EPA/600/R-06/030 

 April 2006 

Design Manual 

Removal of Arsenic 

from Drinking Water Supplies 

by Iron Removal Process 

by 

Gary L. Hoffman 

ARCADIS Finkbeiner, Pettis & Strout, Inc. 

Cleveland, Ohio 44113 

Darren A. Lytle and Thomas J. Sorg 

U.S. EPA National Risk Management Research Laboratory

Cincinnati, Ohio 45268 

Abraham S.C. Chen and Lili Wang 

Battelle 

Columbus, Ohio 43201 

U.S. EPA Contract No. 68-C-00-185 

Task Order No. 0012 

Awarded to 

Battelle 

Columbus, Ohio 43201 

Task Order Manager 

Thomas J. Sorg 

Water Supply and Water Resources Division 

National Risk Management Research Laboratory

Office of Research and Development 

U.S. Environmental Protection Agency

Cincinnati, Ohio 45268 
Disclaimer 

The work reported in this document is funded by the United 

States Environmental Protection Agency (EPA) under Task 

Order (TO) No. 0012 of Contract No. 68-C-00-185 to Battelle. It 

has been subjected to the Agency’s peer and administrative 

reviews and has been approved for publication as an EPA 

document. Any opinions expressed in this paper are those of the 

author(s) and do not, necessarily, reflect the official positions and 

policies of the EPA. Any mention of products or trade names 

does not constitute recommendation for use by the EPA. 

ii 
Foreword 

The U.S. Environmental Protection Agency (EPA) is charged by Congress with protecting the 

Nation’s land, air, and water resources. Under a mandate of national environmental laws, the 

Agency strives to formulate and implement actions leading to a compatible balance between 

human activities and the ability of natural systems to support and nurture life. To meet this 

mandate, EPA’s research program is providing data and technical support for solving 

environmental problems today and building a science knowledge base necessary to manage our 

ecological resources wisely, understand how pollutants affect our health, and prevent or reduce 

environmental risks in the future. 

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

investigation of technological and management approaches for preventing and reducing risks 

from pollution that threaten human health and the environment. The focus of the Laboratory’s 

research program is on methods and their cost-effectiveness for prevention and control of 

pollution to air, land, water, and subsurface resources; protection of water quality in public water 

systems; remediation of contaminated sites, sediments and ground water; prevention and control 

of indoor air pollution; and restoration of ecosystems. NRMRL collaborates with both public and 

private sector partners to foster technologies that reduce the cost of compliance and to anticipate 

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

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

scientific and engineering information to support regulatory and policy decisions; and providing 

the technical support and information transfer to ensure implementation of environmental 

regulations and strategies at the national, state, and community levels. 

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

It is published and made available by EPA’s Office of Research and Development to assist the 

user community and to link researchers with their clients. 

Sally C. Gutierrez, Director 

National Risk Management Research Laboratory 

iii 
iv
Abstract 

This design manual presents the steps required to design and operate a water treatment plant for removal of arsenic (As) from drinking water supplies using iron removal 

processes. It also discusses the capital and operating costs, including the many variables that can raise or lower costs for identical treatment systems. 

Iron removal processes are generally simple, reliable, and cost-effective. Arsenic 

removal is accomplished by adsorption of As(V) onto ferric hydroxides formed in the 

iron removal process. Several iron removal treatment methods can remove arsenic 

from drinking water supplies to levels below the new arsenic maximum contaminant 

level (MCL) of 0.010 mg/L; these methods include oxidation and filtration, and the 

use of solid oxidizing media products and manganese greensand. Many existing 

water utilities have much if not all of the appropriate technology in place for iron 

removal, but may need to modify or adjust the processes in order to meet the new 

MCL. 

Iron removal processes have operational options that vary with the oxidants used and 

the media selected for filtration. Selection of the most appropriate process for a water 

supply should be evaluated on a life-cycle basis. This design manual provides examples for performing an economic evaluation, including the development of an equivalent annual cost. The arsenic removal capacity may be affected by the raw water 

quality, particularly hydrogen sulfide, organics, and, in some cases, the pH of the 

water. Treatment processes incorporating oxidants require careful handling and storage of corrosive chemicals, such as chlorine and potassium permanganate. 

v 

Contents 

Abstract.........................................................................................................................v

Acronyms and Abbreviations.......................................................................................xi

1.0 Introduction ............................................................................................................1

1.1 Purpose and Scope.......................................................................................1

1.2 Background ...................................................................................................1

1.3 Arsenic Speciation.........................................................................................1

1.4 Arsenic Removal Options..............................................................................2

2.0 Arsenic Removal by Iron Removal Treatment Methods........................................3

2.1 Introduction....................................................................................................3

2.2 Oxidation .......................................................................................................4

2.2.1 Chemical Oxidants ..........................................................................5

2.2.1.1 Chlorine.............................................................................5

2.2.1.2 Potassium Permanganate.................................................6

2.2.1.3 Ozone................................................................................7

2.2.2 Solid Oxidizing Media......................................................................7

2.3 Contact Time .................................................................................................7

2.4 Filtration ........................................................................................................7

2.4.1 Anthracite/Sand...............................................................................8

2.4.2 Solid Oxidizing Filtration Media.......................................................8

2.4.2.1 Pyrolusite...........................................................................8

2.4.2.2 Birm.................................................................................11

2.4.3 Manganese Greensand.................................................................11

2.4.4 Other Media...................................................................................14

2.5 Jar Testing/Pilot Plant Studies ....................................................................14

3.0 Central Water Treatment Plant Design ...............................................................15

3.1 Introduction..................................................................................................15

3.2 General Plan ...............................................................................................15

3.3 Preliminary Design ......................................................................................17

3.3.1 Manual or Automatic Operation ....................................................17

3.3.2 Basis of Design .............................................................................19

3.3.2.1 General............................................................................19

3.3.2.2 Project Scope..................................................................20

3.3.2.3 Process Design Data Summary......................................20

3.3.2.4 Site ..................................................................................20

3.3.2.5 Layout of Structure..........................................................20

3.3.2.6 Structural.........................................................................21

3.3.2.7 Mechanics .......................................................................21

3.3.2.8 Electrical..........................................................................21

3.3.3 Treatment Equipment....................................................................22

3.3.3.1 Aerator.............................................................................22

3.3.3.2 Treatment Vessels ..........................................................22

3.3.3.3 Process Piping Material ..................................................23

3.3.3.4 Control Valves.................................................................23
3.3.4 Layout of Facilities ........................................................................23

3.3.5 Preliminary Project Cost Estimate.................................................23

3.3.6 Revisions and Approval ................................................................24

3.4 Final Design ................................................................................................24

3.4.1 General Guidelines .......................................................................24

3.4.2 Plan Content Guidelines ...............................................................24

3.4.2.1 Structural.........................................................................24

3.4.2.2 Schedules........................................................................25

3.4.2.3 Miscellaneous .................................................................25

3.4.2.4 Piping ..............................................................................25

3.4.2.5 Electrical..........................................................................25

4.0 Central Water Treatment Plant Capital Costs .....................................................27

4.1 Introduction..................................................................................................27

4.2 Cost Variables .............................................................................................27

4.2.1 Existing and Planned (Future) Treatment Plant Parameters ........28

4.2.1.1 Number and Location of Wells........................................28

4.2.1.2 Potable Water Storage Facilities.....................................28

4.2.1.3 Distribution and Consumption.........................................28

4.2.2 Water Chemistry............................................................................29

4.2.3 Chemical Supply Logistics ............................................................29

4.2.4 Manual Versus Automatic Operation ............................................29

4.2.5 Backwash and Regeneration Disposal Concept...........................29

4.2.6 Climate ..........................................................................................29

4.2.7 Seismic Zone.................................................................................29

4.2.8 Soil Conditions ..............................................................................30

4.2.9 100-Year Flood Plain ....................................................................30

4.2.10 Financial Considerations...............................................................30

4.3 Example Economic Evaluation....................................................................30

5.0 Central Water Treatment Plant Operation...........................................................35

5.1 Introduction..................................................................................................35

5.2 Chemical Treatment Equipment..................................................................35

5.2.1 Chlorination Equipment.................................................................36

5.2.2 Potassium Permanganate Feed Equipment .................................37

5.2.3 Chemical Feed Pumps..................................................................37

5.3 Pressure Filters ...........................................................................................37

5.3.1 Treatment (Filtration) Operation....................................................36

5.3.2 Backwash Operation .....................................................................38

5.3.2.1 Draindown .......................................................................38

5.3.2.2 Air/Water Wash ...............................................................38

5.3.2.3 Refill ................................................................................40

5.3.2.4 Fast Wash .......................................................................40

5.3.2.5 Slow Wash ......................................................................40

5.3.2.6 Bed Settle........................................................................40

5.3.2.7 Rinse ...............................................................................40

5.3.3 Filter Loadings and Run Termination............................................40

5.3.3.1 Gallons Treated...............................................................41

5.3.3.2 Filter Run Time................................................................41

5.3.3.3 Pressure Drop .................................................................41

5.3.4 Filter Operation..............................................................................41

5.4 Media ......................................................................................................44

5.4.1 Support Media...............................................................................44

5.4.2 Filter Media....................................................................................44

5.4.3 Limitations and Precautions..........................................................45

5.4.3.1 Anthracite Caps...............................................................45

viii 
5.4.3.2 Pyrolusite.........................................................................45

5.4.3.3 Birm.................................................................................45

5.4.3.4 Manganese Greensand...................................................45

5.5 Operator Requirements...............................................................................46

5.6 Laboratory Requirements............................................................................46

5.7 Operating Records ......................................................................................46

5.7.1 Plant Log .......................................................................................46

5.7.2 Operation Log................................................................................46

5.7.3 Water Analysis Reports.................................................................46

5.7.4 Plant Operating Cost Records ......................................................47

5.7.5 Correspondence Files ...................................................................47

5.7.6 Regulatory Agency Reports ..........................................................47

5.7.7 Miscellaneous Forms ....................................................................47

5.8 Treatment Plant Maintenance and Housekeeping......................................48

6.0 Central Water Treatment Plant Operating Costs.................................................49

6.1 Introduction..................................................................................................49

6.2 Treatment Chemicals ..................................................................................49

6.3 Operating Labor ..........................................................................................50

6.4 Utilities ......................................................................................................51

6.5 Media Replacement ....................................................................................52

6.6 Replacement Parts and Miscellaneous Materials .......................................52

6.7 Operating Cost Summary............................................................................52

7.0 References ..........................................................................................................53

Appendix A: Economic Evaluation Example...............................................................55

Appendix B: Operations Procedures for Iron Removal Plants ...................................65

Figures 

2-1. Conventional Iron Removal by Aeration.............................................................3

2-2. Arsenic Treatment Selection Strategy Guide (function of initial As and Fe 

content of water).................................................................................................4

2-3. Recommended Steps for Arsenic(III) Removal Using an Iron Removal 

Process...............................................................................................................5

2-4. Typical Layout of Pressure Vessels Used for Filtration......................................9

2-5. Service Flow Pressure Drop Through Greensand and Birm Media.................12

2-6. Backwash Bed Expansion Characteristics for Greensand and Birm ...............13

2-7. Manganese Greensand Process with Continuous Regeneration ....................13

2-8. Manganese Greensand Process with Batch Regeneration (ineffective for 

As removal).......................................................................................................13

3-1. Example Report of Water Analysis...................................................................16

3-2. Project Development Process ..........................................................................18

4-1. Two Conceptual Iron Removal Water Treatment Plant Floor Plans for 

Cost Estimates..................................................................................................31

4-2. 500,000-gpd Iron Removal Water Treatment Plant with Aeration Followed 

with Filtration.....................................................................................................32

4-3. 500,000-gpd Iron Removal Water Treatment Plant with Manganese 

Greensand Filtration .........................................................................................33

5-1. Valve Number Diagram on a Typical Pressure Filter.......................................36

5-2. Pressure Filter Loss of Head Gauges ..............................................................38

ix 
5-3. Filter Effluent Flow Meter..................................................................................39

5-4. Air Release Valve .............................................................................................39

5-5. Air Wash Blower and Motor..............................................................................40

5-6. Air Wash Blower Controls.................................................................................40

5-7. Typical Two-Filter Control Panel ......................................................................42

5-8. Pneumatically Operated Draindown Valves .....................................................43

5-9. Filtered Effluent Pneumatically Operated Butterfly Valve ................................43

5-10. Electric Valve Operator.....................................................................................44

5-11. Typical Water Treatment Plant Filter Operation Log........................................47

Tables 

2-1. Relative Effectiveness of Various Oxidants........................................................6

2-2. Stoichiometry of Various Chemical Oxidants .....................................................6

2-3. Characteristics of Filter Media for Iron Removal ..............................................10

5-1. Valve Operation Chart for Pressure Filters with Air Wash ...............................36

x 
Acronyms and Abbreviations 

ADA Americans with Disabilities Act 

ANSI American National Standards Institute 

APHA American Public Health Association 

ASME American Society of Mechanical Engineers 

AWWA American Water Works Association 

AWWARF American Water Works Association Research Foundation 

Birm Burgess Iron Removal Method 

EDR electrodialysis reversal 

ETV Environmental Technology Verification 

FRP fiberglass reinforced polyester 

GFAA graphite furnace atomic adsorption 

GHAA gaseous hydroxide atomic adsorption 

gpd gallons per day 

gpg grains per gallon 

gpm gallons per minute 

HDPE high-density polyethylene 

HTH calcium hypochlorite 

HVAC heating, ventilating, air conditioning 

ICP-MS inductively coupled plasma–mass spectrometry 

MCL maximum contaminant level 

mgd million gallons per day 

NEC National Electrical Code 

NSF National Sanitation Foundation International 

NTNC nontransient, noncommunity 

NTU nephelometric turbidity unit 

O&M operations and maintenance 

OSHA Occupational Safety and Health Administration 

P&ID Process and Instrumentation Diagram 

PLC programmable logic controller 

PPD potassium permanganate demand 

psi(g) pounds per square inch (gage) 

PVC polyvinyl chloride 

xi 
SDWA Safe Drinking Water Act (of 1974) 

SMCL secondary maximum contaminant level 

STP stabilized temperature platform 

U.S. EPA United States Environmental Protection Agency 

WEF Water Environment Federation 

WTP water treatment plant 

xii 
1.0 Introduction 

1.1 Purpose and Scope 

This manual presents up-to-date information on how iron 

removal processes can be designed, operated, and 

modified to effectively remove arsenic from drinking 

water supplies. The information provided is primarily for 

small central groundwater treatment plants ranging in 

capacity from 30,000 to 1,000,000 gallons per day (gpd). 

However, this manual also can be adapted to both larger 

and smaller systems. For very small systems having 

capacities of less than 30,000 gpd (20 gallons per minute [gpm]), some equipment may be different and less 

expensive (e.g., fiberglass reinforced polyester [FRP] 

tanks and automatic control valves likely would be 

used). 

1.2 Background 

The Safe Drinking Water Act (SDWA) of 1974 mandated 

that the United States Environmental Protection Agency 

(U.S. EPA) identify and regulate drinking water contaminants that may have adverse effects on human health 

and that are known or anticipated to occur in public 

water supply systems (Public Law, 1974). In 1975, under 

the SDWA, U.S. EPA established a maximum contaminant level (MCL) for arsenic at 0.05 mg/L (U.S. EPA, 

1975). In 1996, Congress amended the SDWA to require 

that the U.S. EPA develop an arsenic research strategy, 

publish a proposal to revise the arsenic MCL by January 

2000, and finalize the new rule by January 2001 (Public 

Law, 1996). 

On January 22, 2001, U.S. EPA published a final 

Arsenic Rule in the Federal Register that revised the 

MCL for arsenic at 0.01 mg/L (10 μg/L) (U.S. EPA, 

2001). Two months later, in March 2001, the effective 

date of the rule was extended to provide time for the 

National Academy of Science to review new studies on 

the health effects of arsenic and for the National Drinking Water Advisory Council to review the economic 

issues associated with the standard. After considering 

the reports by these two review groups, U.S. EPA finalized the arsenic MCL at 0.01 mg/L (10 μg/L) in January 

2002. In order to clarify the implementation of the original rule, U.S. EPA revised the rule text on March 25, 

2003 to express the MCL as 0.010 mg/L (U.S. EPA, 

2003). The final rule requires all community and nontransient, non-community (NTNC) water systems to 

achieve compliance with the rule by January 23, 2006. 

1.3 Arsenic Speciation 

Arsenic is a common, naturally occurring contaminant 

that originates from arsenic-bearing rocks and soils. It is 

transported to natural waters through erosion and dissolution and exists primarily in inorganic form. Common 

sources of contamination include the erosion of natural 

deposits, pesticide runoff from orchards, and runoff from 

glass and electronics production wastes. Inorganic arsenic is the form of arsenic most likely to cause regulatory 

concern. 

The species and valence state of inorganic arsenic 

depend on the oxidation-reduction conditions and pH of 

water. In general, arsenite, the reduced, trivalent form 

[As(III)], is found in groundwater (assuming anaerobic 

conditions); and arsenate, the oxidized, pentavalent form 

[As(V)], is found in surface water (assuming aerobic 

conditions). This rule, however, does not always hold 

true for groundwater. Some groundwaters have been 

found to contain only As(III), others with only As(V), and 

still others with a combination of both As(III) and As(V). 

Arsenate exists in four forms in aqueous solution, 

depending on pH: H3AsO4, H2AsO4 

−

, HAsO4

2−

, and 

AsO4

3−

. Similarly, arsenite exits in five forms: H4AsO3

+

, 

H3AsO3, H2AsO3 

−

, HAsO3

2−

 and AsO3

3−

. 

Until recently, studies on the preservation of arsenic 

species concluded that no effective methods exist to 

preserve As(III) and As(V) in water samples. Because of 

the lack of a good preservation method, field separation 

methods developed by Ficklin (1982), Clifford et al. 

1
(1983), and Edwards et al. (1998), and modified by 

Battelle (U.S. EPA, 2000) have been used to separate 

As(III) from As(V). All of the methods use an anion 

exchange resin column and have been found to be 

effective for speciating. Their use is recommended to 

determine the oxidation state of arsenic in the source 

water to be treated. The speciation of arsenic is important because As(V) is more effectively removed by iron 

removal processes than As(III); therefore, if source 

water contains predominantly As(III), a strong oxidant 

must be added to convert As(III) to As(V) for more effective removal. 

1.4 Arsenic Removal Options 

Arsenic concentrations in surface water supplies normally are less than the finalized U.S. EPA MCL of 

0.010 mg/L. However, groundwater supplies often have 

arsenic concentrations that are higher than the MCL due 

either to the exposure of water to arsenic-bearing geologic materials, or to contamination by arsenic-bearing 

water. Because of the revision of the MCL, a large 

number of utilities that previously have been in compliance will need to install new and/or modify existing 

arsenic removal systems to meet the new MCL. Many 

treatment options exist for the removal of arsenic from 

surface and groundwaters. They include coagulation/filtration using iron or aluminum salts; lime softening; ion 

exchange; adsorptive media; membrane processes 

(such as reverse osmosis [RO] and nanofiltration [NF]); 

electrodialysis reversal (EDR); and iron removal (U.S. 

EPA, 2000). 

This design manual focuses on the removal of excess 

arsenic from source water using iron removal processes. 

The concepts and principles outlined in the manual can 

be adapted to several different types of iron removal 

treatment options: 

1. Chemical oxidation followed by media filtration. 

2. Solid oxidizing media filtration. 

3. Manganese greensand filtration. 

The variation among the different treatment options 

depend on site and water quality factors. 

Two other processes that are particularly cost-effective 

for treatment of groundwater include ion exchange and 

adsorptive media; a design manual for each process has 

been published by U.S. EPA (Rubel, 2003a and 2003b). 

Other non-treatment lower-cost options also exist for 

reducing the arsenic level in a water supply. One option 

is to locate an alternate water source within the service 

area that complies with the arsenic MCL, as it may be 

feasible to blend the two sources and achieve a combined water quality that complies with the arsenic MCL. 

A second option (which includes an element of risk) is to 

drill a new well (or wells) within the service area. This 

approach should be attempted only when there is sound 

reason to believe that a sufficient quantity of acceptable 

water can be located. The costs (both capital and operating) of a new well should not exceed the costs of treating the existing source. 

A third option is to pump water of good quality to the 

service area from another service area. This imported 

source either can be used alone or can be blended with 

the original source to achieve a combined water quality 

that meets the MCL. However, the costs of installing a 

delivery system and delivering the water become increasingly unfavorable as the distance increases, the rise in 

elevation increases, and/or the physical barrier exists. 

Factors to be considered are the reliability, the cost, and 

the assurance that the consumers will only use the 

imported/blended source. 

2
Aeration 

Well Filter 

FIGURE 2-1. Conventional Iron Removal by Aeration 

2.0 Arsenic Removal by Iron Removal Treatment Methods 

2.1 Introduction 

This chapter provides an overview of the design considerations that are applicable to arsenic removal by use of 

iron removal treatment methods. Iron-based treatment 

technology options include chemical coagulation/filtration with iron salts, adsorptive media (iron-based products), and iron removal by oxidation and filtration (Gupta 

and Chen, 1978; Edwards, 1994; McNeill and Edwards, 

1995; Scott et al., 1995; Holm, 1996; Hering et al., 1996; 

McNeill and Edwards, 1997; Chen et al., 2002). These 

processes are particularly effective at removing arsenic 

from aqueous systems because iron surfaces have a 

strong affinity to adsorb arsenic. The adsorption and coprecipitation of As(III) and As(V) on iron oxide surfaces 

have been investigated extensively (Manceau, 1995; 

Waychunas et al., 1996; Sun and Doner, 1998; Jain et 

al., 1999). Research also has shown that As(V) is more 

effectively removed by iron removal processes than 

As(III) (Edwards, 1994; Hering et al., 1996; Leist et al., 

2000; Chen et al., 2002). 

