# 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 4-22i 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 Wa ter Treatment System ..................................................... 10 6.2 Bottom Ash Treatment System.............................................................................. 10 6.3 Flue Gas Desulfurization Wa stewater Treatment System ..................................... 12

7.0 References ................................................................................................................. ...... 15
Appendix A LIST OF ATTENDEES Appendix B PICTURES FROM SITE VISITii LIST OF TABLES
Page

A-1 List of Attendees................................................................................................. A-1iii 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 Treat ment 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 Treat ment System at Conemaugh ........................... B-101 1.0 S ITE V ISITED AND D ATE

Reliant Energy’s Conemaugh Power Plant 1442 Power Plant Road New Florence, PA 15944
February 5, 2007

2.0 A TTENDEES

Appendix A lists the attendees.

3.0 B ACKGROUND AND O BJECTIVES

Section 304(m) of the Clean Water Ac t (CWA) requires EPA to develop and publish a biennial plan that esta blishes a schedule for the annual review and revision of national effluent limitations guidelines and standards (E LGs) 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 to xic-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 co ntrols. Other potential s ources 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 fu rther review of these discharges during the 2007/2008 ELG planning cycle is warra nted. 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 t echnologies/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 ope rations and better un derstand the various wastewater sources present at steam electric plants . This review is expected to largely focus on ash handling wastes, wet flue gas desulfurizati on (FGD) wastes, coal p ile runoff, and final
effluent.

EPA and its contractor, Eastern Resear ch Group, Inc. (ERG), conducted a site visit to the Conemaugh Power Plant (Conemaug h), which is owned by a group of eight coowners and is operated by Reliant Energy, on Febr uary 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 P LANT D ESCRIPTION

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 plan t 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 P LANT O PERATIONS

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 th e generating units and the wastewaters associated with these units. For a general de scription 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 th e wastewater treatment systems is provided in Section 6.0 of this report. The remainder of this secti on describes the following seven process operations at Conemaugh:

• Intake water;

• Coal preparation;

• Boiler operation (includes wet bottom ash handling);

• Particulate control (inclu des 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 cl arifier where ferric chlo ride, sodium hypochlorite and polymer flocculant are added. The treated intake water overflows from the clarifier and is then used in the process, speci fically for the two cooling system s, 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 sout hern 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 br ought in by train from both surface and deep mines in adjacent
counties.4 The plant has a coal storage pile on s ite that contains a bout a 45-day supply, which is approximately 600,000 tons of coal. Figure B-1, in Appe ndix 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 sing le 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 re gulations. The older coal pile pond was designed between pump and pond capacity to hold a 10 y ear 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 tr ansferred to the equalization pond at the ash disposal site, discussed in Secti on 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 tran sports 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 bo iler, it is combusted and gives off heat. The heat produced in the boiler is used to convert water into high-pressure st eam. 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 transfer red out of the boiler with the flue gas exhaust are referred to as fly ash. At Conemaugh, a st ream 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 addi tion, Conemaugh occasionally cleans the fire-side of the boilers during major maintenance outages wh ich are scheduled to occur at three year intervals. Conemaugh cleans the fire-side of the boiler by sand blasting and/or washing the5 boilers. The wastewater genera ted during the washing is treate d in the same manner as the bottom ash sluice water (see Section 6.2).

The Conemaugh plant uses ion exchange re sin 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 ha s to regenerate the resin used in the system, which requires the use of a strong acid and strong ba se. Those acid/base wastes ar e treated in an elementary neutralization unit (ENU) prior to discharge. The wastewater from the ENU is commingled with
the effluent from the FGD wastewater treat ment system (discussed in Section 6.3) and discharged to the Conemaugh River.

5.4 Particulate Control

As described in Section 5.3, ash is gene rated 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 re movals in the ESP by aggl omerating 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 particle s then collect on a metal plate with an opposite electric charge. As the particles begin to laye r on the metal plates, th e 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 ge nerated 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 di sposal 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 emi ssion of sulfur dioxide from the units. Both systems are spray tower systems that use limestone as the sorbent. For a general descrip tion 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 se nt to the ash recycle system. The plant uses
ball mills to crush the limestone on-site. The lime stone is mixed with water from either the ash recycle or cooling water systems and sprayed into the FGD scrubbers.

The limestone slurry is sprayed downw ard within the scrubber towers through spray nozzles located at six spra y 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 scr ubber 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 sc rubber is typically in the rang e of 5.5 and 5.7 S.U. The plant achieves a sulfur dioxide removal efficiency of 95 percent. A ccording 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 e fficiency, improve reliability, and reduce operating costs of FGD systems.7 plant decreases its operating cost s because not as many recycle pum ps 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, kno wn as gypsum, a more useful by-product. The gypsum slurry present at the bottom of the scrubb ers 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 fo r 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 a bove is blown down to treatment. The plant representative estimated that th e gypsum slurry is recirculated approximately seven or eight
times before it is blown down.

