MEMORANDUM 

TO: Ron Jordan, EPA 

Jezebele Alicea, EPA 

FROM: Shelly Schultz, ERG 

 TJ Finseth, ERG 

 

DATE: March 1, 2013 

SUBJECT: Evaluation of Emerging Technologies for the Treatment of Flue Gas 

Desulfurization Wastewater 

ERG is providing technical support to the U.S. Environmental Protection Agency’s Office of 

Water, Engineering and Analysis Division (EAD) for development of effluent limitations 

guidelines and standards (ELGs) for the Steam Electric Power Generating Industry. EPA, with 

the support of ERG, identified and evaluated technologies available for the treatment of power 

plant wastewater, specifically flue gas desulfurization (FGD) wastewater, to form the basis for 

the technology-based effluent limitations included in the proposed revisions to the Steam Electric 

ELGs. Based on the evaluation of the technologies, EPA selected the following three treatment 

technologies as technology options for the treatment of FGD wastewater: 

 Chemical precipitation (including hydroxide and sulfide precipitation); 

 Anoxic/anaerobic biological treatment (used for heavy metals removal); and 

 Vapor-compression evaporation. 

EPA also identified other emerging treatment technologies that can be used for the treatment of 

FGD wastewater; however, most of these emerging technologies are only being evaluated at 

bench- or pilot-scale levels. This memorandum identifies five other emerging technologies, 

describes the processes for treating the FGD wastewater, and presents the data currently 

available regarding the technologies’ treatment performance. 

1.0 IRON CEMENTATION

The iron cementation process consists of contacting a wastewater with an iron powder, which 

reduces a contaminant to its elemental form (i.e., cementation). Iron cementation has been used 

since the 1500s to remove many types of contaminants. The less noble (inert) iron dissolves (i.e., 

corrodes or oxidizes) while the more noble contaminant precipitates from solution (i.e., is 

reduced). The following equation shows this cementation reaction with copper: 

Fe0 + Cu2+  Fe2+ + Cu0 
Memorandum 

March 1, 2013 

Page 2 

For FGD Wastewater, iron cementation is being looked at for heavy metal removals. The 

addition of a source of iron during treatment is showing promise for metals such as arsenic, 

chromium, cadmium, selenium and many others. Some advantages discovered during initial 

studies are that this technology is relatively low cost with associated pollutant removals and does 

not require significant additional pretreatment. A disadvantage of this technology is that for the 

best results, the reaction retention time may be longer than is practical for high volume systems. 

EPRI Study 

The Electric Power Research Institute (EPRI) performed bench and pilot studies at a coal-fired 

power plant to evaluate the potential to utilize iron cementation for selenium removal. Initial 

bench scale testing using the plant’s FGD wastewater suggested iron cementation has the 

potential to reduce the effluent selenium concentration to less than 50 ug/L while minimizing 

sludge production. This was achieved by testing variations to pH, reaction time, and postcementation pH adjustments. 

The conclusions made by the bench-scale study aided in setting test conditions for the follow-on 

pilot-scale study to evaluate the iron cementation technology under continuous flow conditions at 

a coal-fired power plant. For this pilot study, EPRI used FGD wastewater that had already 

undergone hydroxide precipitation and clarification for initial desaturation of the wastewater. In 

the pilot study, as shown in Figure 1, the metallic iron (as an iron powder) is oxidized to ferrous 

iron during the selenium reduction process, which occurred in the Iron Reactor with the addition 

of sulfuric acid to maintain pH. A clarifier was utilized as an iron separator. The iron recovered 

in the clarifier was recycled back into the Iron Reactor. The overflow from the clarifier was sent 

to a pH adjustment tank. In the pH adjustment tank, the pH was maintained at 8.5 S.U. by 

addition of caustic. The pH increase resulted in precipitation of solids that contain the target 

metals as well as the iron dissolved in the process upstream in the Iron Reactor. The pH 

adjustment tank effluent was then sent to a flocculant mixing tank, where it was mixed with a 

diluted flocculant solution. The flocculant aided coagulation and settling of solids in the process 

water.1

 EPRI noted that for a full-scale system, clarifiers could be utilized in series with aeration 

and filtration. 

