Draft Notes from Site Visit at Midwest Generation’s EME Homer City Generation Plant on August 22, 2012
EPA conducted a site visit at Midwest Generation’s EME Homer City Generation Plant (Homer City) located in Homer City, P ennsylvania on Wednesday, August 22, 2012 to learn about operations at the plant and discuss recent upgrades to the FGD and bottom ash systems. These notes describe the information collected during the site visit. Table 2 identifies the site visit participants.

Pla nt Overview

• Homer City operates three electric generating units, all of which are baseload coal

- fired units. The plant’s net generating capacity is 2,012 MW. The table below contains some general information on the current operation of each steam electri c generating unit.

Table 1

. Steam Electric Generating Unit Operations

SE Unit Fuel Net Capacity

(MW) Fly Ash Bottom Ash FGD Flue Gas Mercury Control

1 Coal: Bituminous 660 Dry Ash Handling

– Pressure System Wet Sluiced None None 1

2 Coal: Bituminous 660 Dry Ash Handling

– Pressure System Wet Sluiced None None 1

3 Coal: Bituminous 692 Dry Ash Handling

– Combined Vacuum/Pressure System Wet Sluiced Wet System None
1

– A dry activated carbon injection system , located upstream of the ESPs, was installed in January 2010 to service units 1 and 2. Plant personnel indicate that this system has not been operated since installation.

• Homer City is in the process of upgrading the wet

- bottom ash handling system on all three generating units to a tan k

- based system (i.e., no discharge of bottom ash transport water) . This upgrade is currently under construction and is planned to be completed by November 2012.

• Homer City is also in the process of installing two dry lime scrubber systems, one each on units 1 and 2. Thes e systems are being installed in anticipation of the pending Mercury and Air Toxics Standard (MATS) Rule. These systems are currently under construction with a planned start

- up date in 2014.

Fly Ash Handling System

• Homer City operates d ry fly ash handling systems on all three of its generating units. Units 1 and 2 utilize pressure systems while Unit 3 uses a combined vacuum and pressure system.

• Each unit t ransfers ash to one of three silos, each generating unit has a dedicated silo. Th e plant chose a one

- unit

- per

- silo method for ash collection to allow for the shortest transport time and simplicity. Each silo has the capacity to store roughly three days worth of fly ash.

• Fly ash from each silo is transferred to truck s using a pugmill to moisten the ash to approximately 12 percent moisture

. Homer City unload s the fly ash from Units 1 and 2 five days per week and fly ash from Unit 3 six days per week.

• Homer City either disposes of the fly ash at the ‘Coal Refuse Site’ o r the ‘Ash Disposal Site ’
, depending on whether the ash passes the toxicity characteristic leaching procedure ( TCLP ) analysis. Homer City conducts weekly samples of the ash, using a combination of fly ash from all three units. If the sample passes the TC LP analysis, than the ash can be disposed of at the

‘ Coal Refuse Site ’ , otherwise, the fly ash is disposed of at the ‘ Ash Disposal Site ’

.• Homer City personnel stated that t he loss of ignition ( LOI ) i n the fly ash is too high for the ash to be used by the c oncrete industry ; however, it can be used as structural fill, flowable fill, and for road construction.

• Homer City does not transport any of the fly ash using dry unloaders (i.e., without moistening the ash using a pugmill).

Bottom Ash Handling System

• Currently the bottom ash from all three units is wet sluiced to dewatering bins. The dewatered solids are sold as anti

- skid material or disposed of at the ’Coal Refuse Site’ . Overflow from the dewatering bins is transferred to a series of settling ponds. The effluent from these ponds is either reused in the bottom ash sluice system, used to moisten fly ash, or discharged.

• Homer City evaluated several options for achieving zero discharge of bottom ash sluice, including a mechanical drag system . The deter mined that the closed

- loop tank

- based system currently being installed provided the best solution for managing all of the various plant interferences associated with the bottom ash system.

• The new bottom ash system is planned to be operating by November 20 14. The new system will continue to use water to sluice the bottom ash from the boiler. The sluice will continue to be collected in the dewatering bins where the majority of the bottom ash will settle out and be sold as anti

- skid material or landfilled. The overflow from the dewatering bins will then be transferred to a set of settling tanks operating in parallel

. The underflow from the settling tanks will be sent back to the dewatering bins to remove the solids with the majority of the bottom ash. T he overflow will be routed to a set of surge tanks operated in parallel. Similar to the settling tanks, the underflow from the surge tanks will be sent back to the dewatering bins to remove the solids with the majority of the bottom ash. The overflow from th e surge tanks will be transferred to a clearwell and from there it will be recycled back as sluice water or used to moisten the fly ash. A process flow diagram of the new bottom ash system is included as Attachment 1 of this memorandum.

