, SG1, SG2, SG3, SG6 X X X 

AW-2/3/05-S7-

W-C-F 2/3/2005 Pond 4 Effluent Pipe Yes P1, P2 X 

AW-3/17/05-S1-

W-C 3/17/2005 Syste

m Influent at 

Weir No P1, P2, SG1, SG2, SG6 X X X 

AW-3/17/05-S1-

W-C-F 3/17/2005 Syste

m Influent at 

Weir Yes P1, P2 X 

AW-3/17/05-S2-

W-C 3/17/2005 System 

Effluent No P1, P2, SG1, SG2, SG3, SG6 X X X 

AW-3/17/05-S2-

W-C-F 3/17/2005 Syste

m Effluent Yes P1, P2 X 

AW-3/17/05-S3-W-C 3/17/2005 Bioreactor 1 Influent No SG1, SG6 X X X AW-3/17/05-S3-W-C-F 3/17/2005 Bioreactor 1 Influent Yes SG1, SG6 X AW-3/17/05-S4-W-C 3/17/2005 Bioreactor 1 Effluent No SG1, SG6 X X X AW-3/17/05-S4-W-C-F 3/17/2005 Bioreactor 1 Effluent Yes SG1, SG6 X AW-3/17/05-S5-W-C 3/17/2005 Bioreactor 2 Effluent No SG1, SG3, SG6 X X X AW-3/17/05-S5-W-C-F 3/17/2005 Bioreactor 2 Effluent Yes SG1, SG3, SG6 X AW-3/17/05-S7-

W-C 3/17/2005 Pond 4 Effluent Pipe No SG1, SG3, SG6 X X X 

AW-3/17/05-S7-

W-C-F 3/17/2005 Pond 4 Effluent Pipe Yes SG1, SG3, SG6 X 

AW-4/27/05-S1-

W-C 4/27/2005 Syste

m Influent at 

Weir No P1, P2, SG1, SG2, SG6 X X X 

66
________________________________________________________________________________________

Table A-2. Sa

mple Register for the Co

mpost-Free Bioreactor Treat

ment Syste

m, Recirculation Operations (continued) 

Sa

mple ID Date Location Filtered? 

Project 

Objective 

Total 

Metals Sulfate Alkalinity 

AW-4/27/05-S1-

W-C-F 4/27/2005 Syste

m Influent at 

Weir Yes P1, P2 X 

AW-4/27/05-S2-

W-C 4/27/2005 System 

Effluent No P1, P2, SG1, SG2, SG3, SG6 X X X 

AW-4/27/05-S2-

W-C-F 4/27/2005 Syste

m Effluent Yes P1, P2 X 

AW-4/27/05-S3-W-C 4/27/2005 Bioreactor 1 Influent No SG1, SG6 X X X AW-4/27/05-S3-W-C-F 4/27/2005 Bioreactor 1 Influent Yes SG1, SG6 X AW-4/27/05-S4-W-C 4/27/2005 Bioreactor 1 Effluent No SG1, SG6 X X X AW-4/27/05-S4-W-C-F 4/27/2005 Bioreactor 1 Effluent Yes SG1, SG6 X AW-4/27/05-S5-W-C 4/27/2005 Bioreactor 2 Effluent No SG1, SG3, SG6 X X X AW-4/27/05-S5-W-C-F 4/27/2005 Bioreactor 2 Effluent Yes SG1, SG3, SG6 X AW-4/27/05-S7-

W-C 4/27/2005 Pond 4 Effluent Pipe No SG1, SG3, SG6 X X X 

AW-4/27/05-S7-

W-C-F 4/27/2005 Pond 4 Effluent Pipe Yes SG1, SG3, SG6 X 

AW-6/2/05-S1-

W-C 6/2/2005 Syste

m Influent at 

Weir No P1, P2, SG1, SG2, SG6 X X X 

AW-6/2/05-S1-

W-C-F 6/2/2005 Syste

m Influent at 

Weir Yes P1, P2 X 

AW-6/2/05-S2-

W-C 6/2/2005 System 

Effluent No P1, P2, SG1, SG2, SG3, SG6 X X X 

AW-6/2/05-S2-

W-C-F 6/2/2005 Syste

m Effluent Yes P1, P2 X 

AW-6/2/05-S3-WC 6/2/2005 Bioreactor 1 Influent No SG1, SG6 X X X AW-6/2/05-S3-WC-F 6/2/2005 Bioreactor 1 Influent Yes SG1, SG6 X AW-6/2/05-S4-WC 6/2/2005 Bioreactor 1 Effluent No SG1, SG6 X X X AW-6/2/05-S4-WC-F 6/2/2005 Bioreactor 1 Effluent Yes SG1, SG6 X AW-6/2/05-S5-WC 6/2/2005 Bioreactor 2 Effluent No SG1, SG3, SG6 X X X AW-6/2/05-S5-WC-F 6/2/2005 Bioreactor 2 Effluent Yes SG1, SG3, SG6 X AW-6/2/05-S7-

W-C 6/2/2005 Pond 4 Effluent Pipe No SG1, SG3, SG6 X X X 

AW-6/2/05-S7-

W-C-F 6/2/2005 Pond 4 Effluent Pipe Yes SG1, SG3, SG6 X 

MS/MS

D=Matrix spike/

matrix duplicate TDS=Total dissolved solids TSS=Tota

67
________________________________________________________________________________________

Table A-3. Sa

mple Register for the Co

mpost-Free Bioreactor Treatment System, Solids for Both Modes of Operation 

Sa

mple ID Date Location Filtered? 

