FINAL Engineering Site Visit Report for 

Reliant Energy’s 

 Conemaugh Power Plant 

New Florence, PA 

Prepared for:

 U.S. Environmental Protection Agency

 Engineering and Analysis Division

Office of Water 

 1200 Pennsylvania Avenue 

 Washington, DC 20004 

Prepared by:

Eastern Research Group, Inc. 

14555 Avion Parkway 

Suite 200 

 Chantilly, VA 20151-1102 

September 17, 2007 

EPA Contract No. 68-C02-095 

Work Assignment 4-22 
i

TABLE OF CONTENTS 

Page 

1.0 Site Visited and Date......................................................................................................... 1 

2.0 Attendees ........................................................................................................................... 1 

3.0 Background and Objectives............................................................................................... 1 

4.0 Plant Description ............................................................................................................... 2 

5.0 Plant Operations ................................................................................................................ 2 

5.1 Intake Water............................................................................................................. 3 

5.2 Coal Preparation ...................................................................................................... 3 

5.3 Boiler Operation ...................................................................................................... 4 

5.4 Particulate Control ................................................................................................... 5 

5.5 FGD System............................................................................................................. 6 

5.6 Biofouling Control................................................................................................... 8 

5.7 Ash Disposal Site..................................................................................................... 9 

6.0 Wastewater Management ................................................................................................ 10 

6.1 Contaminated Storm Water Treatment System ..................................................... 10 

6.2 Bottom Ash Treatment System.............................................................................. 10 

6.3 Flue Gas Desulfurization Wastewater Treatment System ..................................... 12 

7.0 References ....................................................................................................................... 15 

Appendix A LIST OF ATTENDEES 

Appendix B PICTURES FROM SITE VISIT
ii

LIST OF TABLES 

Page 

A-1 List of Attendees................................................................................................. A-1 
iii

LIST OF FIGURES 

Page 

6-1 Contaminated Storm Water Treatment System Diagram ..................................... 11 

6-2 Bottom Ash Treatment System Diagram.............................................................. 12 

6-3 Flue Gas Desulfurization Treatment System Flow Diagram................................ 13 

B-1 Coal Pile at Conemaugh...................................................................................... B-1 

B-2 Limestone Pile at Conemaugh ............................................................................ B-2 

B-3 FGD Clarifier at Conemaugh.............................................................................. B-3 

B-4 Gypsum Sludge Entering the Vacuum Belt at Conemaugh................................ B-4 

B-5 Final Gypsum By-Product at Conemaugh .......................................................... B-5 

B-6 Bottom Ash Pond at Conemaugh........................................................................ B-6 

B-7 Bottom Ash Pond Not Operating at Conemaugh................................................ B-7 

B-8 Influent to the Primary Clarifier at Conemaugh ................................................. B-8 

B-9 Inside of an Empty SBR at Conemaugh ............................................................. B-9 

B-10 Discharge From the FGD Treatment System at Conemaugh ........................... B-10 
1

1.0 SITE VISITED AND DATE

Reliant Energy’s Conemaugh Power Plant 

1442 Power Plant Road 

New Florence, PA 15944 

February 5, 2007 

2.0 ATTENDEES

Appendix A lists the attendees. 

3.0 BACKGROUND AND OBJECTIVES

 Section 304(m) of the Clean Water Act (CWA) requires EPA to develop and 

publish a biennial plan that establishes a schedule for the annual review and revision of national 

effluent limitations guidelines and standards (ELGs) required by CWA section 304(b). During 

EPA’s 2005/2006 review of ELGs, EPA determined that the Steam Electric Power Generating 

Point Source Category (40 CFR Part 423) is the second-largest discharger of toxic-weighted 

pollutants. EPA’s analyses indicated that the toxic-weighted loadings are predominantly driven 

by metals present in wastewater discharges, and that the waste streams contributing the majority 

of the metals are associated with air pollution controls. Other potential sources of metals include 

coal pile runoff, metal/chemical cleaning wastes, coal washing, and certain low volume wastes. 