Many arsenic-containing groundwaters also may contain 

significant levels of iron and manganese due to natural 

geochemistry. Like arsenic, iron exists in two primary 

valence states: Fe(II) (ferrous iron) and Fe(III) (ferric 

iron). Manganese has many valence states: Mn(II), 

Mn(III), Mn(IV), Mn(VI), and Mn(VII). The reduced forms 

of both elements (i.e., Fe(II) and Mn(II) [manganous 

manganese]) are soluble. When oxidized, both elements 

are converted to insoluble forms and can cause serious 

aesthetic problems in drinking water. Because of these 

potential problems, secondary maximum contaminant 

levels (SMCLs) were established by U.S. EPA (1979) for 

iron (0.3 mg/L) and manganese (0.05 mg/L). Removing 

iron and manganese levels to below their SMCLs eliminates many of the taste, odor, and color problems caused 

by high concentrations. 

Iron and manganese can be removed from source water 

by several technologies. The traditional removal method 

for both elements involves a two-step process: (1) oxidation of the soluble Fe and Mn forms to the common insoluble forms of Fe(OH)3(s) and MnO2(s) and, (2) filtration of 

these formed precipitates. Figure 2-1 shows a schematic 

of conventional iron removal by aeration. 

Note that, although manganese has properties similar 

to iron, it does not have a high capacity for arsenic 

removal. Thus, the amount of arsenic removed by processes designed to remove both iron and manganese 

depends primarily on the iron removed. Therefore, this 

manual has been devoted to iron removal processes. 

Arsenic in source waters can be removed by taking 

advantage of the arsenic adsorptive capacity of natural 

iron particles formed following the oxidation of Fe(II) to 

Fe(III). Arsenic removal is achieved through two primary 

mechanisms: adsorption, which involves the attachment 

of arsenic to the surface of Fe(III) particles; and coprecipitation, which involves the entrapment of arsenic 

within growing Fe(III) particles by inclusion, occlusion, or 

adsorption (Benefield and Morgan, 1990; Chen et al., 

2002). In essence, iron removal processes also can act 

as effective arsenic removal processes. 

The capacity of a given iron removal process to remove 

arsenic and the potential to meet the new arsenic MCL 

depends largely on the amount of arsenic and natural 

iron in the source water. Sorg (2002) proposed an 

arsenic treatment selection strategy screening guide, 

3
50 

45 Modifi e c s 

40 B 

ed Iron R moval Pro es

C 

Fe - SMCL

Arsenic - ug/L 

35 ratio 

As

e/

30 F - 1

20

25 Media Adsorption 

Iron Coag/Filt 

A 

20 Ion Exchange

Iron Removal(M) 

15 Iron Removal Process RO / NF (Optimized for Maximium As Removal) 

10 As MCL 

5 

0 

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 or above 

Iron - mg/L 

FIGURE 2-2. Arsenic Treatment Selection Strategy Guide (function of initial As and Fe content of water) 

(Sorg, 2002) 

which is derived from the prediction that source waters 

having an iron to arsenic ratio of 20:1 are potential candidates for arsenic removal to below the MCL by removing the iron (U.S. EPA, 2001 and 2002). Converting this 

ratio into a removal guide indicates that 1 mg/L iron 

should be capable of removing 50 μg/L arsenic under 

optimum adsorptive and process operational conditions 

(Figure 2-2). 

The actual capacity to remove arsenic via iron removal 

depends on several factors, including water chemistry, 

operating considerations, and the sequence of treatment 

processes. Studies have shown that the sorption of 

arsenic onto iron solids is affected by many factors, 

including the amount and form of As(III) and As(V) 

present; pH; water chemistry; amount and form of iron 

present; and the existence of competing ions, such 

as phosphate, silicate, and natural organic matter 

(Andreae, 1979; Azcue and Nriagu, 1993; Edwards, 

1994; Al-Juaid et al., 1994; Borho and Wilderer, 1996; 

Chen et al., 2002). Redox relationships between arsenic, iron, and oxidants are particularly important to consider when optimizing the removal of arsenic via an iron 

removal process. 

Several variations on traditional iron removal oxidation/filtration technology for groundwater exist; the basic 

process includes oxidation, contact time (optional), and 

filtration. The most common oxidants used for iron precipitation are oxygen, chlorine, and potassium permanganate; however, aeration is not an effective method for 

oxidizing arsenic (Frank and Clifford, 1986; Lowry and 

Lowry, 2002). To achieve arsenic removal by iron 

removal, the use of a strong chemical oxidant is required. 

The oxidation step is usually followed by detention (contact time) and filtration. 

Filtration options consist of sand (only), anthracite and 

sand (dual media), manganese greensand, and various 

synthetic filtration media. The manganese greensand 

media is a special media that removes iron and manganese by combination of oxidation, adsorption, and filtration all within the media itself. Oxidation and filtration 

processes as well as the significance of contact time and 

jar/pilot testing will be discussed in more detail in Sections 2.2 through 2.5. 

2.2 Oxidation 

When oxidizing iron and arsenic to optimize removal, 

one must consider (1) the addition of a strong oxidant, 

and (2) the point of chemical oxidant addition. 

In general, arsenic in groundwater containing both arsenic and iron will exist in the reduced form, As(III). To optimize arsenic removal, neutrally charged As(III) needs to 

be oxidized to As(V). As(V) exists as a negatively charged 

ion and can be adsorbed onto positively charged surfaces of ferric hydroxide particles. Consequently, if the 

arsenic in the source water is predominately As(III), 

oxidizing As(III) to As(V) using a strong oxidant will 

result in a higher rate of arsenic removal by an iron 

removal process. Figure 2-3 shows the recommended 

sequence of steps for removing As(III) via iron removal 

using a strong chemical oxidant. 

4
Oxidant injection 

Contact basin 

 (Optional) 

Well 

Filter 

FIGURE 2-3. Recommended Steps for Arsenic(III) Removal Using an Iron Removal Process 

2.2.1 Chemical Oxidants 

As(III) can be easily converted to As(V) using chemical 

oxidants such as chlorine, potassium permanganate, 

and ozone, which are known to improve arsenic removal 

(Ghurye and Clifford, 2001 and 2004). The dosage of 

oxidants will depend on the concentrations of other substances in the source water, such as iron, manganese, 

sulfide, and dissolved organic matter. Oxidants that do 

not effectively convert As(III) to As(V) include oxygen 

(i.e., aeration), chlorine dioxide, and chloramine. 

The effectiveness of various chemical oxidants for iron, 

manganese, and arsenic is shown in Table 2-1. The 

table lists the effectiveness of these oxidants for manganese because the oxidation option selected for arsenic 

removal may be determined by the need to oxidize both 

iron and manganese. 

The stoichiometric amount of oxidant necessary to oxidize As(III), Fe(II), and Mn(II) is important when approximating chemical feed dosage in iron/arsenic removal 

systems. It is important not to under-dose on the oxidant 

because under-dosing can result in incomplete oxidation 

of As(III). Table 2-2 presents the stoichiometric relationships between relevant oxidants and Fe(II), Mn(II) and 

As(III). Note that the oxidant demand of Fe(II) and Mn(II) 

dominates relative to that of arsenic. Other water quality 

constituents also may have an oxidant demand (e.g., 

ammonia, dissolved organic matter). Thus, when determining the oxidant dose, the total oxidant demand of the 

source water must be determined. 

The point of chemical oxidant addition also is critical 

in achieving optimal arsenic removal. Research has 

shown that pre-formed iron particles have less capacity 

to remove As(V) than iron particles that are formed in 

the presence of As(V). Edwards (1994) reported that 

pre-formed iron hydroxides only reached a maximum 

adsorption density of 0.1 M As(V)/M hydroxide solid, 

compared to a maximum adsorption density of 0.5 to 

0.6 M As(V)/M for iron hydroxides formed in the presence of As(V). The differences in adsorption densities 

were attributed to different adsorption mechanisms: strict 

surface adsorption of As(V) onto pre-formed iron hydroxides versus adsorption/co-precipitation with iron hydroxides formed in the presence of As(V). 

Hering et al. (1996) examined the water quality factors 

that affect arsenic removal during iron coagulation and 

adsorption to pre-formed hydrous ferric oxides. Based 

on experimental results and surface complexation modeling, the authors demonstrated that, although it is an 

important mechanism, adsorption is not the only mechanism controlling arsenic removal during coagulation. 

Similar results were found at an iron removal treatment 

plant that used aeration to oxidize iron, followed by chlorination or potassium permanganate to oxidize As(III); 

this was another situation where iron particles were 

formed prior to arsenic oxidation. Lytle and Snoeyink 

(2003) observed that arsenic removal would be lower 

during this sequence of treatment steps, as opposed to 

the preferred process of oxidizing both Fe(II) and As(III) 

at the same time. Consequently, oxidation of iron and 

arsenic should occur at the same time to achieve 

optimal arsenic removal. 

2.2.1.1 Chlorine 

Chlorine has long been used as the disinfectant of 

choice for most drinking water supplies. The oxidizing 

power of chlorine is not only effective with iron, but also 

with many other contaminants found in raw water, both 

organic and inorganic. Chlorine also effectively oxidizes 

As(III), Fe(II) and Mn(II). The simple oxidation reactions 

between chlorine and arsenic, iron, and manganese are 

as follows: 

5
TABLE 2-1. Relative Effectiveness of Various Oxidants 

Oxidant Iron (Fe) Manganese (Mn) As(III) 

Oxygen (aeration) Effective Not effective Not effective 

Chlorine Effective Somewhat effective Effective 

Chloramine Not effective Not effective Not effective 

Ozone Effective Effective Effective 

Chlorine dioxide Effective Effective Not effective 

Potassium permanganate Effective Effective Effective 

TABLE 2-2. Stoichiometry of Various Chemical Oxidants 

Iron (Fe) Manganese (Mn) As(III) 

Oxidant (mg oxidant/mg Fe) (mg oxidant/mg Mn) (μg oxidant/μg As[III]) 

Chlorine (Cl2) 0.64 1.29 0.95 

Chloramine (NH2Cl) 0.46 0.94 0.69 

Ozone (O3) 0.43 0.88 0.64 

Chlorine dioxide (ClO2) 

 1-electron transfer ----- 2.45 1.80 

 5-electron transfer 0.24 ----- 0.36 

Potassium permanganate (KMnO4) 0.94 1.92 1.40 

NaOCl + H3AsO3 o H2AsO4 

−

 + Na+ + Cl− + H+ 

HOCl + 5H2O + 2Fe2+ o 2Fe(OH)3 (s)+ Cl− + 5H+ 

HOCl + H2O + Mn2+ o MnO2 (s) + Cl−

 + 3H+ 

Oxidation of As(III), Fe(II), and Mn(II) by chlorine occurs 

fairly rapidly in pH ranges of 6.5-8.0. To determine the 

dosage of chlorine, 0.64 mg/L of chlorine (as Cl2) is 

needed to oxidize 1.0 mg/L of iron. However, because 

other materials in the source water may have a chlorine 

demand, this dose rate may need to be increased. For 

example, water with manganese requires 1.29 mg/L of 

chlorine (as Cl2) to oxidize 1.0 mg/L of manganese. 

Arsenic typically is present at microgram levels, so negligible amounts of additional oxidant are required. It is 

common practice to use the stoichiometric value plus 

10% when establishing initial dosages. 

In recent years, the use of chlorine gas has come under 

increased scrutiny for safety reasons; sodium hypochlorite and calcium hypochlorite are two common alternatives, especially in smaller plants. 

Chlorine gas is delivered by tanker cars (either truck or 

rail) for very large plants; 2,000-lb containers are used 

by most cities. For smaller plants, 150-lb cylinders are 

more typical. The gas is drawn by a vacuum into the 

water, and the resulting solution is injected into the raw 

water stream to oxidize iron. Typically, this oxidation step 

takes place in 10 to 15 seconds (Sommerfeld, 1999). 

Note that the use of chlorine gas requires the ability to 

isolate chlorine leaks. At treatment plants, this normally 

involves the use of specially modified rooms with appropriate safety gear, ventilation systems, and, in some 

cases, gas scrubbers. 

Sodium hypochlorite is delivered in bulk by tankers or in 

smaller quantities such as carboys and 5-gallon cartons. 

It is pumped directly into the raw water stream to oxidize 

soluble iron. One of the other results of adding sodium 

hypochlorite to hard water is the formation of caustic 

soda that tends to soften the water and precipitate calcium and magnesium. These precipitates can harden 

onto pipe walls and eventually restrict pipe flow if not 

maintained. Careful consideration to the point of application must be given for maintenance reasons. Shelf life is 

diminished at higher temperature readings and when 

exposed to sunlight. Control of off-gassing is another 

design issue. 

Calcium hypochlorite is provided in a dry form and is typically used in low-flow applications. It can be provided in 

tablet form for use in automatic feed equipment or in a 

dry powder. Degradation occurs over time. It is the most 

expensive of the three forms of chlorine and can lead to 

scale formation in hard waters. 

2.2.1.2 Potassium Permanganate 

Potassium permanganate (KMnO4) is a strong chemical 

oxidant. When dissolved in water, it imparts a pink to 

purple color depending on the concentration. Potassium 

6
permanganate is similar to chlorine in being able to oxidize Fe(II), Mn(II), and As(III). The chemical also has 

been used for taste and odor control. 

The most common application of potassium permanganate in water treatment is as an oxidant for iron and 

manganese. A byproduct of this oxidation step is insoluble manganese dioxide. Potassium permanganate can 

be used in combination with either gravity filters or pressure filters. The most popular type of pressure filter 

media used is manganese greensand. 

Potassium permanganate also is effective at oxidizing 

As(III) to As(V), which then readily adsorbs to iron particles (not manganese dioxide particles) in water; these 

iron particles are of a size that can be filtered for removal. 

Therefore, filtration must follow oxidation to remove the 

insoluble iron and manganese particles. 

The simple oxidation reactions between potassium permanganate and arsenic, iron, and manganese are as 

follows: 

2KMnO4 + 3H3AsO3 = 3H2AsO4 

−

 + 2MnO2(s) + H2O + 3H+ 

KMnO4 + 7H2O + 3Fe2+ = 3Fe(OH)3(s)+ MnO2(s) + 5H+

 + K+ 

2KMnO4 + 2H2O + 3Mn2+ = 5MnO2(s) +4H+

 + 2K+ 

Potassium permanganate normally is purchased as dry 

solid crystals in bulk or in drum containers. The chemical 

is mixed with water and the solution is pumped directly 

into a raw water line. The maximum solubility of potassium permanganate is about 6.5% at 20°C. After the dry 

crystals are added to the water, the solution should be 

mixed for at least 15 minutes with a mechanical agitator. 

Continuous mixing is recommended. 

2.2.1.3 Ozone 

Ozone (O3) has been shown to effectively oxidize iron 

and manganese at the same time removing arsenic and 

other metals to below detection limits. An ozone generator can be used to make ozone, which can then be 

dispensed into a water stream to convert Fe(II) to Fe(III) 

and As(III) to As(V). It is also a potential disinfectant, but 

unlike chlorine, ozone does not impart a lasting residual 

to treated water. Research has shown that the effectiveness of ozonation can be significantly affected by the 

presence of organic matter and sulfide (S2−

) (Ghurye 

and Clifford, 2001 and 2004). The simple oxidation reactions between ozone and arsenic, iron, and manganese 

are as follows: 

O3 + H3AsO3 = H2AsO4 

−

 + O2 + H+ (@ pH 6.5); 

O3 + H3AsO3 = HAsO4

2−

 + O2 + 2H+ (@ pH 8.5) 

O3 + 5H2O + 2Fe+2 = 2Fe(OH)3(s)+ O2 + 4H+ 

O3 + H2O + Mn2+ = MnO2(s) +2H+

 + O2 

2.2.2 Solid Oxidizing Media 

Current studies indicate that some solid oxidizing media, 

such as Filox-R and Pyrolox, will oxidize As(III) to As(V) 

(Ghurye and Clifford, 2001 and 2004; Lowry et al., 2005). 

Although both media have been used primarily for filtration, Filox-R has been used to oxidize As(III) as a pretreatment step before anion exchange treatment for 

As(V) removal (Lowry et al., 2005). However, stand-alone 

solid oxidizing treatment is better suited for small treatment plants with low iron concentrations. The removal 

capacity of solid oxidizing media depends largely on the 

type of media used and the dissolved oxygen concentration and sulfide levels in the source water. A more 

detailed discussion on solid oxidizing media is provided 

in Section 2.4.2. 

2.3 Contact Time 

Strong chemical oxidants oxidize As(III) and Fe(II) very 

rapidly (AWWARF, 1990; Ghurye and Clifford, 2001 and 

2004), thus contact time generally is not a critical factor 

for optimizing arsenic removal. Lytle and Snoeyink (2004) 

report that a majority of arsenic is incorporated into 

Fe(III) particles during the first several minutes following 

oxidant addition. Relatively small amounts of additional 

arsenic adsorption/removal may occur with extended contact time. Extended contact time may provide some benefit to particle development and filterability, and should be 

considered particularly when anticipated arsenic removal 

is not achieved. Cost savings can be achieved by eliminating the need for contact basins. Also, a detention/settling tank can help reduce the filter load and increase 

filter performance and run time. 

2.4 Filtration 

After the oxidation step (with or without a detention or 

settling tank), the source water is filtered through a filter 

media in either a pressure vessel or a gravity filter to 

remove the iron/arsenic solids formed in the water. A 

typical layout for pressure vessels is shown in Figure 2-4. 

The filtration media in these systems may consist of 

sand, sand and coal anthracite (dual media), or proprietary/patented products, such as Pyrolox, Filox-R, Birm, 

and manganese greensand. Table 2-3 provides the costs 

and physical properties of several commercially available iron removal media. Effective removal of iron particles is critical to good arsenic removal because all iron 

particles in the filter effluent contain (adsorbed) arsenic. 

7
Some media, such as manganese greensand, have the 

ability to both oxidize and filter iron and manganese 

effectively and at the same time. Manganese greensand, 

pyrolusite, Birm, or any media coated with manganese 

dioxide has the capacity to oxidize iron and manganese 

and filter the insoluble precipitates with the filter bed. 

These media also have some, but limited, capacity for 

As(III) oxidation and arsenic adsorption. 

2.4.1 Anthracite/Sand 

Anthracite and sand usually are used in gravity filters to 

remove particles. A coarse anthracite bed in the size 

range of 0.80-1.20 mm generally will capture ferric 

hydroxide solids. Anthracite is generally used in a 12­

18 inch depth followed by 12-18 inches of sand ranging 

from 0.45-0.55 mm. Sand alone may be used without 

the anthracite cap, but terminal head loss may develop 

sooner, requiring more frequent backwashing. 

Iron and arsenic leakage or breakthrough of the filter can 

be caused by a number of factors, including: 

• Inadequate oxidation that may allow soluble Fe, 

As(III), and As(V), to pass through the filter 

media; 

• Improper backwashing that does not adequately 

remove the captured solids containing iron and 

arsenic, causing them to be “pushed” through 

the filter when it is put back into service; 

• Waiting too long to backwash a filter, which can 

cause iron and arsenic particles to leak through 

the filter as the bed becomes packed with these 

particles; and 

• Operating a filter at high loading rates or 

excessive pressure across the filter. 

Properly trained operators can control these factors with 

regular cleaning and maintenance. Cleaning of the filter 

media is accomplished through a water backwash. The 

need for backwashing a gravity filter is usually prompted 

by one of three factors: 

• Head loss up to 8-10 ft due to a “dirty” filter. 

• Turbidity breakthrough or other deterioration of 

the effluent quality. 

• Filter run time exceeding a predetermined limit, 

often set at 80-120 hours. 

Fluidization of the bed is accomplished by an upward 

flow of water through the media of sufficient velocity 

to suspend the grains in water. This flowrate generally 

begins at 4-6 gpm/ft2

 and proceeds up to 15 gpm/ft2. The 

resulting collision of particles and scrubbing action loosens the trapped precipitates, and the carrying velocity of 

the water removes the particles to a waste stream. 

Expansion of the filter media varies according to media 

particle size, specific gravity, and uniformity coefficient. 

For example, a rate that expands the sand media 30­

35% may expand the anthracite 50%. Actual backwashing rates should be determined for the type of media 

used. If pressure vessels are used, adequate freeboard 

within the filtration vessels must be designed so that 

media is not carried out to waste. 

For pressure filters, dual media filtration rates are typically in the range of 3 to 5 gpm/ft2

. Filter run times may 

be affected by the type of media, filtration rate, and the 

levels of iron being removed. Some treatment units 

operating at a high filtration rate (>4 gpm/ft2

) and removing high concentrations of iron (3-10 mg/L) may require 

backwashing daily. Other filters with lower levels of iron 

being removed and lower filtration rates may not need to 

be backwashed for several days. In those cases, good 

operation generally initiates a backwash between 80­

120 hours of operation to prevent potential bacteria 

growth in the filter bed. 

2.4.2 Solid Oxidizing Filtration Media 

Two media that are gaining wider acceptance for filtration use in iron and manganese removal are pyrolusite 

and Birm. Pyrolusite is manganese dioxide in a granular 

form that can be used within a pressure vessel for filtration. Birm, on the other hand, is a manufactured material 

that begins with a base material coated with manganese 

dioxide. 

Both types of media oxidize iron on the media surface 

and trap ferric hydroxide particles in the filter bed. Some 

As(V) can be adsorbed to the ferric hydroxide solids, 

which then are backwashed out of the filter. The use of 

oxidizing media should be considered only as a pretreatment step to remove iron solids and convert As(III) 

to As(V). As such, it is recommended that processes 

such as adsorptive media or ion exchange resins be 

used as a polishing step to remove As(V). 