The gypsum slurry blow down from the sc rubber is sent to multiclones where the solid gypsum is separated from the FGD wastewat er. 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 ex its the top of the system. The gypsum from
the multiclones is transferred to a vacuum be lt filter for cleaning and dewatering, while the
wastewater is sent to a clarifie r. The gypsum material leaving th e multiclones is in the form of a slurry with approximately 55% solids.

The FGD clarifier settles more of the gyps um 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 chlori des concentration is lo w (i.e., less than 20,000 ppm) then the wastewater is recycled back to th e scrubber, but if the ch lorides 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 tr eated intake water to8 lower the chlorides concentrati on 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, pres ents a picture of the dry gypsum cake on the vacuum belt. The gypsum falls off of the belt an d 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 ti mes, the gypsum is not marketable because of low purity; therefore, some gypsum material may be disposed at th e 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 th e cooling system is pretreated using chemical precipitation, as discussed in Section 5.1. The cooling towe r 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 hy poschlorite 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 th e biocide to the cooling system, the plant also discontinues its cooling tower blowdown discharge. Four hours after the applica tion of the biocide, the plant measures the cooling water for free available and to tal 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. Th e 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 th e ESPs and unmarketable gypsum are transported to the ash disposal site. In a ddition, the dewatered bottom ash collected from the boilers is disposed of at the site, as discu ssed in Section 6.2. The active portion of the ash disposal site is lined with a singl e PVC liner. The materials sent to the ash disposal site (i.e., ash and/or gypsum) are not removed or recycled once th ey are sent to the ash disposal site. Storm water that contacts the ash dispos al site is collected in a 135- acre equalization pond located next to the site. The equalization pond is sized to co ntain back to back 10 year 24 hour rain events.10 6.0 W ASTEWATER M ANAGEMENT

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 tr eatment 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 Be thlehem process. Figure 6-1 presents a diagram of the contaminated storm water treatment syst em. Contaminated storm water collects in an equalization pond located at the as h disposal site, described in Section 5.7. Here, the plant adjusts the pH of the wastewater from 3 to 9 with pebbled lime. The wastewat er is then sent to a series of mixing chambers for th e addition of clar ifier sludge and air. Th e wastewater is then
sent to a clarifier for solids and metals remova l. The sludge from the clarifier is placed in settling beds located within the leachate pond. Th e overflow from the clarifier is sent to the bottom ash treatment system, discussed in Sectio n 6.2. This contaminated storm water treatment system treats both leachate collect ed from above the landfill liner system and contaminated
stormwater runoff from the landfill surface. Th e plant design flow rate exceeds the combined influent flows; therefore, it does not operate continuously during the y ear. According to the plant representative, this treatment system ope rates 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 hydr obins where most of the solids are removed from
the wastewater. The bottom ash removed from th e hydrobins is transported to the ash disposal
site described in Section 5.7. Th e wastewater leaving the hydrobins is sent to one of the three ash ponds. The bottom ash ponds also receive the treated wastewater from the contaminated11 storm water treatment system, as discussed in Section 6.1. The three pond s operate in a parallel fashion. Typically, only two of the ash ponds ar e 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 ente r 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 operati ng. When the ash ponds are cleaned, the solids removed are transported to the ash disposal site.

Figure 6-1. Contaminated Storm Wat er 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 ot her end of the pond, it is pumped to a holding pond. The holding pond is used to control the leve l 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 wi ll pump some of the water from the sump to the cooling tower desilting pond.

The wastewater in the desilting pond ma y 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 depe ndent on the amount of ra infall the plant12 receives. If the plant receives a lot of rainfall, then it will need to operate the contaminated storm water treatment system, which w ill 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 pr ior 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 th e surge tank and conti nuously feeds the treatment system. Figure 6-3 presents a flow diagram for the FGD wastewater treatment system.13CONEMAUGH POWER PLANT - WWT FLOW DIAGRAM TREATING DBASurgeTankFGDSBlowdownIWTPrimaryClarifierSecondaryClarifierSBR“A”SBR“B”ThickenerpH AdjustmentSumpClearwellTDSSumpFGDThickenerChemicalCleaning207/107007Hydrochloric Acid/ Muriatic AcidHydratedLimePolyfloc AE1702Ferric ChlorideSodium SulfidePolyfloc AE1702Pressure FiltersBackwashFilterPressesFilter CakeAsh Disposal Site UnderflowDipotassium PhosphateDefoaming Agent Underflow