Project 

Objective 

SPLP 

 Metals 

TCLP 

Metals 

WET 

Metals 

To

Me

AW-7/13/05-S10-S-C 7/13/2005 Pond 3 sludge --- SG4 X X X X AW-7/13/05-S11-S-C 7/13/2005 Pond 4 sludge --- SG4 X X X X AW-7/13/05-S12-S-C 7/13/2005 Aeration Channel sludge --- SG4 X X X X AW-7/13/05-S13-S-C 7/13/2005 Pretreat

ment Pond sludge --- SG4 X X X X 

AW-9/29/05-S15-S-G 9/29/2005 Bag Filter Solids --- SG4 X X X X MS/MS

D=Matrix spike/

matrix duplicate TCLP=

Toxicity characteristic leaching procedure 

SPLP=Synthetic precipitation and leaching procedure W

E

T=Waste extraction test 

68
______________________________________________________________________________ 

APPENDIX B 

DATA USED TO EVALUATE PROJECT PRIMARY OBJECTIVES 

69
_______________________________________________________________________________ 

Table B-1. Data Used to Evaluate Project Objectives for the Bioreactor Treatment System, Gravity Flow Operations 

Sample Number (1) 

Sample 

Date 

Composite 

or Grab? Analyte 

Filtered 

Influent 

Concentration 

(μg/L) 

Filtered 

Effluent 

Concentration 

(μg/L) 

4-Day Average Filtered 

Effluent Concentration(2) 

(μg/L) 

3-AW-01-5-S0X-W-C-F 11/14/2003 Composite Aluminum 38,100 79.8 

3-AW-03-2-S0X-W-C-F 11/25/2003 Composite Aluminum 39,400 203 UJ 

AW-1/29/04-SX-W-C-F 1/29/2004 Composite Aluminum 35,200 160 

4-AW-2/19/04-SX-W-C-F 2/19/2004 Composite Aluminum 35,300 5 U 112 

4-AW-3/24/04-SX-W-C-F 3/24/2004 Composite Aluminum 36,900 144 128 

4-AW-4/29/04-SX-W-C-F 4/29/2004 Composite Aluminum 39,900 25.8 83.7 

3-AW-01-5-S0X-W-C-F 11/14/2003 Composite Arsenic 1.5 U 12.5 

3-AW-03-2-S0X-W-C-F 11/25/2003 Composite Arsenic 2.5 U 3.8 UJ 

AW-1/29/04-SX-W-C-F 1/29/2004 Composite Arsenic 1.6 U 1.6 U 

4-AW-2/19/04-SX-W-C-F 2/19/2004 Composite Arsenic 1.6 U 3 5.2 

4-AW-3/24/04-SX-W-C-F 3/24/2004 Composite Arsenic 3.1 2.4 2.7 

4-AW-4/29/04-SX-W-C-F 4/29/2004 Composite Arsenic 2.3 U 5.1 3.0 

3-AW-01-5-S0X-W-C-F 11/14/2003 Composite Cadmium 0.44 UJ 0.17 U 

3-AW-03-2-S0X-W-C-F 11/25/2003 Composite Cadmium 1 0.21 UJ 

AW-1/29/04-SX-W-C-F 1/29/2004 Composite Cadmium 0.88 0.32 U 

4-AW-2/19/04-SX-W-C-F 2/19/2004 Composite Cadmium 0.34 0.098 U <0.20 

4-AW-3/24/04-SX-W-C-F 3/24/2004 Composite Cadmium 0.4 0.23 U <0.21 

4-AW-4/29/04-SX-W-C-F 4/29/2004 Composite Cadmium 0.57 0.23 U <0.22 

3-AW-01-5-S0X-W-C-F 11/14/2003 Composite Chromium 20.8 J 16.3 

3-AW-03-2-S0X-W-C-F 11/25/2003 Composite Chromium 3.9 9.9 

AW-1/29/04-SX-W-C-F 1/29/2004 Composite Chromium 4.4 0.5 U 

4-AW-2/19/04-SX-W-C-F 2/19/2004 Composite Chromium 4.5 0.45 U 6.8 

4-AW-3/24/04-SX-W-C-F 3/24/2004 Composite Chromium 17.2 6.4 4.3 

4-AW-4/29/04-SX-W-C-F 4/29/2004 Composite Chromium 22.4 13.4 5.2 

3-AW-01-5-S0X-W-C-F 11/14/2003 Composite Copper 701 4.5 

3-AW-03-2-S0X-W-C-F 11/25/2003 Composite Copper 732 1.9 U 

AW-1/29/04-SX-W-C-F 1/29/2004 Composite Copper 630 4.7 

4-AW-2/19/04-SX-W-C-F 2/19/2004 Composite Copper 661 5.6 4.2 

4-AW-3/24/04-SX-W-C-F 3/24/2004 Composite Copper 656 5.6 4.5 

4-AW-4/29/04-SX-W-C-F 4/29/2004 Composite Copper 765 6.5 5.6 

3-AW-01-5-S0X-W-C-F 11/14/2003 Composite Iron 121,000 4,030 

3-AW-03-2-S0X-W-C-F 11/25/2003 Composite Iron 126,000 12,800 

AW-1/29/04-SX-W-C-F 1/29/2004 Composite Iron 114,000 39,200 

4-AW-2/19/04-SX-W-C-F 2/19/2004 Composite Iron 109,000 7,100 15,783 

4-AW-3/24/04-SX-W-C-F 3/24/2004 Composite Iron 113,000 389 14,873 

4-AW-4/29/04-SX-W-C-F 4/29/2004 Composite Iron 120,000 105 11,699 

3-AW-01-5-S0X-W-C-F 11/14/2003 Composite Lead 0.88 UJ 0.88 U 

3-AW-03-2-S0X-W-C-F 11/25/2003 Composite Lead 0.65 U 4.2 UJ 

AW-1/29/04-SX-W-C-F 1/29/2004 Composite Lead 2.9 5.1 

4-AW-2/19/04-SX-W-C-F 2/19/2004 Composite Lead 5.4 9.8 5.0 

4-AW-3/24/04-SX-W-C-F 3/24/2004 Composite Lead 5.3 3.4 5.6 

4-AW-4/29/04-SX-W-C-F 4/29/2004 Composite Lead 6.7 4.8 5.8 

3-AW-01-5-S0X-W-C-F 11/14/2003 Composite Nickel 484 41.7 

70
_______________________________________________________________________________ 