2.4.2.1 Pyrolusite 

Pyrolusite is the common name for naturally occurring 

manganese dioxide and is available in the United States, 

United Kingdom, South America, and Australia. It is distributed under brand names such as Pyrolox, Filox-R, 

8
FIGURE 2-4. Typical Layout of Pressure Vessels Used for Filtration 

9
10

TABLE 2-3. Characteristics of Filter Media for Iron Removal(a) 

Media Color 

Cost(b) 

($/ft3) 

Filter 

Rate 

(gpm/ft2) 

Specific 

Gravity 

(g/cm3) 

Bulk 

Density 

(lb/ft3) 

Effective Size 

(mm) 

Uniformity 

Coefficient 

Mesh 

Size 

Chemical 

Regeneration pH 

Air 

Scouring 

Backwa

Rate 

(gpm/ft

Manganese 

greensand Black 84-90 3.0-5.0 2.4-2.9 85 0.30-0.35 1.3 16 - 60 

1.5-2.0 oz (by 

weight) of 

KMnO4 per ft3 

6.2-8.5 Required 10-12 

Anthracite Black 8-15 5.0 1.6 50 0.8-1.2 < 1.65 Varying Not required Inert Not required 12-20 

Silica sand Light brown 5-10 3.0-5.0 2.6 120 0.45-0.55 1.62 16 x 50 Not required Inert Not required 10-20 

Macrolite Taupe, brown to 

grey 

220 8.0-10.0 2.1 54 0.25-0.35 1.1-1.2 40 x 60 Not required Inert Required 8-10 

Pyrolusite Black 5.0 3.8-4.0 125 0.51 1.7 Not required 6.5-9.0 Recommended 25-30 

“Pyrolox” 92 8 x 20 

“Filox-R” 263 20 x 40 

Birm Black 56-65 3.5-5.0 2.0 40-45 0.48 2.7 10 x 40 Not required 6.8-9.0 Not required 10-12 

Granular 

manganese 

dioxide 

“MTM” 

Dark brown 70-78 3.0-5.0 2.0 45 0.43 2.0 14 x 40 

1.5-2.0 oz (by 

weight) of 

KMnO4 per ft3 

6.2-8.5 Not required 8-10 

Note: Information compiled as of January 2004. (a) Some media are available in various mesh sizes. Contact vendors for more information. 

(b) Costs may vary with the order size. 
and MetalEase. It is a mined ore consisting of 40 to 85% 

manganese dioxide by weight. The various configurations 

of pyrolusite provide extensive surface sites available for 

oxidation of soluble iron and manganese. Removal rates 

of iron in excess of 20 mg/L are achievable. 

Pyrolusite is a coarse oxidizing media available in 8 to 

20 mesh with a high specific gravity of about 4.0. Like 

silica sand, pyrolusite is a hard media with small attrition 

rates of 2-3% per year. Pyrolusite may be used in the 

following two ways: (1) Mixing with sand, typically at 10­

50% by volume, to combine a filtering media with the 

oxidizing properties of pyrolusite; (2) Installing 100% 

pyrolusite in a suitably graded filter to provide oxidation 

and filtration. Maximum hydraulic loading rates of 3­

5 gpm/ft2

 should be the basis of design for a pressure 

vessel. No chemical regeneration is required. 

Backwash is critical for proper operation. Attrition during 

backwash can be a benefit as it exposes more surface 

sites for oxidation of soluble iron and manganese. The 

density of pyrolusite is in the range of 120 lb/ft3

, requiring 

a backwash rate of 25-30 gpm/ft2 to fluidize the bed, 

scrub the media, and redistribute the media throughout 

the bed. Air scour and backwashing are recommended 

in simultaneous mode. If water backwash alone is used, 

air scour prior to backwash is recommended with a 

water backwash designed for 30 gpm/ft2

 in order to fluidize the bed at least 30%. If a gravel support over the 

underdrain is used, a gravel retaining screen should be 

included in the design. The manufacturer recommends 

daily backwashing to maintain the effectiveness of the 

media for oxidizing and removing iron. 

2.4.2.2 Birm 

Birm is an acronym that stands for the “Burgess Iron 

Removal Method” and is a proprietary product manufactured by the Clack Corporation in Wisconsin. Typical 

applications have been point-of-use treatment, but it has 

been used in municipal treatment plants. Birm has the 

capacity to oxidize iron, but is not very effective at 

oxidizing As(III) to As(V). 

Birm is produced by impregnating manganous salts to 

near saturation on aluminum silicate sand, a base 

material. The manganous ions then are oxidized to a 

solid form of manganese oxide with potassium permanganate. This process is similar to that used to manufacture manganese greensand. The manufacturer indicates 

that the presence of dissolved oxygen is necessary for 

Birm to function as an oxidizing media for iron oxidation. 

Birm is available in a 10 × 40 mesh with an effective size 

of 0.48 mm and a specific gravity of 2.0. To be effective, 

it must be used in water with a pH range of 6.8-9.0. 

Alkalinity should be greater than two times the combined 

sulfate and chloride concentration. Injection of compressed air ahead of the media to maintain a dissolved 

oxygen content of at least 15% of the iron content may 

be required, especially for source water with iron at concentrations of 3 mg/L or greater. The dissolved oxygen 

oxidizes iron with Birm media serving as a catalyst that 

enhances the reaction between dissolved oxygen and 

dissolved iron and manganese in the water. Further, 

formed ferric hydroxide attracts oxidized arsenic, which 

then is captured in the filter bed. 

Filter loading rates should be between 3.5-5.0 gpm/ft2 

with a bed depth of 30-36 inches. Birm is not suitable for 

use with water containing hydrogen sulfide or organic 

matter exceeding 4-5 mg/L. Chlorination greatly reduces 

Birm’s effectiveness and at high concentrations can 

deplete the catalytic coating. Polyphosphates can coat 

the media, thus reducing its effectiveness for iron 

removal. Manufacturer information is available at 

www.clackcorp.com. 

No chemical addition or regeneration is required for 

Birm. Backwash rates should be controlled in the range 

of 10-12 gpm/ft2

 in order to achieve suitable bed expansion of approximately 30% for cleaning. An excessively 

high backwashing rate and air scour should be avoided 

to minimize attrition loss. Underdrains may include a 

gravel support bed or may be of the gravel-less type. 

Figures 2-5 and 2-6 provide information for normal service pressure drops and backwash bed expansion characteristics for Birm and manganese greensand. 

2.4.3 Manganese Greensand 

Another media that converts soluble forms of iron and 

manganese to insoluble forms that can then be filtered is 

manganese greensand. Manganese greensand has 

been used in North America for several decades and is 

formed from processed glauconite sand. The glauconite 

is synthetically coated with a thin layer of manganese 

dioxide, which gives the dark sand a definite green color 

and thus its name. There is only one North American 

manufacturer of manganese greensand and it is located 

in New Jersey. Limitations for manganese greensand 

include a maximum limit of 5 mg/L of hydrogen sulfide 

removal and 15 mg/L for iron removal; also, water pH 

should be in the range of 6.2-8.5 (Zabel, 1991). 

The combination of a strong oxidant and manganese 

greensand filtration media for iron removal is commonly 

referred to as the “Manganese Greensand Process.” 

Either potassium permanganate or chlorine can be used 

to effectively regenerate manganese greensand filters. 

However, if chlorine is used alone, it may be necessary 

to periodically regenerate the manganese greensand 

11
FIGURE 2-5. Service Flow Pressure Drop through Greensand and Birm Media 

(Source: Hungerford & Terry, Inc. and Clack Corporation) 

using potassium permanganate by a batch process in 

order to maintain optimum effectiveness of the media. 

Prechlorination is often recommended if iron levels are 

significantly greater than 1 mg/L in order to reduce the 

need for the more expensive potassium permanganate. 

Continuous regeneration of greensand with a strong oxidant serves two purposes: (1) it reactivates the manganese dioxide on the greensand and (2) it oxidizes Fe(II) 

and As(III). This allows the newly formed As(V) and any 

residual As(V) to adsorb to the ferric hydroxide particles, 

which then are captured in the filter bed. Potassium 

permanganate should be fed in the piping far enough 

ahead of the filter to allow mixing and contact for several 

seconds before entering the filter. Figures 2-7 and 2-8 

illustrate continuous versus batch regeneration. 

Manganese greensand is somewhat smaller than typical 

filter sand, with an effective size of 0.30-0.35 mm and a 

specific gravity of about 2.4. The density of greensand at 

85 lb/ft3

 is considerably lower than pyrolusite, but greater 

than Birm. A vigorous backwash with air scouring is 

recommended. Backwash rates typically are in the range 

of 10-12 gpm/ft2

 and should be preceded by an air scour 

of the media to attain at least 30% bed expansion. A 

gravel support bed with a gravel retaining screen is 

recommended over the underdrain system. 

12
Oxidant

Injection 

Continuous

Well Filter 

FIGURE 2-7. Manganese Greensand Process with 

Continuous Regeneration 

Batch

KMn04

Well Filter

Batch 

KMn04

FIGURE 2-8. Manganese Greensand Process with 

Batch Regeneration (ineffective for 

As removal) 

FIGURE 2-6. Backwash Bed Expansion Characteristics for Greensand and Birm 

(Source: Hungerford & Terry, Inc. and Clack Corporation) 

13 
It is common to implement a dual media system for iron 

and arsenic removal that consists of anthracite followed 

by manganese greensand. Anthracite readily captures 

most of the iron hydroxides containing As(V). The water 

then passes through the manganese greensand, which 

oxidizes and precipitates any residual iron and manganese. Similar to conventional dual media filters, it is 

common to have a 12-18 inch depth of anthracite (with a 

size range of 0.80-1.20 mm) followed by at least 15­

24 inches of greensand. 

Greensand can be used without an anthracite cap, but 

filter runs may be shortened significantly. The actual 

depth of manganese greensand will depend on the oxidizing capacity desired of the media. As a rule of thumb, 

oxidizing capacity of 1 ft3

 of manganese greensand media 

for raw water with 1 mg/L of iron is exhausted after 

10,000 gallons of throughput. Therefore, a filter with 3 ft3 

of greensand filtering a raw water with 1 mg/L of iron 

would need to be backwashed after filtering 30,000 gallons. However, because the continuous regeneration 

system is recommended for removing arsenic, the oxidizing function of the greensand is not critical to the 

process. 

2.4.4 Other Media 

A variety of filtration media are available for iron-removal 

systems, and some companies have developed their own 

proprietary filtration media. One example is the Macrolite 

media used by Kinetico of Newbury, OH. Macrolite is a 

patented ceramic, round-shaped media with a diameter 

of 0.215 mm. The media is marketed as having the ability to operate at a filtration rate of 10 gpm/ft2 to have an 

indefinite service life. It is always good to research the 

different types of filtration media and their ability to meet 

the treatment objectives. 

2.5 Jar Testing/Pilot Plant Studies 

Jar tests and pilot plant studies are important tools in 

drinking water treatment design, process control, and 

research. In the drinking water field, jar tests often are 

used as a “bench-scale” simulation of full-scale water 

treatment processes. Although more commonly associated with coagulation/flocculation/sedimentation of surface waters, jar tests can successfully simulate iron, 

manganese, and arsenic removal. Jar tests are relatively 

simple, low-cost, and can be completed in a short time 

frame (Lytle, 1995). These procedures are highly recommended as they can provide very valuable information to 

address arsenic removal efficiency, oxidant type, contact 

time, filtration media removal efficiency, and other water 

quality issues well before full-scale removal systems are 

planned. Small pilot studies may be very valuable in 

some cases to evaluate the filtration system for iron 

removal. 

14
3.0 Central Water Treatment Plant Design 

3.1 Introduction 

When designing a central water treatment plant, the 

design engineer typically divides the project into three 

phases: 

1. General Plan – This is the conceptual design with 

basic design information and is often required for 

regulatory agency review. 

2. Preliminary Design – This typically includes the 

completion of 30% of system design drawings, which 

are used to establish a cost estimate and select 

potential major equipment suppliers. 

3. Final Design – This is the completion of the contract 

documents, which are used to bid and construct the 

central treatment plant, subject to regulatory agency 

review and approval. 

The concepts and principles outlined in this chapter can 

be adapted to the design of several different types of iron 

removal treatment systems including: 

1. Chemical oxidation followed by media filtration. 

2. Solid oxidizing media filtration, including pyrolusite, 

Birm, and other solid oxidizing media filtration 

processes. 

3. Manganese greensand filtration. 

3.2 General Plan 

The General Plan is prepared to provide background 

information on the project and outline specific issues that 

must be addressed in order to treat the source water. 

The General Plan should summarize the basis of design 

for all elements of the project and evaluate those against 

any regulatory standards to make sure that regulatory 

compliance will be met. Key elements of the plan include 

an analysis of the source water, reliability of supply, 

evaluation of the appropriate treatment process, establishment of design data in accordance with regulatory 

requirements, and conceptual layout. Budget cost estimates are derived using general guidelines with conservative contingencies provided for unknown items, 

which may be determined during the preliminary and 

final design. 

An analysis of the raw or source water is perhaps the 

most critical consideration during this phase of system 

design. The data from the source water analysis will 

impact all aspects of system design, from treatment 

selection to labor and materials costs. An example of the 

different types of information required for a raw water 

analysis is provided in Figure 3-1. 

Another major consideration at this phase is siting of the 

central water treatment plant. The treatment facility should 

be placed in such a location that expensive improvements do not need to be made in order to convey the 

water to the customers of the central water treatment 

plant. In some cases, the existing well pumps may be 

able to provide adequate flow and pressure through the 

central treatment plant to customers. The well pumps 

also may need to be modified to allow for the additional 

pressure required to pump the water through the treatment plant. Another option to consider is the possibility 

of providing storage at the water treatment plant site and 

re-pumping the finished water to the distribution system. 

In this case, the well pumps may need to be modified to 

reduce the pressure being discharged to the water 

treatment plant. 

Other items that need to be determined in the General 

Plan include the following: 

• Hours of operation and whether the facility will 

be automatically or manually operated. With 

manual operation, personnel must be available 

or on site during operation of the water treatment plant. Automatic operation can save labor 

costs if designed properly. 

15
excepted as noted.

Report of Water Analysis 

Name and Address: Source of Water: 

Container: 

Sample Date: 

Taken By: 

Analysis * #1 #2 #3 #4 #5 #6 #7 #8 

Calcium 

Magnesium 

Sodium 

Potassium 

Total Cations 

Total Alkalinity (M)** 

Phenolphthalein Alkalinity (P)** 

Total Hardness** 

Sulfate 

Chloride 

Nitrate 

Phosphate (PO4) 

Silica (SiO2) 

Free Carbon Dioxide 

Hydrogen Sulfide 

Iron (Fe) Unfiltered 

Iron (Fe) Filtered 

Manganese 

Turbidity (NTU) 

Color (Units) 

Fluoride 

Total Arsenic 

Soluble Arsenic 

Particulate Arsenic 

Arsenic (III) 

Arsenic (V) 

pH (Units) 

Specific Conductance (micro-mhos) 

Temperature (°C) 

* All units reported in mg/L except as noted. 

** As CaCO3. 

FIGURE 3-1. Example Report of Water Analysis 

16 
• Water storage facilities must be evaluated to 

balance the hours of operation against the sizing 

of the plant. In general, storage for an average 

day of use is desirable. This would theoretically 

provide complete turnover of the water and 

storage on a daily basis, thus preserving quality 

and providing quantity in case of an emergency. 

• Construction materials must comply with 

Occupational Safety and Health Administration 

(OSHA) standards, local building codes, and 

health department requirements. Materials also 

must be suitable for the pH range of the water 

and be compatible with any pretreatment 

chemicals. Consideration for oxidants being 

used will determine the types of materials and 

ventilation system used in the treatment 

facilities. Both drinking water chemicals and 

system components should comply with 

NSF/ANSI STD 60 and 61, respectively. 

• Treatment system equipment should be protected from ambient weather. It is recommended 

that the system be housed within a treatment 

building, although housing is not mandatory in 

some locations. 

• The cost of wastewater disposal is a major 

consideration in the design of any central water 

treatment system. Wastewater resulting from 

backwash and regeneration of the treatment 

media can only be disposed of in a manner permitted by state and/or local regulatory agencies. 

Wastewater handling options should be carefully 

evaluated including performing a life-cycle 

analysis to determine the best options. Separate local and state regulatory reviews may be 

required for wastewater disposal. Quantifying 

the backwash waste and determining the 

disposal requirements also should be outlined. 

A General Plan report containing all of this information 

as well as a preliminary project estimate and schematic 

drawings should be submitted for review and approval 

by the appropriate authorities. This document can be 

used to establish funding requirements for the project. A 

determination of what funding is available should be 

made before the project is authorized for preliminary and 

final design. If the preliminary estimate of project costs 

exceeds the available funds, adjustments should be 

made to increase the funding or reduce the scope of the 

project. Figure 3-2 illustrates the steps of the project 

development process from project authorization through 

final design. 

3.3 Preliminary Design 

Once funding is in place and the General Plan has been 

reviewed and approved by the appropriate authorities, 

preliminary design can begin on the project. 

3.3.1 Manual or Automatic Operation 

One of the first decisions to be made is whether the 

plant should be manually or automatically operated. In a 

manual operation, the plant operator personally performs 

all of the operating functions and makes all operating decisions. The treatment plant equipment does not 

accomplish any function independent of the operating personnel. The equipment is simple and performs the basic 

functions that the operator implements. Manual operation includes the following: 

1. Motors (pumps, chemical pumps, etc.) with manual 

start/stop controls. Some motors have manual speed 

adjustment capability. Chemical pumps have manual 

speed and stroke length adjustment capability. 

2. Valves with manual handle, lever, hand wheel, or 

chain wheel operators. 

3. Instrumentation sensors with indicators. Instrumentation is installed in-line when operating data such 

as flowrates, total flow, pressure, pH and liquid levels are indicated. Besides the pump operations and 

the chemical feed adjustments, the biggest single 

function performed by the operator is the backwashing of the filters. 

In the automatic operation of a treatment plant, computer 

controls will basically control the plant. Initial programming of the computer controls is done by an outside 

specialist who works with the treatment plant operator to 

program the plant. The equipment used by the operator 

during the performance of treatment plant functions is 

the operator interface and the printer. 

Controls can be used for many other purposes to assist 

the operator in the proper operation of the plant. These 

controls can automatically shut down equipment or notify 

the operator of high/low pressure; levels control of tanks 

(high or low); problems with chemical feed equipment 

that can be automatically shut off; and other items particular to each individual system. 

The addition of automatic controls increases the initial 

cost of the system, but the plant will require minimal 

operator attention (i.e. decreases associated operation 

costs). For remote treatment plants or where operator 

17
Project Authorized 

Preliminary Design 

 Surveying

 Geotechnical Services 

 Client Meetings 

 Basis of Design 

 Drafting of Existing Treatment 

Facilities 

 Design Sketches 

 Equipment Information 

 Hydraulic Profiles 

 Electrical/Mechanical Data 

 Operational Description 

 Estimate of Costs 

Pre-Planning 

Budget 

Milestones 

Schedule 

Specialty Requirements 

Identify Critical Decisions 

Review 

 Client Comments 

 Resolve Potential Regulatory Issues 

Final Design 

 Detailed Drawings 

 Detailed Specifications 

 Quality Control Review 

 Agency Reviews 

 Client Reviews 

 Estimate of Cost 

 Revisions 

 Final Contract Documents Completed 

FIGURE 3-2. Project Development Process 

18
availability is limited, automatic operation can be a great 

advantage. 

Automatic operation includes the following: 

1. Motors for pumps, chemical pumps, air compressors, 

etc. are automatically turned on and off and may have 

speed adjustment controls. Chemical pumps may 

have a manual stroke length adjustment but can be 

paced by the flow and on/off operation of the plant. 

2. Valves with either pneumatic/hydraulic or electric 

operators are required on the equipment. Valves 

require manual overrides during startup, power failure, or compressed air failure. Valves should have 

opening and closing speed controls to prevent water 

hammer during automatic operation, especially on 

pump systems. 

3. Instrumentation may be electronic, pneumatic, or a 

combination of both. The instruments and controls 

should always be capable of transmitting and receiving electronic information to and from the computer 

system. Backup manual instruments are recommended to provide verification of automatic instrumentation. Comprehensive automatic alarms that 

notify operators and/or shutdown key components of 

the system are necessary and need to be incorporated in the design. 

4. Filter backwashing also can be accomplished by 

automatic controls. However, systems can be modified so that major operations will not occur without 

operator initiation. For example, when a filter needs 

to be backwashed, a warning or an alarm can be 

provided to notify the operator that a filter needs to 

be backwashed. The operator then can choose to 

continue to run the filter, take it offline, or backwash 

the filter. At that point, the operator would initiate 

backwashing by giving the command through the 

computer system to do so. 

It is the responsibility of an operator to calibrate and 

check all components of the automatic operating equipment system on a routine basis. Regular maintenance 

by the operator or a qualified instrumentation and control 

specialist should be performed. The person responsible 

for maintenance should also be capable of emergency 

repair of all components. Every function included in an 

automatic system should be capable of manual operation by the operator. 

3.3.2 Basis of Design 

The Basis of Design is a document, outline, or strategic 

plan that is developed early in a water treatment system 

project in order to record and summarize decisions that 

have a major and extensive impact on project design 

and implementation. The Basis of Design also helps 

minimize late changes, additions, or modifications to the 

project, as well as minimize the high expenses commonly associated with late changes. The following subsections discuss elements that should be addressed in a 

Basis of Design. 

Note that the development of the Basis of Design should 

not be performed solely by the Project Manager; the 

owner of the water treatment system must have opportunity to review and comment on the content of each 

design element. 

3.3.2.1 General 

1. State the purpose of the project (i.e., what problem 

the project is designed to correct?). 

2. Identify areas of new or unique design and provide 

criteria. 

3. Identify areas where evaluation of alternatives must 

first be completed before initiating final design. Identify alternatives to be evaluated. 

4. Identify critical structures, processes, or complex 

areas that require early engineering and design effort 

to avoid later delays. 

5. State major constraints such as maximum construction cost, and court-imposed or client-imposed deadlines. 

6. Note availability of prior drawings and dates when 

previous on-site project work was done. 

7. Note major potential trip-up items (i.e., flood plain 

location? historic register? property or easement 

availability? financing?). 

8. Identify provisions to be made for future construction 

and expansion, beyond present scope, for sizing of 

or location of structures or equipment. 

9. Note who has jurisdiction for permit approvals (i.e., 

plumbing, electrical, building, elevator, elevated tank, 

groundwater protection, U.S. EPA, etc.). 

10. Identify unusual situations that will affect design (i.e., 

rock, unstable soil, high groundwater, corrosion). 

11. List specific points where client has expressly requested to be advised of design decisions, or where 

client will require involvement of staff in decisionmaking. 

19
12. Identify hazards or hazardous areas (i.e., asbestos, 

windowless building story, confined space, fire, NEC 

explosion areas, corrosion, fumes, dust, odor). For 

asbestos, determine responsibility for discovery, 

arrange testing, and determine level of abatement 

required. 

13. Identify large or complex structures that will require 

special building code compliance review prior to 

initiating final design. 

3.3.2.2 Project Scope 

1. Provide a schematic process flow diagram (i.e., 

show such items as water or wastewater flow, chemical feed, site sanitary sewer, and drain piping). 