 In presenting the findings of the 2005/2006 study, EPA noted certain data 

limitations affect the Agency’s estimate of the potential hazard posed by discharges from this 

category and, therefore, EPA determined that further review of these discharges during the 

2007/2008 ELG planning cycle is warranted. Due to the limited resources and time available for 

conducting this study, EPA is concentrating its efforts for the 2007/2008 study on better 

characterizing pollutant sources and available pollution control technologies/practices for the 

pollutants responsible for the majority of the toxic-weighted pollutant loadings from steam 

electric facilities. This will focus the review on wastewater discharges from coal-fired power 

plants. 
2

 EPA intends to review overall plant operations and better understand the various 

wastewater sources present at steam electric plants. This review is expected to largely focus on 

ash handling wastes, wet flue gas desulfurization (FGD) wastes, coal pile runoff, and final 

effluent. 

 EPA and its contractor, Eastern Research Group, Inc. (ERG), conducted a site 

visit to the Conemaugh Power Plant (Conemaugh), which is owned by a group of eight coowners and is operated by Reliant Energy, on February 5, 2007. The purpose of the visit was to: 

1) gather information about the plant’s operations, the wastewater discharges from the plant, and 

the wastewater management practices used to control the discharges; and 2) determine the 

feasibility of collecting and analyzing wastewater samples from steam electric power plants. 

4.0 PLANT DESCRIPTION

 Conemaugh began operation in May 1970, when Unit 1 came on line. Unit 2 

began operation in 1971. Units 1 and 2 both have coal-fired, tangential-fired boilers, with a 

combined total capacity of 1700 megawatts (MW). The Conemaugh plant is located on 

approximately 2,500 acres in New Florence, Pennsylvania, along the Conemaugh River. The 

plant employs approximately 200 people. 

 In December 1994, Conemaugh retrofitted Unit 1 with a wet FGD scrubber to 

control the sulfur dioxide releases from the plant. Conemaugh also retrofitted Unit 2 with a wet 

FGD scrubber in November 1995. When the plant installed the Unit 1 FGD scrubber, it also 

built a FGD treatment system to control the wastewater discharges generated during the 

operation of the scrubbers. 

 

5.0 PLANT OPERATIONS

 Both of the generating units at Conemaugh have coal-fired boilers. The plant uses 

approximately 650 tons of coal per hour (i.e., 15,600 tons per day) when operating at full 

capacity. The operation of these two coal-fired units generates wastewater. 
3

 The Conemaugh site visit focused on the generating units and the wastewaters 

associated with these units. For a general description of the steam electric power generation 

process, see Section 3.2.1 of the Interim Detailed Study Report for the Steam Electric Power 

Generating Point Source Category. A detailed description of the wastewater treatment systems 

is provided in Section 6.0 of this report. The remainder of this section describes the following 

seven process operations at Conemaugh: 

• Intake water; 

• Coal preparation; 

• Boiler operation (includes wet bottom ash handling); 

• Particulate control (includes dry fly ash handling); 

• FGD system operation; 

• Biofouling control; and 

• Ash disposal site. 

5.1 Intake Water 

 The plant withdraws water from the Conemaugh River for use in the steam 

electric generating process following treatment for metals removal. The plant first adjusts the 

pH using lime, and then sends the water to a clarifier where ferric chloride, sodium hypochlorite 

and polymer flocculant are added. The treated intake water overflows from the clarifier and is 

then used in the process, specifically for the two cooling systems, the FGD system, and rinsing 

the gypsum at the vacuum belts. Conemaugh also uses the intake water as make up to the ash 

recycle and fire water systems. 

 

5.2 Coal Preparation

 The Conemaugh plant uses eastern bituminous coal in its boilers. The coal comes 

from 15 to 20 different sources, located in the southern and central parts of Pennsylvania. Thirty 

percent (30%) of the plant’s coal supply is trucked in from local mines. The remaining 70% of 

the plant’s coal supply is brought in by train from both surface and deep mines in adjacent 

counties. 
4

 The plant has a coal storage pile on site that contains about a 45-day supply, 

which is approximately 600,000 tons of coal. Figure B-1, in Appendix B, presents a picture of 

the coal pile at Conemaugh. The storm water runoff that contacts the coal pile is collected in the 

coal pile runoff pond. The coal pile runoff pond is equipped with a single PVC liner. A newer 

pond with a double liner system collects contaminated stormwater that has come in contact with 

coal and ash in the areas around the power block (i.e. the precipitators). The newer pond has a 

double synthetic liner because of newer state regulations. The older coal pile pond was designed 

between pump and pond capacity to hold a 10 year 24 hour rain event. The newer pond 

(receiving stormwater from areas surrounding the power block) can hold a 10 year 24 hour event 

in the pond alone with no pump capacity needed. In the case of both ponds, the runoff collects 

and undergoes settling in the ponds until it is transferred to the equalization pond at the ash 

disposal site, discussed in Section 5.7. The pH of the stormwater transferred to the coal pile 

runoff pond varies depending on the length of time the water is in contact with the coal, but it is 

typically in the range of 2.0 to 7.0 S.U. The frequency and volume of the transfers to the 

equalization pond are dependent on the amount of rainfall. 