Figure 1: Basic Schematic of EPRI Iron Cementation Pilot Study 

The pilot-study showed that selenium removal improved as the pH was lowered and reaction 

time was increased; however, this combination also resulted in higher costs (i.e., higher iron 

 

1

 The report does not describe any solids removal mechanisms used to remove solids from the pH adjustment tank or 

the flocculation tank, but ERG expects that additional solids removal would be required. 
Memorandum 

March 1, 2013 

Page 3 

consumption) and increased sludge production. The pilot study also showed that the 

effectiveness of removing selenium from the FGD wastewater using iron cementation is 

dependent on the species of the selenium present. During the pilot study, the iron cementation 

system was able to remove greater than 99% of the selenite at each pH tested. In comparison, the 

system was able to remove 95% of selenate at a pH of 4.5 S.U., but the system was only able to 

remove 37.4% of the selenate at a pH of 5.5 S.U. EPRI noted that the system also achieved 

significant removals of mercury, ranging from 84.5 to 97.8 percent.2

 

This pilot study showed that the iron cementation technology can remove selenium from FGD 

wastewater containing elevated selenium levels3

; however, like chemical precipitation, the 

removal of selenite is more easily achieved than removal of selenate. Ultimately, the study was 

not able to achieve the target effluent total selenium concentration of 50 ug/L; the lowest effluent 

selenium concentration that the system achieved was 159 ug/L, while the highest effluent 

selenium concentration was 2,240 ug/L. Additionally, relationships between iron retention time, 

dissolved iron, and selenium reduction were identified to allow further optimization of the 

process and possibly achieve the target effluent concentrations during future studies [EPRI, 

2009]. 

Texas A&M University Study 

In addition to the research conducted by EPRI, researchers at Texas A&M University 

demonstrated successful heavy metals removals using an Activated Iron Process (AIP) which 

uses what the researchers call hybrid zero-valent iron (hZVI). The study confirmed that the 

technology can simultaneously reduce many heavy metals, including selenium, mercury, arsenic, 

iron, chromium, copper, and cadmium from FGD wastewater at relatively low costs. Based on 

results from successful bench-scale tests, a pilot study was implemented at an unidentified power 

plant located in the Southeastern United States. The pilot system consisted of four stainless steel 

zero-valent iron (ZVI) reactors where the iron cementation occurs followed by post-treatment 

units including aeration, clarification, and sand filtration. Figure 2 presents a diagram of the set 

up for the pilot scale test. 

The study occurred over approximately five months and consisted of two phases. The first phase 

(January-April) was set up to treat 3.8 L/min (1 gpm), while the second phase (April-May) was 

set up to treat 7.6 L/min (2 gpm). As shown in Figure 2, the pilot study used the effluent from the 

plant’s FGD pond as the influent to the system. The FGD wastewater had typical characteristics 

of the 22 coal-fired plants that are operated by the host power company. As the researchers were 

concerned mostly with the removal of selenium and mercury, each of those contaminants were 

spiked in the feed water to raise their concentrations. In addition, researchers were interested in 

results from just the initial ZVI reactor (i.e., stage one reaction tank) and from the combination 

of all four ZVI reactors. Table 1 shows the average influent and effluent results from the study. 

 

2

 Because mercury was not a defined target pollutant for the study, only a limited set of data were evaluated for 

mercury. The range of percent removals is based on three measurements. 

3

 The selenium concentrations of the primary clarifier effluent entering the pilot study ranged from 6,840 ug/L to 

8,350 ug/L for total selenium and 5,620 ug/L to 7,060 ug/L for dissolved selenium. 
Memorandum 

March 1, 2013 

Page 4 

Source: [Huang, 2012a] 

Figure 2 Diagram of Hybrid ZVI Treatment System Pilot Study 

 

Table 1. Average Influent and Effluent Concentrations for 

Hybrid ZVI Treatment System Pilot Study 

Contaminant FGD Wastewater 

Influent (ug/L) 

One Reactor 

Effluent (ug/L) 

Four Reactors 

Effluent (ug/L) 

Selenium 

(as Selenate) 

22,000 (spiked) 8,000 4,000 (< 1000 towards the 

end of the study) 

Mercury (total) 1,150 (spiked) 0.05 0.025 (< 0.01 towards the 

end of the study) 

Lead (dissolved) 5,000 <1 <1 

Cadmium (total) 2,500 10 <1 

Copper (dissolved) 5,000 1-3 1 

Arsenic (total) 20 <1 <1 

Chromium (as 

chromate) 

5,000 10 2 

Nitrate 10,000 NR 100 

Source: [Huang, 2012] 

NR - Not reported in the study. 