Table B-1. Data Used to Evaluate Project Objectives for the Bioreactor Treatment System, Gravity Flow Operations (continued) 

Sample Number(1) 

Sample 

Date 

Composite 

or Grab? Analyte 

Filtered 

Influent 

Concentration 

(μg/L) 

Filtered 

Effluent 

Concentration 

(μg/L) 

4-Day Average Filtered 

Effluent Concentration(2) 

(μg/L) 

3-AW-03-2-S0X-W-C-F 11/25/2003 Composite Nickel 493 36.7 

AW-1/29/04-SX-W-C-F 1/29/2004 Composite Nickel 448 125 

4-AW-2/19/04-SX-W-C-F 2/19/2004 Composite Nickel 467 42.3 61.4 

4-AW-3/24/04-SX-W-C-F 3/24/2004 Composite Nickel 481 53.1 64.3 

4-AW-4/29/04-SX-W-C-F 4/29/2004 Composite Nickel 547 94.2 78.7 

3-AW-01-5-S0X-W-C-F 11/14/2003 Composite Selenium 12.8 UJ 13.9 

3-AW-03-2-S0X-W-C-F 11/25/2003 Composite Selenium 11.6 10 UJ 

AW-1/29/04-SX-W-C-F 1/29/2004 Composite Selenium 16.3 13.3 

4-AW-2/19/04-SX-W-C-F 2/19/2004 Composite Selenium 18 8 11.2 

4-AW-3/24/04-SX-W-C-F 3/24/2004 Composite Selenium 9.6 8.7 10.0 

4-AW-4/29/04-SX-W-C-F 4/29/2004 Composite Selenium 14.9 13.3 10.8 

3-AW-01-5-S0X-W-C-F 11/14/2003 Composite Zinc 701 29 

3-AW-03-2-S0X-W-C-F 11/25/2003 Composite Zinc 732 14.2 J 

AW-1/29/04-SX-W-C-F 1/29/2004 Composite Zinc 677 13.5 

4-AW-2/19/04-SX-W-C-F 2/19/2004 Composite Zinc 677 16.2 18.2 

4-AW-3/24/04-SX-W-C-F 3/24/2004 Composite Zinc 702 10.3 13.6 

4-AW-4/29/04-SX-W-C-F 4/29/2004 Composite Zinc 802 11.5 12.9 

1 - For the influent sample, X in the sample number = 1; for the effluent sample, X=2 

2 - The data from four consecutive sampling events were used in the calculation of the average instead of four consecutive days 

μg/L - Micrograms per liter NC - Not calculated U - Non-detect 

71
_______________________________________________________________________________ 

Table B-2. Data Used to Evaluate Project Objectives for the Bioreactor Treatment System, Recirculation Operations 

Sample Number(1) 

Sample 

Data 

Composite 

or Grab? Analyte 

Filtered 

Influent 

Concentration 

(μg/L) 

Filtered 

Effluent 

Concentration 

(μg/L) 

4-Day Average Filtered 

Effluent Concentration(2) 

(μg/L) 