 For the two generating units, the plant transports the coal from the coal pile to 

individual unit bunkers by conveyor belts. From the bunkers, the coal is sent to the pulverizers, 

where it is ground into a fine powder that is blown into the boiler using air. 

5.3 Boiler Operation

 As the pulverized coal is blown into the boiler, it is combusted and gives off heat. 

The heat produced in the boiler is used to convert water into high-pressure steam. As the coal is 

combusted, solid, non-combustible constituents of the coal, referred to as ash, are generated. 

The heavy ash particles that collect on the bottom of the boiler are referred to as bottom ash. The 

finer particles that are light enough to be transferred out of the boiler with the flue gas exhaust 

are referred to as fly ash. At Conemaugh, a stream of sluice water collects and removes the 

bottom ash and other slag from the bottom of the boiler. The bottom ash sluice water is treated 

prior to discharge (see Section 6.2). In addition, Conemaugh occasionally cleans the fire-side of 

the boilers during major maintenance outages which are scheduled to occur at three year 

intervals. Conemaugh cleans the fire-side of the boiler by sand blasting and/or washing the 
5

boilers. The wastewater generated during the washing is treated in the same manner as the 

bottom ash sluice water (see Section 6.2). 

 

 The Conemaugh plant uses ion exchange resin to pretreat the water used in the 

boiler. The feed water to the ion exchange resin system comes from the local municipal water 

system. Occasionally, the plant has to regenerate the resin used in the system, which requires the 

use of a strong acid and strong base. Those acid/base wastes are treated in an elementary 

neutralization unit (ENU) prior to discharge. The wastewater from the ENU is commingled with 

the effluent from the FGD wastewater treatment system (discussed in Section 6.3) and 

discharged to the Conemaugh River. 

5.4 Particulate Control

 As described in Section 5.3, ash is generated during the coal combustion process 

and fly ash is transported out of the boiler with the flue gas. Conemaugh utilizes electrostatic 

precipitators (ESPs) to remove the fly ash from the flue gas emitted from Units 1 and 2. Prior to 

the flue gas entering the ESPs, the plant injects ammonia into the flue gas stream. The ammonia 

added to the flue gas improves the particulate removals in the ESP by agglomerating the particles 

together. By creating larger particles, it is more difficult for the particles to become re-entrained 

in the flue gas. The ESPs use high voltage to generate an electric charge on the particles 

contained in the flue gas. The charged particles then collect on a metal plate with an opposite 

electric charge. As the particles begin to layer on the metal plates, the plates are tapped/rapped 

to loosen the particles, which fall into a collection hopper. The plant collects approximately 55 

tons of fly ash per hour. 

 There is no wastewater generated from the operation of the ESPs. The fly ash 

collected from the ESPs is conveyed to silos for temporary storage. From the silos, the plant 

transports the fly ash to the ash disposal site, discussed in Section 5.7. 
6

5.5 FGD System

 The Conemaugh plant operates FGD systems on both Units 1 and 2 downstream 

of the ESPs to control the emission of sulfur dioxide from the units. Both systems are spray 

tower systems that use limestone as the sorbent. For a general description of the FGD process 

and the chemical reactions involved, see Section 3.2.1.6 of the Interim Detailed Study Report for 

the Steam Electric Power Generating Point Source Category. 

 Although the plant has two units with FGD systems, the plant actually has five 

FGD scrubber vessels, two for each unit and one redundant scrubber. The plant typically 

operates four of the five scrubbers at any one time. Each of the scrubbers is capable of handling 

approximately one-half of the flue gas stream from a unit. 

 The plant has a limestone storage pile on-site that has a capacity of 185,000 tons 

of limestone. Figure B-2, in Appendix B, presents a picture of the limestone pile at Conemaugh. 