Over the five-month period of the pilot test, the average consumption rate was 0.3 kg ZVI per 1 

m3 FGD wastewater treated (0.0025 lbs ZVI/gal FGD wastewater treated). This consumption rate 

resulted in a cost of approximately $0.6-1.0 per 1 m3

 ($0.0023-0.0038 per gal) FGD wastewater 

for just the chemical consumption. Costs associated with sludge generation and disposal were not 

reported. The pilot study demonstrated that the ZVI process is scalable (i.e., multiple reactors can 

be utilized to achieve additional removals or expand treatment capacity) [Huang, 2012]. 

2.0 REVERSE OSMOSIS

Reverse osmosis (RO) is a well-established membrane treatment process used for desalination of 

seawater and removal of dissolved materials from industrial wastewater. RO systems uses thin 

film membranes that are semi-permeable, meaning they allow water but not dissolved solids to 

flow through; they are permeable to water, but impermeable to dissolved solids. In an RO 
Memorandum 

March 1, 2013 

Page 5 

system, high-pressure pumps are used to apply pressure to the solution from one side of the 

semi-permeable membrane to force the water through the membrane, leaving behind the 

dissolved solids and a portion of the water. The rate that water passes through the membrane 

depends on the operating pressure, concentration of dissolved materials, and temperature, as well 

as the permeability of the membrane. 

As described above, the RO system separates the feed wastewater into two product streams: the 

permeate, which is the clean water that has passed through the membrane, and the concentrate, 

which has been retained (“rejected”) by the membrane. The percentage of membrane system feed 

that emerges from the system as permeate (i.e., the volume of permeate divided by the volume of 

feed) is known as the water recovery. One of the advantages of a RO system is that it can be used 

to achieve zero liquid discharge in certain applications. One of the disadvantages is that the 

system requires pretreatment to remove excess total suspended solids (TSS) and organics to 

prevent scaling and fouling4

. 

RO systems are currently in use at steam electric power plants, usually to treat boiler make-up 

water or cooling tower blowdown wastewaters. For example, the Harry Allen Gas Turbine 

Combined Cycle power plant, located in Nevada, utilizes RO as part of a zero liquid discharge 

system. This system design operates at an overall recovery of greater than 95% while 

discharging a stream of wastewater to evaporation ponds and trucking solids off site (Alexander, 

2012). 

While RO systems may be compatible for the treatment of boiler make-up water or cooling 

tower blowdown, they are of limited use for the treatment of FGD wastewater because of the 

high chloride levels present in FGD wastewater. These high chloride levels lead to a high 

osmotic pressure, which limits the effectiveness of a reverse osmosis system. To date, there are 

no cost-effective ways to reduce the chlorides present in the FGD wastewater, and therefore, 

reverse osmosis systems are not practical for the treatment of FGD wastewater at most plants. 

However, a RO system could be evaluated at specific plants that have low levels of chlorides in 

the FGD wastewater (e.g., once-through FGD systems). 

Allegheny Energy’s Hatfield’s Ferry Power Plant, located in Pennsylvania, considered RO as a 

potential treatment option to reduce total dissolved solids (TDS) from their FGD wastewater. 

However, based on research conducted by the plant, they did not feel RO was a practical 

treatment method. Part of their treatment goals included volume reduction for a zero liquid 

discharge system and the RO process would have added increased flow to the remaining 

treatment processes. Furthermore, the wastewater to be treated contained high levels of organic 

constituents that would produce scaling and fouling issues of the membrane causing the 

technology to be inefficient. No laboratory or field tests were performed as part of this evaluation 

[Black and Veatch, 2008]. 

3.0 SORPTION MEDIA

Sorption media systems adsorb pollutants onto the media’s surface area using physical and 

chemical reactions. A variety of sorption media technologies have been used for water treatment. 