Underflow

Underflow

UnderflowChemical AdditivesOutfallsCONEMAUGH RIVERBackwashFigure 6-3. Flue Gas DesulfurizationTreatment System Flow Diagram14 The FGD wastewater from the surge tank is first sent to the industrial waste treatment (IWT) system at appr oximately 150 to 175 gallons per mi nute. At the IWT, the plant adds hydrated lime to increase the pH of the wa stewater to approximate ly 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 chem icals to the primary clarifier: ferric chloride and sodium sulfide, both for metals preci pitation; and a polymer to aid in agglomeration and settling. The primary clar ifier 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 wastewat er 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 thicke ner is sent to a filter press for final dewatering. The filter cake generated by the pre ss is transported to the ash disposal site, described in Section 5.7. The supe rnatant overflow from the thic kener and the wastewater from the filter press are sent to a total dissolved soli ds (TDS) sump. The wast ewater in the TDS sump is then recycled back to the IWT.

The plant sends the overflow from the sec ondary clarifier to a sump for additional pH adjustment prior to biological treatm ent. The plant uses carbon dioxide (CO 2 ) to lower the pH from 8.6 to approximately 7.8. However, the plant representative stat ed that the use of CO 2 for pH adjustment causes scaling problems in the equipment which requires occasionally cleaning with muriatic acid to remove the sc aling. The plant tranfers the acid cleaning
wastewater to the IWT for treatment.

From the pH adjustment sump, the wastew ater is sent to one of two sequencing batch reactors (SBRs), which are fill-and-draw ac tivated 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 th e SBRs as a nutrient for the bacteria. In addition, the plant adds a de foaming agent to prevent foaming in the aerobic reactor. The plant aerates the SBR for approximately 50 minutes . After the aeration pe riod, 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 sl udge from the SBRs is sent to a thickener to dewater the sludge. From the thickener, the biol ogical treatment sludge is transported to the ash disposal site. The wastewater ove rflow 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 multimed ia pressure filters. These filters serve as a polishing step for the final efflue nt from the treatment system prio r to being discharged from the plant to the Conemaugh River. Figure B-10, in A ppendix 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 gp m). The total residen ce time for the entire system is approximately 57 hours. The plant ba ckwashes each of the filters once every three days. The wastewater generated from th e 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 plan t representative also st ated that boron passes through the treatment system and is not removed.

7.0 R EFERENCES

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 ATTENDEESA-1Table A-1. List of AttendeesNameOrganization (Representing)TelephoneE-mailRich Beer Reliant EnergyChet Sewalk Reliant EnergySara Marie Baldi Reliant Energy(724) 597-8633 smbaldi@reliant.comDana Krach Pennsylvania DEP (412) 442-4202Kristin Margut Pennsylvania DEP (8114) 472-1932Kareen Milcic Pennsylvania DEP (412) 442-4033Donna Hill Southern Company (205) 257-5234 dbhill@southernco.comLindy Johnson Tennessee Valley Authority (423) 751-3361 lpjohnson@tva.govLiz AldridgeHunton & Williams(804) 788-8549 ealdridge@hunton.comMindy Gampel EPA/ Office of the Administrator (202) 564-1213 gampel.mindy@epa.govRon Jordan EPA/Office of Water(202) 566-1003 jordan.ronald@epa.govJosh Hall EPA/Office of Water (202) 566-1002 hall.josh@epa.govJan MatuszkoEPA/Office of Water(202) 566-1035 matuszko.jan@epa.govAhmar Siddiqui EPA/Office of Water(202) 566-1044 siddiqui.ahmar@epa.govT.J. Finseth ERG (Contractor to EPA) (703) 633-1698 thomas.finseth@erg.comSarah Holman ERG (Contractor to EPA) (703) 633-1661 sarah.holman@erg.comAppendix B

PICTURES FROM SITE VISITB-1 Figure B-1. Coal Pile at ConemaughB-2 Figure B-2. Limestone Pile at ConemaughB-3 Figure B-3. FGD Clar ifier at ConemaughB-4 Figure B-4. Gypsum Sludge Entering the Vacuum Belt at ConemaughB-5 Figure B-5. Final Gypsum By-Product at ConemaughB-6 Figure B-6. Bottom Ash Pond at ConemaughB-7 Figure B-7. Bottom Ash Pond Not Operating at ConemaughB-8 Figure B-8. Influent to the Pr imary Clarifier at ConemaughB-9 Figure B-9. Inside of an Empty SBR at ConemaughB-10 Figure B-10. Discharge From the FG D Treatment System at Conemaugh