September 2002

NSF 02/01/EPAWQPC-SWP

Environmental Technology

Verification Report

Removal of Mercury from Dental 

Office Wastewater

Dental Recycling North America (DRNA)

Mercury Recovery Unit (MRU)

Prepared by

NSF International

Under a Cooperative Agreement with

U.S. Environmental Protection Agency
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ETV Joint Verification Statement

THE ENVIRONMENTAL TECHNOLOGY VERIFICATION

PROGRAM

TECHNOLOGY TYPE: SEDIMENTATION AND ADSORPTION OF MERCURY 

AMALGAM AND MERCURY COMPOUNDS

APPLICATION: REMOVAL OF MERCURY AMALGAM PARTICULATE 

AND SOLUBLE AND INSOLUBLE MERCURY FROM 

DENTAL OFFICE WASTEWATER

TECHNOLOGY NAME: DENTAL RECYCLING NORTH AMERICA (DRNA) 

MERCURY RECOVERY UNIT (MRU) 

COMPANY: DENTAL RECYCLING NORTH AMERICA, INC.

ADDRESS: 145 WEST 58th STREET PHONE: (800) 360-1001

NEW YORK, NY 10019 FAX: (212) 247-4420

WEB SITE: http://www.drna.com

EMAIL: marcs@drna.com

NSF International (NSF), in cooperation with the U.S. Environmental Protection Agency (EPA), operates 

the Water Quality Protection Center under EPA’s Environmental Technology Verification (ETV)

Program. As part of the center’s activities in verifying the performance of source water protection (SWP) 

technologies, NSF recently evaluated the performance of a mercury removal unit used in dental offices 

for removal of mercury from wastewater. This verification statement provides a summary of the test 

results for the Dental Recycling North America (DRNA) Mercury Recovery Unit (MRU). The NSF 

laboratories, in conjunction with Scherger Associates, performed the verification testing.

The Environmental Technology Verification Program was created by EPA to facilitate the deployment of 

innovative or improved environmental technologies through performance verification and dissemination 

of information. The goal of the ETV program is to further environmental protection by accelerating the 

acceptance and use of improved and more cost-effective technologies. ETV seeks to achieve this goal by 

providing high quality, peer reviewed data on technology performance to those involved in the design, 

distribution, permitting, purchase, and use of environmental technologies. 

ETV works in partnership with testing organizations and stakeholder advisory groups consisting of 

buyers, vendor organizations, permitters, and with the full participation of individual technology

developers. The program evaluates the performance of innovative technologies by developing test plans 

that are responsive to the needs of stakeholders, conducting field or laboratory tests (as appropriate), 

collecting and analyzing data, and preparing peer reviewed reports. All evaluations are conducted in 

U.S. Environmental 

Protection Agency NSF International
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accordance with rigorous quality assurance protocols to ensure that data of known and adequate quality 

are generated and that the results are defensible.

ABSTRACT

Verification testing of the DRNA Mercury Recovery Unit (MRU) was conducted during a seven-week 

period, at a dental office in Michigan that had three operatory rooms and two hygiene rooms. The office 

operated four days per week and averaged approximately eight (8) mercury amalgam surfaces

removed/placed per day. The MRU was installed in the vacuum system ahead of the air/water separator, 

and operated continuously over the verification test period. During an eleven-week period prior to the 

verification test period, a baseline characterization test was conducted with the total volume of untreated 

wastewater generated at the office being sampled and analyzed. The characterization data provided 

representative influent data for comparison with the treated water effluent data collected during the 

verification test. Mercury removal was calculated by two methods. One approach used the data colle cted 

during the characterization test to represent the influent wastewater quality. The second approach used a 

mass balance that measured all of the mercury captured and discharged by the MRU during the

verification test. The MRU achieved mercury removal, on a total mass-loading basis, of 98.3 to 99.4 

percent depending on the approach used. The removal of settleable mercury, which represented 77 to 81 

percent of the mercury in the wastewater, averaged 99.6 to 99.9 percent. Mercury present in the liquid 

fraction after settling (soluble and suspended particulate) was removed by the adsorption media in the 

92.3 to 94.0 percent range. Both settleable mercury and mercury present in the liquid after settling 

(soluble and suspended particulate) were effectively removed from the wastewater. The system operated 

throughout the verification test with no maintenance or down time. There was evidence that the activated 

carbon adsorption media was breaking down and exiting the unit during the verification test. DRNA 

indicated this was due to excess bleach being fed to the unit. The concentration of the bleach solution 

was subsequently decreased during the verification test, and reflects the recommended bleach

concentration in the Operations and Maintenance Manual currently being supplied with their units.

TECHNOLOGY DESCRIPTION

The DRNA Mercury Recovery Unit is designed to remove mercury from dental wastewater using a twostep process to address both the insoluble and soluble mercury present in wastewater. Soluble mercury is 

defined as the mercury, whether in solution or fine particulate, that can pass through a 0.45 micron filter. 

The verification testing was performed using a full scale, commercially available MRU. The test unit was 

received as a self-contained system that included all of the parts needed for installation. The equipment 

included the BullfroHgTM Air/Water/Amalgam Separator, an adsorbent column with particle filter, pump 

timers, twin peristaltic pumps with waste sensor, and a 10-liter bleach reservoir. The unit came with all 

of the tubing and fittings to connect the unit to the dental office vacuum system.

The BullfroHg unit is designed to remove mercury amalgam particles from dental wastewater by gravity 

settling. It is a combined solid and air/water separator that is installed on the suction side of a dental 

vacuum pump. Three-phase flow (air/water/solids) enters the BullfroHg, where the entrained solids and 

liquids are retained within the unit and the air flows out to the system vacuum pump. Particles are 

allowed to settle for several hours after the vacuum system is shut down at the end of the operating day. 

At the conclusion of settling, a timer-activated pump transfers wastewater from the settling chamber to 

the adsorbent column, where it passes through adsorbents and a fine particle filter. Amalgam particles 

remain trapped within the gravity separator unit, while soluble mercury and mercury associated with 

suspended fine particles are adsorbed onto the column media. A particle filter is located at the end of the 

column to capture fine particulate not adsorbed by the column media. The treated wastewater is

discharged to the sewer system. Approximately 200 mL of bleach solution is pumped into the adsorbent 

column each day to control biological growth within the column. Mercury captured within the MRU is 
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typically returned to DRNA for recycle. DRNA has arrangements with mercury recovery companies to 

recycle the mercury trapped or adsorbed by the MRU, as well as from the chair side traps that are part of a 

typical vacuum system. The mercury recovery/recycling process used by DRNA was not part of this 

verification process. 

VERIFICATION TESTING DESCRIPTION 

Test Site

The verification test was performed at a dental office in Southeast Michigan. This general dentistry 

practice was representative of a small dental office with one or two dentists. The office had five chairs, 

with two chairs being used for dental hygiene work and three chairs for general dentistry procedures, and 

typically operated four days per week. During the initial characterization period, there was one dentist in 

the office. During the verification test period, a second dentist was added on a part time basis. The office 

uses a dry vacuum system. 

Methods and Procedures

During both the wastewater characterization and verification test periods, the entire wastewater flow from 

the vacuum collection system was collected each day the dental office was open, and was sent to the NSF 

laboratory by courier service in iced coolers. The samples were prepared in the laboratory and analyzed 

for total mercury in the settleable solids, total mercury in the decant liquid from the settling procedure and 

soluble mercury in the decanted liquid. The daily wastewater volume, mass of settleable solids, and pH 

were also determined. A special procedure was used to separate the settleable solids in the wastewater. 

The entire sample was placed in a large settling chamber and solids were allowed to settle for at least 

eight (8) hours. After settling, the liquid fraction containing suspended particles was removed from the 

settling chamber. The settled solids were collected, filtered, weighed and analyzed for total mercury. The 

liquid fraction was split into two samples. One sample was analyzed for total mercury, the other sample 

was filtered through a 0.45 micron filter, and the filtrate analyzed to determine soluble mercury. At the 

end of the verification test period, residue samples were obtained by removing the solids from the 

BullfroHg separator, and by removing the adsorbents and particle filter from the adsorbent column. 

These residues were analyzed for total mercury in order to complete a mass balance of mercury in the 

MRU.

All samples were preserved and analyzed in accordance with EPA approved methods. Mercury was 

determined using EPA Method 245.1 for liquids and 245.5 for solids, and Method 150.1 was used for pH 

determinations.

PERFORMANCE VERIFICATION

System Operation

The MRU was installed in accordance with the manufacturer’s instructions received with the unit. The 

total time to install the unit was less than three hours. The system was wet tested for leaks and to verify 

the pumps were working properly. After this initial check, the unit operated with no mechanical changes 

or maintenance for the duration of the seven-week verification test period. 

The bleach solution was initially made at the recommended concentration of one part bleach to one part 

water. After approximately three weeks of operation, the effluent from the MRU was very black in color, 

and the mercury levels in the effluent increased from less than 1 μg/L to between 1 and10 μg/L. 

According to DRNA, it was likely that the bleach solution was too strong and was causing a breakdown 

of the activated carbon, resulting in carbon fines passing through the particle filter and exiting in the 

effluent. During the characterization phase of the technology verification, DRNA revised their O&M 

Manual to recommend one part bleach to two parts water. However, this information was not provided 
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until NSF contacted DRNA about the change in the MRU effluent quality. The bleach concentration was 

subsequently changed to the revised recommended concentration of one part bleach to two parts water. 

Carbon fines continued to be discharged from the MRU at reduced levels after the bleach concentration 

was reduced. DRNA has since revised the recommended bleach concentration once again to one part 

bleach to three parts water. However, no testing was performed using this concentration. 

Wastewater Characterization Results

The wastewater characterization test was conducted from July 10 through September 21, 2001, with 44 

complete sample sets being collected over the eleven-week period. The dental office normally operated 

four days per week, and samples were collected at the end of each normal business day. Three hundred

thirty four (334) mercury amalgam surfaces were removed and/or placed during the characterization test. 

Each wastewater sample was allowed to settle in the laboratory to separate the settleable solids from the 

wastewater, resulting in three samples for mercury measurement - total mercury in the settleable solids, 

total mercury in the liquid fraction (decant after settling, including both suspended particulate matter and 

soluble mercury), and soluble mercury in the liquid fraction. The wastewater flow (all flow collected as 

sample) averaged 2.2 liters per day, ranging from a high flow of 5.9 liters per day to a low of 0.13 liters 

per day.

The average total mercury concentration in the wastewater (settleable solids plus mercury in the decant 

liquid) was 657 μg/L, varying from a high of 1810 μg/L to a low of 73 μg/L. The average mass of 

mercury was 1.60 mg/day, varying from 0.05 mg/day to 6.81 mg/day. The decanted liquid fraction (after 

settling) averaged 192 μg/L. The soluble mercury fraction in the decanted liquid averaged 127 μg/L, and 

typically represented 50-70 percent of the mercury in this fraction of the wastewater. The summary 

statistics for the wastewater characterization are presented in Table 1.

Table 1. Mercury Data Summary – Wastewater Characterization Test

Hg Mass (mg/day) Total 

Wastewater

Decant Liquid

Concentration

(mg/L)

Total Soluble

Total 

Wastewater

Volume

(mL)

Settleable 

Solids

Decant 

Liquid 

Concentration

(μg/L)

Mass

(mg/day)

Average 0.192 0.127 2180 1.23 0.364 657 1.60

Maximum 0.676 0.632 5880 6.49 1.90 1810 6.82

Minimum 0.0446 0.0044 129 <0.01 0.0094 72.6 0.0537

Std. Dev 0.152 0.139 1410 1.81 0.369 581 1.94

Total

Mass/ vol. 100,000 54.2 (mg) 16.7 (mg)

Verification Test Results

The verification test was performed from September 24 through November 8, 2001, with 32 complete 

sample sets of MRU treated effluent being collected and analyzed. During the seven-week verification 

period, the dental office added a dentist on a part time basis. The office operated on a four or five day per 

week schedule with 243 mercury amalgam surfaces being removed/placed on 29 operating days. The 

average amalgam surface removal/placement rate of 8.38 surfaces per operating day was similar to the 

rate during the characterization test (7.73 – 7.95 surfaces per day). 

MRU effluent wastewater samples were handled in the same manner as during the characterization test, 

resulting in three samples for mercury measurement - total mercury in the settleable solids, total mercury 

in the liquid fraction (decant after settling, including both suspended particulate and soluble mercury), and 
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soluble mercury in the liquid fraction. The results of the analyses are presented in Table 2. The average 

total mercury discharge concentration from the MRU was 10.3 μg/L, with a maximum of 39.8 μg/L and a 

minimum of <0.2 μg/L. The average mass of mercury discharged on a daily basis was 0.036 mg/day, 

with the settleable solids portion representing an average of 0.007 mg/day and the liquid fraction having 

an average of 0.0284 mg/day. The mercury contribution from the settleable solids represented 19 percent 

of the mercury present in the discharge after treatment versus 77 percent in the untreated wastewater. 

Table 2. Summary Statistics Mercury Results for DRNA MRU Effluent

Decant Liquid Hg Mass (mg/day) Total Wastewater

Concentration (mg/L)

Total Soluble

Total 

Wastewater

Volume 

(mL)

Settleable 

Solids

Decant 

Liquid

Concentration

(μg/L)

Mass

(mg/day)

Average 0.0079 0.0027 2550 0.0073 0.0284 10.3 0.0357

Maximum 0.0337 0.0135 6060 0.043 0.177 39.8 0.217

Minimum <0.0002 <0.0002 177 0.00 <0.0002 <0.2 <0.0003

Std. Dev 0.0108 0.0037 1770 0.0103 0.0507 12.8 0.0601

Total 

mass 81,700 0.234 (mg) 0.909 (mg)

Note: All Values below Detection Limit set equal to zero in calculation

The mercury concentration in the discharge was either below the detection limit (<0.2 μg/L) or in the 0.2 

to 3.5 μg/L range for the first eighteen days of the verification test. During the first few days, the effluent 

had no settleable solids and had very low suspended solids in the liquid fraction. The effluent then began 

to darken in color and became very black, with noticeable suspended particulate present; however, only a 

small portion of these solids settled. The amount of solids being filtered from the liquid fraction began to 

increase and the solids were very black and fine in appearance. The bleach solution was changed to the 

new recommended strength about 31⁄2 weeks into the test, and over the next 11⁄2 weeks, the total mercury 

concentration in the effluent, the mass of settleable solids found in the separation procedure, and the 

amount of solids being filtered from the decant liquid reached peak levels. For the last two weeks, the 

mass of dry solids and the mercury concentration in the MRU effluent stabilized and began to decrease. 

On the last two days of the verification test, the mass of solids and the mercury concentration in the 

effluent again increased. It was noted that the total flow from the dental office was higher than average on 

these final two days. The final day’s flow was impacted by the extra flushing of the vacuum system 

performed to clear the lines at the end of the test. On the second to last day of the test, the number of 

mercury amalgam surfaces removed and placed was higher than average. These factors may have 

impacted the performance of the MRU.

DRNA MRU Performance

As described in the general protocol for test plan development, it was not possible to collect influent and 

effluent samples simultaneously during the verification period due to the small volume of the influent 

flow, the operation of the system under vacuum, and the difficulty of obtaining representative samples 

(particularly of solids) from small pipes, with small intermittent flow under vacuum. The test plan was 

designed to obtain data that could be used for two different approaches to determine the treatment

efficiency of the unit. The first approach used the characterization test data, collected for the eleven 

weeks prior to the verification test period, to determine the average mercury concentration and average 

mercury mass discharged from the dental office on a daily basis. The dental office operation was similar 

during both the characterization period and the verification period, which allowed the characterization 

data to be used as a substitute for the actual influent characteristics during the verification test period. For 
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the second approach, effluent quality was measured directly during the verification test period. At the end 

of the test period, a mass balance for the MRU was completed using the effluent data collected during the 

verification test period and the mass of mercury retained in the MRU.

Characterization Data vs. Verification Data

Comparing the characterization data to the treated effluent data shows that the DRNA MRU was effective 

in removing the settleable solids and the mercury in these solids, achieving better than 99 percent removal 

either on an average concentration basis or on a total mass basis. As shown in Table 3, the overall 

removal of mercury (solids and liquid combined) was 98.7 percent on a concentration basis and 98.3 

percent on a total mass basis. Removal efficiency for the mercury associated with the settleable solids 

was 99.6 percent. The MRU also was effective in removing the mercury associated with the decant liquid 

fraction (soluble and suspended mercury) showing an efficiency of 92.8 percent.

Table 3. Removal Efficiency Based on Characterization Data- Total Mass and 

Average Concentration

Settleable Solids Total Wastewater

Mass (mg)

Decant Liquid 

Mass (mg) Concentration (μg/L) Mass (mg)

Characterization 

(7/30-9/20/2002)

53.3 12.7 778 66.0

MRU Discharge

(9/25-11/9/2002)

0.234 0.909 10.3 1.14

% Removal 99.6 92.8 98.7 98.3

Mass Balance of Verification Data

The second approach to calculating removal efficiency is based on measuring all of the mercury retained 

in the unit during the verification test and calculating the total load to the MRU (retained mercury + 

discharged mercury = total influent mercury). Using this approach, the DRNA MRU removed over 99 

percent of the mercury in the settleable solids and over 99 percent of the total mercury delivered to the 

MRU. The MRU was also effective in reducing the mercury in the liquid fraction by 94 percent. The 

results for the verification test mass balance are shown in Table 4. The removal efficiencies calculated by 

the mass balance are similar to the removal efficiencies found using the characterization data. In general, 

the mass balance approach does tend to show somewhat larger removal efficiencies because there was a 

greater total mass of mercury, particularly in the settleable solids, during the verification test than during 

the characterization test.

Under these conditions, verification testing demonstrated the DRNA MRU to be capable of removing 

greater than 99 percent of the mercury associated with settleable solids, 92 to 94 percent of the mercury 

associated with the liquid fraction (soluble plus suspended particulate), and 98 to 99 percent of the total 

mercury present in the wastewater.
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Table 4. Removal Efficiency based on Mass Balance of Retained and Discharged Mercury

Mass of Mercury

Settleable Solids

(mg)

Decant Liquid

(mg)

Total Wastewater

(mg)

Separator-Retained 181 - 181

Filter-Retained - 0.049 0.049

Carbon-Retained - 4.98 4.98

Resin-Retained - 9.24 9.24

Discharge 0.234 0.909 1.14

Total Mass Load 182 15.2 197

% Removal 99.9 94.0 99.4

Operation and Maintenance Results

The MRU was easy to operate, requiring no operator intervention except for occasionally verifying pump 

operation and weekly checks of the bleach solution level. Once the unit was installed and operational, 

there were no maintenance requirements other than replenishing the bleach solution, and the unit 

performed without interruption for seven weeks. DRNA’s recommended maintenance interval is 6-12 

months depending on the amount of material treated in the wastewater stream. Visual observations made 

during the verification test, and a review of the type of pumps and materials of construction used in the 

MRU, did not indicate otherwise. The only operational problem encountered during the verification test 

was the increase in solids in the MRU effluent, apparently from the bleach solution causing the carbon to 

breakdown and be discharged. The bleach solution to water ratio was adjusted to what DRNA

recommends for units currently being sold. 

Two quantifiable O&M factors that apply to the DRNA MRU are electrical usage and chemical usage. 