AW-6/14/04-SX-W-C-F 6/16/2004 Composite Aluminum 38,700 31.2 

AW-8/19/04-SX-W-C-F 8/19/2004 Composite Aluminum 40,400 105 

AW-12/3/04-SX-W-C-F 12/3/2004 Composite Aluminum 39,000 33.9 

AW-2/3/05-SX-W-C-F 2/3/2005 Composite Aluminum 38,400 39.4 UJ 52.4 

AW-3/17/05-SX-W-C-F 3/17/2005 Composite Aluminum 34,300 54.8 J 58.3 

AW-4/27/05-SX-W-C-F 4/27/2005 Composite Aluminum 39,300 63.1 47.8 

AW-6/2/05-SX-W-C-F 6/2/2005 Composite Aluminum 50,100 41.8 49.8 

AW-6/14/04-SX-W-C-F 6/16/2004 Composite Arsenic 10.2 UJ 11.2 

AW-8/19/04-SX-W-C-F 8/19/2004 Composite Arsenic 2.1 U 14.7 UJ 

AW-12/3/04-SX-W-C-F 12/3/2004 Composite Arsenic 1.9 U 1.9 U 

AW-2/3/05-SX-W-C-F 2/3/2005 Composite Arsenic 1.9 U 2.4 J 7.6 

AW-3/17/05-SX-W-C-F 3/17/2005 Composite Arsenic 4.8 5.3 UJ 6.1 

AW-4/27/05-SX-W-C-F 4/27/2005 Composite Arsenic 18.7 J 2.9 3.1 

AW-6/2/05-SX-W-C-F 6/2/2005 Composite Arsenic 12.4 7.2 4.5 

AW-6/14/04-SX-W-C-F 6/16/2004 Composite Cadmium 1.1 UJ 0.28 U 

AW-8/19/04-SX-W-C-F 8/19/2004 Composite Cadmium 0.94 0.16 UJ 

AW-12/3/04-SX-W-C-F 12/3/2004 Composite Cadmium 1.3 0.12 U 

AW-2/3/05-SX-W-C-F 2/3/2005 Composite Cadmium 0.12 U 0.12 U <0.17 

AW-3/17/05-SX-W-C-F 3/17/2005 Composite Cadmium 0.3 U 0.3 U <0.18 

AW-4/27/05-SX-W-C-F 4/27/2005 Composite Cadmium 0.12 U 0.12 U <0.17 

AW-6/2/05-SX-W-C-F 6/2/2005 Composite Cadmium 0.3 0.28 U <0.21 

AW-6/14/04-SX-W-C-F 6/16/2004 Composite Chromium 17.9 J 14.1 

AW-8/19/04-SX-W-C-F 8/19/2004 Composite Chromium 19.3 11.6 J 

AW-12/3/04-SX-W-C-F 12/3/2004 Composite Chromium 4.8 2.7 

AW-2/3/05-SX-W-C-F 2/3/2005 Composite Chromium 4.6 1.2 UJ 7.4 

AW-3/17/05-SX-W-C-F 3/17/2005 Composite Chromium 14.9 6.7 5.6 

AW-4/27/05-SX-W-C-F 4/27/2005 Composite Chromium 5.8 J 0.88 U 2.9 

AW-6/2/05-SX-W-C-F 6/2/2005 Composite Chromium 10.6 7.5 4.1 

AW-6/14/04-SX-W-C-F 6/16/2004 Composite Copper 851 7.6 

AW-8/19/04-SX-W-C-F 8/19/2004 Composite Copper 766 9.5 J 

AW-12/3/04-SX-W-C-F 12/3/2004 Composite Copper 702 1.7 

AW-2/3/05-SX-W-C-F 2/3/2005 Composite Copper 697 1.6 U 5.1 

AW-3/17/05-SX-W-C-F 3/17/2005 Composite Copper 598 5.4 UJ 4.6 

AW-4/27/05-SX-W-C-F 4/27/2005 Composite Copper 769 1.7 U 2.6 

AW-6/2/05-SX-W-C-F 6/2/2005 Composite Copper 1,180 4.6 3.3 

AW-6/14/04-SX-W-C-F 6/16/2004 Composite Iron 104,000 3,160 

AW-8/19/04-SX-W-C-F 8/19/2004 Composite Iron 99,500 269 

AW-12/3/04-SX-W-C-F 12/3/2004 Composite Iron 126,000 9,060 

AW-2/3/05-SX-W-C-F 2/3/2005 Composite Iron 124,000 2,550 3,760 

AW-3/17/05-SX-W-C-F 3/17/2005 Composite Iron 111,000 635 3,129 

AW-4/27/05-SX-W-C-F 4/27/2005 Composite Iron 109,000 975 3,305 

AW-6/2/05-SX-W-C-F 6/2/2005 Composite Iron 137,000 2,280 1,610 

AW-6/14/04-SX-W-C-F 6/16/2004 Composite Lead 6.7 J 3.6 

72
_______________________________________________________________________________ 

Table B-2. Data Used to Evaluate Project Objectives for the Bioreactor Treatment System, Recirculation Operations (continued) 

Sample Number(1) 

Sample 

Data 

Composite 

or Grab? Analyte 

Filtered 

Influent 

Concentration 

(μg/L) 

Filtered 

Effluent 

Concentration 

(μg/L) 

4-Day Average Filtered 

Effluent Concentration(2) 

(μg/L) 

AW-8/19/04-SX-W-C-F 8/19/2004 Composite Lead 5.9 3.1 UJ 

AW-12/3/04-SX-W-C-F 12/3/2004 Composite Lead 1.7 0.73 

AW-2/3/05-SX-W-C-F 2/3/2005 Composite Lead 1.4 0.72 U 2.0 

AW-3/17/05-SX-W-C-F 3/17/2005 Composite Lead 5.3 3.3 J 2.0 

AW-4/27/05-SX-W-C-F 4/27/2005 Composite Lead 2.3 J 1.1 1.5 

AW-6/2/05-SX-W-C-F 6/2/2005 Composite Lead 5.9 4.6 2.4 

AW-6/14/04-SX-W-C-F 6/16/2004 Composite Nickel 525 36.8 

AW-8/19/04-SX-W-C-F 8/19/2004 Composite Nickel 531 18.9 J 

AW-12/3/04-SX-W-C-F 12/3/2004 Composite Nickel 531 154 

AW-2/3/05-SX-W-C-F 2/3/2005 Composite Nickel 551 50.5 J 65.1 

AW-3/17/05-SX-W-C-F 3/17/2005 Composite Nickel 481 59.1 70.6 

AW-4/27/05-SX-W-C-F 4/27/2005 Composite Nickel 497 79.4 85.8 

AW-6/2/05-SX-W-C-F 6/2/2005 Composite Nickel 585 89.5 69.6 

AW-6/14/04-SX-W-C-F 6/16/2004 Composite Selenium 17.7 12.3 

AW-8/19/04-SX-W-C-F 8/19/2004 Composite Selenium 14.4 7.8 UJ 

AW-12/3/04-SX-W-C-F 12/3/2004 Composite Selenium 9.5 5.6 

AW-2/3/05-SX-W-C-F 2/3/2005 Composite Selenium 18 13.3 UJ 9.8 

AW-3/17/05-SX-W-C-F 3/17/2005 Composite Selenium 7 6.3 UJ 8.3 

AW-4/27/05-SX-W-C-F 4/27/2005 Composite Selenium 7.1 UJ 3.6 7.2 

AW-6/2/05-SX-W-C-F 6/2/2005 Composite Selenium 7 10.5 8.4 

AW-6/14/04-SX-W-C-F 6/16/2004 Composite Zinc 774 8.4 

AW-8/19/04-SX-W-C-F 8/19/2004 Composite Zinc 755 4.5 UJ 

AW-12/3/04-SX-W-C-F 12/3/2004 Composite Zinc 772 17.5 

AW-2/3/05-SX-W-C-F 2/3/2005 Composite Zinc 780 0.97 UJ 7.8 

AW-3/17/05-SX-W-C-F 3/17/2005 Composite Zinc 709 0.92 U 6.0 

AW-4/27/05-SX-W-C-F 4/27/2005 Composite Zinc 761 11.3 7.7 

AW-6/2/05-SX-W-C-F 6/2/2005 Composite Zinc 880 18.8 8.0 

1 - For the influent sample, X in the sample number = 1; for the effluent sample, X=2 