2. Provide a list of building, structures, and equipment. 

3. Based on client’s input, identify major equipment or 

brands of equipment to be used or not used. 

4. Prepare tentative list of plan sheets. 

3.3.2.3 Process Design Data Summary 

1. List design data summary. Note average, maximum, 

and peak hydraulic flowrate capacities. Define concentrations and loading to be removed or treated. 

Identify “Design Parameters” and “Units Furnished” 

for each unit process or major equipment item. 

3.3.2.4 Site 

1. Provide a simple site plan with locations of existing 

and new structures, including sanitary and stormwater pumping stations as applicable. 

2. Note any special consideration related to design 

(i.e., location in flood plain, dike construction, location to adjacent residential areas or parks, requirements for site clearing, major underground facilities 

that will affect location of new improvements). 

3. Summarize concept for removing stormwater from 

site. 

4. Identify any site constraints (i.e., required area set 

aside for future expansion, other client land uses). 

5. Identify structures to be demolished. 

6. Determine general fencing requirements and whether 

motorized gates are desired. 

7. Identify extent of landscaping if desired by client. 

8. Identify 100-year flood plain elevation if applicable. 

3.3.2.5 Layout of Structure 

1. Identify approximate structure size and preliminary 

location of rooms and/or major equipment on a floor 

plan. 

2. Determine building(s) use group, fire resistance ratings, ceilings, stairwells, height and area restrictions, 

special fire and life safety requirements, and means 

of egress strategy to at least the level that they will 

affect preliminary building layouts and costs. Address 

requirements of the Americans with Disabilities Act 

(ADA). 

3. Coordinate location and layout of chlorine rooms. 

4. Identify particular client preferences early for architectural details. 

5. Determine architectural style and requirements, with 

consideration to insulation requirements: 

a. Wall construction (i.e., brick and block, concrete 

block, glazed structural block, sound block, metal 

siding, pre-engineered, aggregate panels). 

b. Roof construction (i.e., pre-cast concrete, pouredin-place concrete, steel deck and bar joists, wood 

trusses). Consider type of structure and its interior use (i.e., wet areas, chemical feed area, etc.). 

c. Roofing materials (i.e., single-ply ballasted or 

adhered membrane, built up, shingles, metal). 

d. Windows (i.e., natural light, ventilation, aesthetics). Match or replace existing windows: material 

(i.e., aluminum, steel, wood, vinyl) and/or finish 

(i.e., anodized, painted, primed). 

e. Doors. Match or replace existing doors: material 

(i.e., hollow metal, aluminum, FRP, stainless 

steel, wood, acoustical). 

f. Overhead and/or roll-up doors. Identify electric 

operator versus manual lift doors. 

6. Provide room finish schedules based on client input. 

Items to include are listed as follows: 

a. Interior wall construction (non-load bearing); 

material (i.e., concrete block, glazed block, steel 

or wood stud walls); finishes (i.e., unfinished, 

painted, gypsum board, wallpaper, paneling, chair 

railing, molding at ceiling and floor). 

b. Flooring. Unfinished or sealed concrete, seamless floor covering, vinyl, carpeting, tile (i.e., thinset or thick-set), terrazzo, applied composite 

20
material with urethane overcoats, embedded 

steel mats where heavy steel wheel loads are 

anticipated (i.e., dumpster containers). 

c. Ceilings. Material and finishes. 

7. Identify stair type (i.e., concrete pan, metal, cast in 

place). 

8. Identify method of removing rainwater from roofs of 

each building and point of discharge (i.e., roof drains, 

gutters and downspouts, roof scuppers discharging 

to ground, or storm sewers). 

9. Identify locations of rest rooms (for both genders) in 

building. 

10. Identify locations of drinking fountains and coolers. 

11. Identify areas where service sinks or portable sampler wash down basins will be provided. 

12. Specify grating material (i.e., aluminum, steel, FRP 

such as in certain chemical feed and fill areas). 

13. Determine extent of laboratory improvements. 

14. Identify any existing structures to be re-roofed or repainted. 

15. Write preliminary outline of requirements for OSHA 

(i.e., signing, color coding, fire extinguishers) and 

ADA. 

3.3.2.6 Structural 

1. Identify local code requirements for seismic design, 

frost depths, wind loads, and snow loadings. 

2. Identify design of live load requirements for stairway, 

office, and corridor floors. Also floor loadings for 

operating and storage areas. 

3. Identify design for water, earth, and live load requirements for foundation walls. 

4. Identify likely areas where peripheral drains and 

hydrostatic pressure relief valves will be necessary 

to prevent flotation and reduce exterior pressures (if 

high groundwater conditions are known to exist prior 

to obtaining soil boring data). 

5. Identify requirements for protection of existing adjacent structure foundations that could be damaged 

during excavation. 

6. Identify any material handling that is required (monorails, crane, davit, dock access, eyebolts) and approximate lifting capacities. 

7. Identify major equipment and provide approximate 

weights (i.e., pumps, blowers, generators, engines). 

8. Note any structural repairs required in existing buildings or any new or enlarged wall or floor openings. 

Note any concrete repairs or masonry rehabilitation 

and coordinate with client. 

9. Identify design strength criteria for reinforced concrete and steel. 

3.3.2.7 Mechanics 

1. For heating, ventilating, and air conditioning (HVAC) 

and other mechanical building systems, identify any 

special or specific expectations or the client. 

2. Identify energy source(s) to be used for providing 

building heat (i.e., natural gas or electric) and supplier(s). 

3. State method of providing heat to each structure, 

building, or section of building such as a lab or office 

area. Identify preliminary location of central heating 

and cooling facilities. 

4. Identify ventilation method for each building and preliminary location of exhaust fans, louvers, air handling systems and ventilation rate criteria (air changes, 

cfm/ft2

, cfm/person). 

5. Provide conceptual strategy for dealing with dust 

control, explosion resistance, fire protection, humidity control, emergency showers and/or eyewash, and 

hazard detection interlocks with ventilation. Describe 

equipment to be provided. 

6. Identify mechanical building system requirements for 

generator and engine rooms (ventilation, combustion 

air, cooling system strategy, fuel system and storage, and drainage). 

7. Identify areas to be air conditioned or de-humidified. 

3.3.2.8 Electrical 

1. Provide any special or specific expectations of the 

client. Note any problems with existing equipment, if 

applicable, or certain manufacturer’s equipment to 

be used or not used. 

2. Identify power supply source. 

21
3. Identify source and location of emergency power 

generator if required. 

4. Provide general control descriptions that will be used 

to develop loop descriptions for automatic controls. 

5. Complete an “Equipment and Controls Listing” as 

completely as possible. 

6. Confirm instrumentation and control philosophy with 

the client (i.e., completely manual, data acquisition 

and logging with manual control, automated control 

of specific equipment or processes, or completely 

automated). 

7. Identify work required at remote site from the project 

site (i.e., lift stations, well sites, booster stations, elevated tanks, other plants). 

8. Identify equipment that is to be driven by variable 

speed systems. 

9. Determine whether plant power distribution is to be 

overhead and/or underground. 

10. Identify if existing lighting is to be revised with the 

client. 

11. Identify method of providing outdoor lighting (i.e., 

high mast lights, pole-mounted street lights, or wallmounted exterior building lights). 

12. Identify whether Process and Instrumentation Diagram (P&ID) drawings are required and how many 

there will be. 

13. Identify areas where electrical equipment including 

computers must be located in rooms with special 

temperature or humidity environments. 

14. Identify pumps requiring seal water systems with 

solenoid valves, pressure switches, and controls for 

alarm/lockout. 

3.3.3 Treatment Equipment 

From the General Plan, the basic treatment equipment 

has been determined from one of the following treatment 

alternatives: 

1. Chemical Oxidation and Filtration – Elements comprising this alternative include aeration (optional); 

chemical oxidant addition (chlorine); and filtration 

(sand and anthracite). 

2. Solid Oxidizing Media Filtration – Elements comprising this alternative include filtration with the solid 

oxidizing media. Depending on the media used, the 

addition of air may be required to maintain manufacturer suggested dissolved oxygen levels in the source 

water. 

3. Manganese Greensand Filtration – Elements comprising this alternative include continuous chemical 

oxidant addition (potassium permanganate and/or 

chlorine) with time for mixing followed by manganese greensand filtration. 

For each alternative, disposal of backwash waste streams 

is a design consideration to be addressed. 

A general discussion of treatment equipment in this section should be applied to the appropriate alternative 

selected. Certain elements, such as aeration, do not apply 

to each alternative, but a discussion of the filtration pressure vessel does. 

3.3.3.1 Aerator 

For aeration, in most cases, one aerator is required 

along with one detention tank and a bypass around both 

the aerator and detention tank to the filters. A minimum 

of two filters must be provided so that the peak flow can 

be met if the largest filter goes out of service. Depending 

on the configuration constraints, the designer should 

determine how many filters need to be provided for the 

project. 

3.3.3.2 Treatment Vessels 

Treatment vessels generally are piped in parallel with a 

downflow treatment mode through the filters. Up to a 

diameter of approximately 12 ft, most pressure vessels 

are vertical but horizontal pressure vessels can be used 

as well. Treatment vessel piping should be configured to 

provide for media backwashing up through the filters. 

The materials of construction are generally FRP or carbon steel with fabrication, assembly, and testing that 

complies with the American Society of Mechanical Engineer’s (ASME) code section VIII, Division 1. The interior 

should be lined with abrasion-resistant vinyl ester or 

epoxy coating. Interior lining material should be NSFcertified for potable water application and suitable for pH 

range of 2.0-13.5. Vessel pressure rating should be 

50 pounds per square inch gage (psig) or the minimum 

necessary to satisfy the system requirements. In general, the rating should be at approximately 25 psig 

greater than the normal service pressure. Other vessel 

materials of construction for the internal components of 

the vessels should take into consideration the abrasion 

and corrosive atmosphere that the components will face. 

Materials such as abrasion-resistant epoxy, rubber, stainless steel, brass, and fiberglass all can be used within 

the pressure vessel. 

22
Depending on the depth of media selected and the type 

of space requirements available, underdrain systems 

should be evaluated for the vessels. Underdrains can be 

of a slotted nozzle type installed on a plate and installed 

with or without gravel supporting media to the sand and 

anthracite. Other systems including header laterals systems with a gravel supporting bed may be used. Unused 

areas below the underdrain system, which could potentially hold stagnant water, should be filled with concrete. 

Fabrication of pressure vessels is typical in 6-inch increments over a range of diameters from 6 inches up to 

several feet in diameter. 

Distribution of water in the pressure vessels typically is 

done through a header system in the top of the pressure 

vessels that distributes the water evenly over the top of 

the media. A system of collection pipes also should be 

available to allow the backwash waste to go through this 

piping during the backwash sequence. 

Placement of air release valves on the highest point of 

the piping at each vessel needs to be considered so that 

air binding will not occur. This air release piping can 

either be automatic or manual. The discharge from the 

air release valves should be piped to waste because of 

the spray, which will occur as the vessel dispels air. 

Cross-connections must be avoided. At least two access 

ports of sufficient size to meet OSHA requirements 

should be provided for entrance into the pressure vessel 

as well as for providing a means of changing media. 

3.3.3.3 Process Piping Material 

When considering process piping for use in conveying 

the water between treatment units and connecting pressure vessels and pumping systems, selection of materials becomes critical. For piping 4 inches and larger in 

diameter, ductile iron is recommended. For smaller 

diameters, polyvinyl chloride (PVC), FRP, carbon steel, 

and copper may be used as long as the limitations of 

each of the types of piping are evaluated for plantspecific conditions. If temperature conditions vary dramatically or if temperatures in a treatment facility exceed 

99°F, then PVC materials should be avoided due to their 

loss in strength and thermal expansion features. FRP 

may be a better choice for the strength and support that 

is required at elevated temperatures. Carbon steel may 

present a corrosion concern and copper may not be 

strong enough for the type of piping necessary. Care 

should be taken to economically match the right piping 

system with the application. 

3.3.3.4 Control Valves 

Isolation and process control valves may be wafer style 

butterfly type, except in low-flowrate systems where 

small pipe size dictates the use of true union ball valves. 

The use of inexpensive, easily maintained valves that 

operate manually provide minimum capital costs. The 

valves can be automated by the inclusion of pneumatic, 

hydraulic, or electric operators. Valves on the face of 

pressure vessels, which are automatically operated, may 

include pneumatic-type diaphragm valves. These valves 

are somewhat more expensive than butterfly valves, but 

give a positive control and are very reliable. As a part of 

the preliminary design, the electrical and instrumentation 

needs should be analyzed and summarized in tables to 

determine the power requirements and the monitoring 

and control points in the system. One-line diagrams and 

process and instrumentation diagrams should be provided at this stage. 

3.3.4 Layout of Facilities 

Once all of the individual components have been determined and preliminary choices have been made, the 

pieces need to be laid out and assembled in an efficient 

design that will meet the needs of the operator. It is 

recommended that the operator and those responsible 

for maintaining the facility provide design input to 

address the needs of the treatment system operators. 

Sufficient space for proper installation, operation, and 

maintenance of the treatment system needs to be evaluated. Clearances and constructability reviews should 

be performed to determine the adequacy of the building. 

Items such as workshops, storage facilities, and maintenance facilities are sometimes overlooked but add significant costs to the project when included. The layout also 

should include a projection of potential future expansion 

at the site. Factors such as duplicating facilities and the 

design of the external components of the building (e.g., 

driveways and utility locations) also should be evaluated. 

The type of building used needs to meet the requirements of the local personnel maintaining the facility. 

Protection from the elements will depend on the climate. 

Standard pre-engineered steel buildings may be adapted 

for use, as well as concrete block or other masonry type 

structures. Standard building dimensions should be used 

with adequate access doors, lighting, security, ventilation, emergency showers, and laboratory facilities to 

monitor and control the process. 

3.3.5 Preliminary Project Cost Estimate 

A preliminary cost estimate for the treatment facilities 

can be made once the following has been completed: 

• The Basis of Design is finished; 

• Preliminary drawings have been completed that 

show the layout of the building, the selection of 

23
building materials, and an inventory of the power 

supply needs and instrumentation points; and, 

• The preliminary selection of equipment and 

capital cost quotes of the equipment from manufacturers and suppliers is completed. 

This preliminary cost estimate should be within approximately 20% of the final cost estimate. A full discussion of 

key cost factors is provided in Section 4.2 of this manual. 

3.3.6 Revisions and Approval 

To complete the preliminary design process, additional 

floor plans and even sections of the proposed treatment 

facility should be completed. Specialty items should all 

be compiled and summarized in a detailed design memo 

with the drawings and cost estimate, and explained to 

the client. These specialty items can include checking for 

natural gas for heating purposes; subsurface investigation to determine foundation requirements; and disposal 

requirements that may require special permitting. Upon 

review of the preliminary design by the client, revisions 

should be incorporated for which the final scope of 

design details can be determined. With these revisions, 

a final design can be drafted and authorized. 

3.4 Final Design 

After completion of the preliminary design and approval 

by the client, the final design can be drafted. The final 

design includes a detailed design of all process equipment and piping, a complete process system design with 

all of the chemical feed equipment incorporated, building 

modifications, and site work. The final capital cost should 

be within 10% of the estimated final cost and should 

include a 15% contingency allowance. 

The deliverable items at the completion of final design 

include a set of contract documents containing the construction drawings and specifications, and a final capital 

cost estimate. The final design includes treatment system equipment; continues with the building specifications 

including heating, cooling, painting, lighting, utilities, 

laboratory, personnel facilities, etc.; and finishes with the 

site specifications, including outside utilities, drainage, 

paving and landscaping. 

3.4.1 General Guidelines 

Some ways to simplify the final design and keep costs 

under control include minimizing the amount of customized details on the project; allowing shop fabrication of 

platforms, pipe supports, and other items which then 

would not have to be done in the field; providing skidmounted equipment where feasible; and using the inherent heating and cooling capabilities of groundwater with 

the treatment vessels in the building system. Humidity 

issues must be considered, but heating and cooling may 

be tempered by allowing the pressure vessels to moderate the indoor temperature of the facilities. 

The drawings and specifications should provide all 

information necessary to manufacture and install the 

treatment system equipment. The general principle is to 

provide enough information on the drawings and in the 

specifications that a contractor can clearly determine 

what is intended and needs to be accomplished. It is up 

to the contractor to provide the means and the methods 

for finishing the project. 

The specifications should include spare parts as part of 

the deliverables during the construction project for the 

equipment. All specialty tools such as forklifts or barrel 

dollies, or other such items which may not be common to 

most utilities, should be included as well. 

3.4.2 Plan Content Guidelines 

To receive competitive bids and to avoid costly change 

orders during construction, it is important to provide sufficient information in the final design to accurately portray 

what is intended by the design. Duplication of information can be a hindrance as it provides opportunities for 

errors. The following guidelines should be used by the 

designer to be accurate without duplicating unnecessary 

information. 

3.4.2.1 Structural 

1. Use bold lines for walls, slabs, etc. where new concrete is proposed. 

2. Where drawings become complex, use separate 

drawings to show reinforcing steel. 

3. Try to limit showing re-steel to section views. Only 

show re-steel on sectional plans when necessary to 

cover changes in steel shown in sections. Where 

possible to identify re-steel clearly, do so via plan 

notes covering bar size and spacing and do not 

show lines and dots in walls, slabs, etc. 

4. Provide required job-specific structural notes on 

drawings when additional drafting can be minimized. 

Make use of specifications for notes that do not 

relate directly to the drawings. 

24
3.4.2.2 Schedules 

1. Use room finish schedules to eliminate separate call 

outs, which tend to clutter drawings. 

2. Develop schedules and details for doors, windows, 

louvers, vent fans, meters, valves, pipe support 

beams, room finish, and ladders, and locate these in 

one specific location in a drawing set rather than 

scattered throughout the drawings. 

3.4.2.3 Miscellaneous 

1. Avoid excessive call outs of items that appear more 

than once on a sheet, such as piping sizes, grating 

thickness, downspouts, gutters, types of masonry 

walls. Label items once. 

2. Reduce the amount of detail shown on existing 

structures to avoid clutter on drawings, which confuses bidders and causes wasted time during bidding. For example, for existing wall sections where 

no work is being done, just show wall outlines and 

eliminate all the fill-ins depicting the type of wall 

construction. 

3. With existing structures, do not dimension and call 

out items within these structures if no work is to be 

performed or if the information is not related to the 

new construction proposed. 

4. For site plans, show building outlines only if there 

are specific areas where new construction is to 

connect to existing construction. 

5. Avoid excessively precise depictions of building 

materials such as shingles, grating and checker 

plate hatching, brick, block, and filter media. The 

lines clutter the drawings and make it difficult to 

assess the quality of materials. 

6. Avoid showing unnecessary background information 

when cutting sections. Only show background information not shown in other views or to avoid interferences. 

7. Avoid repeating details of similar structures in plan 

views or site plans. Actually, it is not necessary to 

show the “inner workings” of any treatment tanks on 

site plans. Only the outside wall lines of the tanks 

are of interest to the contractor. 

8. Do not overly detail layouts or dimensions for manufactured items such as pumps, motors, blowers, 

couplings, etc. Let the specifications describe these 

products. 

9. Reduce the amount of dimensioning to avoid clutter 

and confusion and reduce possibility for error. For 

vertical dimensioning, if slab thicknesses and slab 

elevations are provided, do not add more dimensions. Also reduce repetition on dimensioning. Do it 

once for a section, plan, or sectional plan, but unless 

dimensions change, do not repeat dimensions on 

the same sheet or another sheet where a similar 

view is shown. 

10. On the Location Plan, show a street address for the 

job site and provide a statement noting the city or 

county the project is located in. 

11. Do not provide roof plans of simple structures if 

sections cut through the building convey adequate 

information concerning the dimensions and construction of the roof. 

12. Leave details of equipment off drawings that are 

made to show other information on the structure and 

piping within it. 

3.4.2.4 Piping 

1. Do not overly detail small piping layouts. Leave the 

small piping off structure plan views and sections. 

Small piping could be defined as 2-inch-diameter 

and less for water supply and process piping. Show 

this piping on piping schematics for each structure. 

3.4.2.5 Electrical 

1. Do not show electrical conduit routes on bidding 

documents. Use one-line diagrams for clarity and 

simple understanding of the project. Use schedules 

to illustrate what electrical components (such as 

motor control centers and lighting panels) are to be 

installed in each location. 

25

4.0 Central Water Treatment Plant Capital Costs 

4.1 Introduction 

This chapter discusses factors that affect the capital 

costs of an iron removal treatment plant, and provides 

an example economic evaluation between two iron 

removal system alternatives. The owner of a central 

water treatment plant should be provided with the most 

cost-effective iron/arsenic removal system possible, one 

that can remove the excess arsenic from a sufficient 

quantity of water but that also will satisfy all water consumption requirements. 

4.2 Cost Variables 

An economic evaluation should include the initial capital 

costs, operation and maintenance (O&M) costs, and 

replacement costs over a 20-year period. The water 

treatment design flowrate is the major variable affecting 

capital costs. Other factors which have varying impacts 

on the capital costs include, but are not limited to, the 

following: 

1. Existing and planned (future) potable water system 

parameters: 

• Number of wells, location, storage, distribution 

• Water storage (amount, elevation, location) 

• Distribution (location, peak flows, total flow, 

pressure, etc.) 

• Consumption (daily, annual) 

2. Raw water arsenic and iron concentrations 

3. Chemical and physical parameters including but not 

limited to pH, alkalinity, iron, manganese, hydrogen 

sulfide, hardness, silica, sulfate, sodium, and turbidity 

4. Stability and/or pH adjustment of water supply 

5. Media selected for treatment system 

6. Chemical and media supply logistics 

7. Manual versus automatic operation 

8. Backwash wastewater disposal 

9. Climate (temperature, precipitation, wind, etc.) 

10. Seismic zone 

11. Soil conditions 

12. 100-year flood elevation 

13. Financial considerations (cost trends, capital financing costs, cash flow, labor rates, utility rates, chemical costs, etc.). 

Ideal conditions for designing and operating an effective, 

minimum-cost iron/arsenic removal water treatment system would resemble the following: 

1. Well capacity for peak consumption day 

2. Raw water quality presents no problem (moderate 

temperature, adequate alkalinity, moderate iron levels, no interference of treatment due to hydrogen 

sulfide, organics, sulfate, etc.) 