The electrical power requirement was 120VAC, 4 amps for each of the two pumps in the unit. Total 

electrical use can be expected to average about 2,400 watts per day. At a mix ratio of 1 part bleach to 3 

parts water, approximate ly 1.2 liters of bleach per month will be used. 

The MRU did not require cleanout or maintenance during the verification test period. Observation during 

the recovery of the settleable solids from the separator showed that less one percent of the solids separator 

volume (<100 mL of solids in a 10 liter unit) was accumulated during the seven-week test period. The 

separator should therefore have sufficient capacity to hold six months to one year of solids at the 

accumulation rate experienced during the verification test. DRNA provided proprietary information on 

the mercury adsorbing capacity of the adsorbent material. Measurement of the weight of adsorbent in the 

MRU combined with results of quality control samples that independently measured the adsorption of 

mercury, indicated sufficient adsorption capacity to treat soluble mercury for six months to one year, 

assuming no breakdown of the adsorbent material. The costs associated with cleanout of the MRU on the 

regularly scheduled change out (6 – 12 months) are the cost to ship the unit to DRNA and the cost 

associated with the recycling service. The MRU has been designed to facilitate the change out for return 

to DRNA, with quick disconnects and an arrangement that will assure complete containment of the MRU 

content during shipping.
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Original Signed by

E. Timothy Oppelt 09/27/02

Original Signed by

Gordon Bellen 10/04/02

E. Timothy Oppelt Date

Director

National Risk Management Research Laboratory

Office of Research and Development

United States Environmental Protection Agency

Gordon E. Bellen Date

Vice President

Research

NSF International

NOTICE: Verifications are based on an evaluation of technology performance under specific, 

predetermined criteria and the appropriate quality assurance procedures. EPA and NSF make no 

expressed or implied warranties as to the performance of the technology and do not certify that a 

technology will always operate as verified. The end user is solely responsible for complying with 

any and all applicable federal, state, and local requirements. Mention of corporate names, trade 

names, or commercial products does not constitute endorsement or recommendation for use of 

specific products. This report in no way constitutes an NSF Certification of the specific product 

mentioned herein.

Availability of Supporting Documents

Copies of the ETV Protocol for Verification Testing for Mercury Amalgam Removal 

Technologies dated April 2001, the Verification Statement, and the Verification Report 

are available from the following sources:

Source Water Protection ETV Pilot Manager (order hard copy)

NSF International

P.O. Box 130140

Ann Arbor, Michigan 48113-0140

NSF web site: http://www.nsf.org/etv (electronic copy)

EPA web site: http://www.epa.gov/etv (electronic copy)

(NOTE: Appendices are not included in the Verification Report. Appendices are

available from NSF upon request.)
September 2002

Environmental Technology Verification Report

Removal of Mercury from Dental Office Wastewater

Dental Recycling North America (DRNA)

Mercury Recovery Unit (MRU)

Prepared for:

NSF International

Ann Arbor, MI 48105

Prepared by

Scherger Associates

Under a cooperative agreement with the U.S. Environmental Protection Agency

Raymond Frederick, Project Officer

ETV Source Water Protection Pilot

National Risk Management Research Laboratory

Water Supply and Water Resources Division

U.S. Environmental Protection Agency

Edison, New Jersey 08837
ii

Notice

The U.S. Environmental Protection Agency (EPA) through its Office of Research and

Development has financially supported and collaborated with NSF International (NSF) under a 

Cooperative Agreement. The Source Water Protection Pilot, now part of the Water Quality 

Protection Center, operating under the Environmental Technology Verification (ETV) Program 

supported this verification effort. This document has been peer reviewed and reviewed by NSF 

and EPA and recommended for public release.
iii

Foreword

The following is the final report on an Environmental Technology Verification (ETV) test 

performed for NSF International (NSF) and the United States Environmental Protection Agency 

(EPA) by a testing organization comprised of the NSF laboratory and Scherger Associates in 

cooperation with Dental Recycling North America, Inc. The test was conducted from July

through November 2001 at a dental office in Michigan. 

Throughout its history, the EPA has evaluated the effectiveness of innovative technologies to 

protect human health and the environment. The Environmental Technology Verification Program 

was initiated in 1995 by EPA, to verify the performance of innovative technical solutions to 

environmental pollution or human health threats. ETV was created to substantially accelerate the 

entrance of new environmental technologies into the domestic and international marketplace. 

Verifiable, high quality data on the performance of new technologies are made available to end 

users regulators, developers, consulting engineers, and those in the public health and 

environmental protection industries. This encourages rapid availability of new and innovative 

approaches to environmental protection and reduction of human health risks.

The EPA has partnered with NSF, an independent, not-for-profit testing and certification 

organization, to verify the performance of commercial-ready treatment systems designed to 

remove pollutants and protect water quality. A goal of verification testing is to enhance and 

facilitate the acceptance of small treatment systems and equipment by state regulatory officials 

and consulting engineers while reducing the need for testing of equipment at each location where 

the equipment’s use is contemplated. NSF will meet this goal by working with manufacturers 

and NSF-qualified Testing Organizations (TO) to conduct verification testing under the approved 

protocols. NSF’s testing laboratory and Scherger Associates is one such TO.

NSF is conducting the Source Water Protection (SWP) Pilot, now part of the Water Quality 

Protection Center, with participation of manufacturers, under the sponsorship of the EPA Office 

of Research and Development, National Risk Management Research Laboratory, Water Supply 

and Water Resources Division, Edison, New Jersey. It is important to note that verification of 

the equipment does not mean that the equipment is “certified” by NSF or “accepted” by EPA. 

Rather, it recognizes that the performance of the equipment has been determined and verified by 

these organizations for those conditions tested by the TO.
iv

Table of Contents

Verification Statement .............................................................................................................VS-i

Notice.............................................................................................................................................. ii

Foreword....................................................................................................................................... iii

Table of Contents......................................................................................................................... iv

List of Tables................................................................................................................................ vi

List of Figures............................................................................................................................... vi

Glossary of Terms ....................................................................................................................... vii

Abbreviations and Acronyms ..................................................................................................... ix

Acknowledgments ......................................................................................................................... x

Chapter 1 – Introduction...........................................................................................................1-1

1.0 ETV Purpose and Program Operation .........................................................................1-1

1.1 Testing Participants and Responsibilities ................................................................1-1

1.1.1 NSF International – Verification Organization (VO)......................................1-2

1.1.2 U.S. Environmental Protection Agency...........................................................1-2

1.1.3 Testing Organization........................................................................................1-3

1.1.4 Technology Vendor..........................................................................................1-5

1.1.5 ETV Test Site...................................................................................................1-6

1.1.6 Technology Panel.............................................................................................1-6

1.1.7 Stakeholder Advisory Group ...........................................................................1-6

1.2 Sources and Fate of Mercury in the Environment ...................................................1-6

1.3 Mercury Amalgam in Dental Offices.......................................................................1-9

Chapter 2 - Technology Description and Operating Processes ............................................2-1

2.0 Technology Description...............................................................................................2-1

2.1 DRNA Mercury Recovery Unit (MRU) ..................................................................2-1

2.2 Equipment Specifications ........................................................................................2-3

2.3 Operation and Maintenance .....................................................................................2-4

2.4 Vendor Claims .........................................................................................................2-5

Chapter 3 - Methods and Test Procedures..............................................................................3-1

3.0 Test Plan and Procedures.............................................................................................3-1

3.1 Influent Characterization - Procedures ....................................................................3-1

3.1.1 Introduction......................................................................................................3-1

3.1.2 Objectives.........................................................................................................3-1

3.1.3 Sampling Location, Container Type, and Sampling Frequency......................3-2

3.1.4 Analytical Testing and Record Keeping..........................................................3-4

3.2 MRU Installation and Commissioning - Procedures ...............................................3-5

3.2.1 Introduction......................................................................................................3-5

3.2.2 Objectives.........................................................................................................3-5

3.2.3 Installation and Startup Procedures.................................................................3-6

3.3 Verification Testing - Procedures............................................................................3-7

3.3.1 Introduction......................................................................................................3-7

3.3.2 Objectives.........................................................................................................3-8

3.3.3 Sample Location, Sampling Approach, and Frequency...................................3-8

3.3.3.1 Treated Water Sample Collection................................................................3-8

3.3.3.2 Residuals Sample Collection .......................................................................3-9
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3.3.4 Analytical Testing and Record Keeping........................................................3-10

3.3.5 Operation and Maintenance Performance......................................................3-12

Chapter 4 - Results and Discussion..........................................................................................4-1

4.0 Characterization Test ...................................................................................................4-1

4.1 Mercury Amalgams Removed and Placed...............................................................4-1

4.2 Mercury Results.......................................................................................................4-1

4.3 pH Results – Characterization Study.......................................................................4-9

4.4 Installation and Startup of DRNA MRU .................................................................4-9

4.5 Verification Test ....................................................................................................4-10

4.6 Mercury Amalgams Removed and Placed.............................................................4-11

4.7 Mercury Results – Verification Test......................................................................4-13

4.8 pH Results Verification Study ...............................................................................4-19

4.9 Residue Results for DRNA MRU..........................................................................4-20

4.10 Performance of the DRNA MRU ..........................................................................4-22

4.10.1 Comparison Approach...................................................................................4-22

4.10.2 Removal Efficiency Based on Characterization Data....................................4-22

4.10.3 Removal Efficiency Based on Verification Data Mass Balance....................4-24

4.11 MRU Operational Characteristics..........................................................................4-25

4.11.1 Qualitative Factors.........................................................................................4-25

4.11.2 Quantitative Factors.......................................................................................4-26

4.12 Quality Control Results..........................................................................................4-27

Chapter 5 – References..............................................................................................................5-1
vi

List of Tables

Table 2-1. Equipment List.....................................................................................................2-4

Table 2-2. Recommended Maintenance Schedule ................................................................2-5

Table 3-1. Summary of Influent Analytical Requirements...................................................3-4

Table 3-2. Analytical Methods and Detection Limits...........................................................3-5

Table 3-3. Summary of Effluent and Residual Analytical Requirements...........................3-11

Table 4-1. Summary of Number of Surfaces Removed and Placed - Characterization Test 4-2

Table 4-2. Settleable Solids Results – Characterization Study .............................................4-5

Table 4-3. Mercury Results – Characterization Study ..........................................................4-6

Table 4-4. Summary Statistics for Mercury – Characterization Study .................................4-8

Table 4-5. Summary Statistics for Mercury in Settleable Solids – Characterization Study .4-8

Table 4-6. pH Results – Characterization Study.................................................................4-10

Table 4-7. Summary of Number of Surfaces Removed and Placed – Verification Test ....4-11

Table 4-8. Mercury Results - Verification Test...................................................................4-15

Table 4-9. DRNA MRU Settleable Solids Results..............................................................4-16

Table 4-10. Summary Statistics Mercury Results for DRNA MRU Effluent .......................4-18

Table 4-11. Summary Statistics Settleable Solids Results for DRNA MRU Effluent ..........4-19

Table 4-12. pH Results Verification Test..............................................................................4-19

Table 4-13. Solid Residue Results – DRNA MRU ...............................................................4-21

Table 4-14. Removal Efficiency Based on Characterization Data - Daily Averages ...........4-23

Table 4-15. Removal Efficiency Based on Characterization Data - Total Mass and Average 

Concentration.....................................................................................................4-23

Table 4-16. Removal Efficiency based on Mass Balance of Retained and Discharged Mercury

............................................................................................................................4-24

List of Figures

Figure 2-1. DRNA Mercury Recovery Unit (MRU) ..............................................................2-3

Figure 3-1. MRU Installation Schematic Diagram.................................................................3-7

Figure 4-1. Mass of Mercury in Office Wastewater – Characterization Test.........................4-7

Figure 4-2. Mass of Mercury Discharged from MRU..........................................................4-17
vii

Glossary of Terms

Accuracy - a measure of the closeness of an individual measurement or the average of a number 

of measurements to the true value and includes random error and systematic error.

Bias - the systematic or persistent distortion of a measurement process that causes errors in one 

direction.

Commissioning – the installation of the mercury amalgam removal technology (free of mercury 

residuals) and start-up of the technology using test site wastewater.

Comparability – a qualitative term that expresses confidence that two data sets can contribute to 

a common analysis and interpolation.

Completeness – a qualitative term that expresses confidence that all necessary data have been 

included.

Infrastructure and Watershed Protection Stakeholder Advisory Group - a group of

individuals, established under the VO, consisting of any or all of the following: buyers and users 

of mercury amalgam removal and other technologies, developers and vendors, consulting

engineers, the finance and export communities, and permit writers and regulators.

Mercury Free Water – laboratory prepared water used in analysis and cleaning procedures that 

is tested to ensure the mercury concentration in the water is <0.2 μg/L.

Mercury, Filterable – mercury that can be removed from a wastewater sample by settling and 

filtration through a 0.45 micron filter. Determined by subtracting the soluble mercury from the 

total mercury in the liquid sample after settling and adding the settleable mercury concentration 

or mass. Filterable mercury = (Total mercury – soluble mercury) + settleable mercury.

Mercury, Settleable – total mercury measured in the settled residue from the wastewater sample 

after settling the wastewater for eight to sixteen hours in accordance with the SOP for sampling 

handling and settling. 

Mercury, Soluble – mercury measured in the filtrate from a liquid sample that has been filtered 

through a 0.45 micron filter.

Mercury, Total – mercury measured in the liquid sample after removal of settleable solids. The 

sample is allowed to settle for 8-16 hours and the liquid is decanted. The liquid sample is not 

filtered. The entire sample, including liquid and any remaining particulate present, is used for the 

analysis. 

Owner – the owner of a dental office used as a test site for verification testing.

Precision - a measure of the agreement between replicate measurements of the same property 

made under similar conditions. 

Protocol – a written document that clearly states the objectives, goals, scope and procedures for 

the study. A protocol shall be used for reference during Vendor participation in the verification 

testing program.

Quality Assurance Project Plan – a written document that describes the implementation of 

quality assurance and quality control activities during the life cycle of the project.

Residuals – the waste streams, excluding final effluent, which are retained by or discharged 

from the technology.
viii

Glossary of Terms (cont.)

Representativeness- a measure of the degree to which data accurately and precisely represent a 

characteristic of a population parameter at a sampling point, a process condition, or

environmental condition.

Standard Operating Procedure – a written document containing specific procedures and 

protocols to ensure that quality assurance requirements are maintained.

Surfaces - refers to the surface of a tooth. There are five possible surfaces per tooth, top and 

four sides.

Technology Panel - a group of individuals established by the VO with expertise and knowledge 

in mercury amalgam removal technologies.

Testing Organization – an independent organization qualified by the Verification Organization 

to conduct studies and testing of mercury amalgam removal technologies in accordance with 

protocols and test plans. 

Vendor – a business that assembles or sells mercury amalgam removal equipment.

Verification – to establish evidence on the performance of mercury amalgam removal

technologies under specific conditions, following a predetermined study protocol(s) and test 

plan(s).

Verification Organization – an organization qualified by USEPA to verify environmental

technologies and to issue Verification Statements and Verification Reports.

Verification Report – a written document containing all raw and analyzed data, all QA/QC data 

sheets, descriptions of all collected data, a detailed description of all procedures and methods 

used in the verification testing, and all QA/QC results. The Verification Test Plan(s) shall be 

included as part of this document.

Verification Statement – a document that summarizes the Verification Report and is reviewed 

and approved by USEPA.

Verification Test Plan – A written document prepared to describe the procedures for conducting 

a test or study according to the verification protocol requirements for the application of mercury 

amalgam removal equipment at a particular test site. At a minimum, the Verification Test Plan 

includes detailed instructions for sample and data collection, sample handling and preservation, 

and quality assurance and quality control requirements relevant to the particular dental office test 

site.
ix

Abbreviations and Acronyms

ANSI American National Standards Institute

ASQC American Society for Quality Control

DRNA Dental Recycling North America, Inc.

DQI data quality indicators

DQO data quality objectives

EPA United States Environmental Protection Agency

ETV Environmental Technology Verification

MSDS material safety data sheets

MRU Mercury Recovery Unit

NSF NSF International

NRMRL National Risk Management Research Laboratory

O&M Operation and maintenance

ORD Office of Research and Development, USEPA

OSHA Occupational Safety and Health Administration

QA quality assurance

QAPP quality assurance project plan

QC quality control

QMP quality management plan

SAG Stakeholders Advisory Group

SOP standard operating procedure

SWP Source Water Protection

SWPP Source Water Protection Pilot

TCLP toxicity characteristic leaching procedure

TO Testing Organization

USEPA United States Environmental Protection Agency

VO Verification Organization

VTP Verification Test Plan
x

Acknowledgments

The Testing Organization (TO), a coalition comprised of the NSF International laboratory, 

Scherger Associates, and Mr. Adam Markie, was responsible for all elements in the testing 

sequence, including collection of samples, calibration and verification of instruments, data

collection and analysis, data management, data interpretation and the preparation of this report.

Scherger Associates

3017 Rumsey Drive

Ann Arbor, MI 48105

(734) 213 8150

Contact: Mr. Dale A. Scherger

Email: Daleres@aol.com

The laboratory that conducted the analytical work of this study was:

NSF International

789 N Dixboro Road

Ann Arbor, Michigan 48105

(734) 769-5357

Contact: Mr. Steve Williams

Email: williams@nsf.org

Equipment Installation and Sample Collection was performed by:

Mr. Adam Markie

68661 Stoecker Lane

Richmond, MI 48062

(810) 727-7980

email: None

The Manufacturer of the Equipment was:

Dental Recycling North America, Inc.

145 West 58th Street

New York, NY 10019

1-800-360-1001

Email: www.drna.com

Contact: Mr. Marc Sussman

(212) 956-5188 

Email: mmsussman@aol.com

The TO wishes to thank NSF International, especially Mr. Thomas Stevens, Project Manager, 

and Ms. Maren Roush, Project Coordinator, for providing guidance and program management.
xi

Mr. Craig Turchi, Dental Recycling North America, provided treatment system information and 

excellent technical and product expertise.

Mr. Michael Richards, Environmental Chemist at NSF, was invaluable in his coordination of all 

laboratory analyses, performing the special mercury analysis procedures, and processing of the 

resulting data. Mr. Steve Williams at NSF handled the incoming sample and processing program 

and provided hands-on expertise in removing the solid residues from the MRU at the end of the 

verification test. 
1-1

Chapter 1 – Introduction

1.0 ETV Purpose and Program Operation

The U.S. Environmental Protection Agency (EPA) has created the Environmental Technology

Verification (ETV) Program to facilitate the deployment of innovative or improved

environmental technologies through performance verification and dissemination of information. 

The goal of the ETV Program is to further environmental protection by substantially accelerating 

the acceptance and use of innovative, improved and more cost-effective technologies. ETV 

seeks to achieve this goal by providing high quality, peer reviewed data on technology

performance to those involved in the design, distribution, permitting, purchase, and use of

environmental technologies.

ETV works in partnership with recognized standards and testing organizations; stakeholders 

groups which consist of buyers, vendor organizations, consulting engineers, and regulators; and 

with the full participation of individual technology developers. The program evaluates the 

performance of innovative technologies by developing test plans that are responsive to the needs 

of stakeholders, conducting field or laboratory (as appropriate) testing, collecting and analyzing 

data, and preparing peer reviewed reports. All evaluations are conducted in accordance with 

rigorous quality assurance protocols to ensure that data of known and adequate quality are 

generated and that the results are defensible.