• The set of settling tanks and surge tanks are open topped tanks and were sized by United Conveyor Corporation (UCC) to include 100 percent redundancy (i.e., o ne settling tank and one surge tank would have been sufficient to handle the dewatering bin overflow for all three units)

. Once construction on the tanks is complete the plant will operate both the tank based system and the pond system until the new system can achieve equilibrium. At which point the bottom ash system is designed to require no discharge of wastew ater and the bottom ash sluice discharge to O utfall 005 will be sealed.

• Homer City expects that m ake

- up water will need to be added to the system to account for the water remaining in the bottom ash solid, evaporation, and water used to moisten the fly ash

. Homer City is planning to use stormwater from the area around the bottom ash system as part of the make

- up water for the syste m.

• Homer City does not anticipate any build up of constituents or scaling issues within the system and therefore

, has no plans t o add any chemicals to the system.

• Homer City made no other changes to the bottom ash sluicing system itself (e.g., no changes to the sluice pumps)

.

• Once the new bottom ash system is operating and the settling ponds are no longer needed, the ponds will b e closed. The space currently occupied by these ponds will be used for the new dry FGD systems.

Flue Gas Desulfurization (FGD) Systems

• Homer City is in the process of installing dry FGD scrubbers on Units 1 and 2. Both units are expected to be operating by 2014. These systems will be dry lime scrubbers and will include theaddition of activated carbon for increase d mercury removal. The plant plans to landfill solids produced by the dry FGD systems. These solids will undergo TCLP testing to determine which disposal site can be used for the solid disposal

. Homer City personnel believe that the dry FGD solids could potentially be used as a soil amendment because of its elevated pH.

• Homer City is currently operating a limestone forced oxidation FGD system on Unit 3.

• Homer City personnel indicated that DBA and formic acid w ere previously added to the wet FGD system to increase the sulfur dioxide removal of the system. Homer City det ermined that these additives were resulting in some of the selenium to be organically bound , which is more difficult to remove in the downstream wastewater treatment system. Homer City is no longer using DBA or formic acid in the wet FGD system.

• The c hlori de level in the wet FGD system is typically between 17,000 to 18,000 ppm.

• Blowdown from the FGD system is transferred to the primary hydro cy clone s for initial solids separation. The overflow can be transferred to the secondary hydro cy clone s or recycled back to the absorber. The underflow is transferred to the vacuum belt filter s

.

• From the secondary hydro cy clone, the overflow (i.e., FGD purge) is transferred to the FGD wastewater treatment system , while the underflow is transferred to the vacuum belt fil ters . The flow rate of th e FGD purge stream can range from 30 to 1 5 0 gpm depending on the dewatering cycle. The average flow rate of the FGD purge is 110 gpm

. [NOTE TO HOMER CITY: Please confirm these flow rates.] The typical solids concentration of the FGD purge is two percent (but it ranges from one to four percent ) . Underflow from the secondary hydro cy clone is transferred to the vacuum belt filter along with the underflow from the primary hydro cy clone.

• Homer City uses a vacuum belt filter to d ewater the gypsum. [QUESTION FOR HOMER CITY: To where is the filtrate from the vacuum belt filters transferred?]

• Dewatered gypsum from the vacuum belt filter is either transferred to the ’Coal Refuse Site’ or the ’Ash Disposal Site’ , depending on the resu lts of a TCLP analysis . Prior to 2008, Homer City was able to sell 100 percent of the gypsum to the wallboard industry. The influx of scrubbers and slow housing market has caused the demand for gypsum to decrease and the plant has been unable to sell gyp sum recently.

• Homer City has not conducted any studies on the oxidation reduction potential (ORP) within the scrubber and its effects on the FGD wastewater characteristics

. FGD Wastewater Treatment System

• The FGD purge is transferred to the wastewater trea tment feed tank. The water from the feed tank is then transferred to the first stage neutralization tank where 40 ppm ferric chloride and lime slurry a re added to adjust the pH to between 6.8 and 6.9 S.U . Homer City noted that historically it sees better selenium removal at a lower pH.

• From the first stage neutralization tank

, the wastewater is sent to the first stage clarifier. A n anionic polymer is injected inline as a coagulant. Overflow from the clarifier , which the plant adds 15 to 20 ppm of ferric chloride, is sent to the second stage neutralization tank

, while the underflow is transferred to a thickener

.

• In the second stage neutralization tank more lime slurry are added to adjust the pH to 7.0 S.U

. From the second stage neutralization the waste water is sent to the second stage clarifier, where more polymer is added.