 

4

 Fouling occurs when both dissolved and suspended solids deposit onto a membrane surface and degrade its overall 

performance, thereby decreasing permeate quality and water recovery percentage. 
Memorandum 

March 1, 2013 

Page 6 

The sorbents are typically designed for the removal of specific pollutants; however, they may 

also remove other pollutants simultaneously. The advantages of sorption media are the ease of 

installation, efficiency of contaminant removal, and effectiveness under various pH and 

contaminant conditions. Some disadvantages with sorption media are that they are typically 

single use products that require replacement instead of regeneration. Furthermore, they are 

subject to fouling that may require pretreatment to remove suspended solids and organics. 

EPRI Study 

EPRI research determined that the most common types of adsorbents are metal-based, single use 

applications, such as granular ferric oxide (or hydroxide) and titanium based oxides. The 

advantages of the adsorption media are that it operates over a wide pH range and it has relatively 

few interferences from other contaminants present in FGD wastewater. One of the disadvantages 

of the adsorption media is that it requires pretreatment to remove excess TSS and bioactive 

organics to prevent plugging and fouling of the media [EPRI, 2009]. 

MAR Systems, Inc. Study 

A study by MAR Systems, Inc. examined a proprietary functionalized alumina adsorbent 

technology for its ability to remove both selenite and selenate. It is a single pass through media 

in a standard filtration vessel. This proprietary adsorption media was developed from various 

other proprietary chemistries to form functionalized sites in the media that will form covalent 

bonds with selected soluble metals. As these materials and reactions are all proprietary, details of 

the chemistry were not reported in this study. At least three of the chemical components forming 

the functionalized sites on the media are known to complex with soluble selenium in the selenate 

and selenite oxyanion forms. The removal is accomplished by the formation of various selenite 

and selenate complexes such as aluminum selenite, aluminum selenate, and others. The study 

observed selenium removal rates from 16% to 50% [Sherwood, 2012]. 

Siemen’s Industry Technologies 

Siemens Industry, Inc. installed two types of full-scale sorbent media systems at the Public 

Service Company of New Hampshire's Merrimack Station for removal of mercury and arsenic. 

Siemens provided details of these media to ERG in a conference call held on January 2, 2013. 

These systems include the SCU Adsorbent and the GFH® Media. The SCU Adsorbent is a single 

use granular carbonaceous adsorbent media which selectively adsorbs dissolved metal cations, 

including cadmium (Cd), trivalent chromium (Cr+3), copper (Cu), lead (Pb), mercury (Hg), 

nickel (Ni), and zinc (Zn). At the Merrimack Station, the SCU Adsorbent is specifically used for 

mercury removal. The permitted maximum effluent mercury concentration at the Merrimack 

Station was set at 14 parts per trillion (ppt), based on the plant’s projected performance (i.e., the 

technology vendor’s guarantee). The plant operates a physical/chemical precipitation system, 

including hydroxide and sulfide precipitation, prior to the sorption media systems. Siemens 

designed the system based on an influent mercury concentration entering the media at 100 ppt. 

According to Siemens personnel, the system has been achieving low single digit ppt mercury 

levels. 

To address the arsenic concerns at the Merrimack Station, Siemens utilized its GFH® Media. 

The GFH® Media is a granulated ferric hydroxide media that is used primarily for the removal 
Memorandum 

March 1, 2013 

Page 7 

of arsenic, but it also achieves removals of other heavy metals. According to Siemens personnel, 

the GFH® Media is best suited for arsenic removals from wastewater with low silica 

concentrations. Siemens did not disclose arsenic removal rates during the call. 

Both media developed by Siemens are single use media, with no regeneration. Therefore, when 

the media are spent, which is determined based on effluent sampling results, the plant must 

replace the spent media with new media. The media can either be replaced by swapping out the 

entire vessel or vacuuming out the spent media and replacing with new media. Siemens estimates 

that the capital costs for a system utilizing both media could range from $200,000 to $2,000,000, 

depending on the flow rate, influent concentrations, and system configuration. Specific costs 

associated with the Merrimack Station are proprietary; however, Siemens provided some general 

operation and maintenance (O&M) cost estimates based on their operations. From April to 

December 2012, the system processed approximately 10 million gallons of water at a rate of 

approximately 40 gallon per minute. Based on the replacement frequency observed at 

Merrimack, the media costs for the SCU Adsorbent is approximately $2 per 1,000 gallons and 

the GFH® Media is approximately $1 per 1,000 gallons. There are additional costs associated 

with these systems, such as O&M labor and analytical monitoring/sampling that are not included 

in these estimates [Peschman, 2013]. 