NSF International (NSF) in cooperation with the EPA operates the Source Water Protection Pilot 

(Pilot), one of 12 technology areas under ETV. This Pilot evaluated the performance of the 

Dental Recycling North America Mercury Recovery Unit (DRNA MRU), which is designed to 

remove mercury amalgam from wastewater from dental offices. DRNA sells the MRU unit to 

remove particulate and soluble mercury that is present in the discharge from dental office 

vacuum systems. The MRU includes a mercury amalgam separator unit based on sedimentation 

theory for removal of particulate and an adsorbent system that removes soluble mercury by 

adsorption onto a solid media. This document provides the verification test results for the Dental 

Recycling North America Mercury Recovery Unit. DRNA recycles the mercury trapped in the 

MRU when the MRU is returned to them. The mercury recycling process was not part of this 

verification. 

1.1 Testing Participants and Responsibilities

The ETV testing of the DRNA MRU was a cooperative effort between the following

participants:

NSF International

Scherger Associates

Mr. Adam Markie

DRNA

USEPA
1-2

1.1.1 NSF International – Verification Organization (VO)

The Source Water Protection ETV Pilot is administered through a cooperative agreement

between USEPA and NSF International (NSF). NSF is the verification partner organization for 

the Source Water Protection Technologies Pilot (SWPP). NSF administers the Pilot, and

organized the Testing Organization to develop and implement the Verification Test Plan (VTP).

NSF’s responsibilities as the Verification Organization include:

• Reviewing and commenting on the VTP;

• Coordinating with peer-reviewers to review and comment on the VTP;

• Coordinating with the EPA Pilot Manager and the technology vendor to approve the VTP 

prior to the initiation of verification testing;

• Reviewing the quality systems of all parties involved with the Testing Organization and 

subsequently, qualifying the companies making up the Testing Organization;

• Overseeing the technology evaluation and associated laboratory testing;

• Carrying out an on-site audit of test procedures;

• Overseeing the development of a verification report and verification statement;

• Coordinating with EPA to approve the verification report and verification statement; and

• Providing QA/QC review and support for the TO.

Key contacts at NSF for the Verification Organization are:

Mr. Thomas Stevens, Program Manager

(734) 769-5347 email: stevenst@nsf.org

Ms. Maren Roush, Project Coordinator

(734) 827-6821 email: mroush@nsf.org

NSF International

789 N. Dixboro Road

Ann Arbor, Michigan 48105

(734) 769-8010

1.1.2 U.S. Environmental Protection Agency

The USEPA Office of Research and Development through the Urban Watershed Branch, Water 

Supply and Water Resources Division, National Risk Management Research Laboratory

(NRMRL), provides administrative, technical, and quality assurance guidance and oversight on 

all ETV Source Water Protection pilot activities. The USEPA reviews and approves each phase 
1-3

of the verification project. The USEPA’s responsibilities with respect to verification testing 

include:

• VTP review and approval; 

• Verification Report review and approval; and

• Verification Statement review and approval.

The key USEPA contact for this program is:

Mr. Ray Frederick, Project Officer, ETV Source Water Protection Pilot

(732)-321-6627 email: frederick.ray@epa.gov

U.S. EPA, NRMRL

Water Supply and Water Resources Division

2890 Woodbridge Ave. (MS-104)

Edison, NJ 08837-3679

1.1.3 Testing Organization

The Testing Organization (TO) for the DRNA MRU verification testing was a consortium of the 

NSF International laboratory, Scherger Associates, and Mr. Adam Markie. This group was 

organized by NSF to bring together resources that could complete a high quality verification test 

program in a cost effective manner. Each participant in the consortium had a well-defined role in 

planning and executing the VTP. 

Mr. Dale Scherger of Scherger Associates served as the Project Manager for the TO and was 

responsible for coordination and development of the VTP, obtaining all of the information

needed to plan and execute the VTP, managing the data collected during the test period, 

preparing the draft final report, and providing technical guidance in conjunction with the

Technology Panel. Mr. Adam Markie provided field support at the test site, including setup and 

operation of the MRU, collection of the daily and weekly records from the dental office, and 

collection and shipment of the samples on a daily basis. Mr. Markie provided any maintenance 

support required during the verification test period in consultation with the vendor, DRNA.

NSF International provided the laboratory services for the testing program and provided

consultation on and implementation of any sampling and analytical issues addressed during the 

verification test period. NSF was responsible for all quality assurance for the VTP through its 

QA group. NSF provided administrative and technical support for review and production of the 

VTP and the Final Report. NSF also handled project management and cost tracking support for 

the project. The NSF staff involved in the verification testing process as members of the TO 

were separate from the NSF management and staff that provided the oversight for the ETV 

program as members of the VO.
1-4

The responsibilities of the TO consortium included:

• Preparation of the VTP;

• Conducting Verification Testing, according to the VTP;

• Installation, operation, and maintenance of the MRU in accordance with the Vendor’s 

O&M manual(s);

• Controlling access to the area where verification testing was carried out;

• Maintaining safe conditions at the test site for the health and safety of all personnel 

involved with verification testing;

• Scheduling and coordinating all the activities of the verification testing participants, 

including establishing a communication network and providing logistical and technical 

support on an “as needed” basis; 

• Resolving any quality concerns that were encountered and reporting all findings to the 

Verification Organization;

• Managing, evaluating, interpreting and reporting on data generated by verification

testing; 

• Evaluation and reporting on the performance of the technology; and,

• Documenting changes in plans for testing and analysis, and notifying the Verification 

Organization of any and all such changes before changes were executed.

The key personnel and contacts for the TO are:

Scherger Associates

Mr. Dale Scherger

(704)-947-7050 email: daleres@aol.com

Scherger Associates

3017 Rumsey Drive

Ann Arbor, MI 48105

Adam Markie – Field Support

Mr. Adam Markie

(810) 727-7980 email: None

68661 Stoecker Lane

Richmond, MI 48062

NSF International – Laboratory Support

Mr. Steve Williams,

(734) 769-5357 email: williams@nsf.org
1-5

NSF International – Quality Assurance Support

Bruce DeMaine, Manager, QA and Safety

 (734) 769-5143 email: demaine@nsf.org

1.1.4 Technology Vendor 

The mercury removal technology evaluated was the Mercury Recovery Unit (MRU)

manufactured and distributed by Dental Recycling North America, Inc. (DRNA). DRNA was 

responsible for supplying all of the equipment needed for the test program and supporting the TO 

in ensuring that the equipment was properly installed and operated during the verification test 

period. Specific responsibilities of the vendor included:

• Initiating application for ETV testing;

• Providing input regarding the verification testing objectives to be incorporated into the 

VTP;

• Selecting the test site;

• Providing complete, field-ready equipment and the operations and maintenance (O&M) 

manual(s) typically provided with the technology (including instructions on installation, 

start-up, operation and maintenance) for verification testing;

• Providing any existing relevant performance data for the technology; 

• Providing assistance to the Testing Organization on the operation and monitoring of the 

technology during the verification test period, and logistical and technical support as 

required;

• Reviewing and approving the VTP;

• Reviewing and commenting on the Verification Report and Statement; and

• Providing funding for verification testing.

The key contact for DRNA is:

Mr. Marc Sussman

(212) 956-5188 email: mmsussman@aol.com

Dental Recycling North America, Inc.

145 West 58th Street

New York, NY 10019

www.drna.com
1-6

1.1.5 ETV Test Site

The verification test was performed at a general practice dental office in Michigan, which is 

representative of a small dental office with one or two dentists. The dentist requested that his 

name and address not be disclosed in the verification report. The dental office typically operated 

four (4) days per week. The office had five chairs, with two being used for dental hygiene work 

and three for general dentistry procedures. During the characterization period, there was one 

dentist in the office using two general dentistry chairs. During the verification test period, a 

second dentist was added on a part time basis using the third general dentistry chair. The office 

uses a dry vacuum system. The host test site was responsible for some record keeping and 

providing information on activities that may have affected the characterization and verification 

test results. These responsibilities included:

• Providing logistical support and reasonable access to the equipment and facilities for 

sample collection and equipment maintenance; 

• Notifying the Testing Organization of any significant changes in dental practices that 

could affect the volume and composition of wastewater produced at the site; and,

• Recording the tooth number and number of amalgam surfaces placed and removed, the 

flushing procedure used (chemicals used, volume and frequency) and when chair side 

traps or vacuum filters were changed (this system was a dry system so there were no 

filters).

1.1.6 Technology Panel

Representatives from the Technology Panel assisted the Verification Organization in reviewing 

and commenting on the VTP. The Panel also provided technical and professional support to the 

TO during all phases of the verification test period. Panel members reviewed and commented on 

the Verification Report. 

1.1.7 Stakeholder Advisory Group

The Watershed Protection Stakeholder Advisory Group was instrumental in approving the

development of the Verification Protocol that served as the basis for the development of the ETV 

Protocol for the Verification of Mercury Amalgam Removal Technologies.

1.2 Sources and Fate of Mercury in the Environment

The following discussion is taken as excerpts from the USEPA website maintained by the agency 

to inform the public and scientific community on issues related to mercury in the environment. 

The reader is referred to the EPA website (http://www.epa.gov/mercury/index.html) and to 

reports by the Science Advisory Board, the USEPA and others for more information. The EPA 

website provides references on the topic of mercury contamination and discharge to the
1-7

environment. The EPA produced a white paper regarding mercury in the environment, which can 

be found at www.epa.gov/ttn/oarpg/t3/memoranda/whtpaper.pdf. 

Mercury is a naturally occurring element that is present throughout the environment. Human 

activity can release some of that mercury into the air, water and soil. In the U.S., coal-fired 

power plants are the biggest source of mercury emissions to the air. Mercury concentrations in 

air are usually low and of little direct concern. However, when mercury enters water, biological 

processes transform it to a highly toxic form that builds up in fish and animals that eat fish. 

People are exposed to mercury primarily by eating fish. The Environmental Protection Agency is 

working to reduce the amount of mercury in the environment.

Most of the mercury entering the environment is the result of air emissions; however, mercury 

also can directly contaminate land and water as a result of the release of industrial wastewater or 

from the disposal of waste-containing batteries and other sources of mercury. Once mercury 

enters waters, either directly or through air deposition, it can bioaccumulate in fish and animal 

tissue in its most toxic form, methylmercury. Bioaccumulation means that the concentration of 

mercury in predators at the top of the food web (for example, predatory fish and fish-eating birds 

and mammals) can be thousands or even millions of times greater than the concentrations of 

mercury found in the water. More information on the sources, fate, and risks of mercury in the 

environment can be found in EPA’s 1997 Mercury Report to Congress and 1998 Utility Air 

Toxics Report to Congress.

Health Effects and Exposure

For the general U.S. population, exposure to mercury occurs primarily through eating

contaminated fish. Women of childbearing age, and people who regularly and frequently eat 

highly contaminated fish (or large amounts of moderately contaminated fish), are the most likely 

to be at risk from mercury exposure. Those groups include subsistence fishermen (people who 

fish for their food) and some Native American populations. Freshwater fish (caught by

recreational or subsistence fishermen) from contaminated waters have been shown to have 

particularly high levels of methylmercury. Mercury contamination is the most frequent basis for 

fish advisories. Fish consumption advisories have been issued for thousands of water bodies 

nationwide, including all of the Great Lakes and their connecting waters, which include more 

than 52,000 lakes and more than 238,000 miles of rivers. As of July 2000, 40 states and one 

territory (American Samoa) had issued fish consumption advisories for mercury. Thirteen of 

those states issued advisories for all water bodies in their state; the remaining 27 states issued 

advisories for more than 1,900 specific water bodies. High mercury levels also have been found 

in certain saltwater fish. In March 2000, for example, Florida, Georgia, North Carolina and 

South Carolina issued a joint fish consumption advisory because of high mercury levels in large 

king mackerel. Certain species of commercially available saltwater fish, such as shark and 

swordfish, also have high levels of mercury. The U.S. Food and Drug Administration (FDA) 

issues consumption advice for commercial marine fish. The FDA plans to re-evaluate its current 

advice in light of a July 2000 report by the National Academy of Sciences that confirmed EPA’s 

mercury reference dose. A reference dose is the level at which people could be exposed to a toxic 

(in this case, mercury) without the risk of health problems.
1-8

Neurotoxicity is the health effect of greatest concern with mercury exposure. Ingested

methylmercury is almost completely absorbed into the blood and distributed to all tissues 

(including the brain); it also readily passes through the placenta to the fetus and fetal brain. The 

developing fetus is considered the most sensitive to the effects of mercury; therefore, women of 

childbearing age are the population of greatest concern. Children born of women exposed to 

relatively high levels of methylmercury during pregnancy have exhibited a variety of

developmental neurological abnormalities, including delayed onset of walking and talking,

cerebral palsy, and reduced neurological test scores. Far lower exposures during pregnancy have 

resulted in delays and deficits in learning abilities in children.

In July 2000, the National Academy of Sciences completed a review of the latest scientific 

evidence regarding the health effects of methylmercury. The Academy confirmed EPA’s

assessment of the health risks related to mercury exposure and noted that children exposed to 

mercury in the womb as a result of their mothers’ diets during pregnancy may be at special risk 

of neurological problems. In addition, children exposed after birth are also potentially more 

sensitive to the toxic effects of methylmercury than adults, because their nervous systems are 

still developing. Mercury also poses risks to fish-eating wildlife, including some birds and 

mammals, such as the mink and otter.

Recent Actions to Reduce Mercury Pollution

EPA has taken a number of actions to reduce mercury pollution, including issuing stringent 

regulations for industries that significantly contribute to mercury pollution. Once fully

implemented, these actions will reduce U.S. mercury emissions caused by human activities by 

nearly 50 percent from 1990 levels. In addition, U.S. industrial demand for mercury dropped 75 

percent from 1988 to 1997. The drop can be attributed to a number of actions, including:

• Federal bans on mercury additives in paint and pesticides;

• Industry efforts to reduce mercury in batteries; 

• Increasing state regulation of mercury emissions and mercury in products;

• State-mandated recycling programs; and 

• Voluntary actions by industry.

EPA also provides technical assistance to state and local governments to develop mercury

pretreatment programs at wastewater treatment plants (WWTP). Some WWTP are now requiring 

monitoring of mercury levels entering the public sewer system, and some systems have set limits 

on the levels of mercury allowed to enter the sewer system. The Agency has recently lowered the 

threshold for reporting mercury emissions to the Toxic Release Inventory, which began in 2000. 

The lower threshold will help ensure that citizens know about significant mercury emissions in 

their communities. 
1-9

Planned Actions to Reduce Mercury Pollution

In addition to developing regulations to limit mercury emissions from utilities, EPA has

developed an action plan to address other sources of mercury pollution. Already there are a 

number of planned activities under way: EPA is developing a revised human health-based 

mercury standard for water quality and has identified the need to develop a standard that will 

protect wildlife from mercury’s effects.

EPA is making meaningful progress in addressing the mercury pollution problem in the United 

States and is exploring the regional, intercontinental and global dimensions of this problem. EPA 

is committed to increasing public awareness about the dangers associated with exposure to 

mercury and will continue to take actions that will provide increased protection of public health. 

1.3 Mercury Amalgam in Dental Offices

Mercury amalgam is a major material used in dental offices throughout the United States. The 

amalgam can enter the wastewater at a dental office either during the removal process, when old 

amalgams are removed or during the placement process when new amalgam is used. In a modern 

dental office, a vacuum system is used to remove liquid and particulate, including mercury 

amalgam, that accumulate in the mouth during dental procedures. The liquid contains particles of 

mercury amalgam of varying size. A coarse chair side trap is used to remove very large particles 

from the vacuumed liquid and to protect the vacuum lines from becoming plugged. The liquid 

and small particles are carried through the vacuum system to an air/water separator near the 

central vacuum pump for dry systems or directly to the vacuum pump in a wet system. The 

wastewater carrying the mercury material is then typically discharged to the sanitary sewer or 

septic tank system along with other wastewater from the office or building. Most of the mercury 

present in the wastewater is in the particulate form (insoluble). The larger particles are settleable 

and can be trapped in sedimentation chambers/devices that provide quiescent conditions. Smaller 

particles (>0.45 micron) are also present, contain mercury, and will pass through settling devices 

and contribute to the total mercury load in effluent from these devices. Some portion of these 

smaller particles can be filtered by various filtration systems. Data collected over the past few 

years has shown that a small amount of mercury will also be present in the soluble form (either 

dissolved or in particles < 0.45 micron in size). 
2-1

Chapter 2 - Technology Description and Operating Processes

2.0 Technology Description

The package treatment unit evaluated during the verification test was the DRNA Mercury

Recovery Unit (MRU). This unit is sold by DRNA as a complete package that can be installed 

upstream of the air/water separator of dry vacuum systems or before the filters and vacuum 

pump in a wet system commonly used at dental offices. The MRU is comprised of two main 

treatment components - a BullfroHg amalgam separator for particulate removal based on the 

sedimentation process, and a mercury filter unit containing an adsorbent material for soluble 

mercury removal and a fine particulate filter. Figure 2-1 shows a picture of the MRU unit. This 

combination of technologies addresses both insoluble and soluble mercury typically present in 

the wastewater from dental office vacuum systems.

2.1 DRNA Mercury Recovery Unit (MRU)

The BullfroHg is a combined solid and air/water separator designed for installation on the 

vacuum side of a dental vacuum pump to remove mercury amalgam particles from dental

wastewater. Three-phase flow (air/water/solids) enters the BullfroHg from the dental office 

vacuum line. The entrained solids and liquids are retained within the BullfroHg while the air 

flows out to the system vacuum pump. Particles are allowed to settle for several hours after the 

vacuum system is shutdown at the end of the operating day. At the conclusion of the settling 

time, a timer activates a pump to transfer the wastewater from the settling chamber through two 

adsorbents (carbon and a proprietary resin) and through a fine particle filter. Solid amalgam 

particles remain trapped within the separator unit.

Soluble mercury present in the wastewater is adsorbed onto two types of media. The wastewater 

first passes through granular activated carbon and then through a proprietary resin designed to 

specifically adsorb mercury. A fine particulate filter made of progressive density polypropylene, 

nominally rated at 1 micron, is located after the resin to capture any particulate in the effluent or 

from the absorption zone of the adsorbent column. The treated wastewater exits the adsorbent 

filter and discharges to the sewer system. A bleach solution is added to the filter unit to control 

biological growth in the media.

Mercury retained in the BullfroHg sedimentation chamber and captured on the adsorbents and 

filter can be returned to DRNA for recycling. DRNA has arrangements with mercury recovery 

companies to recycle the mercury trapped or adsorbed by the MRU and captured by the chair 

side traps that are part of a typical vacuum system. The mercury recovery/recycling process was 

not part of this verification process.

The MRU is designed to remove fine amalgam particles that can damage a vacuum pump in a 

wet vacuum system. The MRU is designed so that flow will bypass the MRU and allow

continued operation of the dental suction system if any problem occurs with the unit. This 

bypassed water will not have particulate removed and will be filtered either by the filter before a 

wet vacuum pump or by the air/solids separator in the dry system, assuming the original
2-2

separator remained inline after MRU installation. The MRU is a self-priming system and holds a 

vacuum when turned off. The MRU system pump can run dry without damaging the motor or 

the drive unit.