• Homer City personnel noted that the second stage clarifier is operating with an effluent turbidity of 20 to 30 NTU, which is slightly higher than the normal level of 10 to 20 NTU

. The plant speculates the increased solids are due to chemicals (i.e., dispersants) used to treat the cooling
water to allow for additional cycling within the cooling towers . Cooling water is used as FGD make

- up and slurry and reagent preparation water.• H omer City maintains a sludge blanket of roughly 5 feet in the second stage clarifier to help remove the smaller finer particles. During the site visit the sludge blanket was approximately 2.5 feet thick. [ QUESTION FOR HOMER CITY: Was this smaller sludge blanket due to the increased solids in the clarifier?]

• The underflow from the second stage clarifier is combined with the underflow from the first stage clarifier and sent to the thickener. The overflow from the thickener is transferred back to the first

s tage neutralization tank. The thickened solids are dewatered by a vacuum drum filter and the solids are hauled to the ‘Ash Disposal Site’

. [QUESTION FOR HOMER CITY: To where is the vacuum drum filter filtrate transferred?]

• The o verflow from the second st age clarifier is sent to a pH adjustment tank , which was previously used to adjust the pH prior to the downstream biological treatment system. Homer City no longer operates the biological treatment system as the system was designed and therefore, Homer Cit y no longer adds any chemicals to the pH adjustment tank

.

• The wastewater is then bypassed around the existing heat exchanger and sent to the biological system, which consists of an aerobic biological reactor. This system was operated to remove the organic content in the wastewater added from the organic acids (i.e., DBA/formic acid) as well as the biochemical oxygen demand (BOD) present . Because Homer City no longer adds organic

ac id to the FGD system , th e biological system is not needed. Homer City still transfers the wastewater to the reactor and aerates the system

. Solids accumulated in the biological reactor are transferred to the thickener and handled with the clarifier solid s.

• Effluent from the biological reactor is transferred to sand filters and then onto the effluent tanks and discharged. Filter backwash from the sand filters is recycled back to the initial wastewater feed tank.

• Using the two stage chemical precipitation system, Homer City indicated that they are able to achieve over 90% removal of selenium (from 7 ppm to 0.5 ppm). For the most part only soluble selenium remains in the treated effluent.

• Homer City indicated that the mercury concentration in the treated FGD wastewater effluent is normally at non

- detect levels using EPA M ethod 245.1 [ QUESTION TO HOMER CITY: Please confirm the method used to test mercury in the treated FGD wastewater ? ]

• Homer City has not yet evaluated whether the treated FGD wastewater cou ld be used as make up for the dry FGD systems to eliminate the FGD discharge; however, Homer City personnel stated that there are concerns regarding times when Unit 3 is operating (which generates FGD wastewater) and Unit 1 and/or Unit 2 are not operating, in which case some or all of the FGD wastewater would need to be discharged because one or both of the dry FGD systems would not be operating.

Flue Gas Mercury Control (FGMC) Systems

• In January 2010, Homer City installed a dry upstream activated carbon injection system on Units 1 and 2. [ QUESTION FOR HOMER CITY: Why were these systems installed? What State requirement resulted in the installation of these systems? ] The plant has never operated either of these systems because the State requirement was not upheld.

• Homer City indicated that no changes were made to the ash handling system as a result of the added FGMC systems. The added solids resulting from the FGMC system would have been minimal

, resulting in no need for added storage space in the silos

.

• Homer City had expected that the f ly ash samples including the FGMC solids would have still passed the TCLP analysis and therefore, could have been disposed of at the ‘Ash Disposal Site’

.

• The dry lime scrubbers being installed on Units 1 and 2 will inclu de the injection of activated carbon to control mercury.Landfills and Leachate Treatment Systems

• Homer City operates three landfills. Two active landfills and one retired landfill. The active landfills are referred to as the ‘Ash Disposal Site’ and the ‘Coal Refuse Site’. The retired landfill is known as the ’ Strike Pile’.

• The ‘Ash Disposal Site’ receives fly ash, bottom ash, and calcium sulfate (gypsum), in addition to other plant solids. The ‘Coal Refuse Site’ also receives fly ash, bottom ash, and c alcium sulfate (gypsum), as well as coal refuse. The State of Pennsylvania has specific beneficial reuse practices that mandate what type of solids can be disposed of in refuse sites. If waste samples pass the TCLP analysis the plant disposes of the solids in the ‘Coal Refuse Site’ but if does not, the plant disposes of the solids in the ‘Ash Disposal Site’.

• The ‘Ash Disposal Site’ has an underdrain system to collect leachate. The leachate alone is sent to a leachate treatment system. Landfill runo ff from the ‘Ash Disposal Site’ is sent to a separate stormwater system.