3. Existing wastewater disposal capability adjacent to 

treatment site 

4. Warm moderate climate (no freezing, no high temperature, minimal precipitation, no high wind) 

5. No seismic requirements 

6. Foundation on well compacted, high-bearing-capacity 

soil 

7. Secure site not in a neighborhood 

8. Low-cost utilities 

27
9. Accessibility for deliveries 

10. Financial capability. 

The more these ideal conditions exist, the more favorable and significant the cost savings are. 

4.2.1 Existing and Planned (Future) 

Treatment Plant Parameters 

Many existing and planned (future) plant configurations 

can influence capital costs. The most important factors 

are discussed in this section. 

4.2.1.1 Number and Location of Wells 

When only one well requires treatment, the removal of 

arsenic from source water should be accomplished prior 

to the water entering the distribution system. Theoretically, treatment can occur before or after entering storage. Practically speaking, treatment prior to entering 

storage is much easier to control because the treatment 

plant flowrate will be constant. If treatment takes place 

after storage, or if there is no storage, the treatment 

flowrate is intermittent and variable, and pH control is 

only achievable using a sophisticated automatic pH control/acid feed system. 

When more than one well requires treatment, it must be 

determined whether a single plant treating water from all 

wells manifolded together is more efficient and costeffective than operating individual treatment plants at 

each well. Factors such as distance between wells, distribution arrangement, system pressure, and variation in 

water quality should be evaluated for that decision. If all 

of the wells are in close proximity and pump similar 

quantity and quality water, a single treatment plant 

serving the entire system is preferable. When wells are 

widely dispersed, manifolding costs become prohibitively 

expensive, so individual treatment plants must be 

installed at each well. Frequently, the distances may be 

such that the decision is not clear; in that case, other 

variables should be evaluated such as water quality, 

system pressure, distribution configuration, and land 

availability. 

Systems that require multiple treatment plant installations can achieve cost savings by employing an identical 

system at each location. This results in an assembly-line 

approach to procurement, manufacture, assembly, installation, and operation. Material cost savings, labor reduction, and engineering for a single configuration will 

reduce costs for the individual plant. 

4.2.1.2 Potable Water Storage Facilities 

The number, size, and location of storage tanks can 

affect treatment plant size (flowrate) and capital costs. If 

there is no storage capacity in the water treatment system, the well pump should be capable of delivering a 

flowrate equal to the system’s momentary peak consumption; this could be many times the average flowrate 

for a peak day. Therefore, if no storage capacity exists, a 

storage tank should be added to the system for storage 

of treated water. Otherwise, automatic disinfection and 

pH instruments and controls will be required to pace 

chemical feedrates to the varying process water flowrates. 

Most water treatment systems have an existing storage 

capacity. The storage may be underground reservoirs, 

ground-level storage tanks, or elevated storage tanks 

(located on high ground or structurally supported standpipes). The first two require repressurization; the latter 

does not. The elevated storage tanks apply a backpressure on the ground-level treatment system, requiring 

higher pressure (and more costly) construction of treatment vessels and piping systems. 

The amount of storage capacity also affects treatment 

system costs. The larger the storage capacity (within 

limits), the lower the required treatment plant flowrate 

(and resulting costs). Some regulatory agencies require 

a one day, average day storage capacity. A minimum 

storage capacity of one-half of a system’s peak day consumption is recommended. 

4.2.1.3 Distribution and Consumption 

The factors that determine the sizing of the treatment 

system are the well (or feed) pump flowrate, the storage 

capacity, and the system consumption characteristics. 

Those factors should be coordinated to provide a capacity to deliver a peak treated water supply to satisfy all 

possible conditions of peak consumption. If there is 

adequate storage capacity, the momentary peaks are 

dampened. The peak day then defines the system 

capacity. The well (or feed) pump should be sized to 

deliver the peak daily requirement and the treatment 

system in turn should be sized to treat the volume of 

water that the well (or feed) pump delivers. 

The distribution system may anticipate future growth or 

increased consumption. The well (or feed) pump then 

either should pump a flow equal to or greater than the 

maximum anticipated peak daily flows, or should be able 

to adjust to future increased flowrate. The treatment plant 

in turn should incorporate capacity to treat the ultimate 

peak flowrate or include provisions to increase the treatment capacity in the future. 

28
4.2.2 Water Chemistry 

Water chemistry can affect both capital and operating 

costs. With a clear understanding of the raw water quality, its possible variations, and adverse characteristics, 

the effect on capital costs can be determined readily. 

Required pH adjustment to make the water treatable or 

to stabilize the treated water before distribution can add 

significantly to chemical costs and, therefore, the capital 

costs for equipment. Treatment for hydrogen sulfide, 

organics, or other contaminants may require additional 

treatment processes such as aeration and/or significantly escalated oxidant chemical requirements. High 

hardness levels may require an additional softening 

treatment process to bring water to acceptable quality 

parameters. In addition, byproducts from the additional 

treatment processes may significantly impact waste 

disposal requirements. 

Each of the physical and chemical characteristics of the 

raw water should be evaluated. The technical as well as 

the economic feasibility for the entire project could hinge 

on these factors. 

4.2.3 Chemical Supply Logistics 

Chlorine in its various forms (gas and liquid) varies in 

price depending on the quantities involved. For example, 

a Midwest survey in 2002 of gas chlorine costs found 

that ton containers were approximately $0.24/lb and 

150-lb cylinders were approximately $0.40/lb. The same 

survey revealed that sodium hypochlorite delivered in 

4,000-gallon bulk trucks was $0.70/gal; partial bulk 

truckload deliveries were $0.75/gal; and 330-gallon totes 

were $0.90/gal. In very small plants, the cost of storage 

tanks for those volumes is not justified and, therefore, 

smaller volumes with higher unit prices should be 

procured. 

For small applications, potassium permanganate is 

available in 25-kg (55-lb) pails made of high-density 

polyethylene (HDPE). Most commonly, steel containers 

weighing 150 kg (331 lb) are provided in drums about 

20 inches in diameter and 30 inches high. Large quantities in 1,500-kg (3,307-lb) bins are available as well as 

bulk shipments up to 48,000 lb. The price of potassium 

permanganate averaged approximately $1.35/lb in 2002. 

4.2.4 Manual Versus 

Automatic Operation 

Automatic operation is feasible, but semi-automatic operation is most common in iron removal treatment systems. However, the presence of an operator is required 

periodically in any mode of operation. The capital costs 

of automation (computer hardware/software, valve operators, controls, instrumentation, etc.) as well as maintenance costs may exceed budget limits that the client 

can accept. Therefore, either manual or semiautomatic 

operation may be more economical. The advantages 

and disadvantages of manual, automatic, and semiautomatic operation require careful evaluation. 

4.2.5 Backwash and Regeneration 

Disposal Concept 

Disposal of waste backwash water and waste solids is 

not included in the scope of this manual. Depending on 

wastewater discharge limits established by U.S. EPA, 

state, and local regulatory agencies, wastewater disposal is a significant cost item that should be evaluated 

in the capital (and operating) cost projection. Requirements can vary from zero discharge to discharge into an 

existing and available receiving facility. If the regulatory 

agency permits disposal by conventional methods (such 

as surface discharge and percolation), the disposal costs 

are minimal. The total volume of wastewater backwash 

generally is 100-300 gal/ft3

 of filter media when washed 

on a daily basis for the types of iron removal systems 

outlined in this manual. Compared to filtration daily volumes of 4,000-7,000 gal/ft3 of filter media, the waste 

disposal requirements range from 2-7% of filtered water 

flows. 

4.2.6 Climate 

The installation costs for the buildings along with their 

associated civil work are a major portion of the overall 

capital cost. Care in interpreting the climatological conditions and their requirements is necessary. Temperature 

extremes, precipitation, and high wind will necessitate a 

building to house the treatment system equipment. High 

temperature and direct sunlight adversely affect the 

strength of plastic piping materials. Freezing can damage piping and in some extreme cases can damage 

treatment vessels. Temperature variation introduces 

requirements for special thermal expansion/contraction 

provisions. A building with heating and/or cooling and 

adequate insulation will eliminate these problems and 

their costs, but will increase the cost of the building. The 

building cost should accommodate wind and snow loads 

as well as thermal and seismic requirements. Operator 

comfort in place of economic considerations may dictate 

the building cost. 

4.2.7 Seismic Zone 

Compliance with the seismic design requirements of the 

local building codes can impact capital costs. Buildings 

and tall slender equipment are vulnerable to seismic 

29
loads. The magnitude of seismic design requirements 

should be determined. In zones of extreme seismic 

activity, low-profile equipment and buildings are recommended. 

4.2.8 Soil Conditions 

Unless soil boring data are already available for the 

treatment plant site, at least one boring in the location of 

the foundation for each heavy equipment item (treatment 

vessels, chemical storage tanks, and backwash waste 

tank) is required. If the quality of the soil is questionable 

(fill, or very poor load-bearing capacity), additional soil 

borings should be obtained. Poor soil may require costly 

excavation/backfill and foundations. 

Combinations of poor soil with rock or large boulders 

can make foundation work more complex and costly. 

Rock and boulders in combination with extreme temperatures can result in very high installation costs for subsurface raw, treated, and wastewater piping. 

4.2.9 100-Year Flood Plain 

For water treatment facilities located within a 100-year 

flood plain, the entire site should be relocated to another 

site outside of the 100-year flood plain, be elevated 3 ft 

above the 100-year flood level, or be protected on all 

sides by a dike system that extends a minimum of 3 ft 

above the 100-year flood level. 

4.2.10 Financial Considerations 

Many financial factors should be considered by the 

treatment plant designer and the owner. The client can 

impose financial restrictions (beyond any of the technical 

factors mentioned above), which result in increased (or 

decreased) capital costs. These restrictions include, but 

are not limited to, the following: inflationary trends, interest rates, financing costs, land costs (or availability), 

cash flow, labor rates, electric utility rates, chemical 

costs, and auxiliary features to the basic building 

required. If interest rates are low, inflation is anticipated, 

cash is available, and labor and electric utility rates are 

high, the designer and the owner may consider increasing capital investment and reducing operating costs; or 

the opposite can be true. 

4.3 Example Economic Evaluation 

This section provides an example cost evaluation for two 

hypothetical iron/removal treatment systems. For this 

example, the costs to design and operate two 500,000­

gpd iron removal treatment plants over a 20-year period 

were evaluated and compared. One system is based on 

aeration and chlorination followed by filtration for the 

treatment process, and the other is a manganese greensand filtration plant. Simple floor plans for each are 

shown in Figure 4-1, and were used as a basis for developing cost estimates outlined in Figures 4-2 and 4-3. A 

detailed breakout of the design data and equivalent 

annual cost calculations for each system is included in 

Appendix A. 

Estimated costs were organized into three categories: 

capital, O&M, and replacement costs. Assumptions made 

for the analysis were: 

• Iron levels at 1.0 mg/L, arsenic at 0.03 mg/L, 

and manganese at 0.1 mg/L 

• Backwash holding tank sized to hold two 

backwashes 

• Building on concrete slab with metal siding and 

shingles 

• Maximum flowrate is 500,000 gpd and average 

is 250,000 gpd 

• Normal plant operation is 12 hours at 

500,000 gpd rate 

• High service pump discharge is 60 psi at 

500,000 gpd 

• O&M costs average increase 3% annually 

• Chemical feed and high-service pumps replaced 

after 15 years 

• Filter media replaced after 10 years 

• All other equipment assumed to have a life of 

20 years 

• 20-year analysis using federal interest rate 

of 57⁄8%. 

The capital cost for the manganese greensand filtration 

plant is slightly less than the aeration/filtration plant. The 

manganese greensand system had an Equivalent Annual 

Cost of $165,774, which is 4% higher than the aeration/ 

filtration treatment plant cost of $159,611. The difference 

was due to the impact of the slightly higher operational 

cost for the manganese greensand plant on a 20-year 

basis. Overall, the two treatment plant options are within 

10% on an equivalent annual cost basis, making them 

essentially equal from an economic perspective. 

30
FIGURE 4-1. Two Conceptual Iron Removal Water Treatment Plant Floor Plans for Cost Estimates 

31 
QTY UNIT Unit ($) Total ($) 

Building/Structure 

Building 2400 SF $100 $240,000 

Backwash holding tank, 25,500 gal, concrete 1 LS $30,000 $30,000 

Laboratory casework and equipment 1 LS $10,000 $10,000 

Clearwell, 10,500 gal, steel 1 LS $15,000 $15,000 

HVAC and Plumbing 1 LS $8,000 $15,000 

Electrical 1 LS $30,000 $30,000 

Civil Site 1 LS $20,000 $20,000 

$360,000 

Process Equipment - 20 Yr 

Aerator and detention tank 1 EA $30,000 $30,000 

Vertical pressure filters, 9 ft diameter, w/o media 2 EA $125,000 $250,000 

Blower and air piping 1 LS $6,000 $12,000 

NaOCl drum scale 1 EA $2,500 $2,500 

NaOCl day tank 1 EA $1,500 $1,500 

Piping and valves 1 LS $25,000 $25,000 

$321,000 

Process Equipment - 15 Yr 

NaOCl feed pumps 2 EA $2,500 $5,000 

$5,000 

Auxiliary Equipment - 15 Yr 

High service pumps 2 EA $10,000 $20,000 

$20,000 

Auxiliary Equipment - 10 Yr 

Filter Media, sand and anthracite 1 LS $17,500 $17,500 

$17,500 

Subtotal $723,500 

Contingency 15% $108,525 

Total - Preliminary Construction Cost Opinion 

(nearest $1000) 

$832,000 

FIGURE 4-2. 500,000-gpd Iron Removal Water Treatment Plant with Aeration Followed with Filtration 

32
QTY UNIT Unit ($) Total ($) 

Building/Structure 

Building 2400 SF $100 $240,000 

Backwash holding tank, 25,500 gal, concrete 1 LS $30,000 $30,000 

Laboratory casework and equipment 1 LS $10,000 $10,000 

Clearwell, 10,500 gal, steel 1 LS $15,000 $15,000 

HVAC and Plumbing 1 LS $8,000 $15,000 

Electrical 1 LS $30,000 $30,000 

Civil Site 1 LS $20,000 $20,000 

$360,000 

Process Equipment - 20 Yr 

Vertical pressure filters 2 EA $125,000 $250,000 

Blowers and air piping 1 LS $6,000 $12,000 

KMnO4 mixing tank and mixer 1 LS $2,000 $2,000 

NaOCl drum scale 1 EA $2,500 $2,500 

NaOCl day tank 1 EA $1,500 $1,500 

Piping and valves 1 LS $25,000 $25,000 

$293,000 

Process Equipment - 15 Yr 

NaOCl feed pumps 2 EA $2,500 $5,000 

KMnO4 Feed Pumps 2 EA $2,500 $5,000 

$10,000 

Auxiliary Equipment - 15 Yr 

High service pumps 2 EA $10,000 $20,000 

$20,000 

Auxiliary Equipment - 10 Yr 

Greensand Filter Media 1 LS $30,500 $30,500 

$30,500 

Subtotal $713,500 

Contingency 15% $107,025 

Total - Preliminary Construction Cost Opinion 

(nearest $1000) 

$821,000 

FIGURE 4-3. 500,000-gpd Iron Removal Water Treatment Plant with Manganese Greensand Filtration 

33

5.0 Central Water Treatment Plant Operation 

5.1 Introduction 

Upon completion and approval of the final water treatment plant design package (plans and specifications), 

the owner/client proceeds to advertise for bids for construction of the treatment plant. The construction contract normally is awarded to the firm submitting the 

lowest qualified bid. 

Upon award of the construction contract, the engineer 

may be requested to observe the work of the construction 

contractor in order to notify the client of the compliance 

or lack of compliance with the design. This responsibility 

may be limited to periodic visits to the site to assure the 

client that the general intent of the design is being fulfilled; or it may include day-to-day field observation and 

reporting of the work as it is being performed. Payment 

to the contractor should be made by the client after 

receiving the written review of the pay estimate by the 

engineer. The engineer should state that the amount is in 

accordance with the construction completed and with certifications from the contractor that he has paid all subcontractors and suppliers for the work completed. The 

engineer should review all shop drawings and other information submitted by the contractor. All acceptable substitutions should be approved in writing by the engineer. 

Upon completion of the construction phase of the project, the engineer normally is requested to perform a final 

inspection along with the client before final payment is 

made. This entails a formal approval indicating to the 

client that all installed items are in compliance with the 

requirements of the design. Any corrective work required 

at that time is covered by a punch list and/or warranty. 

The warranty period (normally one year) commences 

upon final acceptance of the project by the client from the 

contractor. Final acceptance and final payment usually 

take place upon completion of all major punch list items. 

Preparation for treatment plant startup and operation is 

important, but training for these functions may or may not 

be included in the construction contract. Before system 

startup, it is essential that system operating supplies, 

such as treatment chemicals, laboratory supplies, and 

recommended spare parts, are procured and stored on 

site. The treatment plant operating and maintenance 

instructions (or O&M Manual) also should be available 

for use. Included in the O&M Manual are diagrams and 

operational procedures for basic operation, maintenance, 

and troubleshooting of equipment. Valves, pumps, and 

other similar equipment should be identified by a numbering system for ease of correlation with the O&M Manual. 

For example, valves may be designated as “V-1”, “V-2”, 

etc. which corresponds to identification tags on the 

valves (see Figure 5-1). A valve directory should be 

included in the O&M Manual and reference made to these 

numbers in the explanation of operating procedures (see 

Table 5-1). 

The following sections discuss the activities and events 

that lead up to routine plant startup and operation. They 

also address different process elements of the three 

alternative treatment types (i.e., oxidation and filtration, 

solid oxidizing media filtration, and manganese greensand filtration). Note that discussion of pressure filters 

operation applies to all three treatment types. Appendix B 

provides operation procedures for iron removal plants. 

5.2 Chemical Treatment Equipment 

Proper training and instruction in the handling and use of 

chemicals at a water treatment plant is critical for operators. Appropriate protective apparel and safety stations 

which include eyewashes or showers in the event of a 

spill need to be a part of the treatment facility. Maintenance of chemical storage areas to prevent contamination and appropriate isolation is to be observed. 

Chemical storage tanks should be clearly labeled or 

color coded, indicating the chemical contained within the 

tank. The piping, valves, pumps, etc., also should be 

clearly labeled or color coded. It is the responsibility of 

the client to properly label or color code the storage 

tank, pump, and associated equipment in accordance 

with the plant color system or labeling. 

35
 V-1

 V-2

 V-3

 V-4

 V-5 

V-6

 V-7

 V-8

 V-12

 V-13 

FIGURE 5-1. Valve Number Diagram on a Typical Pressure Filter 

TABLE 5-1. Valve Operation Chart for Pressure Filters with Air Wash(a)

 Valve No. 

Mode 1 2 3 4 5 6 7 8 12 13 

Treatment – in service ● ● x x x x x x x ●

Backwash 

Draindown x x ● x ● x x ● x x 

Air/Water Wash x x ● x x ● ● ● ● x 

Refill x x ● x x ● x ● ● x 

Fast Wash x ● ● x x x x ● ● x 

Slow Wash x ● ● x x x x ● ● x 

Bed Settle x x x x x x x x ● x 

Rinse ● x x ● x x x x x x 

Treatment Start 

Treatment – offline x x x x x x x x x x 

Treatment – in service ● ● x x x x x x x ●

(a) Refer to Figure 5-1 for valve location. 

Legend: x = valve closed; ● = valve open. 

Maintenance personnel should be familiar with the safety 

precautions associated with the chemical contained in 

the system and warned about the potential hazards 

before starting to work. 

If a color coding system is used, the personnel should 

be familiar with the system so they know what chemical 

is contained within the equipment on which they are 

about to work. 

5.2.1 Chlorination Equipment 

Gas chlorination operation should only be accomplished 

by trained personnel. Training includes proper procedures 

in connecting gas cylinders; repair and maintenance 

practices for piping, chlorination equipment, and safety 

equipment, including ventilation; proper use of safety 

equipment; and a thorough understanding of an emergency plan in the event of a leak. 

Liquid chlorination systems with the use of a sodium 

hypochlorite or a calcium hypochlorite solution need to 

be maintained in the proper environment to preserve 

shelf life. These systems typically are comprised of a 

day tank on a scale with a chemical feed pump to withdraw the solution to an application point. If calcium hypochlorite (HTH) is supplied in dry powder, then mixing 

the powder into a solution tank will be required. Typical 

36
available chlorine is about 65% in a calcium hypochlorite 

solution. Sodium hypochlorite is delivered in liquid form 

within a range of 5-15% available chlorine. 

To calculate the pounds of calcium hypochlorite required 

on a daily basis, the following equation may be used: 

lb/day hypochlorite = 

(million gallons per day) (8.34) (mg/L) 

(percent available chlorine in hypochlorite) 

To determine the amount of HTH required at 65% 

strength for treated water flow of 80,000 gpd (0.080 

million gallons per day [mgd]) and a dosage of chlorine 

required of 3.0 mg/L, the calculation is: 

0.08 mgd (8.34)(3.0 mg/L) / 0.65 = 3.1 lb/day of HTH 

5.2.2 Potassium Permanganate 

Feed Equipment 

Similar to liquid chlorination systems, potassium permanganate systems typically are comprised of a day 

tank on a scale with a chemical feed pump. It is important to maintain a fixed and uniform concentration of the 

solution in the tank by accurate addition of the chemical 

and frequent stirring. A 1% solution can be prepared by 

dissolving one ounce of potassium permanganate in one 

gallon of water: 

1 oz. KMnO4 (dry weight) per gallon of water 

One of the common maintenance problems is the occasional plugging of chemical feed pumps with permanganate crystals. This is usually the result of inadequate 

stirring in the day tank. Many operators keep a continuous stirring of the day tank to insure chemical dissolution. If crystal formation continues, then it is possible that 

the solution strength is too high and better accuracy in 

the solution preparation is required. 

Cleaning and flushing of permanganate systems is easily 

accomplished with water. Hot water will dissolve any 

residues or buildups more quickly. 