The system timer controls both the bleach pump and the settled wastewater transfer pump. The 

timer can be set to initiate the pumping of settled wastewater to the adsorbent column at a 

predetermined time each day. The timer is set at the factory to start the pumping cycle at 3 a.m., 

which provides about 10 hours of settling time for an office that closes at 5 p.m.. The timer also 

turns off the pump based on the programmed time and is normally set to shut down the pump 

after two to three hours of operation. The pump is also shut off by the low level sensor in the 

BullfroHg, which detects the presence of liquid in the settling chamber. If liquid is not present, 

the MRU pump will not activate or will shut down if operating.

The bleach system is designed to operate using normal household or commercial bleach. The 

bleach solution is pumped into the wastewater as it is transferred from the BullfroHg separator to 

the adsorbent column to control bacterial growth in the adsorbent system. Bleach can affect the 

solubility of mercury, causing particulate mercury to be dissolved or leached into solution. The 

bleach may also oxidize some of the organics in the wastewater, which could have a negative 

effect the adsorption of mercury on the proprietary resin. When the verification test began the 

O&M manual recommended using one part bleach to one part water. This ratio was changed 

during the test to one part bleach to two parts water. The current recommended method for 

making the bleach solution is to mix one part bleach with three parts water.
2-3

Figure 2-1. DRNA Mercury Recovery Unit (MRU)

BullfroHg

Amalgam

Separator

Control Timer

Bleach Reservoir

Sorbent

Column

Discharge Line

Air/water 

separator 

Settling 

chamber

2.2 Equipment Specifications

The equipment specifications for the MRU are given below. Table 2-1 lists the components and 

parts that are included with an MRU as shipped to a dental location.

Physical Dimensions:

Height 24 inch (61 cm)

Width 24 inch (61 cm)

Depth 12 inch (31 cm)

Capacity 10 liters per day / up to six chairs (operatories)

Weight 90 lbs (41 kg)

Vacuum Rating 15 inch Hg

Pressure Rating not rated

Temperature Range: 40-104oF / 4-40oC

Electrical Requirements:

Input Voltage 4 amp, 120 VAC 
2-4

Table 2-1. Equipment List

Description

MRU Enclosure containing:

• BullfroHgTM Air/Water/Amalgam Separator

• Twin peristaltic pumps with waste sensor

• 10-liter bleach reservoir

• Adsorbent column

• Particle filter 

Instruction Manual

Fittings & Hose:

• 1” hose barb x female cam-lock fitting

• 1” hose barb x male cam-lock fitting

• 1” x 1” hose barb coupling

• 1” hose clamps

• 1” ID x 6-ft long vacuum hose

• 1⁄4” ID x 6-ft long discharge hose

• 1” x 1” x 1⁄4” hose barb for discharge connection

• 1” x 3⁄4” hose barb coupling (to adapt to 3⁄4” ID hose)

Programmable Timer/Controller

Each standard MRU unit is designed to handle the flow for up to six (6) operatories (chairs). 

DRNA must be consulted for larger clinics.

2.3 Operation and Maintenance

The MRU is designed for ease of operation and minimal maintenance once installed in the 

vacuum system. The unit is plumbed into the vacuum system ahead of the vacuum pump and 

upstream of the air/water separator if one is present. The system is self-contained and operates 

automatically based on a timer that activates the pump that removes water from the separator 

unit and pumps it through the filter and adsorbent material. No daily operator intervention is 

required other than to conduct periodic checks that the timer, tubing, and pumps are working 

properly. The operator does need to check the bleach solution on a regular basis (requires 

replenishing about once per month). The installation, operation and maintenance manual is 

presented in Appendix A.

Maintenance activities are minimal for the MRU. The large surface area of the adsorbent 

provides possible sites for biological growth. If biomass builds up on the adsorbent, it can reduce 

the adsorbent’s effectiveness of the adsorbent for the removal of soluble mercury. The biomass 

can also cause the column to plug, reducing the flow rate of treated wastewater through the unit. 

A bleach solution is used to disinfect the adsorbent system and help reduce clogging. This 

solution needs to be prepared periodically (about once per month in normal use) and placed in 

the container that is supplied with the MRU. Replacement should occur whenever the volume in 

the container becomes low. The original recommended formula for this solution was one part 
2-5

commercial bleach and one part water. DRNA has subsequently changed the recommended 

solution to one part commercial bleach and three parts water. The bleach concentration was 

changed during the verification test as discussed in section 4.7. The tubing that runs through the 

pump needs periodic replacement (approximately once per year), as it will become worn over 

time. The recommended maintenance activities and schedule are shown in Table 2-2.

Table 2-2. Recommended Maintenance Schedule

Item Required Maintenance Recommended 

Interval*

Pump (s) Replace pump tubing with new section of 

tubing.

12 months

Bleach Reservoir Add 1 part commercial bleach, 3 parts water. Check volume 

weekly

BullfroHgTM Separator

Adsorbent Column

Recycle

Recycle

6 to 12 months

6 to 12 months

Particle filter Replace 6 to 12 months

* Actual interval may vary depending on the type and amount of wastewater treated

The MRU system is designed so that operators are not exposed to any residues and do not have 

to open any mercury contaminated equipment. DRNA ships a complete replacement adsorbent 

column, filter and BullfroHg when it is time to recycle these devices. When the replacements 

arrive, the operator exchanges the new BullfroHg, adsorbent column, and filter for those in the 

MRU. Disinfectant is placed in the separator prior to recycling the unit. The amalgam separator 

is first sealed in a 4-mil plastic bag containing an adsorbent. This bag and adsorbent provide 

secondary containment in the event of a leak. The unit is then packed in a 275#, heavy-wall box 

with custom-made foam padding to protect the separator from damage during shipping. It is 

labeled as amalgam for shipping. DRNA then arranges for the residues from the units to be 

removed and recycled/reclaimed.

2.4 Vendor Claims

DRNA states in its literature that the mercury amalgam separator is effective at capturing 95 

percent of all particles that are greater than 10 microns in size. DRNA states that these particles 

(>10 micron) typically account for 95 percent of the total mercury sent to the unit. Further, the 

mercury specific adsorbent column typically reduces the mercury concentration in the treated 

wastewater to below detection limits (author’s statement – MDL for mercury is typically less 

than 0.2 μg/L).

The verification testing process did not measure particle size distribution, but did measure the 

total mercury load (soluble and insoluble) in the wastewater during the characterization period. 

The total mercury (filterable, settleable, and soluble) in the treated wastewater after treatment by 

the MRU was measured during the verification test period. The results of the verification test 
2-6

determined the amount of mercury removed by the MRU during operation at the dental office 

and the total mass balance for mercury during the verification period.

The vendor has stated that the DRNA BullFroHg (the solids separator) is ISO 11143 certified. A 

statement from the annex to a report indicating the certification was provided to NSF. The ISO 

certification report was not reviewed or confirmed. A copy of the information provided is given 

in Appendix A with the O&M manual.
3-1

Chapter 3 - Methods and Test Procedures

3.0 Test Plan and Procedures

A VTP was prepared and approved for the verification of the DRNA MRU and is attached in 

Appendix B. This VTP, “Verification Test Plan for The Dental Recycling North America 

Mercury Removal System, June 2001”(1) detailed all of the procedures and analytical methods 

that were to be used to perform the verification test. The VTP was prepared in accordance with 

the SWP protocol, “Protocol for the Verification of Mercury Amalgam Removal Technologies, 

April 2001”(2). The VTP included tasks designed to verify the mercury removal capability of the 

MRU and to obtain information on the installation, operation, and maintenance requirements of 

the MRU. There were three distinct phases of fieldwork that needed to be accomplished as part 

of the VTP: initial characterization of the wastewater, installation and start-up of the MRU, and 

verification testing with the MRU operating and treating the wastewater. 

Each of these testing elements, performed during the technology verification, are described in 

this section. In addition to a description of the sample collection methods, equipment installation, 

and equipment operation, this section also describes the analytical protocols. Quality Assurance 

and Quality Control procedures and data management approach are discussed in detail in the 

VTP. 

3.1 Influent Characterization - Procedures

3.1.1 Introduction

The purpose of influent characterization testing was to obtain an understanding of the influent 

wastewater volume and water quality characteristics before the verification test of the DRNA 

MRU. There was no analytical data available for the wastewater from the test site prior to the 

test. Therefore, a thorough characterization of the influent (untreated) wastewater was needed to 

provide credible information for determining the mercury removal effectiveness of the MRU. 

Influent characterization occurred during a 44-day business period (eleven weeks) before the 

MRU was installed for testing.

3.1.2 Objectives

The objectives of influent characterization were to:

• Determine the daily flow of the wastewater stream to be used for verification testing;

• Evaluate the concentrations and daily mass loading of mercury in settleable, filterable 

and soluble forms;

• Determine operational conditions for the MRU technology; 

• Record and document all influent characterization conditions and results;

• Identify any required modifications to the VTP prior to beginning verification of the 

MRU (adjustments in sampling, analysis, etc.); and,

• Provide a basis for evaluating the removal efficiency of the DRNA MRU.
3-2

3.1.3 Sampling Location, Container Type, and Sampling Frequency

The dental office selected as the site for this verification test operated a dry vacuum system with 

an air/water separator upstream of the vacuum pump. The vacuum collection system piping was 

one inch diameter PVC pipe located in the office floor. Flexible one inch plastic pipe connected 

the chair side trap unit to the main collection piping in the wall. The office is located on the first 

floor and all piping and the vacuum system are located on the first floor. A 10-liter vacuum-rated 

polypropylene container was used for the sample collection container. The container was

plumbed into the vacuum system just prior to the current air/water separator collection vessel and 

was set up to maintain the vacuum in the system. Therefore, if the bottle were to overfill, the 

extra wastewater would be collected in the current system prior to reaching the vacuum pump. 

The entire flow during a 24-hour period of operation was collected to characterize the

wastewater. Collection of the entire flow eliminated concerns about obtaining non-representative 

samples that could contain large heterogeneous particles and eliminated the need to consider 

flow weighted composite samples versus time composite samples. The use of the 10-liter 

container ensured that sufficient volume was available to contain all of the flow for a full day of 

office activities. The typical flow in the system was 2-3 liters per day (1⁄2 to 3⁄4 gallons) with a 

potential for an additional 2.5 liters of flushing solution on line cleaning days. Sample volume 

did not exceed the container capacity during the test period.

The sample location for this verification test was located upstream of the air/water separator as 

the DRNA MRU is designed to be installed before the air/water separator. Therefore, the 

characterization sampling location was the same as the inlet location of the MRU during the 

verification test. By placing the sample bottle at this location, the wastewater sampled during the 

influent characterization was as similar as possible to the wastewater that entered the BullfroHg 

separator in the MRU. The elevation of the sample container inlet (approximately three feet 

above the floor) was located at a height similar to the inlet of the MRU air/water/solid separator 

for this installation. The inlet to the original dry system air/water separator was approximately 

four feet above the floor. The wastewater that was being collected in the sample container was 

the same wastewater that is normally collected in the dental office air/water separator, and 

discharged to the public the sewer system in the absence of a treatment system. 

The dental office normally operated from 8 a.m. to 5 p.m. The sample containe r was changed 

daily at the end of the office-operating day. The daily sample, representing all of the previous 

24-hour flow, was capped and prepared for shipment to the laboratory. A chain of custody form 

was prepared daily and signed by the sampler and by a witness. In addition, a custody seal was 

placed over the cap of the container when the cap was placed on the bottle. Each sample bottle 

was placed in a cooler with ice for shipment to the laboratory and was delivered to the NSF 

laboratory within a few hours by a courier service. 

After receipt at the laboratory, the contents of the 10-liter sample collection container were 

poured into a 7 gallon rectangular polypropylene settling tank and allowed to settle for 8 to 16 

hours. The supernatant in the settling tank was decanted into a 2 L polypropylene graduated 

cylinder using a variable speed peristaltic pump and food grade Tygon tubing. The supernatant 

was transferred from the graduated cylinder to a clean 10 L polypropylene container, which was 

agitated using a circular motion for 30 seconds, and three individual samples of the supernatant 
3-3

were poured into 125 mL HDPE bottles containing 2.5 mL of 50 percent (by volume) nitric acid. 

These samples were for total mercury analysis. Approximately 400 mL of the supernatant was 

passed through pre-weighed glass fiber filters under vacuum as needed. The filtrate was poured 

in to a polypropylene beaker, and three samples were created by agitating the beaker for 30 

seconds and pouring the filtrate into 125 mL HDPE bottles containing 2.5 mL of 50 percent (by 

volume) nitric acid. The filters were dried and weighed and the weight of the filtered solids was 

recorded. 

Solids remaining in the settling tank were transferred to a polypropylene beaker using mercuryfree water to rinse the solids remaining in the tank into the beaker. The rinse bottle and beaker 

were weighed prior to rinsing the settling tank and the initial tare weights were recorded. After 

the contents of the settling tank had been transferred into the beaker, both the rinse bottle and 

beaker were weighed again. The solids wet weight was calculated by subtracting the weight of 

the rinse water used and the tare weight of the beaker from the final weight of the beaker. The 

solids and rinse water were filtered through glass fiber prefilters and then through 0.45 micron 

membrane filters. The filters and retained solids were oven dried for a minimum of 24 hours, 

then weighed to the nearest 0.1 mg. The filters were placed in a plastic bag and delivered to the 

laboratory for digestion and analysis. 

The Laboratory weighed aliquots of the solids and filter samples. These samples were digested 

and the mercury concentration was determined. In most cases, all of the collected solids were 

included in the digested sample. In a few cases, the sample size was too large for a single 

digestion, and a representative cross section of the filtered solids was digested. The

representative sample was typically at least 50 percent of the total solids collected.

The complete sample settling and handling procedures are presented in Appendix C.

The sampling container(s) and any fittings were cleaned by the laboratory and returned to the 

field for reuse. Cleaning involved scraping to remove any solids adhered to the surface of the

container or fittings and rinsing with mercury-free water (<0.2 μg/L). All solids collected during 

cleaning, along with all the rinse water, were added to the sample being settled and included in 

the analysis. The method used to clean the sampling container(s) is described in Appendix C. 

Rinse water volumes and weights were recorded so that dilution by the rinse water could be 

accounted for and the data adjusted accordingly. Copies of the spreadsheets showing these 

calculations are presented in Appendix D.

New chair side traps were installed just before the start of the influent characterization program. 

These traps were changed approximately once per week, in accordance with normal office 

procedures. The trap, with the amalgam and related materials, was placed in sealable plastic bags 

and transported to the laboratory for weighing. A log was maintained by the dental office to 

document the replacement of the chair side traps. 
3-4

3.1.4 Analytical Testing and Record Keeping

Forty-four samples were collected during an eleven-week characterization period. Table 3-1 

presents the influent parameters measured for the solids collected and the liquid sub-samples. 

Industry standard procedures (USEPA Methods (3,4,5) or Standard Methods (6)) were used for 

sample analysis. Table 3-2 shows the specific method numbers used for the mercury and pH 

analyses. The procedures were checked using standard reference solids samples containing 

known amounts of mercury and by testing a sample of the actual mercury amalgam from the 

dental office. All liquid samples were analyzed in triplicate for mercury. 

Table 3-1. Summary of Influent Analytical Requirements

Parameter Solid Fraction1 Liquid Fraction1

Volume (liters) 2 X

pH X

Approximate volume of solids 

(particle(s)) (mL) 3

X

Wet weight of solids (grams) X

Solid (Particle) mercury (mg) 4 X

Total mercury (mg/L) 5 X

Soluble mercury (mg/L) 5 X

Chair side Trap Material – weight

(grams)6

X

Note:

(1) Minimum of 25 samples, each a complete sample of all the waste generated 

over a 24 hour period.

(2) Total volume of wastewater and rinse water recorded separately.

(3) Volume estimated after as much as possible of the liquid fraction has been 

removed.

(4) Digestion required before analysis.

(5) Analysis carried out on a representative sub-sample of the liquid fraction after 

settleable solids removed.

(6) Chair side trap material weighed

The dental office staff maintained a record of the number of amalgams and surfaces placed and 

removed each day. A copy of the log was obtained each day when the sample was collected. 

Copies of the dental amalgam logs are presented in Appendix E. 

The dental assistant was responsible for the flushing procedure, which was performed on a 

regular basis in accordance with office procedures and observed by the TO field representative. 

Using a “calibrated” bottle, the volume was standardized at 500 mL per chair. The cleaning 
3-5

solution used was the brand name PureVac. The material safety data sheet for PureVac is 

provided in Appendix F.

Table 3-2. Analytical Methods and Detection Limits

Sample Matrix Analyses Standard Methods

USEPA Methods Detection Limit

 LIQUID pH

 Mercury (Total)

 Mercury (Soluble)

 

150.1

7470A/245.1

7470A/245.1

N/A (range 1-13 S.U.)

0.2 μg/L

0.2 μg/L

 SOLID Mercury (Total)

 TCLP 

7471A/245.5

1311

0.25 mg/kg

N/A

3.2 MRU Installation and Commissioning - Procedures

3.2.1 Introduction

DRNA provided an installation, operation, and maintenance manual for the MRU. This manual 

is presented in Appendix A. A new MRU unit with all components was shipped to the site by 

DRNA. The installation and startup were straightforward, as described in Section 3.2.3 and in the 

installation manual. A representative from NSF was present at the site during installation to 

confirm that the installation was in accordance with the VTP and the DRNA O&M manual.

3.2.2 Objectives

The objectives of the installation and start-up phase of the VTP were to:

• Install the Mercury Recovery Unit (MRU) in accordance with the DRNA O&M manual; 

• Start-up and test the MRU to ensure all processes were operating properly, timers were 

set for proper automatic operation, and any leaks that occurred during the installation 

were eliminated; 

• Make any modifications needed to achieve operation; and,

• Record and document all installation and start-up conditions prior to beginning the 

verification test.
3-6

3.2.3 Installation and Startup Procedures

The installation and start-up of the MRU was performed by the Testing Organization’s field 

support person and was observed by the NSF staff. No on site support was needed from DRNA. 

The MRU, as shown previously in Figure 2-1, was shipped as a self-contained unit that required 

connections to the vacuum system using standard tubing and fittings. Installation was at the same 

location in the vacuum system as the sample container used for the characterization testing. The 

sample container connections were removed and the proper connections for the MRU were 

installed. The entire installation and system checks took less than three hours.

A new, clean MRU system was installed in the vacuum line upstream of the existing air/water 

separator, as recommended by DRNA. The one-inch vacuum line was connected to the inlet of 

the MRU with a one-inch quick-connect connection, which is the standard inlet size for the 

MRU. The outlet vacuum port on the MRU was connected to the one-inch line running to the 

current air/water separator. The air/water separator remained in-line downstream of the MRU as 

a protection for the vacuum pump in the case the settling unit should overflow. The schematic of 

the DRNA system installation is shown in Figure 3-1.

The internal units and pumps in the MRU came ready for connection and operation. Tubing was 

supplied with fittings to connect the outlet port of the BullfroHg separator to a small pump, 

which pumps the wastewater through the adsorbent and filter unit. The pump and timer

components arrived ready for use with the timer preset for activating the pump to transfer the 

settled wastewater to the adsorbent column. The treated effluent discharge line from the MRU 

was directed into a 10-liter polypropylene container that collected all of the effluent from each 

twenty-four period of dental office operation. The sample bottle was located at the utility sink so 

that in the case of an overflow the treated water would discharge to the sink and the sewer 

system. No overflows occurred during the testing period.

Once the installation was complete, the timer was checked and set to activate the pump at 3 a.m.. 