The storm water runoff from the limestone pile is sent to the ash recycle system. The plant uses 

ball mills to crush the limestone on-site. The limestone is mixed with water from either the ash 

recycle or cooling water systems and sprayed into the FGD scrubbers. 

 The limestone slurry is sprayed downward within the scrubber towers through 

spray nozzles located at six spray levels in the tower. As the absorbent liquid is sprayed 

downward, the flue gas flows up through the tower and counter-current to the spray. Flue gas 

sulfur dioxide is absorbed onto the droplets of the absorbent. To increase the sulfur dioxide 

removal efficiency of the scrubber, the plant adds dibasic acid (DBA)1

 to the system, which 

buffers the solution and keeps it at the optimum pH. The pH in the scrubber changes with the 

height in the tower because as more sulfur dioxide is absorbed, the pH decreases. The pH of the 

slurry at the bottom of the scrubber is typically in the range of 5.5 and 5.7 S.U. The plant 

achieves a sulfur dioxide removal efficiency of 95 percent. According to the plant 

representative, the addition of the DBA allows the plant to achieve the same sulfur dioxide 

removal efficiency while operating with one less spray level. By using one less spray level, the 

 

1

 DBA is an aliphatic dibasic acid product containing primarily glutaric, succinic, and adipic acids. Organic acid 

additives, such as DBA, are used to improve scrubbing efficiency, improve reliability, and reduce operating costs of 

FGD systems. 
7

plant decreases its operating costs because not as many recycle pumps are required to recirculate 

the gypsum slurry. 

 All of the FGD scrubbers at Conemaugh introduce an air stream to oxidize the 

calcium sulfite product into calcium sulfate, known as gypsum, a more useful by-product. The 

gypsum slurry present at the bottom of the scrubbers is recycled back up to the various spray 

levels using pumps. A side stream of the scrubber slurry is pulled through multiclones and 

clarifiers to remove the gypsum. The resultant water is tested for chloride concentration. Water 

with a chloride concentration of less than 18,000 ppm is recycled back to the absorber. Water 

with a chloride concentration of 18,000 ppm and above is blown down to treatment. The plant 

representative estimated that the gypsum slurry is recirculated approximately seven or eight 

times before it is blown down. 

 The gypsum slurry blow down from the scrubber is sent to multiclones where the 

solid gypsum is separated from the FGD wastewater. The multiclones use centrifugal force for 

the separation process. The solid gypsum is forced outward to the wall of the multiclones and 

falls downward, while the supernatant wastewater exits the top of the system. The gypsum from 

the multiclones is transferred to a vacuum belt filter for cleaning and dewatering, while the 

wastewater is sent to a clarifier. The gypsum material leaving the multiclones is in the form of a 

slurry with approximately 55% solids. 

 The FGD clarifier settles more of the gypsum out of the wastewater. Figure B-3, 

in Appendix B, presents a picture of the FGD clarifier at Conemaugh. The solids removed from 

the clarifier are transferred to the vacuum belt filter and the wastewater overflow from the 

clarifier is sent to a holding tank. Within the holding tank, the plant checks the chlorides 

concentration of the wastewater. If the chlorides concentration is low (i.e., less than 20,000 

ppm) then the wastewater is recycled back to the scrubber, but if the chlorides concentration is 

high (i.e., around 20,000 ppm or greater) then the wastewater is sent to a surge tank for the FGD 

treatment system, discussed in Section 6.3. 

 The gypsum slurry from the multiclones and clarifier is transferred to the vacuum 

filter and poured upon the belt. The gypsum on the belt is washed with treated intake water to 
8

lower the chlorides concentration in the gypsum. Figure B-4, in Appendix B, presents a picture 

of the gypsum sludge being poured onto the vacuum belt. The vacuum filter extracts the water 

from the gypsum and creates a solid gypsum cake on the belt. All of the water removed from 

this system is recycled back to the scrubber. 

 At the end of the vacuum belt is a dry gypsum product that has a moisture content 

of 12 percent. Figure B-5, in Appendix B, presents a picture of the dry gypsum cake on the 

vacuum belt. The gypsum falls off of the belt and is conveyed to the gypsum dome for storage. 