5.2.3 Chemical Feed Pumps 

For chemical pumping systems, it is most common to 

use either piston stroke pumps or, for smaller applications, electronic pulse pumps. For piston stroke pumps, 

chemical feed adjustment is by the length of the piston 

stroke on the pump. The stroke length is adjusted by a 

lever or knob, graduated from 0% to 100% of stroke. For 

electronic pulse pumps, the number of pulses per minute 

can be set on a keypad to control chemical feed. Pump 

instruction manuals should be used for complete O&M 

details. 

5.3 Pressure Filters 

The filter vessel and piping should be disinfected in 

accordance with American Water Works Association 

standard procedures (AWWA, 1984 and 1999) and as 

outlined in the specifications. The media then is placed 

in the treatment vessels and is ready for operation. 

There are two basic modes of operation: treatment and 

backwash. Slight variations to each mode depend on the 

media being used and the use of air scouring during 

backwash. Operating details for each of these modes 

are discussed as follows. 

5.3.1 Treatment (Filtration) Operation 

Figure 5-1 shows the position of the valves on a typical 

pressure filter. During normal filtration, water is routed 

through Valve No. 1 to the influent distribution header. 

The influent distribution header is a large-diameter, lowvelocity piping array at the top of the filter vessel designed 

to evenly distribute the water over the surface of the 

media. It also serves as a collection header for wash 

water during the backwash cycle. 

The water moves through the media at an approved rate 

(depending on media type). After filtration, the water is 

collected by the underdrain system. The underdrain system is designed to collect filtered water and to evenly 

distribute backwash water across the bottom of the 

media. After being collected by the underdrain system, 

the water exits the bottom of the filter and passes into 

the finished water piping through Valve No. 2. 

While in operation, the influent pressure above the 

media and the effluent pressure below the media are 

indicated on pressure gauges (Valve No. 10 in Figure 5-1; 

a photo is provided as Figure 5-2). For plants monitored 

or controlled automatically, the lines connecting the 

gauges to the influent and effluent pipes also connect to 

pressure transducers at the filter. These devices convert 

the pressures to electrical signals that are monitored by 

a programmable logic controller (PLC) inside the control 

panel. The pressure drop indicated by these gauges 

(Influent-Effluent) should be monitored regularly. The 

filter must not be operated if the differential pressure is 

in excess of 8-10 psi. This condition will result in fracture 

to some media types. For accuracy, gauges should be 

selected to have normal operating points in the midrange of the gauge. 

37
Inlet Pressure Outlet Pressure 

FIGURE 5-2. Pressure Filter Loss of Head Gauges 

Filter effluent flow is used to balance the flow between 

the filters. Each effluent pipe is equipped with a flow 

meter, such as depicted in Figure 5-3. The signal from 

this meter is used by the PLC to control the motorized 

operator and position of the valve on each effluent pipe. 

Additionally, these meters provide a direct display of the 

present flow and provide totalized flow with reset. This 

feature is useful for manual initiation of backwash based 

on gallons filtered. For automatic operation, totalized 

flow resets automatically upon backwash initiation. 

5.3.2 Backwash Operation 

The importance of proper backwashing of the filter media 

cannot be overemphasized. Backwashing is essential to 

maintaining the efficiency of the filter media and the 

quality of the finished water. 

The backwash process can vary slightly depending on 

whether the use of air scouring is employed in backwashing. Some media, such as Birm, do not require nor 

can it withstand the turbulent collision of particles, which 

occur during an air scouring operation. Other media, such 

as manganese greensand, require air scouring to clean 

the media. In general, the backwash sequence can be 

broken into seven stages: 

• Draindown 

• Air/Water Wash 

• Refill 

• Fast Wash 

• Slow Wash 

• Bed Settle 

• Rinse. 

5.3.2.1 Draindown 

During draindown, the water level in the filter is lowered 

to approximately six inches above the media. To do this 

Valve No. 1 (the influent valve), Valve No. 2 (the effluent 

valve), and Valve No. 6 (the slow wash/refill valve) are 

closed, isolating the filter from the rest of the system. 

Once these valves are closed there will be a programmed delay of one minute. Then, Valve No. 5, the 

draindown valve, and Valve No. 3, the backwash outlet 

valve, are opened. The draindown valve is programmed 

to remain open for five minutes. While draindown is in 

progress, Valve No. 8 (the air release valve) will allow air 

to enter the top of the filter (see Figure 5-4). 

5.3.2.2 Air/Water Wash 

This phase of the backwash process mixes air with 

water under the media, agitating the media and causing 

the media grains to rub together producing a very efficient scrubbing action. During this phase, the blower and 

the backwash pump are used (see Figures 5-5 and 5-6). 

The valves will be configured as follows: Valve No. 6 

(the slow wash valve), Valve No. 7 (the air wash valve), 

38
FIGURE 5-3. Filter Effluent Flow Meter 

FIGURE 5-4. Air Release Valve 

and Valve No. 12 (the wash water isolation valve) are 

opened. Valve No. 3 (the backwash outlet valve) remains 

open, while Valve No. 13 (the effluent isolation valve) 

and Valve No. 5 (the draindown valve) are closed. 

Once the valves are properly configured, the blower will 

start. At the same time, the backwash pump will start 

and its rate is held by the backwash control valve at 

approximately one-third of the maximum backwash rate 

used in the fast wash sequence. In automatic mode, this 

low rate is monitored by the backwash flow meter 

reading, and is controlled by the backwash rate valve. 

This process is programmed to continue for a short 

period, usually about three minutes. During this time the 

filter will partially refill. 

39
FIGURE 5-5. Air Wash Blower and Motor FIGURE 5-6. Air Wash Blower Controls 

5.3.2.3 Refill 

After the air/water wash the blower stops and Valve 

No. 7 closes, the wash water will continue for two more 

minutes. This ensures that there is sufficient water above 

the media to prevent any initial surges in the fast wash 

flow from disrupting the media. 

5.3.2.4 Fast Wash 

During the fast wash, water is forced through the media 

counter to its normal flow at velocities sufficient to expand 

the media to the desired level, usually 30-40% depending on the manufacturer’s recommendation. This allows 

the previously entrained filtered particles to be suspended 

and then flushed from the filter by the backwash water. 

After refill, the backwash rate control is stepped from the 

refill rate to a maximum rate prescribed for the media 

type. For example, manganese greensand would typically have a refill rate of 4 gpm/ft2

, and the maximum 

backwash rate would be 12 gpm/ft2

. Wash water leaving 

the filter should be checked periodically for the presence 

of anthracite. If anthracite is present in more than trace 

quantities, the fast wash flow may need to be lowered. 

This phase of the backwash cycle is typically programmed to continue for 20 minutes. 

5.3.2.5 Slow Wash 

After the fast wash has ended, the backwash rate is 

decreased to the refill rate for one minute. This low rate 

allows the media to reclassify and settle evenly inside 

the filter. 

5.3.2.6 Bed Settle 

After the slow wash has ended, all wash water flow to 

the filter is stopped and the media is allowed to settle for 

approximately two minutes. 

5.3.2.7 Rinse 

This stage also is referred to as filter-to-waste. During 

this phase Valve No. 2 (the filtered effluent valve), Valve 

No. 3 (the backwash outlet valve), Valve No. 6 (the slow 

wash/refill valve), and Valve No. 12 (the backwash water 

isolation valve) are closed; and Valve No. 1 (the raw influent valve) and Valve No. 4 (the rinse valve) are opened. 

The filter is operated at its normal filtration rate with the 

effluent going to waste. The purpose for this is to make 

sure any particles dislodged but not removed from the 

lower portion of the media go to waste rather than into 

the finished water. 

5.3.3 Filter Loadings and 

Run Termination 

For treatment systems involving solid oxidizing media 

filtration (i.e., pyrolusite and Birm), daily backwashing is 

recommended for optimal filter efficiency. For oxidation 

and filtration as well as manganese greensand systems, 

three methods can be used to assess the need for backwashing this type of filter: 

• Gallons treated 

• Filter run time 

• Pressure drop across the media. 

40
5.3.3.1 Gallons Treated 

The “gallons treated” method is used because the total 

volume of water filtered can be directly converted to the 

quantity of iron and manganese precipitated. When this 

reaches a predetermined limit, backwash is initiated. This 

method is used most frequently for filtration media that 

filters the precipitates, such as dual media anthracite 

and silica sand or anthracite and manganese greensand. 

Iron and manganese precipitates often are extremely 

small and will move down into the media bed rather than 

being stopped on the surface of the bed. When the precipitates collect evenly throughout the depth of the media, 

there will be only a slight pressure drop across the media, 

compared to the pressure drop encountered when the 

precipitates collect primarily in the upper three to four 

inches of the bed. As such, breakthrough may occur 

without significant pressure buildup through the filter. 

For a manganese greensand system, the filter run 

between regenerations/backwashes can be calculated 

based on the potassium permanganate demand (PPD) 

of the water and the PPD capacity of greensand (Ficek, 

1994). The PPD of water is defined as the stoichiometric 

amount of KMnO4 necessary to oxidize Fe(II) and and 

Mn(II) (see Table 2-2), as calculated using the following 

equation: 

PPD = Fe as mg/L + (2 × Mn as mg/L) = mg/L Fe and Mn 

mg/L Fe and Mn / 17.1 = gpg Fe and Mn 

Concentrations of iron and manganese are expressed 

as mg/L, which can be converted to grains per gallon 

(gpg) by dividing by 17.1. 

According to the greensand manufacturer, one cubic 

foot of greensand has about 300 grains (or 19.4 grams) 

of manganese removal capacity. Since two parts of permanganate are required to oxidize each part of manganese, the PPD capacity of greensand is twice that for 

manganese or 600 grains (or 38.8 grams). 

The following calculations are an example of how to 

determine the gallons filtered between regenerations/ 

backwashes for a manganese greensand system. For a 

water containing 1.5 mg/L Fe, 0.5 mg/L Mn, and no 

other oxidizable contaminants, the PPD is: 

PPD of water = 1.5 mg/L + (2 × 0.5 mg/L) = 2.5 mg/L 

2.5 / 17.1 = 0.146 gpg 

Assuming that greensand has a PPD capacity of 600 

grains per cubic foot, a filter with an area of 50 ft2

 (8-ftdiameter pressure vessel) and an 18-inch media depth 

has a total capacity: 

600 gr/ft3

 × 1.5 ft × 50 ft2 = 45,000 grains 

If each gallon of raw water contains 0.146 grains of 

KMnO4 demand, the number of gallons of water a filter 

can treat would be: 

45,000 grains / 0.146 gpg = 308,219 gallons 

This is the amount of water that may be treated before 

the filter would require regeneration and backwashing. 

5.3.3.2 Filter Run Time 

Filter run time can be used to initiate backwash when the 

filter is operated at a constant flowrate. This allows the 

run time to be directly converted to volume throughput. 

Using the previous example that determined 308,219 

gallons of water treated between two backwash cycles, 

and filtering at a 3.0 gpm/ft2

 rate, the filter run time is: 

3.0 gpm/ft2

 × 50 ft2 = 150 gpm 

308,219 gallons / 150 gpm = 2,055 minutes. 

This would allow for a run time of: 

2,055 minutes / 60 minutes per hour = 34.2 hours. 

5.3.3.3 Pressure Drop 

Pressure drop is used to initiate a backwash when the 

pressure difference between the inlet and outlet pressure reaches 8-10 psig. As larger precipitates accumulate on the top of the media bed, the head loss through 

the filter increases. Depending on the size of the precipitates, the filter run time could be significantly shorter 

than that calculated based on the gallons filtered 

method. 

When the head loss across the filter reaches 10 psig, a 

backwash cycle must be initiated regardless of the gallons that have been filtered. Monitoring the head loss 

across the filters also can be used to identify operating 

problems with the filter. As the media ages, it will generally decrease in size and the difference between the 

smallest grains and the largest grains will increase. This 

condition will cause the filter to exhibit higher initial head 

loss under clean bed conditions. 

5.3.4 Filter Operation 

Filters may be operated manually or automated through 

a PLC in the filter control panel (see Figure 5-7). The 

startup and shutdown of plant production and filter operation are typically based on the level of water storage 

facilities. An example of a common sequence of operation is described as follows: 

41
 

 

 

 

 

 

 

 

Two-Filter Control Panel 

Effluent Rate Meters Influent Meter Disconnect 

Filtering/Washing Plant Effluent Backwash 

 Indicators Flow 

Filtering—Washing 

 Inlet Valve Switches Blower Motor Switch 

OPEN—CLOSE—AUTO HAND—OFF—AUTO 

Valve Position Meters As % 

Effluent Valve Bank A Backwash Bank B Backwash 

 Switch Full Flow—Low Flow—Close—Auto 

OPEN/CLOSE/ 

AUTO 

Backwash Inlet Valves Hypochlorite Filter 

OPEN—CLOSE—AUTO Pump #3 PLC Interface 

Backwash Outlet Unit Air/Water Wash 

OPEN/CLOSE/ Select Wash Start 

AUTO Auto/ INCLUDE PUSH 

 1-2-3-4-5-6 OMIT TO 

 START 

Rinse Outlet Valves Backwash Backwash 

OPEN/CLOSE/ Resume Stopped 

AUTO PUSH TO START 

Draindown Valves Filter Sequence/ Backwash 

 OPEN/ CLOSE/ Time Control Pump 

AUTO Prolong—Auto HAND/OFF 

AUTO 

Air Wash Inlet Valves 

OPEN—CLOSE—AUTO 

FIGURE 5-7. Typical Two-Filter Control Panel 

• When the storage tank falls below a pre-designated low level 1, the well pump control panel 

starts the well pump(s) designated under a 

LEAD/LAG matrix. 

• If the storage tank continues to fall until it 

reaches low level 2, additional well pump(s) 

designated under the LAG steps of the matrix 

will be started. 

• When the pumps are started, the filter control 

PLC will configure the influent and effluent 

valves for normal filtering. 

• This process continues as the storage tank level 

rises. When the storage tank level reaches high 

level 1, the LAG pump(s) will stop. When the 

storage tank level reaches high level 2, the 

LEAD pump(s) will be signaled to stop. 

Displayed on the control panel are the vital flow parameters which consist of: 

• Flow from each filter 

• Plant effluent and influent 

• Backwash flow 

• Filter effluent valve positions. 

Provisions are made available on the panel for both the 

manual and automatic operation of the following system 

components and operations: 

• Filter valves 

• Individual filter backwash operations 

• Air wash operations. 

An operator interface is provided for control and adjustment of automatic filter operations. The PLC has an 

42
operator interface on the right side of the panel (see Figure 5-7), providing direct access to the control panel. 

Valves operated with pneumatic or hydraulic actuators 

can be either open or closed (see Figures 5-8 and 5-9). 

The switches present on the control panel for electric 

operators will allow the plant operator to manually open 

or close the valves. Additionally, the controls on the filter 

control panel should be designed to allow the plant operator to open and close the valve. Valves operated with 

electrical operators may be positioned at any point 

between fully opened and fully closed. The position of 

these valves is indicated as to what percentage the 

valve is fully opened (see Figure 5-10). 

FIGURE 5-8. Pneumatically Operated Draindown Valves 

Pneumatic Cylinder 

Solenoid-Operated Air Valve Position 

Sensor/Transmitter 

Butterfly Valve 

FIGURE 5-9. Filtered Effluent Pneumatically Operated Butterfly Valve 

43
Position Sensor/Transmitter 

OPEN 

CLOSED 

STOP 

LOCAL/REMOTE 

FIGURE 5-10. Electric Valve Operator 

5.4 Media 

The placement of the media in the treatment vessel, 

which takes place immediately prior to initial startup or 

during replacement of spent media, is a critical step in 

the future system performance. The media is usually 

delivered in bags on pallets. The volume of the media is 

determined on a dry weight basis. 

5.4.1 Support Media 

Some filters are designed to have an underdrain system 

that does not require support media; these are usually of 

a porous plate or strainer nozzle design. For an underdrain system that requires support media (e.g., gravel, 

garnet, and/or torpedo sand), care must be taken in the 

placement of the support media. 

Before packing the support media, it is important to be 

sure that the interior of the tank is clean and that the 

underdrain is clear and secure. The support media then 

is placed around and over the underdrain system and 

each gradation is measured for proper depth. Support 

media should be properly leveled before adding the next 

size layer. 

For vessels with air scour, the air distribution laterals 

should be inspected to ensure that the openings are 

facing downward into the support media. Gravels in 

3/16-inch, 10 mesh then are placed in the tank to cover 

the air wash distributor. Care must be taken to prevent 

debris from entering the tank, as it may cause interference with the air distribution. 

Air scour systems which require a gravel retaining screen 

should place the screen at the junction where the top 

layer of gravel will be leveled off and the layer of greensand will be started. In packing the last layer of gravel, it 

must be mounded slightly above the top of the screen 

support angle so that, when the screen is installed, the 

gravel will be tight underneath the screen. 

5.4.2 Filter Media 

The filter media should be packed under water. With 

water available to the unit, clean water is fed to the tank 

until it stands about 12-18 inches deep above the supporting bed. The filter media may be placed in the filter 

tank by pouring it through the tank opening until the 

required amount is packed. Care should be taken to 

prevent bags or any portion of the shipping containers 

44
from entering the tank, as this could cause excessive 

pressure loss and/or channeling of water through the 

bed during the service run. 

After the required filter media has been placed in the 

tank and leveled, the filter must be given a conditioning 

backwash and the fines must be skimmed from the bed 

surface. The filter then should be backwashed at the 

flowrate required to achieve bed fluidization for at least 

15 minutes. Following this backwash, the filter should be 

given a short downflow rinse, and then the filter should 

be backwashed again. 

Following this second backwash, the filter should be 

drained completely. An inspection will show a layer of 

fine material on the bed surface from 1⁄2-inch to 3⁄4-inch 

thick, which must be removed with a flat trowel or flat 

shovel and discarded. It is important not to rake or 

scrape this material across the bed surface, as this will 

only push the fines down into the bed. 

For dual media filters, anthracite may be added after the 

fines have been skimmed from the bed. Water should be 

allowed to enter the filter until it stands about 6-8 inches 

above the bed. Anthracite then is placed into the filter to 

the required depth. Caution should again be exercised to 

prevent debris from entering the tank. After the required 

amount of anthracite has been placed into the tank, the 

filter may be backwashed again until the water passing 

to waste is clear and clean. Anthracite should be 

skimmed to remove fines. A short rinse should then be 

performed before the unit is drained. 

While the unit is draining, it is important to observe the 

draindown and close the rinse valve when the water level 

is about 12 inches above the bed surface. The filter then 

is ready for conditioning (if required) and disinfecting. 

5.4.3 Limitations and Precautions 

Depending on the filter media, certain limitations and 

precautions should be observed. 

5.4.3.1 Anthracite Caps 

When using anthracite, the backwash wastewater should 

be monitored closely to determine media loss. Because 

anthracite is more easily fluidized than other media, it is 

more likely to experience a greater rate of attrition and 

carryover in the backwash waste. Also, it may be more 

likely to fracture under air scour or high rate backwashing, thus reducing its effective size and beginning to plug 

the filter bed, resulting in higher head loss through the 

filter. Besides periodically taking samples of backwash 

waste during high-rate backwashing, annual inspection 

of the anthracite cap is recommended to determine the 

depth and effective size of the media. 

5.4.3.2 Pyrolusite 

Along with silica sand, pyrolusite is among the most durable of the available iron filter media. However, because 

of its high specific gravity, backwash rates must be able 

to redistribute the pyrolusite evenly throughout the sand 

filter bed. Using water alone for backwash requires 25­

30 gpm/ft2

, a rate difficult to achieve for many smaller 

treatment plants. The use of air scour with water backwash is best in redistributing the pyrolusite. If iron 

removal effectiveness begins to decline, it may be due to 

uneven distribution of the media, and backwashing practices should be examined. 

5.4.3.3 Birm 

The effectiveness of the Birm media is compromised 

when it is operated outside of defined ranges. Free 

chlorine concentration in backwash water should not 

exceed 0.5 mg/L (as Cl2). Water containing hydrogen 

sulfide or polyphosphates will reduce the oxidizing 

capacity of the media and must be avoided. During 

installation, disinfection of the treatment tank with chlorine should take place just prior to the addition of the 

Birm media. The tank should be thoroughly rinsed of any 

chlorine residue before placing the media. Careful placement of media to avoid contamination must be observed. 

5.4.3.4 Manganese Greensand 

Before manganese greensand is placed into service, it 

must be conditioned and disinfected. Conditioning is 

accomplished by filling the filter until the water level is 

approximately 12 inches over the bed. In accordance 

with the manufacturer recommendation, a prescribed 

amount of potassium permanganate is dissolved in 

water and then added to the filter by any convenient 

means (bucket or pump) through the tank top opening. It 

is important to prevent undissolved crystals of permanganate from entering the tank. The tank top opening 

should then be closed and the tank completely filled with 

water. With all valves closed, the inlet valve should be 

opened, followed by the slow opening of the rinse valve. 

Rinsing should continue until the rinse water tests free of 

iron and manganese. The filter then is ready for service. 

Sometimes it is impractical to add potassium permanganate in solution. Although it is not desirable to add permanganate crystals because they dissolve very slowly, if 

necessary, they may be added to the 12 inches of water 

over the bed. The time required for rinsing may be 

extended considerably if potassium permanganate crystals are added. 

45
5.5 Operator Requirements 

A qualified operator for an arsenic removal water treatment plant, licensed in accordance with any regulatory 

requirements, should have thorough arsenic removal 

process training, preferably at an existing treatment 

plant. The operator should be able to service pumps, 

piping systems, instrumentation, and electrical accessories. The operator should be fully informed about the 

safety requirements and physical/chemical characteristics of all chemicals required for use at the plant. 

Corrosive chemical safety requirements for clothing, 

equipment, antidotes, and procedures must be thoroughly understood. The operator should be thoroughly 

trained to run routine water analyses including the method for determining arsenic levels. The operator should 

be well grounded in mathematics for operation cost 

accounting and treatment run recordkeeping. The operator, above all, should be dependable and conscientious. 

5.6 Laboratory Requirements 

In addition to the O&M Manual, the treatment plant should 

have the latest edition of Standard Methods for the 

Examination of Water and Wastewater prepared jointly 

by the American Public Health Association–American 

Water Works Association–Water Environment Federation (APHA-AWWA-WEF). This manual supplies the 

plant operators with necessary information for acceptable methods for analyzing water. A recommended list 

of items for analysis is illustrated in Figure 3-1. The 

primary requirement is accurate analysis for arsenic, 

iron, manganese, and pH. As long as pH meters are 

calibrated and cleaned regularly, high precision measurements are easily obtained. Care should be exercised to prevent contamination of pH buffers. 