The waste level sensor in the separator shuts the pump off when all wastewater is removed from 

the separator. The sensor and timer were checked for proper operation in accordance with the 

installation manual. The entire system was wet tested. Clean water was placed in the separator 

unit and the vacuum lines were reconnected with the fast connect/disconnect fittings. The manual 

operation button was pushed which activated the pump and clean water was pumped through the 

adsorbent filter, particle filter, and into the sample collection bottle. The MRU was inspected for 

leaks and no leaks were found. Once the system checks were completed, the MRU was ready for 

operation and the verification-testing period started. 
3-7

Figure 3-1. MRU Installation Schematic Diagram

Dental Chair

Coarse Chairside Trap 

Five Chairs connected 

via a main header

Water to drain

(Dry during 

Verification Test)

Vacuum 

Pump

Air/water 

Separator

DRNA MRU

BullFrog

Amalgam 

Separator 

and 

Settling 

Chamber

Liquid Pump (timed)

Mercury 

Adsorber and 

Particle Filter

Sample 

Bottle

3.3 Verification Testing - Procedures

3.3.1 Introduction

The verification test period was designed to measure treatment performance of the DRNA MRU 

under field conditions. The treated wastewater effluent discharged from the MRU was collected 

and analyzed every day the dental office was operating. Residuals retained by the MRU in the 

separator, particle filter, and adsorbent filter (four separate samples, note that the adsorbent filter 
3-8

contained two materials) were collected and measured individually, and analyzed individually at 

the end of the verification test. All samples of wastewater and residue were analyzed to 

determine the performance of the MRU for the removal of mercury from the dental office 

wastewater vacuum systems.. Operation and maintenance conditions were monitored and

documented. Verification testing conditions, observations and results are presented in this 

Verification Report in Chapter 4, Results and Discussion.

3.3.2 Objectives

The objectives of verification testing were to:

• Evaluate the treatment performance of the MRU for the removal of soluble and insoluble 

mercury, operating under standard conditions as specified by DRNA;

• Evaluate the MRU operation and maintenance requirements; and

• Record and document test conditions, observations and results

3.3.3 Sample Location, Sampling Approach, and Frequency

3.3.3.1 Treated Water Sample Collection

The installed DRNA MRU collected the entire day’s flow of wastewater from the vacuum

system and retained the liquid and solids in the BullfroHg separator. After several hours of 

settling, from approximately 5 p.m. until 3 a.m., the liquid in the separator was pumped through 

the adsorbent filter and particle filter unit. The pumping time was typically 2-4 hours, resulting 

in an empty BullFroHg Separator (except for retained settled solids) and filled sample container 

by 7 a.m. The sampling location for the daily treated-water discharge was from the end of the 

discharge tube from the MRU unit. The treated effluent would normally discharge directly to the 

sewer system, but for this test, the discharge tube was secured in a 10-liter polypropylene sample 

bottle that collected the entire volume discharged from the system. Each sample represented a 

24-hour period comprised of one day of operation at the dental office, followed by overnight 

treatment in the MRU. During the verification testing period, the sample was retrieved in the 

morning after the treatment was completed, and the samples were sent to the laboratory by 

courier service.

Collection of the entire flow for each 24-hour period eliminated any concern about obtaining 

”representative” subsamples and eliminated the need to consider flow weighted composite

samples or time composite samples. The use of the 10-liter container provided sufficient volume 

to contain all of the flow for a full day of office activities. The typical flow in the system was 2 –

3 liters per day (1⁄2 to 3⁄4 gallons) with an additional 2.5 liters of flushing solution on line cleaning 

days. At no time during the test did the sample container approach being completely full or 

overflow.

Effluent samples were collected for 32 days to yield 32 samples for analysis. At the end of each 

24-hour period of office and MRU operation, the filled sample bottle was replaced with a clean 

sample bottle. The filled sample bottle was capped and prepared for shipment to the laboratory. 

A chain of custody form was prepared and signed by the sampler and a witness, and a custody 
3-9

seal was placed over the cap of the container. The sample bottle was placed in a cooler with ice 

and remained cool during shipment to the laboratory. The wastewater was delivered to the NSF 

laboratory by a courier service and generally arrived within a few hours of sample collection. 

After logging the sample in at the NSF laboratory, recording the temperature of the sample, and 

noting the cooler condition, the entire sample was transferred to a plastic settling tank (12 inches 

x 12 inches x 12 inches). The sample was settled and the sampling container was cleaned 

following the same procedures used during the characterization period, as described in Section 

3.1.3. Sample containers were checked for residual mercury contamination by adding distilled 

water to selected bottles after they were cleaned. The “blank” was then allowed to sit in the 

bottle for several hours. The bottle blank(s) were then sent to the laboratory for analysis. 

3.3.3.2 Residuals Sample Collection

The DRNA MRU is designed to retain solid amalgam and other dental waste particles in the 

BullfroHg separator and the particle filter. The system is sized to retain these residuals for a six 

month to one-year period. At that time, the separator, particle filter, and adsorbent filter units are 

returned to DRNA for reclamation of mercury and silver in the amalgam and cleaning. Cleaned 

units are provided to the dental office to replace the used units. The recycle/reclamation of 

mercury and silver was not part of this verification.

Based on this normal operating condition, the residuals from the separator, particle filter, and 

adsorbent filter were scheduled to be collected one time at the end of the verification test. At the 

end of the verification test and after the final line flushing to remove any residues in the vacuum 

lines, the MRU pump was manually activated to remove any wastewater present in the separator. 

The pumped wastewater was collected in the sample bottle for the last day of the verification 

test. Once all of the water had been removed, the BullFroHg separator unit, the particle filter, and 

the adsorbent unit were disconnected and removed from the MRU housing. Replacement units 

and filters were provided by DRNA and were installed in the MRU housing at the dental office. 

The test units used during the verification test were then taken to the NSF laboratory for 

residuals sampling and analysis. An NSF representative was present during the dismantling of 

the equipment at the dental office and drove the equipment containing the residuals to the NSF 

laboratory under chain of custody.

The BullFroHg separator unit is designed for ease of cleaning and reuse with a removable lid that 

allows ready access to the unit. At the laboratory, the separator unit was opened and the entire 

residue from the separator was removed and collected as sample. The separator walls were 

scraped and cleaned to remove the residue, which was added to the separator residue sample. 

After scraping, the separator was rinsed and the rinsate added to the wet solids. The residue and 

liquid were placed in containers and dried at low temperature until the moisture was removed. 

The dried solids were then well mixed in preparation for sampling. Six subsamples of the residue 

were collected over the surface and depth of the residue and sent to the laboratory for mercury 

analysis. The original plan was to also perform TCLP analysis on the residue but there was 

insufficient sample to perform the TCLP analysis. While information on the leachable level of 

mercury in the residue would have been of interest, all mercury retained by the MRU is typically 
3-10

recycled and is not disposed of in landfills. Therefore, the TCLP results do not have a direct 

impact on the methods used for disposal of the residues.

The particle filter (nominally rated at 1 micron) contained a heavy load of small particles that did 

not settle in the separator or were from the carbon and resin material in the adsorbent column. 

The filter was removed from the unit (threaded connection) and placed in a pan for drying. The 

filter was dried at low temperature and a final dry weight obtained. The filter was then divided 

into sections (six samples) and three samples were sent to the lab. The other three samples were 

held to determine if they required analysis. The decision not to analyze additional samples was 

based on the reasonable reproducibility of the three samples selected for analysis. The samples 

were weighed and digested using the mercury solids procedure (EPA 245.5), in order to 

determine the mass of mercury present in the particle filter subsample. The average

concentration of mercury in the filter samples (on a filter weight basis, i.e. mg/kg) was then used 

to determine the total mass of mercury present on the entire filter.

The adsorbent material (carbon and resin) adsorbed soluble mercury that may have been present 

in the wastewater. The adsorbents were removed from the filter housing, keeping the carbon and 

resin separate as much as possible. Each residue was placed in a dish, dried at low temperature, 

and weighed in the laboratory. The material was thoroughly mixed and six subsamples of each 

adsorbent (resin and carbon) were taken for analysis. The six samples were digested and

measured for mercury concentration. The average concentration of the six samples was used with 

the total dry weight of adsorbent to calculate the mass of mercury collected by the adsorbents. 

New chair side traps were installed just before the start of the verification test. These traps were 

changed a regular basis, approximately once per week from July 27 through September 19, 2001, 

in accordance with normal office procedures. The trap, with the amalgam and related materials, 

was placed in sealable plastic bags and transported to the laboratory for weighing. A log was 

maintained by the dental office to document the replacement of the chair side traps. 

3.3.4 Analytical Testing and Record Keeping

A total of 32 samples were collected over a seven-week verification period. Table 3.3 presents 

the effluent parameters that were measured for the solids collected and liquid sub-samples. 

Industry standard procedures (USEPA Methods(3,4,5) or Standard Methods(6)) were used for 

sample analysis. The method reference numbers are shown in Table 3.2. The procedure for the 

digestion of solids for mercury analysis was checked using standard reference solids samples 

containing known amounts of mercury, and by testing a sample of the actual mercury amalgam 

form the dental office. All liquid samples were analyzed in triplicate for mercury. 
3-11

Table 3-3. Summary of Effluent and Residual Analytical Requirements

Effluent1, 2 Parameter Residuals

Solid 

Fraction

Liquid 

Fraction

Solid 

Fraction

Liquid 

Fraction

Volume (liters)

3 X X

pH X X

Approximate volume of solids 

(particle(s)) (mL) 4

X X

Wet weight solid particles (grams) X X

Solid (particle) mercury (mg) 5 X X

Total mercury (mg/L) 6 X X

Soluble mercury (mg/L) 6 X X

TCLP7 X

Chair side Trap material weighed

(grams) 8

X

Note:

(1) Minimum of 25 samples, except for TCLP analysis. 

(2) Collect all of the effluent over a 24-hour period.

(3) Total volume of wastewater and rinse water recorded separately.

(4) Volume estimated after as much as possible of the liquid fraction has been removed.

(5) Digestion required before analysis.

(6) Analysis carried out on a representative sample of the liquid fraction.

(7) Toxicity characteristic leaching potential, as per USEPA method SW 846 1311. 

Required for minimum of one sample (not completed due to insufficient sample weight).

(8) Chair side trap material were collected and weighed. Paper and non-amalgam/tooth 

debris were excluded from the sample.

The dental office staff maintained a record of the number of amalgams and the surfaces placed 

and removed each day. A copy of the log was obtained each day when the sample was collected. 

Copies of the dental amalgam logs are presented in Appendix E.

The dental assistant was responsible for performing the flushing procedure, which was

performed on a regular basis, as described in Section 3.1.4. 
3-12

3.3.5 Operation and Maintenance Performance

Both quantitative and qualitative performance of the MRU was evaluated during the verification 

test. The MRU was self-contained and designed to have minimal operator intervention once the 

installation was complete. As stated earlier, a field log was maintained that included all

observations made during the installation, startup and operation of the MRU. Observations 

regarding the condition of the MRU, any changes in the setup or operation (timer adjustments, 

filter changes, etc.), or any problems that required resolution were recorded in the log by the 

field personnel. 

Qualitative operation and maintenance performance information included:

• Observations regarding ease of operation;

• Observations regarding the effect of the MRU, if any, on the operation of the vacuum 

system;

• Documentation of any operating problems encountered during testing; 

• Quality of the O&M manual (e.g., actual experience in the field compared to that 

indicated in the manual, clarity of instructions); and,

• Observations regarding labor requirements.

Several quantitative performance measures were evaluated for the operation of the MRU. The 

information included:

• Duration (in hours) of any clean-out operations (none were expected based on equipment 

design, length of test, and vendor information);

• Frequency and duration (in hours) of any preventative or breakdown maintenance

activities;

• Electrical consumption for the two pumps was projected by estimating the operating time 

of the pumps (timer controlled), and calculating kilowatt hours consumed by using the 

electrical rating for the pumps and hours of operation;

• Chemical consumption of the bleach cleaning solution was monitored by logging the 

quantity of solution made and the remaining material in the container at the end of the 

verification test; and,

• Records of any other consumables used by the MRU over the test period (none were 

expected).
4-1

Chapter 4 - Results and Discussion

4.0 Characterization Test

The wastewater characterization test began on July 10, 2001 and continued through September 

21, 2001. A total of 44 samples were collected during the eleven-week period. The dental office 

normally operated only 4 days per week and samples were collected at the end of each normal 

business day. Two of the samples were collected on days when the dentist was not in the office 

and only hygiene activities occurred. These two days, August 6 and 23, had two of the lowest 

total flows during the characterization. 

4.1 Mercury Amalgams Removed and Placed

Two rooms out of the five rooms in the office were used as operatories during the

characterization study. Records of the number of surfaces placed or removed, and the tooth 

number(s) for each procedure for each day were kept by the dental technician. Table 4-1 shows 

the number of surfaces removed and placed during the characterization test. Three hundred 

thirty-four (334) surfaces over 42 operating days were removed/placed during the sampling 

period. This represents an average of 7.95 surfaces per day or approximately 40 surfaces per 

week on a 5 operating days per week basis. There were three sampling days when no surfaces 

were removed or placed. On two of these days (August 6 and 23), only hygiene activities 

occurred at the office (no dentist in) and there was one day (August 7) of normal office operation 

when no mercury amalgam surfaces were removed or placed. 

4.2 Mercury Results

Each sample collected for wastewater characterization was divided into two phases for mercury 

analysis, the settled solids fraction and the liquid fraction. Upon arrival at the laboratory, the 

sample was placed in a settling chamber and the solids were allowed to settle for eight to sixteen 

hours (See Procedure for Separation of Mercury Amalgam Samples in Appendix C). The liquid 

fraction was then decanted and set aside for filtration and mercury analysis. Care was taken to 

remove as much free liquid as possible, but some free liquid was allowed to remain in the settled 

solids to minimize disturbing the solids. The settled solids sample was then filtered using a 0.45 

micron filter to remove the free liquid. The solids were dried and weighed prior to analysis for 

total mercury. 

The liquid fraction was divided into two samples. One sample was subsampled in triplicate and 

sent to the laboratory for total mercury analysis. The other sample was filtered through a 0.45 

micron filter and then subsampled in triplicate for soluble mercury analysis. Soluble mercury is 

defined as mercury that is either dissolved in the wastewater or associated with particulate that is 

less than 0.45 micron in size. Using a 0.45 micron filter is the standard USEPA approach for 

preparing a soluble mercury sample. All sub sampling was performed by thoroughly mixing 

(shaking) the sample bottle and then quickly pouring the liquid sample into three bottles.
4-2

Table 4-1. Summary of Number of Surfaces Removed and Placed - Characterization 

Test

Operatory Room 1 Operatory Room 2

Date

Surfaces 

Removed

Surfaces 

Placed Notes Surfaces Removed

Surfaces 

Placed Notes

Total 

Surfaces

7/10/01 0 2 0 0 2

7/11/01 6 3 4 3 16

7/12/01 4 0 0 0 4

7/13/01 2 5 6 7 20

7/16/01 3 5 0 3 11

7/17/01 2 0 2 7 11

7/18/01 7 0 4 5 16

7/20/01 0 0 6 0 6

7/23/01 2 0 0 4 6

7/24/01 2 0 0 0 2

7/25/01 0 0 6 0 6

7/27/01 0 0 0 2 2

7/30/01 3 0 7 6 16

7/31/01 1 0 7 0 8

8/1/01 0 0 0 4 4

8/3/01 3 0 (1) 4 0 (1) 7

8/6/01 0 0 (2) 0 0 (2) 0

8/7/01 0 0 0 0 0

8/8/01 0 0 0 2 2

8/9/01 0 0 6 4 10

8/10/01 0 0 3 0 3

8/13/01 3 2 1 0 6

8/14/01 1 5 0 0 6

8/15/01 2 2 2 7 13
4-3

Table 4-1. (continued) Summary of Number of Surfaces Removed and Placed -

Characterization Test

Operatory Room 1 Operatory Room 2

Date

Surfaces

Removed

Surfaces

Placed Notes SurfacesRemoved

Surfaces

Placed Notes

Total 

Surfaces

8/17/01 5 0 0 0 5

8/20/01 0 0 (1) 3 0 (1) 3

8/21/01 3 8 4 0 15

8/22/01 0 2 0 6 8

8/23/01 0 0 (2) 0 0 (2) 0

8/24/01 5 6 0 0 11

8/27/01 11 0 0 0 11

8/28/01 7 0 3 3 13

8/29/01 0 1 0 0 (3) 1

8/31/01 3 0 2 0 (3) 5

9/4/01 4 0 0 3 7

9/5/01 1 0 0 5 6

9/7/01 4 0 6 7 17

9/10/01 4 0 (1) 0 2 (1) 6

9/11/01 0 2 0 1 3

9/12/01 1 3 0 0 4

9/14/01 2 0 (3) 0 0 (3) 2

9/17/01 8 4 1 3 16

9/18/01 2 8 0 0 10

9/19/01 6 8 (1,4) 0 0 (1,4) 14

(1) Chair side traps were changed.

(2) No dentist was in office; it was not a normal operating day. However, a sample was collected. The normal procedure 

was to accumulate sample volume over non operating days and collect it at the end of operating days.

(3) Line was flushed with 500 mL of PureVac flushing solution.

(4) Lines were flushed with 1000 mL of PureVac at the end of the characterization period, followed by a 1000 mL flush 

with clean water.

Entire period 7/10-9/20/02 Surfaces = 334 Operating Days = 42 Ave. surfaces / day = 7.95

Period 7/30-9/20/01 Surfaces = 232 Operating Days = 30 Ave. surfaces / day = 7.73

Data summaries do not include 8/6 and 8/23 as these were non-dentist days – i.e. no dentist was in the office. Under normal 

procedures, samples were only collected on normal business days when the dentist was in the office working.
4-4

Each wastewater sample resulted in three mercury concentration values, total mercury in the 

settleable solids, total mercury in the liquid fraction, and soluble mercury in the liquid fraction. 

All data tables report the settleable solids mercury concentration as “mercury from solids” and 

the liquid fraction mercury concentration as “total mercury liquid” and “soluble mercury liquid”. 

It is important to remember the definition of these various fractions when comparing the results 

to other studies and when performing the calculations for total mass of mercury discharged or 

present in an untreated wastewater. A direct discharge of this type of wastewater would contain 

the mercury present in the settleable solids and the total mercury present in the liquid fraction. 

The total mercury concentration in the untreated wastewater would be the sum of the mass of 

mercury in the settled solids added to the mass of mercury (from the total mercury analysis 

sample) in the liquid volume divided by the total volume discharged. 

Total mercury conc. = (conc. in solids x mass of solids) + (conc. in liquid x vol. of liquid ) (Eq. 1)

Total volume of sample

Table 4-2 shows the settleable solids data, including the concentration of mercury in the solids 

and the total dry weight of the settled solids, which are the basis used for calculating the total 

mass of mercury in the settled solids. These results are from the collection and analysis of 

settleable solids using the settling procedure described in Appendix C and Section 3.1.3. Table 4-

3 shows the mercury results for the liquid fraction (after removal of the settleable solids 

fraction), including both the total mercury in the liquid and the soluble portion (after filtration 

through a 0.45 micron filter). Table 4-3 also shows the volume of wastewater collected (total 

daily flow through the vacuum system), the calculated mass of mercury in the liquid and settled 

solids fraction, the calculated total mass of mercury in the discharge (settleable plus liquid 

fraction) and calculated total mercury concentration. The total mercury concentration is

calculated by adding the mass of mercury in the solids and the liquid to calculate the total mass 

of mercury in the sample, and then dividing by the total wastewater (sample) volume for that 

day. The total mass of mercury in the office wastewater is shown graphically in Figure 4-1.