Zorbtech Environmental Solutions Testing 

Zorbtech Environmental Solutions has performed bench- and pilot-scale testing on a nonactivated carbon adsorbent media for mercury removal. The company conducted a bench-scale 

study on power plant scrubber water (which ERG assumes is FGD wastewater, but this is not 

specifically stated in the article). The article describing the study contains limited information 

regarding the treatment steps used in the study and the effluent concentrations achieved, but the 

article did indicate that mercury removal was achieved [Purves, 2013]. 

4.0 ION EXCHANGE

Ion exchange systems remove specific constituents from wastewater; therefore, the system can 

target specific metals to be removed. The ion exchange resin works by substituting one ion for 

another on a specific resin, which must be replaced or regenerated when the resin becomes full 

[AEP, 2010]. While the ion exchange process does not generate a residual waste, it does generate 

a regenerant stream that contains the metals stripped from the wastewater. Ion exchange can be 

complicated by other contaminants present in the wastewater, as such, the ion exchange systems 

require pretreatment to remove excess TSS to prevent scaling and fouling of the resin. A study 

by ResinTech, Inc. discusses how trace contaminant removal in wastewater by ion exchange is 

highly dependent on the other ions that surround the contaminant [Meyers, 2012]. 

Conemaugh Generating Station 

EPA and ERG conducted a visit at GenOn Energy Northeast Management Company’s 

Conemaugh Generating Station, which operates an ion exchange system for the treatment of 

boron in FGD wastewater. Upstream of the ion exchange system, the plant treats the FGD 

wastewater with a physical/chemical precipitation system consisting of hydroxide precipitation 

and clarification. The overflow from the clarifier is fed to the ion exchange system. The ion 

exchange system consists of two parallel trains, each capable of handling 75 percent of the flow. 
Memorandum 

March 1, 2013 

Page 8 

The wastewater is first pumped through pressure sand filters and is then transferred to the ion 

exchange resin vessels. Each train contains two vessels. As designed, the vessels operate in 

series, except when one of the vessels is being regenerated. The system was originally designed 

for regeneration to occur every six hours; however, because of scaling issues, the plant has 

needed to operate the system such that one of the vessels in each train is always being 

regenerated. As the regeneration of one vessel is completed, the other vessel begins its 

regeneration process. 

The plant uses sulfuric acid and caustic soda washes to regenerate the resins. The waste from the 

regeneration process is transferred to a precipitation tank where the plant adds ferric chloride and 

lime. The plant then feeds the water to a clarifier where a polymer is added. The plant operates 

filter presses to create a filter cake with the clarifier underflow; therefore, the ion exchange 

process at this plant does generate a residual sludge, which is landfilled. The clarifier overflow 

and the filtrate from the filter presses are recycled back to the front of the FGD wastewater 

treatment system (i.e., influent to the chemical precipitation process) for additional processing. 

The effluent from the ion exchange vessels is transferred to additional treatment systems prior to 

discharge. 

Plant personnel reported observing a roughly 85% reduction in boron concentrations across the 

chemical precipitation and ion exchange systems. The plant has measured boron concentrations 

between 400 and 600 ppm in the purge stream and concentrations of 75 ppm in the effluent from 

the ion exchange system. Roughly 45% of the boron reduction occurs in the chemical 

precipitation system with the ion exchange system removing approximately 70-75 percent of the 

boron that remains in the wastewater following the chemical precipitation step [ERG, 2012]. 

AEP’s Mountaineer Plant 

ERG is also aware of a plant that conducted pilot testing of an ion exchange system that 

evaluated the removal of mercury in FGD wastewater. As part of American Electric Power’s 

(AEP) permitting process for the several of its power plants along the Ohio River, the company 

conducted a pilot study at its Mountaineer Plant that evaluated four mercury removal 

technologies. One of the four systems evaluated was an ion exchange resin, referred to as 

“Technology B.” The ion exchange resin was formulated to specifically target removal of 

mercury. The objective of the study was to find a technology that will reduce total mercury 

concentrations to less than 12 ppt. Table 2 presents the influent and effluent concentrations for 

the ion exchange resin observed throughout the pilot study as well as a calculated removal 

percentage rate. 