The facility removes the gypsum from the dome and loads it on trucks for sale. The plant 

generates 700,000 tons of gypsum per year. At times, the gypsum is not marketable because of 

low purity; therefore, some gypsum material may be disposed at the ash disposal site, discussed 

in Section 5.7. 

5.6 Biofouling Control

 

 Both of the units at Conemaugh have recirculating cooling systems using 

hyperbolic cooling towers. The intake water for the cooling system is pretreated using chemical 

precipitation, as discussed in Section 5.1. The cooling tower blowdown from the systems is 

discharged directly to the Conemaugh River. 

 

 The Conemaugh plant uses sodium hypochlorite and sodium bromide for 

biofouling control. Conemaugh adds sodium hyposchlorite and sodium bromide concurrently 

during biofouling control and typically feeds them to the system six hours per day, six days a 

week. When the plant applies the biocide to the cooling system, the plant also discontinues its 

cooling tower blowdown discharge. Four hours after the application of the biocide, the plant 

measures the cooling water for free available and total residual chlorine. If the concentrations of 

both free and total residual chlorine are below the plant’s permit limits, then the plant will begin 

discharging cooling tower blowdown again. The plant typically discharges cooling tower 

blowdown approximately 14 hours/day, 6 days/week. 
9

5.7 Ash Disposal Site

 The Conemaugh plant has an ash disposal site located on approximately 400 acres 

of the property. As discussed previously, the fly ash from the ESPs and unmarketable gypsum 

are transported to the ash disposal site. In addition, the dewatered bottom ash collected from the 

boilers is disposed of at the site, as discussed in Section 6.2. The active portion of the ash 

disposal site is lined with a single PVC liner. The materials sent to the ash disposal site (i.e., ash 

and/or gypsum) are not removed or recycled once they are sent to the ash disposal site. Storm 

water that contacts the ash disposal site is collected in a 135-acre equalization pond located next 

to the site. The equalization pond is sized to contain back to back 10 year 24 hour rain events. 
10

6.0 WASTEWATER MANAGEMENT

 The Conemaugh plant has three wastewater management systems on site for the 

treatment of contaminated process wastewaters associated with the coal-fired power plant. This 

section discusses the following treatment systems at the plant: 

• Contaminated storm water treatment; 

• Bottom ash treatment; and 

• FGD wastewater treatment. 

 

6.1 Contaminated Storm Water Treatment System

 The contaminated storm water from the ash disposal site, coal pile runoff ponds, 

and other site storm water is treated using the Bethlehem process. Figure 6-1 presents a diagram 

of the contaminated storm water treatment system. Contaminated storm water collects in an 

equalization pond located at the ash disposal site, described in Section 5.7. Here, the plant 

adjusts the pH of the wastewater from 3 to 9 with pebbled lime. The wastewater is then sent to a 

series of mixing chambers for the addition of clarifier sludge and air. The wastewater is then 

sent to a clarifier for solids and metals removal. The sludge from the clarifier is placed in 

settling beds located within the leachate pond. The overflow from the clarifier is sent to the 

bottom ash treatment system, discussed in Section 6.2. This contaminated storm water treatment 

system treats both leachate collected from above the landfill liner system and contaminated 

stormwater runoff from the landfill surface. The plant design flow rate exceeds the combined 

influent flows; therefore, it does not operate continuously during the year. According to the 

plant representative, this treatment system operates approximately three out of five weeks. 

 

6.2 Bottom Ash Treatment System

 As discussed in Section 5.3, Conemaugh sluices the bottom ash and other slag 

from the bottom of the boiler. Figure 6-2 presents a diagram of the bottom ash treatment system. 

The sluice water from the boiler is sent to hydrobins where most of the solids are removed from 

the wastewater. The bottom ash removed from the hydrobins is transported to the ash disposal 

site described in Section 5.7. The wastewater leaving the hydrobins is sent to one of the three 

ash ponds. The bottom ash ponds also receive the treated wastewater from the contaminated 
11

storm water treatment system, as discussed in Section 6.1. The three ponds operate in a parallel 

fashion. Typically, only two of the ash ponds are operating at a given time, while the third pond 

is being cleaned and having the solids removed. The bottom ash sluice water entering the ash 

ponds is split to allow the wastewater to enter two of the ponds simultaneously. Figure B-6, in 

Appendix B, presents a picture of one of these ash ponds. Figure B-7, in Appendix B, presents a 

picture of a bottom ash pond not currently operating. When the ash ponds are cleaned, the solids 

removed are transported to the ash disposal site. 