2 - The data from four consecutive sampling events were used in the calculation of the average instead of four consecutive days 

μg/L - Micrograms per liter NC - Not calculated U - Non-detect 

73
_______________________________________________________________________________ 

Table B-3. Statistical Summary of the Bioreactor Treatment System, Gravity Flow Operations Data 

Analyte 

Minimum 

Concentration 

(μg/L) 

Maximum 

Concentration 

(μg/L) 

Mean 

Concentration 

(μg/L) 

Median 

Concentration 

(μg/L) 

Standard 

Deviation 

Coefficient of 

Variation 

(%) 

Influent 

Aluminum 35,200 39,900 37,467 37,500 2,011 5 

Arsenic <1.5 3.1 2.1 1.95 0.64 31 

Cadmium 0.34 1.0 0.61 0.51 0.27 45 

Chromium 3.9 22.4 12.2 10.9 8.9 73 

Copper 630 765 691 681 51.2 7 

Iron 109,000 126,000 117,167 117,000 6,242 5 

Lead <0.65 6.7 3.64 4.1 2.5 70 

Nickel 448 547 487 483 33.5 7 

Selenium 9.6 16.3 13.9 13.9 3.1 22 

Zinc 677 802 715 702 47.1 7 

Effluent 

Aluminum <5 160 103 112 78.8 77 

Arsenic <1.6 12.5 4.73 3.4 3.99 84 

Cadmium <0.098 <0.32 <0.21 <0.22 0.07 35 

Chromium <0.45 16.3 7.83 8.2 6.6 84 

Copper <1.9 6.5 4.8 5.2 1.6 33 

Iron 105 39,200 4,885 3,595 4,771 104 

Lead <0.88 9.8 4.7 4.5 2.9 62 

Nickel 36.7 125 65.5 47.7 35.9 55 

Selenium 8 13.9 11.2 11.7 2.6 23 

Zinc 10.3 29 15.8 13.9 6.8 43 

4-Day Average Effluent 

Aluminum 83.7 112 107.9 112 22.4 21 

Arsenic 2.7 5.2 3.63 3.0 1.37 38 

Cadmium <0.20 <0.22 <0.21 <0.21 0.01 5 

Chromium 4.3 6.8 5.77 5.3 0.90 16 

Copper 4.2 5.6 4.77 4.5 0.74 15 

Iron 11,699 15,783 14,118 14,873 2,144 15 

Lead 5.0 5.8 5.47 5.6 0.42 8 

Nickel 61.4 78.7 68.1 64.3 9.27 14 

Selenium 10.0 11.2 10.7 10.8 0.61 6 

Zinc 12.9 18.2 14.9 13.6 2.88 19 

% - Percent μg/L - Micrograms per liter NA - Not applicable 

74
_______________________________________________________________________________ 

Table B-4. Statistical Summary of the Bioreactor Treatment System, Recirculation Operations Data 

Analyte 

Minimum 

Concentration 

(μg/L) 

Maximum 

Concentration 

(μg/L) 

Mean 

Concentration 

(μg/L) 

Median 

Concentration 

(μg/L) 

Standard 

Deviation 

Coefficient of 

Variation 

(%) 

Influent 

Aluminum 34,300 50,100 40,029 39,000 4,837 12 

Arsenic <1.9 18.7 7.43 4.8 6.53 88 

Cadmium <0.12 1.3 0.60 0.30 0.50 84 

Chromium 4.6 19.3 11.1 10.6 6.30 57 

Copper 598 1,180 795 766 187 24 

Iron 99,500 137,000 115,785 111,000 13,509 12 

Lead 1.4 6.7 4.17 5.30 2.27 54 

Nickel 481 585 529 531 34.1 6 

Selenium 7 18 11.5 9.5 5.05 44 

Zinc 709 880 776 772 51.7 7 

Effluent 

Aluminum 31.2 105 52.7 41.8 25.7 49 

Arsenic <1.9 11.2 6.51 5.3 4.87 75 

Cadmium <0.12 <0.3 <0.20 <0.16 0.09 43 

Chromium <0.88 14.1 6.38 6.7 5.15 81 

Copper <1.6 9.5 4.59 4.6 3.15 69 

Iron 269 9,060 2,704 2,280 3,000 111 

Lead <0.72 4.6 2.45 3.1 1.57 64 

Nickel 18.9 154 69.7 59.1 44.2 63 

Selenium 3.6 12.3 8.49 7.8 3.63 43 

Zinc <0.92 18.8 8.91 8.4 7.35 82 

4-Day Average Effluent 

Aluminum 47.8 58.3 52.1 51.1 4.56 9 

Arsenic 3.1 7.6 5.30 5.26 1.93 36 

Cadmium <0.17 <0.21 <0.18 <0.17 0.02 10 

Chromium 2.9 7.4 4.97 4.81 1.95 39 

Copper 2.6 5.1 3.89 3.94 1.14 29 

Iron 1,610 3,760 2,951 3,217 933 32 

Lead 1.5 2.4 1.97 2.0 0.40 20 

Nickel 65.1 85.8 72.8 70.1 8.99 12 

Selenium 7.2 9.8 8.41 8.34 1.05 12 

Zinc 6.0 8.0 7.37 7.76 0.94 13 

% - Percent μg/L - Micrograms per liter NA - Not applicable 

75
________________________________________________________________________________ 