During the preparation and handling of the wastewater samples, it was necessary to use rinse 

water at several steps to ensure transfer of all of the solids and the mercury to the sample 

containers. All rinse water volumes were measured by weighing the rinse water bottle before and 

after each use. All of the rinse water dilutions were accounted for and the laboratory-measured 

concentrations were adjusted for these dilutions. The calculations and data used for these

adjustments are presented in Appendix D.

The average total mercury concentration (settleable solids plus liquid) was 657 μg/L with the 

concentration varying from a high of 1810 μg/L to a low of 73 μg/L. The average mass of 

mercury in the wastewater was 1.60 mg/day varying from 0.05 mg/day to 6.81 mg/day. The 

liquid fraction (after settling) averaged 192 μg/L. The soluble mercury portion in the decant 

liquid averaged 127 μg/L, and typically represented 50-70 percent of the mercury in the liquid 

fraction of the wastewater. The summary statistics for the wastewater characterization are 

presented in Tables 4-4 and 4-5. 
4-5

Table 4-2. Settleable Solids Results – Characterization Study

Settleable Solids Fraction Liquid Fraction

Date Hg Conc. Dry Wt. Mass of Dry Solids

Mass of Hg in 

Sample 

Mass of Solids after 

Settling

mg/kg mg mg mg

(A) (B) (A*B)

7/10/01 220 274 0.0603 36.8

7/11/01 300 169 0.0507 129

7/12/01 310 151 0.0469 85.7

7/13/01 350 197 0.0688 50

7/16/01 74 1580 0.117 74.5

7/17/01 520 73.7 0.0383 52.8

7/18/01 140 71.7 0.0100 38.5

7/20/01 330 377 0.124 77.2

7/23/01 890 98.6 0.0878 90.1

7/24/01 (1) 2220 (1) 244

7/25/01 (1) 1350 (1) 142

7/27/01 2300 125 0.287 78.7

7/30/01 4800 421 2.02 61.4

7/31/01 3700 114 0.421 40.7

8/1/01 2000 1740 3.48 193

8/3/01 2000 267 0.535 68.7

8/6/01 5300 20.6 0.109 14.4

8/7/01 1300 900 1.16 110

8/8/01 6200 292 1.81 195

8/9/01 <0.6 16.4 <0.0002 13.2

8/10/01 4200 170 0.713 45.9

8/13/01 3800 715 2.72 103

8/14/01 410 65.2 0.0267 62.4

08/15/01 2700 1160 3.14 95.3

8/17/01 410 184 0.0754 43

8/20/01 860 120 0.103 38.7

8/21/01 1000 2040 2.04 40.8

8/22/01 4100 1330 5.44 156

8/23/01 390 30.2 0.0118 47.7

8/24/01 1800 525 0.944 47.2

8/27/01 1100 267 0.293 253

8/28/01 250 695 0.174 106

8/29/01 270 210 0.0567 324

8/31/01 160 725 0.116 235

9/4/01 1100 203 0.223 43.2

9/5/01 910 97.1 0.088 57.3

9/7/01 1100 939 1.03 20.2

9/10/01 2300 162 0.373 14.4

9/11/01 180 222 0.0400 45

9/12/01 740 259 0.192 89.2

9/14/01 2100 825 1.73 207.0

9/17/01 2100 862 1.81 25.7

9/21/01a(2) 7000 2280 15.9 184

9/21/01b(2) 4200 1550 6.49 0.4

(1) Lab sample was not analyzed.

(2) The “a” sample was collected after three days of office operation (9/18, 9/19, and 9/20) and included a flush with 

PureVac solution. The “b” sample was collected from a fresh water flush of the system immediately after the “a” 

sample was collected.
4-6

Table 4-3. Mercury Results – Characterization Study

Liquid Fraction Data

Sample Decanted after Settling Procedure

Settleable 

Solids

Total Mass Hg

 Total Hg 

Discharged

Date

Final Conc. 

Liquid

Total Hg

Final Conc. 

Liquid

Soluble Hg Soluble Hg

Total 

Discharge

Volume 

Delivered

Mass

 of Hg

 From Liquid

Mass (1)

of Hg

 From 

Settleable 

Solids

Liquid Fraction 

and Settleable 

Solids

Total Mass 

divided by 

Total 

Volume

(mg/L) (mg/L)

(% Of 

Total) (mL) (mg) (mg) (mg/day)

(mg/L)

(ppb)

7/10/01 0.124 0.0080 6.5 874 0.111 0.0603 0.171 191

7/11/01 0.109 0.0994 91.4 2160 0.238 0.0507 0.289 132

7/12/01 0.113 0.0772 68.4 704 0.0840 0.0469 0.131 176

7/13/01 0.220 0.183 83.4 1630 0.367 0.0688 0.436 261

7/16/01 0.0634 0.0414 65.3 3160 0.204 0.117 0.321 99.7

7/17/01 0.209 0.118 56.4 930 0.203 0.0383 0.241 249

7/18/01 0.175 0.137 78.2 1420 0.251 0.0100 0.261 182

7/20/01 0.190 0.121 63.5 1350 0.262 0.124 0.387 280

7/23/01 0.253 0.187 74.1 1640 0.425 0.0878 0.512 305

7/24/01 0.0947 0.0678 71.5 3290 0.318

7/25/01 0.231 0.114 49.4 5150 1.19

7/27/01 0.345 0.164 47.6 1390 0.479 0.287 0.766 550

7/30/01 0.514 0.632 123 1650 0.850 2.02 2.87 1740

7/31/01 0.435 0.343 79.0 585 0.254 0.421 0.676 1150

8/1/01 0.136 0.113 83.4 3430 0.466 3.48 3.95 1150

8/3/01 0.0546 0.0048 8.8 1220 0.0664 0.535 0.601 494

8/6/01 0.0446 0.0236 52.9 210 0.0094 0.109 0.119 565

8/7/01 0.0984 0.0504 51.2 2560 0.252 1.16 1.42 553

8/8/01 0.149 0.0963 64.6 3600 0.536 1.81 2.34 651

8/9/01 0.416 0.385 92.5 129 0.0537 0.0000 0.0537 416

8/10/01 0.676 0.513 75.9 654 0.442 0.713 1.16 1770

8/13/01 0.526 0.394 75.0 2910 1.53 2.72 4.24 1460

8/14/01 0.510 0.364 71.2 700 0.366 0.0267 0.392 497

8/15/01 0.318 0.196 61.7 2100 0.667 3.14 3.80 1810

8/17/01 0.161 0.0771 47.8 634 0.102 0.0754 0.178 280

8/20/01 0.229 0.154 67.2 1120 0.255 0.103 0.358 321

8/21/01 0.083 0.0392 47.4 3960 0.328 2.04 2.37 599

8/22/01 0.139 0.0657 47.2 4690 0.653 5.44 6.09 1300

8/23/01 0.198 0.143 72.1 273 0.0544 0.0118 0.0662 241

8/24/01 0.213 0.164 77.1 1520 0.324 0.944 1.27 835

8/27/01 0.149 0.0703 47.1 2290 0.341 0.293 0.634 278

8/28/01 0.104 0.0159 15.3 2230 0.232 0.174 0.406 182

8/29/01 0.184 0.102 55.6 1270 0.379 0.0567 0.436 211

8/31/01 0.122 0.0251 20.5 2700 0.320 0.116 0.446 165

9/4/01 0.0574 0.0097 16.9 2030 0.126 0.223 0.349 160

9/5/01 0.0599 0.0235 39.2 1360 0.0812 0.0884 0.170 125

9/7/01 0.0578 0.0417 72.1 5880 0.340 1.03 1.37 234

9/10/01 0.0514 0.0408 79.4 1300 0.0829 0.373 0.456 283

9/11/01 0.0461 0.0044 9.5 1510 0.0784 0.0400 0.118 69.6

9/12/01 0.141 0.119 84.6 3040 0.428 0.192 0.619 204

9/14/01 0.378 0.0979 25.9 5040 1.90 1.73 3.64 722

9/17/01 0.215 0.140 65.0 2320 0.499 1.81 2.31 996

9/18/01 0.0547 0.0126 23.0 3090 0.169 5.31 5.48 1770

9/19/01 0.0547 0.0126 23.0 3090 0.169 5.31 5.48 1770

9/20/01 0.0547 0.0126 23.0 3090 0.169 5.31 5.48 1770

9/21/01b 0.0745 0.0393 52.8 4380 0.326 6.49 6.82 1560

9/18-9/20 – One sample was taken over three-day period.

9/21/01 – Cleaning solution included at the end of the third day – system was flushed.

9/21/01 – Represents water flush at the end of the characterization period to clear the lines before the verification test.

See Table 4-4 for summary statistics of this data.

(1) Data in this column were taken from Table 4-2, second column from the right.
4-7

Figure 4-1. Mass of Mercury in Office Wastewater – Characterization Test

Mass of Mercury by Fraction in Wastewater

0.00

2.00

4.00

6.00

8.00

10.00

12.00

14.00

7/10/20017/12/20017/14/20017/16/20017/18/20017/20/20017/22/20017/24/20017/26/20017/28/20017/30/2001

8/1/20018/3/20018/5/20018/7/20018/9/2001

8/11/20018/13/20018/15/20018/17/20018/19/20018/21/20018/23/20018/25/20018/27/20018/29/20018/31/2001

9/2/20019/4/20019/6/20019/8/2001

9/10/20019/12/20019/14/20019/16/2001

Date

Mass of Mercury (mg)

Mass Mercury in Liquid Decant Fraction Mass Mercury in Settleable Solids Total Mercury Mass per day
4-8

Table 4-4. Summary Statistics for Mercury – Characterization Study

Decant Liquid 

Concentration 

(mg/L)

Hg Mass (mg/day) Total Wastewater

Total Soluble

% of 

Total

Total 

Wastewater

Volume 

(mL) Settleable 

Solids

Decant 

Liquid

Concentration 

(μg/L)

Mass 

(mg/day)

Number 46 46 46 46 32 32 32 32.0

Average 0.192 0.127 66.1 2180 1.23 0.364 657 1.60

Maximum 0.676 0.632 93.5 5880 6.49 1.90 1810 6.82

Minimum 0.0446 0.0044 9.9 129 <0.01 0.0094 72.6 0.0537

Std. Dev 0.152 0.139 91.4 1410 1.81 0.369 581 1.94

Total 

mass

100,000 54.2 (mg) 16.7 (mg)

Table 4-5. Summary Statistics for Mercury in Settleable Solids – Characterization 

Study

Hg Conc.

Dry Wt

Mass of

Dry Solids

Mass of

Hg in

Sample

mg/kg mg mg

Daily Ave 1680 567 1.23

Maximum 7000 2280 6.49

Minimum 74 6.4 <0.01

Std Dev 1831 641 1.81

The Protocol calls for the collection of a minimum of 25 samples over a minimum five-week 

period, and requires that a minimum of 40 amalgam surfaces per week be removed/placed. The 

VTP was designed to meet these minimums by adjusting the sample duration to account for the 

four-day operating week for this dental office. The actual duration of the characterization testing 

was eleven weeks. Samples were collected representing 44 days for two reasons. First, the 

number of surfaces that were being removed/placed during the first weeks of testing was below 

the 200 surfaces (five weeks x 40 surfaces per week = 200 surfaces), the targeted minimum. The 

additional samples provided data that met the minimum surface requirement for the protocol. 

Second, during the first three weeks of sampling, some adjustments needed to be made to the 

sample handling and settling procedures and the analyses to ensure that all needed data were 

being collected. In addition, two settled solids samples were not analyzed by the laboratory 

because of miscommunication. In order to ensure a complete data set for the characterization, the 

sampling was continued for the extended period. Once the data were complete, the subset of data 

from the July 30 - Sept 20 period that met the basic minimum requirement and the entire dataset 

for the period July 10 - Sept 20 were compared and found to be very similar in concentration and 

total mass loadings. Section 4.10.2 presents these comparisons and more information regarding 

this data.
4-9

The settleable solids fraction represented the largest portion of the mercury in the wastewater, 

accounting for 77 percent of the total mercury mass. While removing this fraction will reduce the 

mercury loading, the liquid portion still contained an average of 192 μg/L of mercury, which is 

well above the typical discharge limits allowed to lakes and rivers, and would be a source of 

mercury in wastewater treatment facilities receiving this wastewater. 

4.3 pH Results – Characterization Study

Samples were monitored for pH as they arrived at the laboratory. The pH normally ranged from 

7 to 9 over the characterization period, as shown in Table 4-6. The pH was lower when the 

vacuum lines were flushed with cleaning solution, but not all low values corresponded to the 

days on which flushing occurred.

4.4 Installation and Startup of DRNA MRU

The characterization phase of the test was completed on September 21, 2001. After the lines 

were flushed and the last sample was collected, the DRNA MRU was installed in the vacuum 

system in preparation for the start of the verification test. The MRU inlet line to the solids 

separator was attached to the vacuum system at the location where the characterization sample 

bottle had been installed. The outlet air from the MRU was attached to the vacuum line that had 

been attached to the exit air fitting of the sample bottle during the characterization phase and was 

just upstream of the existing air/water separator. Installation of these lines was straightforward 

and took only a few minutes. See Figure 3-1.

The water discharge line of the BullfroHg separator was connected to the tubing pump on the 

MRU. The adsorption system inlet line was attached to the outlet of the pump and the discharge 

line from the MRU placed in a clean sample bottle. The entire hookup time was less than one 

hour. Once the system was setup, it was wet tested by adding water to the separator. The manual 

operation button was pushed and the pump moved clean water from the separator through the 

adsorption column and into the sample container. All fittings were checked and there were no 

leaks. The low level sensor in the BullFroHg separator shutdown the pump when the water in the 

separator reached the low level shutoff point. The pump timer was set at the factory to turn on at 

3 a.m., which allows sufficient time for all of the settled wastewater accumulated during the 

normal business day to be pumped through the adsorbent filter before the start of the business at 

7:30 a.m. in the morning.

The installation and setup went quickly (less than 3 hours with the wet test included) and only 

required normal tools. Once the unit was setup, it was ready to operate on Monday morning, 

September 24, 2001, when the dental office opened. The installation and startup procedures, 

included in the operation and maintenance manual in Appendix A, were followed as written for 

this test. The instructions were easy to read and follow.
4-10

Table 4-6. pH Results – Characterization Study

Date pH Date pH

(SU) (SU)

7/9/01 3.72 8/14/01 8.91

7/10/01 8.39 08/15/01 8.9

7/11/01 8.93 8/17/01 7.96

7/12/01 9.04 8/20/01 7.53

7/13/01 8.96 8/21/01 6.94

7/16/01 7.01 8/22/01 8.28

7/17/01 8.82 8/23/01 8.6

7/18/01 9.21 8/24/01 8.94

7/20/01 8.9 8/27/01 8.25

7/23/01 8.86 8/28/01 8.57

7/24/01 8.55 8/29/01 7.45

7/25/01 7.96 8/31/01 8.72

7/27/01 6.35 9/4/01 6.07

7/30/01 9.01 9/5/01 6.53

7/31/01 9.17 9/7/01 3.24

8/1/01 8.88 9/10/01 3.57

8/3/01 8.95 9/11/01 7.07

8/6/01 6.88 9/12/01 8.62

8/7/01 7.53 9/14/01 6.82

8/8/01 6.95 9/17/01 5.27

8/9/01 8.73 9/21/01(a) 6.5

8/10/01 8.87 9/21/01(b) 2.89

8/13/02 8.4

Note: The “9/21/01a” sample was after three days of office operation and included a flush with PureVac solution. The “9/21/01b” 

sample was collected from a fresh water flush of the system immediately after the “a” sample was collected.

4.5 Verification Test

The verification test started on September 24, 2001 and concluded on November 8, 2001. A total 

of 32 samples of MRU treated effluent were collected and analyzed in accordance with the VTP 

Procedures. During the seven-week verification period, the dental office added a dentist on a part 

time basis, and the office operated on a four or five day per week schedule. On three of the 

sampling days, the dentists were not in and only hygiene activities were performed.
4-11

Sample collection time during the verification test was in the morning whereas the

characterization test samples were collected at the end of each business day. The wastewater 

generated during a normal day was treated in the MRU overnight (settling of solids and

subsequent pumping of the decant liquid through the adsorbent). Therefore, each day’s sample 

was not available until the next morning. Samples were collected each business day in the 

morning and represent the previous day’s wastewater flow.

4.6 Mercury Amalgams Removed and Placed

Records of the number of mercury amalgam surfaces removed and placed, along with the 

associated tooth number, were maintained during the verification test in the same manner as 

described for the characterization test. During the verification test, 243 surfaces were removed or 

placed on 29 operating days giving an average of 8.38 surfaces placed or removed per operating 

day. This rate of removal and/or placement was similar to the rate during the characterization test 

(7.73 – 7.95 surfaces per day). 

The number of surfaces placed or removed by day is shown in Table 4-7. The addition of a 

second part time dentist resulted in three operatory rooms at the office being used for amalgam 

procedures. 

The dental technician logs also showed the days when flushing of the lines occurred using the 

PureVac cleaning solution. Table 4-7 shows the days when line flushing occurred and the 

quantities of cleaning solution used during the verification test. Chair side traps were also 

changed several times during the verification test period and are noted in Table 4-7.

Table 4-7. Summary of Number of Surfaces Removed and Placed – Verification Test

Room 1 Room 2 Room 3

Date Surfaces 

Removed

Surfaces 

Placed Notes

Surfaces 

Removed

Surfaces 

Placed Notes Surfaces Removed

Surfaces 

Placed Notes

Total 

Surfaces

9/25/01 0 0 4 1 0 0 5

9/26/01 4 5 3 1 0 0 13

9/27/01 0 0 (1,4) 3 3 (1,4) 0 0 (1,4) 6

9/28/01 0 0 (2) 0 0 (2) 0 0 (2) 0

10/1/01 6 0 0 0 0 0 6

10/2/01 4 0 4 10 0 0 18

10/3/01 2 2 0 0 0 0 4

10/4/01 3 0 (3) 3 0 4 4 14

10/5/01 7 7 (1,3) 2 0 (1,3) 0 0 (1,3) 16

10/8/01 0 0 (3) 3 2 0 0 5
4-12

Table 4-7. (continued) Summary of Number of Surfaces Removed and Placed –

Verification Test

Room 1 Room 2 Room 3

Date Surfaces 

Removed

Surfaces 

Placed Notes Surfaces Removed

Surfaces 

Placed Notes Surfaces Removed

Surfaces 

Placed Notes

Total 

Surfaces

10/9/01 0 0 6 4 6 0 16

10/10/01 1 0 0 1 0 0 2

10/11/01 2 2 0 0 16 0 20

10/12/01 1 0 (1,3) 7 0 (1) 0 0 (1) 8

10/15/01 3 0 2 0 0 0 5

10/16/01 2 0 (3) 4 5 0 0 11

10/17/01 0 0 (2) 0 0 (2) 0 0 (2) 0

10/18/01 0 0 (1,3) 0 1 (1,3) 5 0 (1,3) 6

10/19/01 0 0 (2) 0 0 (2) 0 0 (2) 0

10/22/01 0 1 4 4 0 0 9

10/23/01 0 0 1 0 0 0 1

10/24/01 0 3 0 4 0 0 7

10/25/01 4 0 (1,3) 0 0 (1,3) 2 1 (1) 7

10/26/01 0 0 (2) 0 0 (2) 0 0 (2) 0

10/29/01 0 2 0 2 0 0 4

10/30/01 5 2 1 0 0 0 8

10/31/01 0 0 2 2 3 0 7

11/1/01 0 0 0 0 2 0 2

11/2/01 0 0 (1,3) 1 2 (1,3) 0 0 (1) 3

11/5/01 0 0 6 2 0 0 8

11/06/01 0 0 3 4 0 0 7

11/07/01 8 6 3 0 0 0 17

11/08/01 2 0 (5) 3 3 (5) 0 0 (5) 8

(1) Chair side traps were changed.