Figure 6-1. Contaminated Storm Water Treatment System Diagram 

 As the wastewater flows through the ponds, the solids (ash) settle to the bottom of 

the ponds. When the wastewater reaches the other end of the pond, it is pumped to a holding 

pond. The holding pond is used to control the level of the three ash ponds. From the holding 

pond, the water is sent to a sump. Most of the water from the sump is recycled back to the 

boilers to be re-used as bottom ash sluice water; however, if more water is being sent through the 

system then is needed for recycle, the plant will pump some of the water from the sump to the 

cooling tower desilting pond. 

 The wastewater in the desilting pond may be recycled by the plant as make up 

water for the FGD scrubber. However, when the desilting pond begins to reach a level where it 

could overflow, then the plant will discharge some of the wastewater to the Conemaugh River. 

The amount of discharge from the desilting pond is dependent on the amount of rainfall the plant 
12

receives. If the plant receives a lot of rainfall, then it will need to operate the contaminated storm 

water treatment system, which will generate more wastewater in the ash ponds, and will likely 

lead to a discharge from the desilting pond. 

Figure 6-2. Bottom Ash Treatment System Diagram 

6.3 Flue Gas Desulfurization Wastewater Treatment System

 As discussed in Section 5.5, the FGD system generates a slurry that is dewatered, 

and the wastewater is collected in a surge tank prior to further treatment. Because the blowdown 

from the FGD is not continuous, the wastewater flow to the surge tanks is not continuous. 

Therefore, to operate the FGD wastewater treatment system on a continuous basis, the plant 

holds the FGD wastewater in the surge tank and continuously feeds the treatment system. Figure 

6-3 presents a flow diagram for the FGD wastewater treatment system. 
13

CONEMAUGH POWER PLANT - WWT FLOW DIAGRAM TREATING DBA

Surge Tank

FGDS Blowdown

IWT

Primary Clarifier

Secondary Clarifier SBR “A” S

“

Th

pH Adjustment Sump Clearwell

TDS Sump

FGD ThickenerChemical Cleaning

207/107

007

Hydrochloric Acid / Muriatic Acid

Hydrated Lime

Polyfloc AE1702Ferric Chloride

Sodium Sulfide

Polyfloc AE1702

Pressure Filters Backwash

Filter Presses

Filter Cake Ash Disposal Site

Dipotassium Defoaming A

Underflow

Underflow

Underflow

Chemical Additives

Outfalls

CONEMAUGH RIVER

Backwash

Figure 6-3. Flue Gas Desulfurization Treatment System Flow Diagram 
14

 The FGD wastewater from the surge tank is first sent to the industrial waste 

treatment (IWT) system at approximately 150 to 175 gallons per minute. At the IWT, the plant 

adds hydrated lime to increase the pH of the wastewater to approximately 8.6. From the IWT 

(pH adjustment), the plant sends the wastewater to the primary clarifier. Figure B-8, in 

Appendix B, present a picture of the influent to the primary clarifier. 

 

 The Conemaugh plant adds the following chemicals to the primary clarifier: ferric 

chloride and sodium sulfide, both for metals precipitation; and a polymer to aid in agglomeration 

and settling. The primary clarifier removes most of the solids and metals present in the 

wastewater. The overflow from the primary clarifier is sent to a secondary clarifier. The plant 

does not add chemicals to the wastewater in the secondary clarifier. 

 The sludge from the primary and secondary clarifiers is sent to a thickener to 

dewater the sludge. The underflow from the thickener is sent to a filter press for final 

dewatering. The filter cake generated by the press is transported to the ash disposal site, 

described in Section 5.7. The supernatant overflow from the thickener and the wastewater from 

the filter press are sent to a total dissolved solids (TDS) sump. The wastewater in the TDS sump 

is then recycled back to the IWT. 

 The plant sends the overflow from the secondary clarifier to a sump for additional 

pH adjustment prior to biological treatment. The plant uses carbon dioxide (CO2) to lower the 

pH from 8.6 to approximately 7.8. However, the plant representative stated that the use of CO2

for pH adjustment causes scaling problems in the equipment which requires occasionally 

cleaning with muriatic acid to remove the scaling. The plant tranfers the acid cleaning 

wastewater to the IWT for treatment. 