As Table 2 indicates, the ion exchange resin technology was relatively effective at removing 

total mercury with an average removal rate of 88.4 percent; however, researchers concluded that 

although the resign sufficiently removed dissolved mercury it was not effective at removing 

particulate-bound or colloidal mercury. Therefore, an additional ultrafiltration unit would be 

required to achieve the target effluent mercury concentration of 12 ppt [AEP, 2010]. 

 
Memorandum 

March 1, 2013 

Page 9 

Table 2. AEP Pilot Study Ion Exchange Total Mercury Removal Results 

Sample Date 

Influent to Ion 

Exchange 

(ppt) 

Ion Exchange Resin 

Technology Effluent 

(ppt) Removal Rate 

7/23/2008 1,210 451 62.7% 

7/30/2008 1,550 652 57.9% 

8/6/2008 895 231 74.2% 

8/13/2008 1,530 408 73.3% 

8/20/2008 612 48.7 92.0% 

8/27/2008 851 200 76.5% 

9/3/2008 1,940 125 93.6% 

9/10/2008 758 45.2 94.0% 

9/17/2008 1,990 15.4 99.2% 

9/24/2008 1,840 14.1 99.2% 

10/1/2008 643 4.8 99.3% 

10/8/2008 665 NM NM 

10/15/2008 651 NM NM 

10/22/2008 437 13.4 96.9% 

10/29/2008 205 8.9 95.7% 

11/5/2008 282 3.1 98.9% 

11/12/2008 505 4.7 99.1% 

11/19/2008 224 10.3 95.4% 

11/26/2008 342 NM NM 

12/3/2008 181 NM NM 

12/10/2008 261 12.6 95.2% 

Average 836.8 132.2 88.4%

Source: AEP, 2010. 

NM: Not Measured 

5.0 ELECTRO-COAGULATION

Electro-coagulation (EC) is a technique utilized in wastewater treatment in which an electrical 

charge is applied to the water causing a change in particle surface charge, allowing suspended 

solids to fall out of solution. These systems typically use aluminum or iron electrodes, which 

dissolve into the wastestream during the process. The dissolved metallic ions precipitate with the 

other pollutants in the wastewater and form insoluble metal hydroxides. According to EPRI, the 

pollutants removed by iron coprecipitation in a standard chemical precipitation system should 

also be removed by an electro-coagulation system utilizing an iron electrode. One of the 

advantages of the EC system is that is has the potential to remove hard-to-treat pollutants such as 

selenium. Some of the disadvantages of the system are that it requires a constant power source 

and it may increase the wastewater concentrations of the metals forming the electrodes used in 

the system (e.g., aluminum, iron). Additionally, the EC system requires pretreatment to adjust 

the pH to between 7.5 and 9.0 S.U. 

The Duke Energy Mayo plant at one point considered EC as a possible treatment option for 

treating its FGD wastewater; however, the plant has chosen to install a vapor-compression 

evaporation system [Loewenburg, 2012]. 
Memorandum 

March 1, 2013 

Page 10 

University of Florida Study 

A University of Florida study for the installation of a new FGD wastewater system at a power 

plant in Crystal River, Florida proposed using a combination of EC, ion exchange, and zero 

liquid discharge. EC was identified as a potential treatment option based on bench-scale testing 

using FGD wastewater from a plant in Roxboro, NC. The bench scale test determined that EC 

could be used to remove selenium from FGD wastewater and that the best setup for EC was two 

aluminum plates separated with U-shaped rubber spaces. In this bench-scale study, filtered FGD 

wastewater at pH 8 S.U. was pumped through a small Tygon tube using a peristaltic pump into 

the bottom of the EC, through a hole in the rubber space. The pH of 8 S.U. for the influent water 

was chosen because it minimizes the contribution of solids from the electrodes. The researchers 

conducted two separate tests using the same FGD wastewater for the tests. 