(2) No dentist was in office; it was not a normal operating day. However, a sample was collected. The normal procedure 

was to accumulate sample volume over non operating days and collect it at the end of operating days

(3) Line was flushed with 500 mL of Pure Vac flushing solution.

(4) Line was flushed with 1000 mL of Pure Vac flushing solution

(5) Lines were flushed with 1000 mL of Pure Vac at the end of the verification period, followed by a 1000 mL flush with 

clean water.

Total surfaces = 243 Total Days = 33 Operating Days = 29 Ave. surfaces/day = 8.38
4-13

4.7 Mercury Results – Verification Test

The entire wastewater flow was treated in the MRU, and the entire discharge from the MRU was 

collected in the treated wastewater sample bottle in the same manner as for the characterization 

test. The treated water sample did not contain the settleable solids trapped in the BullfroHg, as 

these were retained in the separator until the end of the verification testing. The samples were 

delivered to the laboratory and the settleable solids separation procedure was performed to 

generate both a liquid decant fraction and a settleable solids fraction for analysis. All procedures 

used in the characterization phase, as described in Sections 4.2 and 3.3.3.1, were followed for the 

verification test samples.

The results for the mercury analyses of the treated water are shown in Table 4-8. As described in 

Section 4.2, these results are based on the laboratory analytical data with adjustments made for 

the various volumes of rinse water used during the sample handling and preparation procedures. 

The summary laboratory data and the various calculations are included in Appendix D. The 

calculations described in Section 4.3 were used to combine the settleable solids data and the 

liquid data to determine the final mass and concentration of total mercury in the treated water, 

which would normally be discharged to the sewer system. The mercury concentrations measured 

in the settleable solids samples and the dry weights of the settled solids present in the discharge 

are shown in Table 4-9, and graphically in Figure 4-2.

The mercury concentrations measured in the liquid fraction were below the detection limit (0.2 

μg/L) for several days and there were no settleable solids present in the sample on four (4) days. 

These results require an approach be used to account for “less than values” when determining 

average concentrations and developing other statistical data. Two approaches that have been 

used by USEPA and others is to assume that values below the detection limit are equal to either 

zero or one half (1/2) the detection limit. Both approaches have been used to analyze this data. 

The summary statistics shown in Table 4-10 present the results using both approaches. The data 

show that the differences between the two methods are very small for this data set, yielding an 

average total mercury concentration in the effluent of 10.3 μg/L as shown in Table 4-10 (a) 

(using zero for “<” values) and 10.4 μg/L as shown in Table 4-10 (b) (using 1⁄2 the detection limit 

for “<” values). Based on the similarity of the results, all discussions and comparisons presented 

will be based on assuming values below the detection limit are equal to zero.

The average discharge concentration of total mercury was 10.3 μg/L with a maximum of 39.8 

μg/L and a minimum of <0.2 μg/L. The average mass of mercury discharged on a daily basis was 

0.036 mg/day, with the settleable solids portion representing an average of 0.007 mg/day and the 

liquid fraction having an average of 0.0284 mg/day. The mercury contribution from the

settleable solids thus represented 19 percent of the mercury present in the discharge versus 77 

percent in the untreated wastewater. Tables 4-10 and 4-11 show these summary statistics. 

Clearly, the solids separator was retaining settleable solids and the mercury content of these 

solids. The overall discharge level of mercury is significantly below the levels measured during 

the untreated wastewater characterization test, indicating the DRNA MRU was removing a 

significant amount of the mercury present in the wastewater. A detailed comparison of the results 

and calculations of the removal percentages is discussed in Section 4.10. 
4-14

The mercury concentration in the discharge was either below the detection limit (<0.2 μg/L) or in 

the 0.2 to 3.5 μg/L range for the first eighteen days of the verification test. During the first few 

days, the effluent had no settleable solids and had very low solids suspended in the liquid. As the 

test progressed, the effluent began to darken in color and became very black with noticeable 

suspended particulate present. Only a small portion of these solids settled during the settling 

procedure in the laboratory. The amount of solids being filtered from the liquid fraction began to 

increase and the solids were very black and fine in appearance. DRNA was contacted and their 

technical department suspected that the bleach concentration being used to keep the adsorbent 

clear of organic interference was causing the carbon in the column to breakdown and pass 

through the final filter. DRNA had recently changed the recommended bleach concentration in 

the feed solution from one part bleach to one part water to a new ratio of one part bleach to two 

parts water. On October 17, the bleach solution was changed to the new recommended strength. 

Between October 17 and October 25, the total mercury concentration in the effluent, the mass of 

settleable solids found in the separation procedure, and the amount of solids being filtered from 

the decant liquid reached peak values, as shown in Tables 4-8 and 4-9 and Figure 4-2. After 

October 25, the mass of dry solids and the mercury concentration stabilized and began to 

decrease. Levels of mercury in the discharge continued to decrease until the last two days of the 

verification test. On the last two days, the mass and concentration of mercury present in effluent 

increased to levels similar to those measured earlier in the verification period. Both days had 

higher flows, which may have impacted the removal of mercury. The higher flow on the last day 

was due to the extra flushing of the system that was performed in order to clear the vacuum lines. 

The system was flushed with one quart of PureVac and one quart of water at each chair in order 

to remove as much mercury as possible from the vacuum system. The previous day’s flow 

(November 7) may have be due to the larger than average number of mercury amalgam surface 

removals and placements that were performed, although the overall dataset did not seem to 

substantiate a correlation between amalgam surface removals and/or placements with total flow.

The results clearly indicate that the MRU performed well in the first half of the verification test 

period. Mercury levels were significantly reduced in the second half of the test, however the 

performance was impacted by the condition of the adsorbent column. According to DRNA, the 

problem with the bleach attacking the carbon has not been a widespread problem and they 

changed their bleach solution concentration to resolve this type of problem. While the issue of 

carbon breakdown and the presence of small particulate in the effluent stabilized in the later part 

of the verification test, the discharge levels remained significantly above the levels measured at 

the beginning of the test. These data indicate that once the column is attacked the process cannot 

be reversed in a short period. 
4-15

Table 4-8. Mercury Results - Verification Test

Liquid Fraction Data

Sample Decanted after Settling Procedure

Settleable Solids

Date Final Conc.

Total Hg

Final Conc.

Soluble Hg

Soluble

Hg

Total 

Volume 

Discharged

Mass of 

Hg from 

Liquid

Mass of Hg 

From Solids

Total Mass

Hg

Total Hg

Discharged

mg/L mg/L % of Total mL mg mg mg/day μg/L (ppb)

9/25/01 <0.0002 <0.0002 1250 <0.0003 0 <0.0003 <0.2

9/26/01 0.0003 0.0004 133 2240 0.0007 0 0.0007 0.3

9/27/01 <0.0002 <0.0002 327 <0.0001 0 <0.0001 <0.2

9/28/01 <0.0002 <0.0002 1350 <0.0003 0.0005 <0.0003 <0.4

10/1/01 0.0029 0.0025 86.2 623 0.0018 0.0004 0.0022 3.5

10/2/01 0.0005 <0.0002 2850 0.0014 0.0054 0.0040 1.4

10/3/01 <0.0002 <0.0002 1080 <0.0002 0.0009 <0.0004 <0.8

10/4/01 0.0007 0.0004 69.1 2270 0.0068 0.0005 0.0073 3.2

10/5/01 <0.0002 <0.0002 177 <0.0001 0.0001 <0.0003 <0.6

10/8/01 0.0017 0.0006 35.3 5660 0.0096 0.0096 0.0192 3.4

10/9/01 0.0007 0.0002 28.6 4740 0.0033 0.0020 0.0053 1.1

10/10/01 0.0003 <0.0002 2850 0.0011 0.0013 0.0024 0.8

10/11/01 0.0004 0.0003 75.0 1440 0.0006 0.0005 0.0011 0.8

10/12/01 0.0006 0.0007 117 1280 0.0008 0.0010 0.0018 1.4

10/15/01 0.0006 0.0004 66.7 3770 0.0023 0.0048 0.0071 1.9

10/16/01 0.0006 0.0006 100 1440 0.0009 0.0013 0.0022 1.5

10/17/01 0.0011 0.0006 54.5 4280 0.0047 0.0074 0.0121 2.8

10/18/01 0.0023 0.0012 52.2 319 0.0007 0 0.0007 2.2

10/22/01 0.0057 0.0014 24.6 660 0.0038 0.0052 0.0090 13.6

10/23/01 0.0293 0.0051 17.4 5940 0.174 0.0429 0.217 36.5

10/24/01 0.0322 0.0085 26.4 4120 0.133 0.0148 0.148 35.8

10/25/01 0.0337 0.0115 34.1 1320 0.0445 0.0081 0.0526 39.8

10/26/01 0.0172 0.0049 28.5 2440 0.0420 0.0060 0.0480 19.7

10/29/01 0.0154 0.0038 24.7 3330 0.0513 0.0120 0.0633 19.0

10/30/01 0.0086 0.0023 26.7 4430 0.0381 0.0144 0.0525 11.9

10/31/01 0.0108 0.0029 26.9 1720 0.0186 0.0185 0.0371 21.5

11/1/01 0.0083 0.0026 31.3 1340 0.0111 0.0065 0.0176 13.2

11/2/01 0.0085 0.0008 9.4 1250 0.0106 0.0051 0.0157 12.5

11/5/01 0.0078 0.0038 48.7 3870 0.0302 0.0056 0.0358 9.3

11/7/01 0.0089 0.0056 62.9 1940 0.0172 0.0004 0.0176 9.1

11/8/01 0.0212 0.0135 63.7 6060 0.129 0.0250 0.154 25.3

11/9/01 0.0331 0.0118 35.6 5340 0.177 0.0338 0.211 39.4
4-16

Table 4-9. DRNA MRU Settleable Solids Results

Settleable Solids Fraction Liquid Fraction

Date

 Hg Conc. Dry Wt. Mass of Dry Solids

Mass of Hg in 

Sample 

Mass of Solids after 

Settling

(mg/kg) (mg) (mg) (mg)

(A) (B) (A*B)

9/25/01 <1 0 0 4.4

9/26/01 <1 0 0 5

9/27/01 <1 0 0 7.1

9/28/01 12 39.4 0.0005 30.8

10/1/01 24 15.8 0.0004 18.9

10/2/01 21 258 0.0054 38.7

10/3/01 21 43.1 0.0009 21.4

10/4/01 5 106 0.0005 35.4

10/5/01 7.5 8.2 0.0001 6.3

10/8/01 8 1210 0.0096 74.9

10/09/01 4 490 0.0020 40.5

10/10/01 9 149 0.0013 19.5

10/11/01 8 66 0.0005 46.1

10/12/01 9 111 0.0010 132

10/15/01 3 1610 0.0048 21.1

10/16/01 6 209 0.0013 18

10/17/01 3 2460 0.0074 78.7

10/18/01 <1 0 0 205

10/22/01 28 187 0.0052

10/23/01 76 564 0.0429 146

10/24/01 75 197 0.0148 114

10/25/01 36 224 0.0081 85.7

10/26/01 50 120 0.0060 67.9

10/29/01 48 249 0.0120 81.2

10/30/01 49 293 0.0144 104

10/31/01 37 501 0.0185 96.9

11/1/01 31 211 0.0065 78.6

11/2/01 26 198 0.0051 131

11/5/01 46 121 0.0056 62.7

11/7/01 17 22 0.0004 35.9

11/8/01 160 156 0.0250 32.6

11/9/01 210 161 0.0338 46.7

Bleach concentration changed on October 17, 2001
4-17

Figure 4-2. Mass of Mercury Discharged from MRU

Mass of Mercury in Discharge from MRU

0.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35

0.40

0.45

9/26/20019/28/20019/30/200110/2/200110/4/200110/6/200110/8/2001

10/10/200110/12/200110/14/200110/16/200110/18/200110/20/200110/22/200110/24/200110/26/200110/28/200110/30/2001

11/1/200111/3/200111/5/200111/7/200111/9/2001

Date

Mercury Mass (mg/day)

Mass Mercury Liquid Decant Fraction Mass Mercury in the Settleable Solids Fraction Total Mercury Mass in Discharge
4-18

Table 4-10. Summary Statistics Mercury Results for DRNA MRU Effluent

(a) All Values Below Detection Limit set equal to zero in calculations

Decant Liquid 

Concentration 

(mg/L)

Hg Mass (mg/day) Total Wastewater

Total Soluble

% of 

Total

Total 

Wastewater

Volume 

(mL) Settleable 

Solids

Decant 

Liquid

Concentration 

(μg/L)

Mass 

(mg/day)

Number 32 32 25 32 32 32 32 32.0

Average 0.0079 0.0027 66 2550 0.0073 0.0284 10.3 0.0357

Maximum 0.0337 0.0135 100 6060 0.043 0.177 39.8 0.217

Minimum <0.0002 <0.0002 9.4 177 0.00 <0.0002 <0.2 <0.0003

Std. Dev 0.0108 0.0037 N/A 1770 0.0103 0.0507 12.8 0.0601

Total 

mass

81,700 0.234 (mg) 0.909 (mg)

(b) All Values Below Detection Limit set equal to 1⁄2 the detection limit in calculations

Decant Liquid 

Concentration 

(mg/L)

Hg Mass (mg/day) Total Wastewater

Total Soluble

% of 

Total

Total 

Wastewater 

Volume 

(mL) Settleable 

Solids 

Decant 

Liquid

Concentration 

(μg/L)

Mass 

(mg/day)

Number 32 32 25 32 32 32 32 32

Average 0.0079 0.0027 66 2550 0.0073 0.0284 10.4 0.0357

Maximum 0.0337 0.0135 100 6060 0.0429 0.177 39.8 0.217

Minimum 0.0001 0.0001 9.6 177 0.00 <0.0001 0.100 <0.0001

Stand 

Dev 0.0108 0.0037 N/A 1770 0.0102 0.051 12.8 0.0599

Total 

mass

81,700 0.234 

(mg)

0.909 

(mg)
4-19

Table 4-11. Summary Statistics Settleable Solids Results for DRNA MRU Effluent

Settleable Solids Fraction Liquid Fraction

Hg Conc.

Dry Wt

Mass of

Dry Solids

Mass of 

Hg in

Sample

Mass of Solids

after settling

mg/kg mg mg mg

Average 32.2 312 0.007 58.9

Maximum 210 2460 0.043 205

Minimum 0.00 0.00 0.000 4.40

Std Dev 45.7 521 0.010 48.9

4.8 pH Results Verification Study

The pH was measured for each treated wastewater sample when it arrived at the laboratory. 

Table 4-12 shows the pH results for the verification test period. As shown in the table, the pH 

was very stable in the discharge from the MRU. The changes in pH noted in the characterization 

test (Table 4-6) were dampened by the treatment process. The range of pH for the test period was 

6.42 to 7.48. 

Table 4-12. pH Results Verification Test

Date pH Date pH

(SU) (SU)

9/25/01 6.87 10/18/01 7.27

9/26/01 6.71 10/19/01 7.18

9/27/01 6.69 10/22/01 7.26

9/28/01 6.75 10/23/01 7

10/1/01 6.75 10/24/01 7.21

10/2/01 7 10/25/01 7.38

10/3/01 6.96 10/26/01 7.35

10/4/01 7.05 10/29/01 7.56

10/5/01 7.11 10/30/01 7.27

10/8/01 6.84 10/31/01 7.24

10/9/01 6.7 11/1/01 7.33

10/10/01 6.5 11/2/01 7.24

10/11/01 6.42 11/5/01 7.32

10/12/01 n/a 11/7/01 7.24

10/15/01 6.68 11/8/01 7.48

10/16/01 7.08 11/9/01 7.38

10/17/01 7.09

 n/a – not analyzed
4-20

4.9 Residue Results for DRNA MRU

At the end of the verification test, the MRU was taken to the laboratory to be disassembled and 

the residues sampled for mercury content. Section 3.3.3.2 describes the residue sample collection 

and processing procedure. Collection and analysis of the residues was critical to the verification 

test as it provided data for determining the actual amount of mercury removed and retained 

during the verification test.

The results of the residue analysis are presented in Table 4-13. The separator solids represent the 

solids settled in the BullFroHg separator during the test. A total of 44.8 grams of solids was 

collected over the verification test period. These solids showed an average total mercury

concentration of 4050 mg/kg. The six samples showed a range of concentration from 3800 to 

4400 mg/kg, which indicates that the solids sample was well mixed and consistent in

concentration among the subsamples taken for analysis. The total mass of mercury collected over 

the 32-day period was 181.4 mg. 

The original VTP included analysis of the settleable solids from the separator for leachable 

mercury using the USEPA TCLP. This analysis could not be performed, as the test requires a 

minimum of 200 grams of sample and only 44.8 grams were collected for the entire verification 

test period. TCLP is a test used to evaluate solid materials for hazardous waste classification and 

disposal. It is possible that the solids could leach mercury at levels that would classify this waste 

as hazardous. The total concentration of mercury is above the 260 mg/kg level designated by the 

USEPA as requiring mercury recovery under the Land Disposal Restrictions (LDR). Solids with 

high mercury concentrations must be sent for mercury reclamation. One of the services DRNA 

provides its customers is the return of the separator to them for mercury recycling. The other 

residuals, filter, carbon and resin are also returned to DRNA for mercury recycling as part of the 

DRNA services.

The particle filter weighed 83.2 grams after drying. The original weight of the filter is not known 

so the actual amount of solids retained by the filter (solids, carbon, and resin) cannot be 

determined. The filter did show that it was impregnated with a large amount of small black 

particles, similar to the carbon material present in the adsorption column and similar to the 

particles that were present in the effluent in the second half of the test. The average mercury 

concentration in the filter samples (filter media plus retained solids) was 0.587 mg/kg and the 

calculated mass of mercury on the filter was 0.049 mg. While the actual amount of retained 

solids cannot be determined, the total mass of mercury present is known and is not significant in 

the overall mass balance, representing less than 0.1 percent of the mercury in the residues.

The carbon remaining in the adsorption column was 126 grams (the starting weight is not known 

but DRNA indicated that 250-300 grams of carbon is typically charged to the column) with an 

average concentration of total mercury of 39.5 mg/kg. The total mass of mercury was 4.98 mg. 

The resin material weighed 1130 grams on a dry weight basis and showed an average

concentration of 8.2 mg/kg. The resin contained a mass of 9.24 mg of mercury. These results 

show that mercury was being removed by both the carbon and the selective resin in the 
4-21

adsorption column and serves as a basis for calculating the mercury loading to the adsorption 

column from the liquid fraction of the wastewater.