Total arsenic can be preserved effectively in field samples and analyzed by several analytical methods to the 

MCL of 10 μg/L or less. Preservation of total arsenic is 

accomplished by acidifying the sample to pH <2. The 

Arsenic Rule lists four U.S. EPA-approved analytical 

methods: 

• Inductively coupled plasma–mass spectroscopy 

(ICP-MS), 

• Graphite furnace atomic absorption (GFAA), 

• Stabilized temperature platform (STP) GFAA, 

and 

• Gaseous hydride atomic absorption (GHAA). 

These methods are U.S. EPA-approved for compliance 

requirements and require expensive analytical equipment that is found only at large water treatment plants or 

laboratories. During the past several years, several companies have developed portable test kits for field analysis of arsenic. 

Several arsenic tests kits have been evaluated under the 

U.S. EPA Environmental Technology Verification (ETV) 

program by the Advanced Monitoring Systems Center 

managed by Battelle in partnership with U.S. EPA. 

These kits were tested for monitoring arsenic in the 1 to 

100 μg/L range. Information on the test kits can be found 

on the internet (http://epa.gov/etv/verifications/vcenter1­

21.html). Although they may be adequate for monitoring 

process performance, these test kits are not U.S. EPAapproved methods for use in reporting MCL compliance 

data. For regulatory data, water samples must be analyzed by U.S. EPA and state-certified testing laboratories 

employing U.S. EPA-approved methods. 

5.7 Operating Records 

A system of records should be maintained on file at the 

treatment plant covering plant activity, plant procedures, 

raw water chemical analyses, plant expenditures, and 

inventory of materials (spare parts, tools, etc.). The plant 

operators should have the responsibility of managing all 

aspects of the treatment plant operation. The operators 

are accountable to the water system management. The 

recommended record system should include, but not be 

limited to, items described below. 

5.7.1 Plant Log 

A daily log should be maintained in which the plant operators record daily activities at the plant. This record 

should include a listing of scheduled maintenance, 

unscheduled maintenance, plant visitors, purchases, 

abnormal weather conditions, injuries, sampling for state 

and other regulatory agencies, etc. This record should 

also be used as a tool for planning future routine and 

special activities. 

5.7.2 Operation Log 

The operators should maintain a log sheet for each 

treatment run for each treatment unit, so that a permanent plant performance record will be on file. Figure 5-11 

illustrates a copy of a suggested condensed form. 

5.7.3 Water Analysis Reports 

It is recommended that the plant operators run an analysis of raw and treated arsenic levels once each week for 

each unit, and a total raw water analysis once per 

month. Changes in raw water may necessitate changes 

46
WATER TREATMENT PLANT 

FILTER OPERATION LOG 

DATE: _______________ FILTER NO. _______________ 

Time 

Rate of 

Flow 

(gpm) 

Head 

Loss 

(psi) 

Hours in 

Service 

Total 

Volume 

Filtered 

Filter 

Loading 

(gpm/ft2) 

Backwash 

Start 

Backwash 

Finish 

Backwash 

(gallons) 

Percent 

Waste 

(%) 

Raw 

Arsenic 

(mg/L) 

Treated 

Arsenic 

(mg/L) 

Raw 

Iron 

(mg/L) 

Treated 

Iron 

(mg/L) 

DATE: _______________ FILTER NO. _______________ 

Time 

Rate of 

Flow 

(gpm) 

Head 

Loss 

(psi) 

Hours in 

Service 

Total 

Volume 

Filtered 

Filter 

Loading 

(gpm/ft2

) 

Backwash 

Start 

Backwash 

Finish 

Backwash 

(gallons) 

Percent 

Waste 

(%) 

Raw 

Arsenic 

(mg/L) 

Treated 

Arsenic 

(mg/L) 

Raw 

Iron 

(mg/L) 

Treated 

Iron 

(mg/L) 

FIGURE 5-11. Typical Water Treatment Plant Filter Operation Log 

in the treatment process. Raw water changes that can 

impact the treatment process include, but are not limited 

to, pH, alkalinity, arsenic, iron, manganese, hardness, 

phosphate, silica, sulfate, total dissolved solids, and turbidity. Figure 3-1 illustrates a copy of a suggested water 

analysis form. A permanent file of these reports can be a 

valuable tool. 

5.7.4 Plant Operating Cost Records 

Using accounting forms supplied by the water system’s 

accountants, the plant operators should keep a complete 

record of purchases of all spare parts, chemicals, laboratory equipment and reagents, tools, services, and other 

sundry items. This should be supplemented by a file of 

up-to-date competitive prices for items that have been 

previously purchased. 

5.7.5 Correspondence Files 

The plant operators should retain copies of all correspondence pertaining to the treatment plant in chronological order. Included would be intradepartmental notes 

and memos in addition to correspondence with other 

individuals and/or organizations. Faxes and copies of 

emails should be part of the file. 

5.7.6 Regulatory Agency Reports 

The plant operators should maintain a complete file of 

copies of all reports received from state, county, or other 

regulatory agencies pertaining to the treatment plant. In 

addition, training records of plant staff should be maintained to demonstrate compliance with license and other 

certification requirements. 

5.7.7 Miscellaneous Forms 

The operators should have an adequate supply of accident and insurance forms. 

47
5.8 Treatment Plant Maintenance and 

Housekeeping 

The maintenance concept for the water treatment plant 

is to isolate the equipment to be serviced by means of 

shutoff valves, vent and drain lines (as required), repair 

or replace equipment, fill lines, open valves, and start 

treatment service. All system components are equipped 

with isolating valves and all piping systems have vents 

at high points and drains at low points to improve maintenance efficiency. 

Equipment manufacturers’ recommended spare parts 

should be stocked at the treatment plant to avoid lengthy 

maintenance shutdowns. 

Bypassing of components in the plant should be provided for periods of maintenance on those components. 

However, care should be taken to avoid bypassing treatment and sending untreated water with excessively high 

arsenic to distribution, an event that should not occur 

and would result in a violation of primary drinking water 

standards. 

A preventive maintenance program should be implemented to sustain the reliability of the plant and reduce 

operating costs. Scheduled maintenance should be 

planned and actual maintenance recorded in a systematic manner. 

The plant operator should wash down all equipment at 

least once per month. Floors should be swept. Bathroom 

and laboratory fixtures should be cleaned once per 

week. All light bulbs should be replaced immediately on 

failure. Emergency shower and eyewash stations should 

be tested once per week. Any chemical spill should be 

neutralized and cleaned up immediately. Equipment 

should be repainted at least once every five years. 

48
6.0 Central Water Treatment Plant Operating Costs 

6.1 Introduction 

The primary objectives in central water treatment plant 

design are to provide the owner/client with a low-capital 

cost installation that works efficiently and reliably; is 

simple to operate; and is inexpensive to operate. Iron 

removal systems include chemical pretreatment, filtration, and/or disinfection, and each system should be 

designed with maximum capability and flexibility. 

Similar to capital costs, many variables affect operating 

costs. This chapter discusses the types of operating 

costs that are evaluated during each stage of the design 

phase of the project and the operation of the treatment 

plant. The costs include: 

1. Treatment chemicals 

2. Operating labor 

3. Utilities 

4. Replacement of equipment and media, and 

miscellaneous materials 

5. Waste disposal (not included in this manual). 

Operating costs normally are passed directly onto the 

water user in the monthly water bill. As the consumer’s 

water bill normally is based on metered water consumption, the costs for treatment are prorated on the unit of 

volume measurement. The unit of volume is usually 

1,000 gal, or 100 ft3

 (750 gal). The rate units employed 

in this design manual is $/1,000 gal. Some systems do 

not meter consumption; instead, they charge a flat 

monthly rate based on the size of the branch connection 

to the water main. Although this latter mode of distribution saves the cost of meters as well as the reading of 

meters, it does not promote water conservation. Therefore, far more water is pumped, treated, and distributed, 

resulting in a net increase in operating costs. 

The common denominator that applies to both the operating costs and the bill for water consumption is the unit 

of volume, 1,000 gal. Each operating cost factor can be 

reduced to cost/1,000 gal. The sum total of the annual 

operating costs based on total water production yields 

the cost per 1,000 gallons. 

Treatment system size is another variable that impacts 

costs. Operating labor requirements do not vary directly 

with the size of the system, but do vary with the type of 

operation; smaller systems would tend to employ the 

simplest operation. In general, the labor cost per 1,000 

gallons of water is less for larger plants. For example, if 

it takes the same amount of labor to operate a 50,000­

gpd plant as it does a 500,000-gpd water plant, the labor 

cost will be ten times less per 1,000 gallons for the 

larger plant. 

Besides treatment system size, other variables that influence the costs of operation are the source water concentrations of iron, arsenic, and other contaminants that 

must be removed. Increased chemical addition and 

numbers of backwash cycles per 1,000 gallons increase 

when iron concentrations are higher. For example, water 

with 1 mg/L of raw iron may require chlorination of 

1 mg/L and will not load filter media as quickly as raw 

water with 3 mg/L, which may require 3 mg/L of chlorine 

for oxidation. 

The costs of treatment chemicals, utilities, waste disposal, and availability of operating personnel vary with 

geographic locations and may be deciding factors in the 

best treatment option available for a particular treatment 

system. 

6.2 Treatment Chemicals 

The treatment chemicals discussed in this chapter are 

limited to chlorine in its various forms and potassium 

permanganate. Both are oxidants and are highly corrosive, requiring compatible materials of construction, containment provisions, safety provisions, weather protection, 

49
and operator training. Although special precautions and 

training are required, they are routinely accomplished. 

Other chemicals may be used for other requirements, 

such as corrosion inhibition or pH adjustment; however, 

such site-specific requirements are not covered in this 

manual. 

The chemicals used for treatment of water for public 

consumption require NSF/ANSI STD 61 certification by 

most state regulatory agencies. It also is recommended 

that the chemical supplier be required to certify that the 

containers used to store and deliver the chemicals have 

not been used for any other chemical; or if they have, 

that they have been decontaminated according to procedures required by the governing regulatory agency. 

Chemical costs are variable; recently these costs have 

been volatile. Like all commodities, there is sensitivity to 

the supply and demand fluctuation of the marketplace. 

The geographic location of the treatment plant site in 

relation to that of the supplier has an impact on the delivered cost. In some cases, the delivery costs are greater 

than the costs of the chemical. The conceptual design 

evaluates the chemical logistics and determines the 

most cost-effective mode of procurement as well as 

whether chemicals for pH adjustment are economically 

feasible. 

Chemical costs are sensitive to the volume and containment mode of the commodity purchased. In general, gas 

chlorine is shipped in either 2,000-lb containers or 

smaller 150-lb cylinders. Liquid chlorine (sodium hypochlorite and calcium hypochlorite) come in various containers from bulk deliveries to small containers. Because 

commodity handling is minimized, bulk tank truck quantities entail the least cost. 

Bulk deliveries require chemical storage tanks within 

containment basins located at the treatment plant site 

with necessary safety provisions and weather protection. 

The same commodities can be routinely purchased in 

drums (55-gal or 30-gal), totes, carboys, gallon jugs, etc. 

These packaged quantities result in much higher unit 

prices than bulk quantity. The drum and other small container prices also depend on the quantity procured at 

one time. Small containers also introduce additional 

handling requirements for the treatment plant operator. 

For small treatment systems, bulk procurement and 

storage of liquid chlorine can be a limiting factor. 

Potassium permanganate is delivered in a dry, crystal 

form and can be shipped in 48,000-lb bulk shipments but 

more commonly is provided in 330-lb steel drums or 

55-lb high-density polyethylene (HDPE) pails. 

The following provides an example operational cost 

evaluation for a hypothetical manganese greensand iron 

removal treatment plant. For this example, it is assumed 

that the system that has an average flow of 500,000 gpd 

and uses chlorine and potassium permanganate as 

oxidants. Concentration of raw iron is 1.5 mg/L, and raw 

manganese is 0.10 mg/L. 

The quantity of chlorine and potassium permanganate 

required can be calculated as follows: 

mg/L chlorine = mg/L iron 

mg/L KMnO4 = 0.2 × mg/L iron + 2.1 × mg/L Mn 

With no chlorine, the potassium permanganate demand is: 

mg/L KMnO4 = 1.1 × mg/L iron + 2.1 × mg/L Mn 

Given: 

Flowrate = 500,000 gpd 

Raw Iron = 1.5 mg/L 

Raw Manganese = 0.10 mg/L 

Chlorine (gas) = $0.40/lb 

Potassium Permanganate = $1.35/lb 

Then: 

Chlorine lb/yr: 

(1 × 1.5 mg/L) × 0.5 mgd × 8.34 × 365 = 

2,283 lb/yr 

Potassium permanganate lb/yr: 

[(0.2 × 1.5 mg/L) + (2.1 × 1 mg/L)] × 0.5 mgd × 

8.34 × 365 = 776 lb/yr 

Chlorine cost: 

2,283 lb/yr × $0.40/lb = $913/yr 

Potassium permanganate cost: 

776 × $1.35/lb = $1,048/yr 

Total chemical cost = $1,961/yr 

Total gallons water produced:

500,000 gpd × 365 days/year = 

182,500,000 gal/year 

Chemical Cost/1,000 gallons:

$1,961 / (182,500) = $0.01/1,000 gallons

6.3 Operating Labor 

Operating labor costs are difficult to quantify. The operators are required to be dependable and competent; however, the positions are not always full-time. Depending 

on the size of the system and the other duties available 

50
for the operators, the operators’ time should be distributed 

over several accounting categories. Automatic backwashing of filters can significantly reduce the time required at 

the plant. 

On routine operating days, the operators check the system to see that equipment is operating properly, take and 

analyze water samples, check instruments (flow, temperature, pressure), and make entries in daily logs. Other 

activities, which may occur on a less frequent basis, 

include, but are not limited to, arsenic analyses in the 

treatment plant laboratory, equipment maintenance, and 

chemical tank truck deliveries. During the remainder of 

the time, the operators are able to operate and maintain 

other systems (distribution, pumps, storage, etc.), read 

meters, or handle other municipal responsibilities (e.g., 

operate sewage treatment plant). Backup operators 

should always be available to take over in case of an 

emergency. Those individuals should be well versed in 

the operation of the plant. 

Assuming that the plant operations are charged an average of 20 hours per week for labor, the cost of operational labor will be as follows (it is assumed that the 

hours not used for treatment plant operation will be 

efficiently used on other duties): 

Given: 

Annual average use = 20 hr/wk 

Operator annual salary = $35,000 

Overhead and fringe benefits = 30% 

Available Annual Hour = 2,040 hr 

Then: 

Total plant operator time: 

20 hr/wk × 52 wk/yr = 1,040 hr 

Operator hourly rate: 35,000/2,040 = $17.16/hr 

30% (overhead and fringe benefits): = $ 5.15/hr 

Operator Rate: $22.31/hr 

Total operator cost: 

1,040 hr/year × $22.31/hr = $23,200/yr 

Total gallons water produced:

= 182,500,000 gal/yr 

Labor cost/1,000 gal: 

$23,200/182,500 = $0.13/1,000 gallons

If the operators had no other responsibilities and the operator’s entire salary were expended against this treatment 

plant operation, the operating labor cost would become 

$0.25/1,000 gal. Depending on the operational philosophy of the designer/planner/manager, the operating labor 

costs can be minimized or maximized over a very broad 

range. In the case of a very high production plant, the 

operating labor requirement is not significantly larger 

than that for a very small treatment plant. Therefore, 

depending on relative salaries, the resulting cost per 

1,000 gal can range from a few cents to more than a 

dollar. 

6.4 Utilities 

Utility costs normally are for electrical power, but can 

include costs for telephone and/or for oil or natural gas. 

Telephone service to the treatment building is recommended as a safety precaution in case of accident as 

well as operator convenience. Cost for that service 

should be the minimum available monthly rate. Depending on the local climate, the costs for heating can vary. 

The purpose of the building is to protect the equipment 

from elements (primarily freezing), not for operator comfort. Normally the treatment units act as heat sinks, maintaining an insulated building at a temperature near that 

of the raw water. In cold climates, the building should 

have an auxiliary heat source to prevent freezing of 

pipes in the event that the water is not flowing. If the 

client determines that the treatment building is to serve 

additional functions, heating and air conditioning to a 

comfortable temperature could be an additional required 

cost. 

Electric power is needed for the following functions: 

1. Chemical feed equipment 

2. Instrumentation and controls 

3. Pumps (well and high service) 

4. Lighting 

5. Office/lab/maintenance 

6. Aerator 

7. Air blowers 

8. Backwash pump 

9. Backwash waste holding pumps. 

Items 1, 2, 4, and 5 are negligible. Item 3 is the largest 

use of power and the use of energy efficient motors is 

recommended. Item 6 is a relatively small load (1-3 hp 

blower motor). Items 7, 8 and 9 are intermittent loads, 

but significant. 

Electrical utility rates also vary considerably from one 

geographic location to another. In 2002, rates varied from 

$0.05 to $0.20/kwh. The electrical utility cost can range 

from $0.005 to $0.02 per 1,000 gallon under normal conditions. Under abnormal conditions, the cost could be 

$0.05/1,000 gallon or higher. 

51
6.5 Media Replacement 

Properly maintained media may be replenished annually 

due to attrition, but generally has a useful life of many 

years. It is not uncommon to use media for 10 years or 

longer before total replacement. Media is typically priced 

per cubic foot. Costs of media in 2002 were in the following ranges: 

Silica sand $5-10/ft3

Anthracite $8-15/ft3

Pyrolusite $70-92/ft3

Birm $56-65/ft3. 

6.6 Replacement Parts and 

Miscellaneous Materials 

This is a very small operational cost item. Replacement 

parts (e.g., chemical pump diaphragms, seals, and 

replacement pump heads) should be kept in stock in the 

treatment plant to prevent extended plant shutdown if a 

part is required. Also included are consumables such as 

laboratory reagents (and glassware), and recordkeeping 

supplies. An operating cost allowance of $0.01/1,000 gal 

of treated water is conservative. 

6.7 Operating Cost Summary 

The range of iron removal water treatment plant operating costs discussed above are impacted by the factors 

presented in Sections 6.2 through 6.6. For the manganese greensand water treatment plant example used in 

Section 6.2, the sum of the operating costs would be: 

Chemical cost: $0.01/1,000 gallons 

Labor cost: $0.13/1,000 gallons 

Utility cost: $0.02/1,000 gallons 

Miscellaneous cost: $0.01/1,000 gallons 

Total Operating Cost: $0.17/1,000 gallons 

For an average flow of 500,000 gpd, the annual operating cost for the plant is $31,025. This annual cost does 

not include waste disposal. Other water-related costs 

including distribution maintenance or administrative costs 

such as meter reading and billing are not included. 

52
7.0 References 

Al-Juaid, S.S., P.B. Hitchcock, J.A. Johnson, and J.F. 

Nixon. 1994. "First Structural Evidence for Complexes 

Containing Arsadiphospholyl Anions: Crystal Structure of 

the Iron(II) Complex [Fe([eta]5-C5H5) ([eta]5­

C2tBu2AsP2)W(CO)5]." Jour. Organometallic Chemistry, 480(1-2): 45. 

Andreae, M.O. 1979. "Arsenic Speciation in Seawater 

and Interstitial Waters: The Influence of BiologicalChemical Interaction on the Chemistry of a Trace Element." Limnology and Oceanography, 24(3): 440. 

American Water Works Association (AWWA). 1984. 

Introduction to Water Treatment, Volume 2, “Principles 

and Practices of Water Supply Operations.” AWWA, 

Denver, CO. 

American Water Works Association (AWWA). 1999. 

Water Quality and Treatment, 5th ed., R.D. Letterman 

(Ed.) McGraw-Hill, Inc., New York, NY. 

American Water Works Association Research Foundation (AWWARF). 1990. Alternative Oxidants for the 

Removal of Soluble Iron and Manganese. AWWARF, 

Denver, CO. 

Azcue, J.M., and J.O. Nriagu. 1993. "Arsenic Forms in 

Mine-Polluted Sediments of Moira Lake, Ontario." Environment International, 19(4): 405. 

Benefield, L.D., and J.M. Morgan. 1990. "Chemical Precipitation." Water Quality and Treatment. 

Borho, M., and P. Wilderer. 1996. "Optimized Removal 

of Arsenate(III) by Adaptation of Oxidation and Precipitation Processes to the Filtration Step." Water Science 

and Technology, 34(9): 25. 

Chen, A.S.C., K.A. Fields, T.J. Sorg, and L. Wang. 2002. 

“Field Evaluation of Arsenic Removal by Conventional 

Plants.” Jour. Amer. Water Works Assoc., 94(9): 64-77. 

Clifford, D., L. Ceber, and S. Chow. 1983. "Arsenic(III)/ 

Arsenic(V) Separation by Chloride-Form Ion-Exchange 

Resins." Proceedings of the XI AWWA WQTC. 

Edwards, M. 1994. "Chemistry of Arsenic Removal During Coagulation and Fe-Mn Oxidation." Jour. AWWA, 

86(9): 64. 

Edwards, M., S. Patel, L. McNeill, H. Chen, M. Frey, 

A.D. Eaton, R.C. Antweiler, and H.E. Taylor. 1998. "Considerations in As Analysis and Speciation." Jour. AWWA, 

103. 

Ficek, K. 1994. “The Potassium Permangate/Greensand 

Process for Water Treatment”. 20th Annual Water Quality Association Convention, Phoenix, AZ. March 17. 

Ficklin, W.H. 1982. "Separation of Arsenic (III) and 

Arsenic (V) in Groundwaters by Ion Exchange." Talanta, 

30(5): 371. 

Frank and Clifford. 1986. Arsenic (III) Oxidation and 

removal from Drinking Water. Summary Report, 

EPA/600/S2-86/021. 

Ghurye, G., and D. Clifford. 2001. Laboratory Study on 

the Oxidation of Arsenic III to Arsenic V. EPA/600/R01/021. United States Environmental Protection Agency, 

Cincinnati, OH. 

Ghurye, G., and D. Clifford. 2004. "As (III) Oxidation 

Using Chemical and Solid-Phase Oxidants." J. AWWA, 

96(1): 84. 