APPENDIX C 

DETAILED COST ELEMENT SPREADSHEETS 

76
________________________________________________________________________________ 

Table C-1. Cost Element Details for the Compost-Free Bioreactor Treatment System - Gravity Flow Operation 

Description Quantity Unit Unit cost Subtotal 

I Site Preparation 

Design (20% of capital cost) 1 lump sum $109,686.20 $109,686.20 

Construction Management (15% of capital cost) 1 lump sum $82,264.65 $82,264.65 

Project Management (10% of capital cost) 1 lump sum $54,843.10 $54,843.10 

Preconstruction Site Work (Clearing and Chipping, Topsoil 

Removal, and Debris Removal) 1 lump sum $41,392.00 $41,392.00 

Subtotal $288,185.95 

II Permitting and Regulatory Requirements 

Superfund Site, No Permitting Costs $0.00 

Subtotal $0.00 

III Capital and Equipment 

1 Compost-Free Bioreactor Treatment System

 a Equipment Mobilization/Demobilization 1 lump sum $73,550.00 $73,550.00 

b Pond and Pipe Trench Earthwork 1 lump sum $136,442.00 $136,442.00 

Seep collection pond excavation, bioreactor ponds and settling 

ponds excavation, sloping/riprap, trench excavation and placement 

of bedding for piping 

c Installation of Pond Liners, Stairs, Decent Structures 1 lump sum $63,756.00 $63,756.00 

Placement and seaming of liners and installation of boots for 

piping in the pretreatment pond, the two bioreactor ponds, and the 

two settling ponds. Installation of settling pond stairs and decant 

structures. Placement of geotextile in the bottom of the aeration 

channel. 

d Installation of Distribution Piping and Valve Vaults 1 lump sum $149,263.00 $149,263.00 

Placement of 6-inch system main drain and valves, 

4-inch distribution piping and valves, and 4-inch perforated 

influent and effluent loops in the two bioreactors; installation of 

two precast flushing vaults and ten 24-inch diameter HDPE 

standpipe vaults 

e Placement of Bioreactor Substrate 1 lump sum $47,173.00 $47,173.00 

Placement of manure layer, 3- to 6-inch cobble layer, and 6- to 9­

inch round rock layer 

f Erosion Control and Revegetation/Reseeding 1 lump sum $10,907.00 $10,907.00 

g Water Turbine and Storage Batteries 1 lump sum $14,700.00 $14,700.00 

4 KW turbine and 60 KW battery (48 volt) 

Subtotal $495,791.00 

2 Reagent Storage and Distribution 

a Ethanol Storage Tank and Delivery System 1 lump sum $13,400.00 $13,400.00 

Two 2,300 gallon bulk tanks, a reagent pump and viton tubing, and 

line containment pad 

b Sodium Hydroxide Storage Tank and Delivery System 1 lump sum $15,800.00 $15,800.00 

One 1,000 gallon bulk tank, a stainless steel transfer pump, a daily 

make up tank, a reagent pump and viton tubing, and line 

containment pad 

c Make up Water Storage Tank and Delivery System 1 lump sum $2,000.00 $2,000.00 

One 1,000 gallon bulk tank, a pump and delivery line. Assumes a 

make up water source is available, otherwise, use treated effluent 

d Reagent Storage Area Fencing 1 lump sum $4,000.00 $4,000.00 

200 feet of eight foot high fencing, double wide access gate, razor 

wire top. 

Subtotal 35,200.00 

77
________________________________________________________________________________ 

Table C-1. Cost Element Details for the Compost-Free Bioreactor Treatment System - Gravity Flow Operation (continued) 

Description Quantity Unit Unit cost Subtotal 

3 Automation

 a Remote Monitoring/Alarm System $9,742.50 

Sensaphone SCADA 3000 (control system, logger, alarm) 1 lump sum $2,495.00 $2,495.00 

Miscellaneous Accessories for SCADA 3000 1 lump sum $500.00 $500.00 

Personal Computer 1 lump sum $2,000.00 $2,000.00 

Professional Series 900 MHz Data Transceivers 1 lump sum $1,000.00 $1,000.00 

Miscellaneous Accessories for Transceivers 1 lump sum $500.00 $500.00 

Installation Cost (assumes 50% of equipment cost) 1 lump sum $3,247.50 $3,247.50

 b pH Controller System $6,202.50 

Pulse Output Controller 2 each $1,160.00 $2,320.00 

Electronic Diaphragm Pumps 2 each $826.00 $1,652.00 

pH Probe and Cable 2 each $220.00 $440.00 

Temperature Sensor and Cable 2 each $200.00 $400.00 

Accessories (cables, calibration solution) 1 lump sum $150.00 $150.00 

Installation Cost (assumes 25% of equipment cost) 1 lump sum $1,240.50 $1,240.50 

Subtotal $15,945.00 

4 Communications 

Motorola 9505 Satellite Phone 1 lump sum $1,495.00 $1,495.00 

Subtotal $1,495.00 

Total Fixed Costs $836,616.95 

IV System Start up and Acclimation (one time event) 

System Start-up Labor (2 Field Technicians for 2 weeks) 160 hour $56.19 $8,990.40 

Acclimation Period Labor (1 Field Technician for 2.5 months) 240 hour $56.19 $13,485.60 

Subtotal $22,476.00 

V Consumables and Rentals (Yearly) 

Ethanol 2,262 gallon $2.50 $5,655.00 

Sodium Hydroxide 5,839 gallon $0.85 $4,963.15 

Personal Protective Equipment (4 days/month) 12 month $28.00 $336.00 

Hydrogen Sulfide Gas Meter (4 days/month) 12 month $300.00 $3,600.00 

Water Quality Meter and Supplies (4 days/month) 12 month $700.00 $8,400.00 

Storage Connex 12 month $325.00 $3,900.00 

Subtotal $26,854.15 

VI Labor (Yearly) 