Table 4-13. Solid Residue Results – DRNA MRU

BullfroHg Collecte d Solids Particle Filter

Total Dry Solids = 

44.8 grams

Total Dry Solids =

83.2 grams

Sample Hg Concentration Sample Hg Concentration

mg/kg mg/kg

1 4300 1 0.93

2 3800 2 0.36

3 3800 3 0.47

4 4100

5 3900

6 4400

Ave 4050 Ave 0.587

Max 4400 Max 0.93

Min 3800 Min 0.36

Std Dev 259 Std Dev 0.3

Total Hg 181 mg Total Hg 0.049 mg

Carbon Solids Resin Solids

Total Dry Solids = 

126 grams

Total Dry Solids = 

1132 grams

Sample Hg Concentration Sample Hg Concentration

mg/kg mg/kg

1 20 1 7.2

2 22 2 7.7

3 24 3 7.1

4 41 4 10

5 85 5 9

6 45 6 8

Ave 39.5 Ave 8.2

Max 85 Max 10

Min 20 Min 7.1

Std Dev 24.6 Std Dev 1.1

Total Hg 4.98 mg Total Hg 9.24 mg
4-22

4.10 Performance of the DRNA MRU

4.10.1 Comparison Approach

The typical approach to measuring the performance of a wastewater treatment device is to 

monitor the influent and effluent during the verification test period and calculate the removal 

efficiency of the unit. However in designing the VTP, it was not possible to collect influent 

samples during the verification period due to the small size of the influent flow, the operation of 

the system under vacuum, and the difficulty of obtaining representative samples (particularly of 

solids) from small pipes, with small intermittent flow under vacuum. The VTP was designed to 

obtain data that could be used to follow two different approaches to determine the treatment 

efficiency of the unit. 

In the first approach, the VTP included the characterization test to obtain data on the wastewater 

concentrations and masses, which could be used to determine the average mercury concentration 

and mass discharged from the dental office. If the dental office operation was similar during both 

the characterization period and the verification period, the characterization data could be used for 

comparison with the treated wastewater data. 

The second approach was to collect and analyze all of the residuals from the treatment process so 

that the total mass of mercury retained by the unit during the verification test could be

determined. The total mass measured in the discharge could then be compared to the total mass 

entering the unit (retained mercury plus discharged mercury) and the removal efficiency could be 

calculated. The calculation of the total load to the treatment unit could also be compared to the 

total mass of mercury measured in the characterization test to serve as a check that conditions 

were similar during both periods. The samples were also separated into the settleable solids 

fraction and decant liquid fraction to provide an additional method for comparing the

characterization data with the treated water data. Both methods have been used in calculating the 

removal percentages given in this section.

4.10.2 Removal Efficiency Based on Characterization Data

The data presented in Tables 4-1 through 4-6 show the concentrations of mercury determined 

during the characterization test and the number of surfaces removed and placed during the test 

period. The characterization test covered a period of 42 operating days with a total of 334 

amalgam surface removals and placements. The verification test occurred over 29 operating days 

during which 243 surfaces were removed and placed. In order to more closely match the 

characterization results with the verification test, a subset of the characterization data was also 

used for determining the total mercury and solids load. During the period July 30 through

September 20, 2001, the last eight weeks of the characterization test, there were 30 operating 

days and 232 surfaces were removed or placed. Further, the total flow during July 30 to 

September 20 was 77 liters compared to 82 liters during the verification test. Thus, this period 

has very similar operating characteristics to the verification period. The Wilcoxon Signed Rank 

Test, a non-parametric statistic, was used to evaluate the two data sets and determine if they were 

statistically similar. The results of the test show that the two test periods (July 30 – September 

20, and September 25 – November 9) were similar (not statistically different, Z= -0.518). A 
4-23

comparison of the full characterization period data set with the verification data set showed that 

these data were also similar (not statistically different). Both tests were evaluated at the 95 

percent confidence level. The results of the statistical evaluation are presented in Appendix D. 

Table 4-14. Removal Efficiency Based on Characterization Data - Daily Averages

Settleable Total Wastewater

Solids

Mass 

(mg/day)

Decant Liquid 

Mass (mg/day) Concentration 

(μg/L)

Mass (mg/day)

Characterization

Data – 7/10-9/20/2002 1.23 0.36 657 1.60

Characterization

Data – 7/30-9/20/2002 1.57 0.37 778 1.94

MRU Discharge

(9/25-11/9/2002) 0.0073 0.0284 10.3 0.0357

% Removal –Compared 

to 7/10-9/20 Data 99.4 92.1 98.4 97.8

% Removal – compared 

to 7/30-9/20 Data 99.5 92.3 98.7 98.2

Table 4-15. Removal Efficiency Based on Characterization Data - Total Mass and 

Average Concentration

Settleable Solids Total Wastewater

Mass (mg)

Decant Liquid 

Mass (mg) Concentration (μg/L) Mass (mg)

Characterization 

(7/30-9/20/2002)

53.3 12.7 778 66.0

MRU Discharge

(9/25-11/9/2002)

0.234 0.909 10.3 1.14

% Removal 99.6 92.8 98.7 98.3

Tables 4-14 and 4-15 show the summary of these data and the calculated removal efficiencies 

attained by the DRNA MRU using the characterization data. The evaluation of removal

efficiency using the two different databases gives very similar results. The data also show that 

the average mass loadings during the characterization test were very similar to the subset data 

from July 30 through September 20, 2001. While the load of mercury and solids varied

considerably on a day-to-day basis, the averages of the data for these two data sets were very 

similar. The DRNA MRU was effective in removing the settleable solids and the mercury in 

these solids, and achieved better than 99 percent removal either on an average concentration 

basis or on a total mass basis. Overall removal of mercury (solids and liquid combined) was 
4-24

between 98.4 and 98.7 percent on a concentration basis and 97.7 to 98.6 percent on a total mass 

basis. The MRU also was effective in removing the mercury associated with the liquid fraction 

(soluble and non settleable mercury), showing efficiencies in the 92.3 to 92.8 percent range.

4.10.3 Removal Efficiency Based on Verification Data Mass Balance

The data shown in Tables 4-8 through 4-11 and 4-13 show the mercury results, and the mass of 

mercury discharged from and retained in the MRU during the verification test. These data allow 

the calculation of the total mercury in the influent to the unit. All of the treated water effluent 

was monitored during the verification test and the mercury retained in the unit was measured at 

the end of the verification test. Table 4-16 shows the removal efficiency of the MRU based on 

the mass balance approach.

Table 4-16. Removal Efficiency based on Mass Balance of Retained and Discharged 

Mercury

Mass of Mercury

Settleable Solids

(mg)

Decant Liquid

(mg)

Total Wastewater

(mg)

Separator-Retained 181 - 181

Filter-Retained - 0.049 0.049

Carbon-Retained - 4.98 4.98

Resin-Retained - 9.24 9.24

Discharge 0.234 0.909 1.14

Total Mass Load 182 15.2 197

% Removal 99.9 94.0 99.4

%Removal = ((Total – Discharge)/ Total) X 100
4-25

Using the mass balance approach, the DRNA MRU removed more than 99 percent of the 

mercury in the settleable solids and more than 99 percent of the total mercury in the wastewater 

discharge. The MRU was also effective in reducing the mercury in the liquid fraction by 94 

percent. 

The removal efficiencies calculated by mass balance are similar to the removal efficiencies 

found using the characterization data. In general, the mass balance approach does tend to show 

somewhat greater removal efficiencies. This is because the total mass of mercury found during 

the verification test, particularly in the settleable solids, was higher in the verification test than 

during the characterization test. The mass of mercury in the liquid fraction during the

characterization test was 12.9 mg and the mass of mercury in the liquid fraction during the 

verification test showed 15.0 mg. These quantities of mercury are very similar. The mass of 

mercury measured in the settleable solids fraction during the characterization test was 53.3 mg, 

whereas the settleable solids retained in the separator during the verification test showed a mass 

of mercury of 182 mg. The high efficiency shown by the MRU for retaining settleable solids and 

the larger contribution of the settleable solids to the total mercury mass in the discharge during 

the verification test, resulted in higher calculated removal efficiency for the MRU.

Overall, these comparisons show that the DRNA MRU can remove more than 99 percent of the 

mercury associated with settleable solids, 98-99 percent of the total mercury present in the 

wastewater, and from 92-94 percent of the mercury associated with the liquid fraction (soluble 

plus non-settleable particulate) of the wastewater. 

4.11 MRU Operational Characteristics

During the verification test, qualitative and quantitative factors were observed or measured to 

help describe the operational characteristics of the DRNA MRU and the cost factors associated 

with operating and maintaining the unit.

4.11.1 Qualitative Factors

The MRU was very easy to operate, requiring virtually no operator intervention except for an 

occasional check that the pump was working, and replenishment of the bleach solution on a 

monthly basis. Once the unit was setup, there were no maintenance requirements and the unit ran 

without interruption for eight weeks. All indications are that the unit could easily operate several 

months without experiencing a mechanical problem (recommended maintenance interval is 6-12 

months, except weekly checks of the bleach reservoir). Labor to operate the unit is minimal. If 

the unit is checked periodically (once per week) and bleach solution is added once per month, the 

total time to operate and maintain the unit would be less than 2-4 hours per month (1⁄2 to 1 hour 

per week). 

The dental office vacuum system was not impacted by the MRU. The MRU easily attaches to the 

vacuum line before the air/water separator, which helps to minimize potential impact on the 

vacuum system. Once the system is installed, the only real impact the MRU could have on the 

system would be if there were a leak in one of the vacuum lines or if the BullFroHg separator 

lost the vacuum seal. 
4-26

The entire unit is self contained and designed to eliminate operator contact with the untreated 

wastewater or the residuals. The treated effluent can be plumbed direct to the sewer system. The 

normal DRNA approach is for the dental office to return the used separator and adsorbent 

column and replace them with clean units. DRNA arranges for removal of the mercury and waste 

material from the MRU components at an appropriate facility. Based on the design, operational 

approach, and use of DRNA to handle the residual, the unit is considered a very safe unit from a 

health or waste contact perspective. 

The Operations and Maintenance Manual is provided in Appendix A. Review of the manual and 

using it to install the MRU show that it is easy to read and follow. The instructions for 

installation are simple step-by-step instructions. Operational concepts explained in the technical 

section are easy to understand. The maintenance section uses text and tables to help explain the 

maintenance procedures required and the time interval for these activities.

The only operational problem encountered during the verification test was the increase in solids 

in the discharge. The apparent attack of the carbon by the bleach solution, causing the carbon to 

breakdown and be discharged, could be a major operational issue if it continued unnoticed or 

unabated. The discharge of the carbon fines reduced the removal efficiency. Carbon breakdown 

should have no impact on the settleable solids removal, the major source of mercury, as these 

solids are removed before the carbon unit and are completely separate from the adsorbent 

column. The liquid discharge showed degradation in mercury removal as fine particulate

(apparently the carbon adsorbent) began to escape from the adsorbent column. If this breakdown 

of the carbon continued over a long period, it would be expected that the mercury removal from 

the liquid fraction would continue to decease and ultimately all of the activated carbon in the 

column would be gone. DRNA has stated that this problem is an isolated problem and that other 

units have not shown this problem. The lower bleach concentration appeared to help slow the 

breakdown over the short duration of this test. If DRNA has solved this problem by using the 

lower bleach concentration, then removal of mercury can be expected to be even better than 

shown in the verification test. However, until the issues are resolved, those using the MRU need 

to occasionally monitor the effluent to determine if it has turned black or contains fine particles, 

an indication the carbon may be exiting the unit.

4.11.2 Quantitative Factors

There are two basic O&M quantitative factors that apply to the DRNA MRU - electrical usage 

and chemical usage. The electrical power used was 120VAC, 4 amp for the pump in the unit. 

The pumps run about 2-3 hours per day, depending on the daily volume in the separator. Total 

electrical use can be expected to average 2400 watts per day.

The only consumable was the bleach (household bleach was used for the verification test, either 

commercial or household bleach can be used according to DRNA) used to make the bleach 

solution. Approximately ten liters of bleach solution were used over the eight-week verification 

test period. The mixing ratio for the bleach solution was 1 part bleach to 1 part water for the first 

part of the verification test period and 1 part bleach to two parts water for the last three weeks of 

the verification test period. Approximately 3.3 liters of bleach was used per two-month period or 
4-27

1.6 liters per month. DRNA has subsequently changed the recommended bleach ratio to one part 

bleach to three parts water, which will lower the bleach consumption.

There were no cleanouts or maintenance required during the verification and it would appear that 

no costs for cleanout would be expected. Based on observation during the recovery of the 

residuals, the separator has sufficient capacity to hold six months to one year of solids. DRNA 

provided proprietary information on the mercury adsorbing capacity of the adsorbent material. 

Based on the weight of adsorbent measured in the MRU, and results of quality control samples 

that measured the adsorption of mercury on the material, there should be sufficient capacity to 

treat soluble mercury for six months to one year, assuming the material remains in the unit. The 

only costs associated with cleanout of the MRU should be the costs to ship the unit to DRNA and 

costs associated with the recycling service.

4.12 Quality Control Results

The VTP had a detailed QA/QC plan for this test. The VTP contained the QA/QC specifications 

and overall requirements for this work. Laboratory QA/QC is included with the analytical results 

in Appendix G. In addition to the normal QC that is run as part of the mercury test procedures, 

some additional work was also performed on the solids matrix.

 Special QC checks using two types of known solids were analyzed for mercury to confirm the 

recovery in the digestion procedure. . A solid sample matrix with known mercury content was 

obtained commercially and analyzed during the testing. Recovery was better than 90 percent. 

There was also concern that the amalgam material might not digest well in the procedure, so a 

sample of the amalgam from the test site office was obtained. The sample was analyzed and 

compared to the manufacturer’s stated mercury content. Recovery was over 85 percent. Thus, the 

mercury digestion and analysis procedures were documented as being able to recover these types 

of mercury materials in the solid matrix.

All of the chain of custody procedures for collecting and transporting samples were followed. 

Copies of the chain of custody sheets and the various logs documenting the testing are presented 

in Appendix H. 

There were three numerical Data Quality Indicators (DQI) specified for this test program. The 

precision specification for mercury was a RPD of <20 percent for water matrices and <35

percent for solids. All sample sets analyzed met the precision requirements and every set of 

mercury analyses had the appropriate number of replicate samples to meet the target of one 

duplicate per ten analyses. Accuracy, as measured by spiked samples, was specified to meet a 

range of 80-120 percent recovery for water matrices and 75-125 percent for solids. All water 

matrices results for spiked samples were within the acceptable range. All but two matrix spikes 

on the solid samples were within the target range. On two occasions, the recovery was just above 

the upper target limit (126 percent and 129 percent). These data were reviewed by the NSF QA 

officer. While the recovery was slightly high, the lab control sample (third party independent 

standard) was well within range. The recoveries were outside the VTP target, but these values 

are within the EPA method limits. Based on a review the entire analytical run, including the lab 

control spikes and standards, the data were considered acceptable. Lab control samples were 
4-28

analyzed with each analytical batch and all lab control samples were within the ± 10 percent 

range of true value as established for the mercury method. The QA review of the mercury data 

showed that the data set did meet the DQI’s for precision and accuracy.

In addition to precision and accuracy numerical targets, the VTP had a target DQI for

completeness of 90 percent. The data sets were reviewed and all mercury analyses were

complete and met the calibration, blank, spike, spike duplicate, standard curve frequencies stated 

in the QAPP. The only data that fell outside of recovery windows were the two recoveries 

mentioned above. Two samples delivered to the lab were not analyzed for settleable solids as 

requested. Based on 44 samples from the characterization test (three types of mercury analysis 

on each sample) and 32 samples from the verification test (three types of mercury analysis on 

each sample) the total number of samples for mercury (not including duplicates, triplicates, 

spikes, etc.) was 228 samples. The four errors or deviations found (2 high recoveries, 2 solid 

analyses not performed) in a set of 228 samples gives a completeness of over 98 percent. 

Completeness was also measured for the amalgams surfaces removed or placed, and the total 

number of samples collected for each part of the test. The VTP stipulated a minimum of 5 weeks 

(25 samples) of testing with 40 amalgam surfaces per week or 200 surfaces over 25 operating 

days. Both the characterization period and the verification period exceeded 25 operating days (42 

and 29 respectively) and exceed the minimum amalgam removal/placement of 200 (334 and 243 

respectively). Therefore, completeness was 100 percent. Forty-four (44) samples were collected 

during the characterization period and thirty two samples during the verification period, which 

exceeds the minimum sample requirement. Therefore, the completeness is shown to be 100 

percent for sample collection minimum and amalgam surfaces.

All of the QA/QC data and supporting information in presented in the Appendices, including the 

lab results, field logs, and other supporting documentation.
Chapter 5 – References

(1) NSF International, Verification Test Plan for the Dental Recycling North America Mercury 

Removal System, May 2001

(2) NSF International, Protocol for the Verification of Mercury Amalgam Removal

Technologies, 2000, Ann Arbor, Michigan.

(3) United States Environmental Protection Agency: Methods and Guidance for Analysis of 

Water, EPA 821-C-99-008, 1999. Office of Water, Washington, DC.

(4) United States Environmental Protection Agency: Methods for Chemical Analysis of Water 

and Wastes, Revised March 1983, EPA 600/4-79-020 

(5) United States Environmental Protection Agency: Test Methods for Evaluating Solid Waste: 

Physical/Chemical Methods, 3rd ed - 4 vols., November 1986, Final Update IIB and 

Proposed Update III, January 1995.

(6) APHA, AWWA, and WEF: Standard Methods for the Examination of Water and

Wastewater, 20th Edition, 1998. Washington, DC.

Additional Reading and Reference Material Supporting the ETV Program

(7) United States Environmental Protection Agency: Environmental Technology Verification 

Program - Quality and Management Plan for the Pilot Period (1995 – 2000), 

USEPA/600/R-98/064, 1998. Office of Research and Development, Cincinnati, Ohio.

(8) NSF International, Environmental Technology Verification – Source Water Protection

Technologies Pilot Quality Management Plan, 2000. Ann Arbor, Michigan.

(9) United States Environmental Protection Agency: USEPA Guidance for Quality Assurance 

Project Plans, USEPA QA/G-5, USEPA/600/R-98-018, 1998. Office of Research and

Development, Washington, DC

(10) United States Environmental Protection Agency, Guidance for the Data Quality Objectives 

Process, USEPA QA/G-4, USEPA/600/R-96-055, 1996. Office of Research and

Development, Washington, DC.

(11) ANSI/ASQC: Specifications and Guidelines for Quality Systems for Environmental Data 

Collection and Environmental Technology Programs (E4), 1994.

(12) United States Environmental Protection Agency: Mercury White Paper, memorandum,

website www.epa.gov/ttn/oarpg/t3/memoranda/whtpaper.pdf

(13) United States Environmental Protection Agency: Mercury Study Report to Congress, 

December 1997, website www.epa.gov/airprogm/oar/mercury.html

(14) United States Environmental Protection Agency: Mercury Emissions and Electric Utilities, 

February 24, 1998, website www.epa.gov/ttncaaa1/t3/fact_sheets/hg17th.pdf
Appendix A - Operations and Maintenance Manual
Appendix B - Verification Test Plan
Appendix C - Field and Lab Special SOP’s
Appendix D - Spreadsheets with calculation and data summary
Appendix E - Amalgam Surfaces Dental Office Logs
Appendix F – Material Safety Data Sheets
Appendix G - Lab Data Reports and QA/QC
Appendix H - Chain of Custody Records and Field Log Sheets