Gupta, S.K., and K.Y. Chen. 1978. "Arsenic Removal by 

Adsorption." Jour. WPCF, March: 493. 

Hering, J.G., P.-Y. Chen, J.A. Wilkie, M. Elimelech, and 

S. Liang. 1996. "Arsenic Removal by Ferric Chloride." 

J. AWWA, 88(4): 155. 

Holm, T.R. 1996. "Removal of Arsenic from Water by 

Iron Removal Processes." Proc. AWWA Water Quality 

Technology Conference. Boston, MA. 

Jain, A., K.P. Raven, and R.H. Loeppert. 1999. "Arsenite 

and Arsenate Adsorption on Ferrihydrite: Surface Charge 

Reduction and Net OH Release Stoichiometry." Environmental Science and Technology, 33(8): 1179. 

53
Leist, M., R.J. Casey, and D. Caridi. 2000. "The Management of Arsenic Waters: Problems and Prospects." 

Jour. Hazardous Materials, 76:125. 

Lowry, J., D. Clifford, G. Ghurye, S. Karori, R. Narasimhan, and B. Thomson. 2005 Arsenite Oxidation by 

Solid-Phase Media or a UV-Sulfite Process. AWWA 

Research Foundation, Denver, CO. 

Lowry, J.D., and S.B. Lowry. 2002. Oxidation of Arsenic 

(III) by Aeration and Storage. EPA/600/R-01/102. United 

States Environmental Protection Agency, Office of 

Research and Development. Washington, DC. 

Lytle, D.A. 1995. "How Do I Run a Proper Jar Test?" 

Proceedings of the 1995 AWWA Water Quality and 

Technology Conference; New Orleans, LA; Nov 12-16, 

1995. 

Lytle, D.A., and V.L. Snoeyink. 2003 "The Effect of 

Dissolved Inorganic Carbon on the Properties of Iron 

Colloidal Suspensions." Jour. of Wat. Supply: Res. and 

Tech. AQUA 52(3): 165-180. 

Lytle, D.A., and V.L. Snoeyink. 2004 "The Effect of Oxidant on the Properties of Fe(III) Particles and Suspensions Formed from the Oxidation of Fe(II)." Accepted for 

publication in Jour. AWWA, April 2004. 

Manceau, A. 1995. "The Mechanism of Anion Adsorption 

on Iron Oxides: Evidence for the Bonding of Arsenate 

Tetrahedral on Free Fe(O,OH)6 edges." Geochimica et 

Cosmochimica Acta, 59(17): 3647. 

McNeill, L.S., and M. Edwards. 1995. "Soluble Arsenic 

Removal at Water Treatment Plants." Jour. AWWA, 

87(4): 105. 

McNeill, L.S., and M. Edwards. 1997. "Predicting Arsenate Removal During Metal Hydroxide Precipitation." 

Jour. AWWA. 89(1): 75. 

Public Law (PL) 93-523. 1974. Safe Drinking Water Act. 

Public Law (PL) 93-523. 1996. Safe Drinking Water Act 

Amendments. 

Rubel, F. 2003a. Design Manual: Removal of Arsenic 

from Drinking Water by Adsorptive Media. EPA/600/R03/019. United States Environmental Protection Agency, 

Cincinnati, OH. 

Rubel, F. 2003b. Design Manual: Removal of Arsenic 

from Drinking Water by Ion Exchange. EPA/600/R03/080. United States Environmental Protection Agency, 

Cincinnati, OH . 

Scott, K.N., J.F. Green, H.D. Do, and S.J. McLean. 

1995. "Arsenic Removal by Coagulation." Jour. AWWA, 

87(4): 114. 

Sommerfeld, E.O. 1999. Iron and Manganese Removal 

Handbook. Prepared for Saskatchewan Environment 

and Resource Management and American Water Works 

Association. American Water Works Association, 

Denver, CO. 

Sorg, T.J. 2002. "Iron Treatment for Arsenic Removal 

Neglected." Opflow, AWWA, 28(11): 15. 

Sun, X., and H.E. Doner. 1998. "Adsorption and Oxidation of Arsenite on Goethite." Soil Science Society of 

America Journal, 163(4): 278. 

U.S. EPA. 1975. National Interim Primary Drinking 

Water Regulations. EPA/570/9-76/003. United States 

Environmental Protection Agency, Office of Water Supply, Washington, DC. 

U.S. EPA. 1979. National Secondary Drinking Water 

Regulations. EPA/570/9-76/000. United States Environmental Protection Agency, Office of Drinking Water, 

Washington, DC. 

U.S. EPA. 2000. Arsenic Removal from Drinking Water 

by Ion Exchange and Activated Alumina Plants. 

EPA/600/R-00/088. U.S. EPA, Cincinnati, OH. 

U.S. EPA. 2001. Federal Register: Final Arsenic Rule. 

40 CFR Parts 9, 141, and 142. 

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Arsenic Rule—Drinking Water Regulations for Arsenic 

and Clarifications to Compliance and New Source 

Contaminants Monitoring. EPA/816/K-02/018. United 

States Environmental Protection Agency, Office of 

Water, Washington, DC. 

U.S. EPA. 2003. Minor Clarification of the National 

Primary Drinking Water Regulation for Arsenic. Federal 

Register, 40 CFR Parts 141. March 25. 

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1996. "Wide Angle X-Ray Scattering (WAXS) Study of 

'Two-Line' Ferrihydrite Structures: Effect of Arsenate 

Sorption and Counterion Variation and Comparison with 

EXAFS Results." Geochimica et Cosmochimica Acta, 

57(10): 2251. 

Zabel, K.R. 1991. “Manganese Options.” Water Technology, (November): 50-51. 

54
Appendix A 

Economic Evaluation Example 

An economic comparison was made between a conventional iron removal water treatment plant (WTP) with aeration 

and a manganese greensand iron removal WTP. The following is a summary of the design data followed by an 

equivalent annual cost analysis. 

Design Data Summary 

Option 1: Iron Removal with Aeration WTP (500,000 gpd) 

Process: Well Pumping  Aeration  Filtration  Disinfection  Clearwell  High Service Pumping  Distribution 

System 

Flow: 

Maximum day: 500,000 gpd (used to size process equipment) 

Average day: 250,000 gpd (used to calculate chemical usage) 

Pressure Filters* 

Max flow, total: 500,000 gpd total (350 gpm) 

Flow per filter: 175 gpm 

Filtration rate: 3 gpm/ft2 

Required filter area: 58.33 ft2 (175 gpm / 3 gpm/ft2) 

Filter diameter: 9’- 0” (nearest size exceeding required area) 

Actual filter area: 63.62 ft2

 per filter 

*actual allowable rate and filter redundancy requirements will vary among state regulatory agencies 

Filter Media 

Media depth: 36” (typical) 

Media volume: 190.9 ft3

 per filter (filter area × depth) 

Media type: Sand and anthracite 

Media cost: $10-$15 per ft3 

Backwash Tanks 

 Backwash rate: 10 gpm/ft2 of filter area 

Backwash duration: 20 min 

Required volume: 25,440 gallon* 

* volume = (filter area) × (rate) × (duration) × (number of filters) 

Clearwell Detention 

Detention time: 30 minutes (groundwater) 

Required volume: 10,500 gallon (350 gpm × 30 min) 

55
Disinfection Chemical 

 Chemical: Sodium Hypochlorite (NaOCl) 

Delivery: Liquid, 12.5% trade strength, no dilution

 Dosage: 1.0 mg/L 

Cl2 required/day: 2.1 lb/day (lb/day = 0.25 mgd x 1.0 mg/L × 8.34) 

Cl2 from NaOCl: Approximately 1 lb Cl2 per gallon 12.5% NaOCl 

NaOCl required: 2.1 gallons/day 

NaOCl cost: $1.00 to $1.50 per gallon delivered 

High Service Pumping 

Pumping head: 60 psi (139 ft TDH) 

Pumps: Horizontal split case centrifugal 

 Power: 20 HP each pump* 

* HP= γQH ; 550η

where γ = 62.4 lb/ ft3

, H = head in ft, Q = flow in cfs, η= pump efficiency 

Energy 

Pumping: kW = HP x 0.746 

Heating/Ventilation: Varies (typically 12.5 to 15.0 kW per 1,000 ft2

) 

Lighting: Varies (typically 0.75 to 1.5 kW per 1,000 ft2

) 

 Miscellaneous Varies 

Electric cost: Varies (typically $0.06 to $0.12 per kW-hr) 

Option 2: Manganese Greensand WTP (500,000 gpd) 

Process: Well pumping  Chemical Oxidation  Filtration  Disinfection  Clearwell  High Service Pumping 

Distribution system 

Process calculations: same as for Option 1 except media type and chemical oxidation. 

Filter Media 

Media depth: 36” (typical) 

Media volume: 190.9 ft3

 per filter (filter area x depth) 

Media type: Manganese greensand and anthracite 

Media cost: $84-$90 per ft3 

Chemical Oxidation 

Chemical: Potassium Permanganate (KMnO4) liquid 

 Dosage: 1.1 lb KMnO4 per lb Fe, 2.1 lb KMnO4 per lb Mn removed 

Iron (Fe): 1.0 mg/L 

Manganese (Mn): 0.1 mg/L 

KMnO4 /day for Fe: 2.3 lb/day (lb/day = 0.25 mgd x 1.0 mg/L x 8.34 x 1.1 lb/lb) 

KMnO4 /day for Mn: 0.4 lb/day (lb/day = 0.25 mgd x 0.1 mg/L x 8.34 x 2.1 lb/lb) 

Total KMnO4/day: 2.7 lb/day* 

KMnO4 cost*: $3.50 to $5.50 per lb in crystal form 

*does not include periodic dosing of filter for media regeneration. 

56
COST-EFFECTIVE ANALYSIS - DATA INPUT

 Project Name: Project Economic Analysis 

Alternative Name: Option 1 - Iron Removal with Aeration WTP 

 Planning Period in years: 

Initial Year of Planning Period: 

 Construction Period, in years: 

20 

0 

1.0 

Interest Rate %: 5.875 

 Structures Value, year 0: $360,000 

 Process Equipment 

 20 yr. Equipment Value, year 0: 

 15 yr. Equipment Value, year 0: 

$321,000 

$5,000 

Auxiliary Equipment 

 15 yr. Equipment Value, year 0: 

 10 yr. Equipment Value, year 0: 

$20,000 

$17,500 

Land Cost: 

 Total Construction Cost: 

 Contingences, % : 

 Technical Services, % : 

$0 

$723,500 

15.00 

0.00 

 Salaries and Administrative Cost, year 

year 

0 

20 

$35,000 

$63,000 

Power and Gas? type Y, just Power? type P: 

 Power Cost, year 

year 

0 

20 

P 

$28,000 

$50,500 

 Chemical Cost, year 

year 

0 

20 

$1,150 

$2,100 

 Repair and Maintenance Cost, year 

year 

0 

20 

$5,000 

$9,000 

57
Project Economic Analysis 

Option 1 - Iron Removal with Aeration WTP 

ESTIMATE OF OPERATION AND MAINTENANCE COST 

Year 0 20 

Salaries and Administrative $35,000 $63,000 

Power 28,000 50,500 

Chemicals 1,150 2,100 

Repair and Maintenance 5,000 9,000 

_________ _________ 

TOTAL O&M COSTS $69,150 $124,600 

TOTAL FIXED O&M 69,150 69,150 

TOTAL VARIABLE O&M $0 $55,450 

Yearly Increase $2,773 

58
Project Economic Analysis 

Option 1 - Iron Removal with Aeration WTP 

REPLACEMENT COST AND SALVAGE COST SUMMARY 

Initial Cost Replacement Replacement Salvage 

at Cost at Cost at Value 

Year 0 Year 10 Year 15 Year 20 

A. Structures 

50 year life $360,000

Salvage Value $216,000 

B. Process Equipment 

20 year life 321,000

15 year life 5,000

 Replacement Cost 5,000 

Salvage Value 3,333 

C. Auxiliary Equipment 

15 year life 20,000

10 year life 17,500

 Replacement Cost 17,500 20,000 

Salvage Value 13,333 

D. Other Costs 

 Contingencies 108,525 

 Technical Services 0 

Land 0 0 0 

TOTAL PROJECT COST $832,025 

TOTAL REPLACEMENT COST $17,500 $25,000 

TOTAL SALVAGE VALUE $232,667 

59
Project Economic Analysis 

Option 1 - Iron Removal with Aeration WTP 

AVERAGE EQUIVALENT ANNUAL COST DETERMINATION 

COST AND OTHER DATA USED 

Planning Period: 20 Years 

Initial Cost of Project: $832,025 Construction Period: 1.0 Year 

Replacement Cost at Year 10: $17,500 

Replacement Cost at Year 15: $25,000 

Salvage Value at Year 20:

 Structures - $216,000 

 Process Equipment - 3,333 

 Auxiliary Equipment - 13,333 

Land 0 

Total $232,667 

Constant Annual O&M Cost: $69,150 

Variable Annual O&M Cost: $0 Year 0 to 

$55,450 Year 20 

Interest Rate: 5.875 % 

DETERMINE PRESENT WORTH AND AVERAGE EQUIVALENT 

ANNUAL COST OF THIS PLAN OVER 20 YEARS 

Factors: ( 20 years at 5.875 %, unless noted) 

Present worth (PW) of constant annual O&M cost: 11.5872 

PW of variable annual O&M cost (annual increase): 88.5484 

Present worth of replacement cost - Year 10: 0.5650 

Present worth of replacement cost - Year 15: 0.4247 

Present worth of salvage value: 0.3193 

Interest during construction = Initial cost x (0.5) x Period of 

 Construction (Years) x Interest rate. 

Equivalent annual cost = Total present worth x 0.0863 

CALCULATIONS - PRESENT WORTH

 1. Initial Cost $832,025 

2a. Constant O&M 801,257 

2b. Variable O&M 245,500 

3. Replacement Cost 20,506 

4. Salvage Value (minus) 74,279 

5. Interest During Construction 24,441 

6. Total Present Worth $1,849,450 

AVERAGE EQUIVALENT ANNUAL COST 

$1,849,450 x 0.0863 $159,611 

60
COST-EFFECTIVE ANALYSIS - DATA INPUT

 Project Name: Plant Economic Analysis

 Alternative Name: Option 2 - Manganese Greensand WTP

 Planning Period in years: 

Initial Year of Planning Period: 

 Construction Period, in years: 

20 

0

1.0 

Interest Rate %: 5.875

 Structures Value, year 0: $360,000

 Process Equipment 

 20 yr. Equipment Value, year 0: 

 15 yr. Equipment Value, year 0: 

$293,000 

$10,000 

Auxiliary Equipment 

 15 yr. Equipment Value, year 0: 

 10 yr. Equipment Value, year 0: 

$20,000 

$30,500 

Land Cost: 

 Total Construction Cost: 

 Contingences, % : 

 Technical Services, % : 

$0 

$713,500

15.00 

0.00 

 Salaries and Administrative Cost, year 

year 

0 

20 

$35,000 

$63,000 

Power and Gas? type Y, just Power? type P: 

 Power Cost, year 

year 

0 

20 

P

$28,000 

$50,500

 Chemical Cost, year 

year 

0 

20 

$6,100

$11,000

 Repair and Maintenance Cost, year 

year 

0 

20 

$5,000

$9,000 

61
Plant Economic Analysis 

Option 2 - Manganese Greensand WTP 

ESTIMATE OF OPERATION AND MAINTENANCE COST 

0 20 

Salaries and Administrative $35,000 $63,000 

Power 28,000 50,500 

Chemicals 6,100 11,000 

Repair and Maintenance 5,000 9,000 

_______ _________ 

TOTAL O&M COSTS $74,100 $133,500 

TOTAL FIXED O&M 74,100 74,100 

TOTAL VARIABLE O&M $0 $59,400 

Yearly Increase $2,970 

62
Plant Economic Analysis 

Option 2 - Manganese Greensand WTP 

REPLACEMENT COST AND SALVAGE COST SUMMARY 

Initial Cost 

at 

Year 0

Replacement 

Cost at 

 Year 10

Replacement 

Cost at 

 Year 15 

Salvage 

Value 

Year 20 

A. Structures 

50 year life 

Salvage Value 

$360,000

$216,000 

B. Process Equipment 

20 year life 

15 year life 

 Replacement Cost 

Salvage Value 

293,000 

10,000 

10,000 

6,667 

C. Auxiliary Equipment 

15 year life 

10 year life 

 Replacement Cost 

Salvage Value 

20,000 

30,500 

30,500 20,000 

13,333 

D. Other Costs 

 Contingencies 

 Technical Services 

Land 

107,025

0 

0 0 

TOTAL PROJECT COST 

TOTAL REPLACEMENT COST 

TOTAL SALVAGE VALUE 

$820,525 

$30,500 $30,000 

$236,000 

63
Plant Economic Analysis 

Option 2 - Manganese Greensand WTP 

AVERAGE EQUIVALENT ANNUAL COST DETERMINATION 

COST AND OTHER DATA USED 

Planning Period: 20 Years 

Initial Cost of Project: $820,525 Construction Period: 1.0 Year 

Replacement Cost at Year 10: $30,500 

Replacement Cost at Year 15: $30,000 

Salvage Value at Year 20:

 Structures - $216,000

 Process Equipment - 6,667

 Auxiliary Equipment - 13,333

 Land - 0 

Total - $236,000 

Constant Annual O&M Cost: $74,100 

Variable Annual O&M Cost: $0 Year 0 to 

$59,400 Year 20 

Interest Rate: 5.875 % 

DETERMINE PRESENT WORTH AND AVERAGE EQUIVALENT 

ANNUAL COST OF THIS PLAN OVER 20 YEARS 

Factors: ( 20 years at 5.875 %, unless noted) 

Present worth (PW) of constant annual O&M cost: 11.5872 

PW of variable annual O&M cost (annual increase): 88.5484 

Present worth of replacement cost - Year 10: 0.5650 

Present worth of replacement cost - Year 15: 0.4247 

Present worth of salvage value: 0.3193 

Interest during construction = Initial cost x (0.5) x Period of 

 Construction (Years) x Interest rate. 

Equivalent annual cost = Total present worth x 0.0863 

CALCULATIONS - PRESENT WORTH

 1. Initial Cost $820,525 

2a. Constant O&M 858,613 

2b. Variable O&M 262,989 

3. Replacement Cost 29,975 

4. Salvage Value (minus) 75,343 

5. Interest During Construction 24,103 

6. Total Present Worth $1,920,862 

AVERAGE EQUIVALENT ANNUAL COST 

$1,920,862 x 0.0863 $165,774 

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Appendix B 

Operations Procedures for Iron Removal Plants 

1) When approaching the plant, first look to see if the 

lights are on around it or listen to hear if the generator is running. Check for power outages, integrity 

of fence, doors, windows, louvers, etc. 

2) Once out of the vehicle, look to see if water is 

coming out from under the doors or up from the 

ground around the plant. Then look to see if everything else appears as it should. 

3) Once inside, listen for familiar sounds: 

• Are the chemical feed pumps running? 

• Are the high service pumps running? 

• Are the backwash pumps running? 

• Are there any unusual sounds? 

• Is anything running that shouldn’t be? 

4) Check the control panel for alarms. 

5) Check chart recorders for normal flow patterns and 

mark abnormalities. 

6) Check the flow split between the filters. 

7) Check totals on filters to see that they are backwashing as required. 

8) Check the filters for anything unusual. 

A common problem with filter systems that use a 

Venturi to measure flow is that the orifices in the 

tube will plug with a slime-like residue from the precipitated iron. In some cases the slime is caused by 

the iron-metabolizing bacteria. 

One cure is to increase the chlorine feed if it is used 

or add a small amount of chlorine if aeration is used. 

If the chlorine feed is increased or started in a 

softening plant, the carryover dose should not be 

greater than 0.1 mg/L. 

The tubing from the Venturi to the sensor should be 

flushed regularly. Do not attempt to adjust the balance valves on the sensor. 

If these procedures do not correct the problem, the 

Venturi will need to be removed and cleaned. All 

orifices and tubing should be cleaned and flushed 

and then reassembled. 

9) When permanganate is being fed, a sample of the 

effluent from each filter should be analyzed daily for 

residual. This can be done quickly with a DPD colorimeter. The reading is multiplied by 0.891 to get the 

permanganate residual. A quick check method is to 

draw the effluent into a white styrofoam cup. If you 

see pink, you are overfeeding. 

The concept of these filters is to remove manganese, so any carryover would be putting it back in. 

Greensand media has an exchange capacity, so the 

best method of operation is to feed an amount of 

permanganate that is very slightly below the demand, 

and once a week increase the feed (KMnO4) until 

pink is seen in the effluent, then turn the feed back 

down. This recharges the media. 

10) When chlorine is used to oxidize iron, there should 

be a slight carryover to keep iron from fouling the 

greensand. This should be checked daily. If the filter 

is followed by softening, the residual must not be 

more than 0.1 mg/L on a continuous basis and not 

be allowed to exceed 0.3 mg/L. Most resins will 

tolerate 0.3 mg/L for very short duration peaks. 

11) If filter backwashing or softener regeneration is set 

up for automatic operation, the operator should be at 

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the plant for several of these occurrences each week 

to make sure the different events are happening on 

schedule and to check the operation of the equipment involved. 

A sample of the washwater should be taken and 

checked for washed out media. 

The operation of the backwash pumps, valves, and 

flow meters should be checked. 

12) If the different pumps are not controlled through a 

pump rotator, reset the LEAD/LAG sequence once a 

week. 

13) Check chemical levels daily. 

14) Check levels in waste holding tanks daily and 

monthly in waste-holding lagoons. 

15) Check dehumidification equipment monthly. 

16) Check air scour systems daily. It is not uncommon for 

water to leak past valves and flood the air blowers. 

17) Compare tank level readings to the stop/start points 

of the equipment operated from those levels. 

18) Open each filter annually and measure and core the 

media. While the filter is open, all of the other components should be checked. 

19) Exercise and inspect all of the valves around each 

filter 2 to 3 times per year. 

20) Depending on the types of valves in use, keep an 

assortment of repair parts on hand. Valves that are 

electric solenoids often have problems. For valves 

where the normal position of the valve requires the 

solenoid to be energized, regular failure of the coil 

can be seen. Coils are quickly and easily replaced. 

Also, repair kits for air switching valves need to be 

kept on hand at the plant. 

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