• Leachate from the ‘Ash Disposal Site’ is piped directly to the leachate treatment system at a rate of roughly 180 gpm. There is no leachate collection pond or tank prior to the tre atment system. In the first step of the treatment system

, c austic is used to raise the pH to 8.9 S.U . The amount of caustic added is based on pH monitoring that occurs at the treatment system influent and effluent. In the second step of the treatment sys tem, the leachate is transferred to a flocculation tank where a gel polymer is added. The treated effluent is sent to one of two settling ponds. Both settling ponds discharge to a single polishing pond. Treated leachate from the polishing pond is discha rged via plant Outfall 004.

• The treatment system for leachate from the ‘Ash Disposal Site’ targets iron and magnesium. Recent permit amendments added new constituents to the limits to include arsenic, boron, nickel, and thallium. These additional limit s are water quality based limits. Homer City expects that additional treatment will be needed to meet the limits; however, the plant does not know how they will meet the limits.

• The ‘Coal Refuse Site’ is lined and includes a leachate collection system. Le achate from the landfill is sent to a separate leachate treatment system. Th is leachate treatment system also treat s stormwater from the ‘Coal Refuse Site’

. Homer City personnel stated that coal pile runoff is not treated in this treatment system ; the ‘C oal Refuse Site’ and coal pile are separate entities.

• Leachate from the ‘Coal Refuse Site’ is collected in a series of six ponds prior to entering the treatment systems. Leachate feeds by gravity from one pond to the next and is then pumped to the leachat e treatment system.

• The commingled leachate and stormwater from the ‘Coal Refuse Site’ are mixed with lime slurry. The target pH of the system is 8.5 S.U . Air is added to the system to encourage iron to oxidize and convert from the ferrous oxidation state (Fe 2+ ) to the ferric oxidation state (Fe 3+ ) . The aerated stream is sent to a clarifier where it is mixed with raw intake water. The oxidized iron, along with coagulants, help to precipit ate and settle any sediment s out of the intake wate r . The clear combined effluent is then used throughout the plant as make

- up water

.

• Homer City stated that leachate from both landfills are similar ; however

, the flows are treated in two different treatment systems. Homer City cited the final destination of each stream as the reason for the different treatment methods. Leachate from the ‘Coal Refuse Site’ is used to help treat the plant intake and then used as make

- up water for various processes within the plant

, while leachate from the ‘Ash Disposal Sit e’ is discharged. Additionally, the ‘Ash Disposal Site’ is larger than the ‘Coal Refuse Site’ and produces roughly twice as much leachate.

• The permit for the ‘Ash Disposal Site’ expires in 2013. Homer City has applied to expand the site both horizontal ly and vertical ly . The State of Pennsylvania requires that the expansion include a synthetic liner.• The ‘Strike Pile’ is the plant’s retired landfill. This landfill was only used for a 108

- day period during a labor strike at the plant. No new waste is bein g added to this landfill.Table 2 . Site Visit Attendees

Name Organization (Representing) Telephone E

- mail

Tom Wilson Homer City Power Plant (724) 479

- 6140 twilson@mwgen.com

Gary Cline Homer City Station (724) 479

- 6255 gcline@mwgen.com

Tom Suda Homer City Station (724) 479

- 6123 tsuda@mwgen.com

Joe Stanek Homer City Station (724) 479

- 6256 jstanek@mwgen.com

John DeMarines Homer City Station (724) 479

- 6237 jdemarines@mwgen.com

Bob Duey Homer City Station (724) 479

- 6145 bduey@mwgen.com

Jeff Lellock Homer City Station (724) 479

- 6247 jlellock@mwgen.com

Jim Beninati HDR Engineering (724) 497

- 6237 james.beninati@hdrinc.com

John VanGehuchten HDR Engineering (724) 497

- 6236 John.vangehuchten@hrdinc.com

Cassandra Shaw GE EFS (508) 596

- 9140 Cassandra1.shaw@ge.com

Donna Hill Southern Company (205) 257

- 5234 dbhill@southernco.com

Ron Jordan EPA/Office of Water (202) 566

- 1003 Jordan.ronald@epa.gov

Cuc Schroeder EPA/Office of Water (202) 566

- 2397 Schroeder.cuc@epa.gov

James Covington EPA/Office of Water (202) 566

- 1034 Covington.james@epa.gov

T.J. Finseth ERG (Contractor to EPA) (703) 633

- 1698 Thomas.finseth@erg.com

Danielle Lewis ERG (Contractor to EPA) (703) 633

- 1703 Danielle.lewis@erg.com