Field Technicians (1 day per week) 416 hour $56.19 $23,375.04 

Administrative Support (5% of field effort) 20 hour $61.16 $1,223.20 

Project Management (10% of field effort) 40 hour $90.00 $3,600.00 

Subtotal $28,198.24 

VII Utilities (Yearly) 

Backup Generator (3 Kilowatt; assume required for 4 months) 4 month $800.00 $3,200.00 

Backup Generator Fuel (105 gallon/month at $2.50/gallon) 4 months $262.50 $1,048.00 

SCADA Communication Service 12 month $75.00 $900.00 

Satellite Phone Communications Service 12 month $50.00 $600.00 

Portable Toilet 8 month $325.00 $2,600.00 

Subtotal $8,348.00 

78
________________________________________________________________________________ 

Table C-1. Cost Element Details for the Compost-Free Bioreactor Treatment System - Gravity Flow Operation (continued) 

VIII Residual Waste Handling and Disposal (Yearly) 

Off-Site Hazardous Sludge Disposal (80% moisture) 40 ton $263.00 $10,520.00 

Sludge Pumping and Bag Filtration 1 lump sum $3,795.00 $3,795.00 

Subtotal $14,315.00 

IX Analytical Services (Yearly) 

Dissolved Metals (Effluent Discharge) 52 each $80.00 $4,160.00 

Total and Leachable Metals (Waste Characterization) 1 each $280.00 $280.00 

Subtotal $4,440.00 

X Maintenance and Modifications (as indicated) 

Replace Storage Batteries (every 5 years) 1 each $5,200.00 $5,200.00 

Replace Water Turbine (every 20 years) 1 each $9,000.00 $9,000.00 

Replace Reagent Pumps (every 2 years) 2 each $1,000.00 $2,000.00 

Subtotal $16,200.00 

Total 1st Year Variable Costs $104,613.39 

 Recurring Variable Costs $82,155.39 

 Periodic Costs $16,200.00 

Description Total 

Total 1st Year Costs $941,248.34 

Total 1st Year Costs/1000 gallons $189.54 

Total Variable Costs/1000 gallons $16.54 

Cumulative 5-Year Total Variable Costs (Present Worth at 7% Rate of Return) $343,834.00 

Cumulative 15-Year Total Variable Costs (Present Worth at 7% Rate of Return) $764,950.00 

Cumulative 30-Year Total Variable Costs(Present Worth at 7% Rate of Return) $1,045,005.00 

% - Percent MHz – Megahertz 

HDPE – High Density Polyethylene SCADA - Supervisory Control and Data Acquisition 

KW - Kilowatt 

79
________________________________________________________________________________ 

Table C-2. Cost Element Details for the Compost-Free Bioreactor Treatment System - Recirculation Operation 

Description Quantity Unit Unit cost Subtotal 

I Site Preparation 

Design (20% of capital cost) 1 lump sum $119,189.00 $119,189.00 

Construction Management (15% of capital cost) 1 lump sum $89,392.00 $89,392.00 

Project Management (10% of capital cost) 1 lump sum $59,595.00 $59,595.00 

Preconstruction Site Work (Clearing and Chipping, Topsoil 

Removal, and Debris Removal) 1 lump sum $41,392.00 $41,392.00 

Subtotal $309,568.00 

II Permitting and Regulatory Requirements 

Superfund Site, No Permitting Costs $0.00 

Subtotal $0.00 

III Capital and Equipment 

1 Compost-Free Bioreactor Treatment System

 a Equipment Mobilization/Demobilization 1 lump sum $73,550.00 $73,550.00 

b Pond and Pipe Trench Earthwork 1 lump sum $136,442.00 $136,442.00 

Seep collection pond excavation, bioreactor ponds and settling 

ponds excavation, sloping/riprap, trench excavation and placement 

of bedding for piping 

c Installation of Pond Liners, Stairs, Decent Structures 1 lump sum $63,756.00 $63,756.00 

Placement and seaming of liners and installation of boots for 

piping in the pretreatment pond, the two bioreactor ponds, and the 

two settling ponds. Installation of settling pond stairs and decant 

structures. Placement of geotextile in the bottom of the aeration 

channel. 

d Installation of Distribution Piping and Valve Vaults 1 lump sum $149,263.00 $149,263.00 

Placement of 6-inch system main drain and valves, 

4-inch distribution piping and valves, and 4-inch perforated 

influent and effluent loops in the two bioreactors; installation of 

two precast flushing vaults and ten 24-inch diameter HDPE 

standpipe vaults 

e Placement of Bioreactor Substrate 1 lump sum $47,173.00 $47,173.00 

Placement of manure layer, 3- to 6-inch cobble layer, and 6- to 9­

inch round rock layer 

f Erosion Control and Revegetation/Reseeding 1 lump sum $10,907.00 $10,907.00 

g Recirculation Pump and Piping 1 lump sum $6,120.00 $6,120.00 

(1) Stainless steel submersible pump; 200 feet of 3-inch HDPE 

piping; 900 feet of 2-inch HDPE piping; wiring 

h Water Turbine and Storage Batteries 1 lump sum $14,700.00 $14,700.00 

4 KW turbine and 60 KW battery (48 volt) 

Subtotal $501,911.00 

2 Reagent Storage and Distribution 

a Ethanol Storage Tank and Delivery System 1 lump sum $13,400.00 $13,400.00 

Two 2,300 gallon bulk tanks, a reagent pump and viton tubing, and 

line containment pad 

b Sodium Hydroxide Storage Tank and Delivery System 1 lump sum $15,800.00 $15,800.00 

One 1,000 gallon bulk tank, a stainless steel transfer pump, a daily 

make up tank, a reagent pump and viton tubing, and line 

containment pad 

c Make up Water Storage Tank and Delivery System 1 lump sum $2,000.00 $2,000.00 

One 1,000 gallon bulk tank, a pump and delivery line. Assumes a 

make up water source is available, otherwise, use treated effluent 

d Reagent Storage Area Fencing 1 lump sum $4,000.00 $4,000.00 

200 feet of eight foot high fencing, double wide access gate, razor 

wire top. 