 

 From the pH adjustment sump, the wastewater is sent to one of two sequencing 

batch reactors (SBRs), which are fill-and-draw activated sludge treatment systems. Figure B-9, 

in Appendix B, presents a picture of the inside of the SBR while it is not operating. The plant 

biologically treats the wastewater to metabolize the DBA used in the FGD system to improve the 

sulfur dioxide removal efficiency. 
15

 The plant adds dipotassium phosphate to the SBRs as a nutrient for the bacteria. 

In addition, the plant adds a defoaming agent to prevent foaming in the aerobic reactor. The 

plant aerates the SBR for approximately 50 minutes. After the aeration period, the plant allows 

the sludge to settle to the bottom before decanting the wastewater off the top of the SBR. Each 

treatment batch takes approximately 3 hours. The sludge from the SBRs is sent to a thickener to 

dewater the sludge. From the thickener, the biological treatment sludge is transported to the ash 

disposal site. The wastewater overflow from the thickeners is sent to the IWT for treatment. 

 The decanted water from the SBR is sent to a clearwell, or holding tank. From 

the clearwell, the wastewater is sent through multimedia pressure filters. These filters serve as a 

polishing step for the final effluent from the treatment system prior to being discharged from the 

plant to the Conemaugh River. Figure B-10, in Appendix B, presents a picture of the discharge 

from the FGD wastewater treatment system. The final discharge from the FGD wastewater 

treatment system is approximately 0.28 MGD (195 gpm). The total residence time for the entire 

system is approximately 57 hours. The plant backwashes each of the filters once every three 

days. The wastewater generated from the backwashes is sent to the IWT. 

 According to the plant representative, the plant achieves a 50 to 55 percent 

removal of selenium from the system. The plant representative also stated that boron passes 

through the treatment system and is not removed. 

7.0 REFERENCES

1. U.S. EPA. 2006. Interim Detailed Study Report for the Steam Electric Power 

Generating Point Source Category. EPA-821-R-01-015. Washington, DC. 

November. DCN 01923. 
Appendix A 

LIST OF ATTENDEES 
A-1 

Table A-1. List of Attendees 

Name Organization (Representing) Telephone E-mRich Beer Reliant Energy Chet Sewalk Reliant Energy Sara Marie Baldi Reliant Energy (724) 597-8633 smbaldi@reDana Krach Pennsylvania DEP (412) 442-4202 Kristin Margut Pennsylvania DEP (8114) 472-1932 Kareen Milcic Pennsylvania DEP (412) 442-4033 Donna Hill Southern Company (205) 257-5234 dbhill@souLindy Johnson Tennessee Valley Authority (423) 751-3361 lpjohnson@Liz Aldridge Hunton & Williams (804) 788-8549 ealdridge@Mindy Gampel EPA/ Office of the Administrator (202) 564-1213 gampel.minRon Jordan EPA/Office of Water (202) 566-1003 jordan.ronaJosh Hall EPA/Office of Water (202) 566-1002 hall.josh@eJan Matuszko EPA/Office of Water (202) 566-1035 matuszko.jaAhmar Siddiqui EPA/Office of Water (202) 566-1044 siddiqui.ahmT.J. Finseth ERG (Contractor to EPA) (703) 633-1698 thomas.finsSarah Holman ERG (Contractor to EPA) (703) 633-1661 sarah.holma
Appendix B 

PICTURES FROM SITE VISIT
B-1 

Figure B-1. Coal Pile at Conemaugh 
B-2 

Figure B-2. Limestone Pile at Conemaugh
B-3 

Figure B-3. FGD Clarifier at Conemaugh 
B-4 

Figure B-4. Gypsum Sludge Entering the Vacuum Belt at Conemaugh 
B-5 

Figure B-5. Final Gypsum By-Product at Conemaugh 
B-6 

Figure B-6. Bottom Ash Pond at Conemaugh 
B-7 

Figure B-7. Bottom Ash Pond Not Operating at Conemaugh 
B-8 

Figure B-8. Influent to the Primary Clarifier at Conemaugh 
B-9 

Figure B-9. Inside of an Empty SBR at Conemaugh 
B-10 

Figure B-10. Discharge From the FGD Treatment System at Conemaugh