Analytical results from the bench-scale study are included in Table 3. For every analyte, two 

detection wavelengths were used and the table presents the results for the two bench-scale tests 

for both wavelengths. The specific wavelengths used for the analyses were not provided in the 

study report. Calcium and magnesium do not have specific goal discharge limits; however, these 

pollutants do need to be controlled in order to meet the total water hardness limit for the plant. 

As shown in Table 3, removals of selenium were achieved for both EC samples, for at least one 

of the wavelengths used for the analyses. However, the EC system increased the aluminum and 

iron concentrations across the treatment system. The researchers determined that aluminum and 

iron could be removed with downstream of the EC system using water softening [University of 

Florida, 2010.] 

Table 3. University of Florida EC Study Results 

Analyte 

Equipment 

Detection 

Limits (ppm) 

Goal 

Discharge 

Limits (ppm) 

Influent 

(ppm) 

EC Treated 

Sample 1 

(ppm) 

EC Treated 

Sample 2 

(ppm) 

Ag 0.0009 0.1 0.006 0.006 BDL 

Ag 0.0009 0.1 0.015 BDL BDL 

Al 0.003 1.5 0.071 528.200 533.900 

Al 0.003 1.5 BDL 1066.000 1080.000 

Ca 0.0002 --- 2179.667 120.700 131.600 

Ca 0.0002 --- 2181.000 109.200 117.900 

Fe 0.002 0.3 0.014 6.453 6.928 

Fe 0.002 0.3 0.012 6.357 6.810 

Mg 0.00007 --- 532.667 21.190 23.330 

Mg 0.00007 --- 534.333 20.430 22.560 

Mn 0.0004 0.1 1.508 25.880 26.520 

Mn 0.0004 0.1 1.490 25.720 26.380 

Se 0.05 0.071 1.580 0.092 BDL 

Se 0.05 0.071 BDL BDL BDL 

BDL – Below detection limit. 
Memorandum 

March 1, 2013 

Page 11 

References 

1. Alexander, Gerald, et al. 2012. A Unique Integrated Membrane Makeup and Zero Liquid 

Discharge System for a Combined Cycle Power Plant Siemens Industries, Inc. DCN 

SE03961.

2. AEP. 2010. American Electric Power Mercury Removal Effectiveness Report. (29 

January). DCN SE02008. 

3. Black and Veatch, 2009. Allegheny Energy Inc. Hatfield’s Ferry Power Stations 

Conceptual Wastewater Treatment Engineering Study and Cost Estimate. DCN SE03960. 

4. Eastern Research Group, Inc. (ERG). 2013. Final Conemaugh Site Visit Notes. (16 

March). DCN SE03756. 

5. Electric Power Research Institute (EPRI). 2009b. Selenium Removal by Iron 

Cementation from a Coal-Fired Power Plant Flue Gas Desulfurization Wastewater in a 

Continuous Flow System – Pilot Study. 1017956. Palo Alto, CA. (July). DCN 

SE00409A2. 

6. Huang, Yong H, et al. 2012. Field Demonstration of the Activated Iron Technology for 

Removing Heavy Metals from Flue-Gas-Desulfurization Wastewater, Texas A&M 

University. DCN SE03966. 

7. Loewenburg, Matthais et al. 2012. Zero‐Liquid Discharge System at Duke Energy Mayo 

Plant. GEA Process Engineering, Inc. DCN SE02027. 

8. Meyers, Peter. 2012. Removal of Trace Contaminants by Ion Exchange. ResinTech, Inc. 

DCN SE03962. 

9. Schultz, Shelly, et al. 2013. Telephone call with ERG. “Discussion of Merrimack Station 

System Operation and Costs.” Eastern Research Group, Inc. DCN SE03901. 

10. Purves, Bill et al. Cost Effectively Removing Mercury in a Wastewater Streams. Accessed 

2013. DCN SE03964. 

11. Sherwood, Nancy et al. 2012. Selenite and Selenate Removal by a Functionalized 

Alumina Adsorption Technology, MAR Systems, Inc. DCN SE03963. 

12. University of Florida, Integrated Product and Process Design Program, 2010. Flue Gas 

Desulfurization Wastewater Mitigation. DCN SE03973.