Subtotal 35,200.00 

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Table C-2. Cost Element Details for the Compost-Free Bioreactor Treatment System - Recirculation Operation (continued) 

Description Quantity Unit Unit cost Subtotal 

3 Automation

 a Remote Monitoring/Alarm System $9,742.50 

Sensaphone SCADA 3000 (control system, logger, alarm) 1 lump sum $2,495.00 $2,495.00 

Miscellaneous Accessories for SCADA 3000 1 lump sum $500.00 $500.00 

Personal Computer 1 lump sum $2,000.00 $2,000.00 

Professional Series 900 MHz Data Transceivers 1 lump sum $1,000.00 $1,000.00 

Miscellaneous Accessories for Transceivers 1 lump sum $500.00 $500.00 

Installation Cost (assumes 50% of equipment cost) 1 lump sum $3,247.50 $3,247.50

 b pH Controller System $6,202.50 

Pulse Output Controller 2 each $1,160.00 $2,320.00 

Electronic Diaphragm Pumps 2 each $826.00 $1,652.00 

pH Probe and Cable 2 each $220.00 $440.00 

Temperature Sensor and Cable 2 each $200.00 $400.00 

Accessories (cables, calibration solution) 1 lump sum $150.00 $150.00 

Installation Cost (assumes 25% of equipment cost) 1 lump sum $1,240.50 $1,240.50 

Subtotal $15,945.00 

4 Communications 

Motorola 9505 Satellite Phone 1 lump sum $1,495.00 $1,495.00 

Subtotal $1,495.00 

Total Fixed Costs $864,119.00 

IV System Start up and Acclimation (one time event) 

System Start-up Labor (2 Field Technicians for 2 weeks) 160 hour $56.19 $8,990.40 

Acclimation Period Labor (1 Field Technician for 2.5 months) 240 hour $56.19 $13,485.60 

Subtotal $22,476.00 

V Consumables and Rentals (Yearly) 

Ethanol 2,630 gallon $2.50 $6,575.00 

Sodium Hydroxide 2,651 gallon $0.85 $2,235.35 

Personal Protective Equipment (4 days/month) 12 month $28.00 $336.00 

Hydrogen Sulfide Gas Meter (4 days/month) 12 month $300.00 $3,600.00 

Water Quality Meter and Supplies (4 days/month) 12 month $700.00 $8,400.00 

Storage Connex 12 month $325.00 $3,900.00 

Subtotal $25,046.35 

VI Labor (Yearly) 

Field Technicians (1 day per week) 416 hour $56.19 $23,375.04 

Administrative Support (5% of field effort) 20 hour $61.16 $1,223.20 

Project Management (10% of field effort) 40 hour $90.00 $3,600.00 

Subtotal $28,198.24 

VII Utilities (Yearly) 

Backup Generator (3 Kilowatt; assume required for 4 months) 4 month $800.00 $3,200.00 

Backup Generator Fuel (105 gallon/month at $2.50/gallon) 4 months $262.50 $1,048.00 

SCADA Communication Service 12 month $75.00 $900.00 

Satellite Phone Communications Service 12 month $50.00 $600.00 

Portable Toilet 8 month $325.00 $2,600.00 

Subtotal $8,348.00 

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Table C-2. Cost Element Details for the Compost-Free Bioreactor Treatment System - Recirculation Operation (continued) 

VIII Residual Waste Handling and Disposal (Yearly) 

Off-Site Hazardous Sludge Disposal (80% moisture) 23 ton $263.00 $6,049.00 

Sludge Pumping and Bag Filtration 1 lump sum $3,795.00 $3,795.00 

Subtotal $9,844.00 

IX Analytical Services (Yearly) 

Dissolved Metals (Effluent Discharge) 52 each $80.00 $4,160.00 

Total and Leachable Metals (Waste Characterization) 1 each $280.00 $280.00 

Subtotal $4,440.00 

X Maintenance and Modifications (as indicated) 

Replace Recirculation Pump (every 5 years) 1 each $5,000.00 $5,000.00 

Replace Storage Batteries (every 5 years) 1 each $5,200.00 $5,200.00 

Replace Water Turbine (every 20 years) 1 each $9,000.00 $9,000.00 

Replace Reagent Pumps (every 2 years) 2 each $1,000.00 $2,000.00 

Subtotal $21,200.00 

Total 1st Year Variable Costs $98,352.59 

 Recurring Variable Costs $75,876.59 

 Periodic Costs $21,200.00 

Description Total 

Total 1st Year Costs $962,471.59 

Total 1st Year Costs/1000 gallons $193.81 

Total Variable Costs/1000 gallons $15.28 

Cumulative 5-Year Total Variable Costs (Present Worth at 7% Rate of Return) $321,654.00 

Cumulative 15-Year Total Variable Costs (Present Worth at 7% Rate of Return) $715,681.00 

Cumulative 30-Year Total Variable Costs(Present Worth at 7% Rate of Return) $977,880.00 

% - Percent MHz – Megahertz 

HDPE – High Density Polyethylene SCADA - Supervisory Control and Data Acquisition 

KW - Kilowatt 

82