Final Notes from Site Visit at Constella tion Energy Generation Group’s Brandon Shores Power Plant on March 8, 2010

EPA conducted a site visit at Constellation Energy Generation Group’s Brandon Shores Power Plant (Brandon Shores) lo cated in Baltimore, MD on March 8, 2010 to learn about the operations at the plant, specifically th e flue gas desulfuriza tion (FGD) wastewater treatment system. These notes describe the in formation collected during the site visit. Table 1, located at the end of these notes, iden tifies the site visit participants. A process flow diagram for the FGD system (Attachment 1) and a process flow diagram for the FGD wastewater treatment system (Attachment 2) are provided as attachments to the

notes.

Plant Overview

 The Fort Smallwood Road Complex, owned by Constellation Energy and operated by Constellation Power Source Group (CPSG), cons ists of two co-located power plants:

 Brandon Shores Generating Station;

 Herbert A. Wagner Generating Station (4 units for a combined 1043 MWnominal);

o Unit 1: 133 MW - Fuel oil and natural gas;

o Unit 2: 136 MW - Eastern bituminous coal;

o Unit 3: 359 MW - Eastern bituminous coal;

o Unit 4: 415 MW - Fuel oil;

o Once through cooling;

o No FGD systems;

o NOx control: Low NOx burners opera ting on Units 2 & 3, SCR system on Unit 3 and SNCR system on Unit 2, both operated during ozone season;

o Particulate control: ESPs on Units 1, 2 & 3;

o Dry fly ash: trucked off-s ite and beneficially used or landfilled; and

o Wet bottom ash: Conveyed wet, dewatere d, then loaded from storage silos onto trucks for disposal.

 Brandon Shores consists of two coal-fire d generating units with a nominal power generation of 1,370 MW. The table below contains some general information for the two generating units.

Unit Installation

Date Capacity (MW) Particulate

Control NOx Control SO 2 Control 1 May 1984 685 Hot-side

ESP SCR operational May 2000 Wet FGD began operation December

2009 2 May 1991 685 Hot-side

ESP SCR operational May 2000 Wet FGD began operation February

2010Page 2

 Both units burn an eastern bituminous coal from approximately 5 different sources. The primary coal is central Appalachian coal. The chlorine content of the coal is less than 1 percent.

 Brandon Shores is testing a northern Appa lachian coal (2% su lfur content) and foreign coals. The plant is considering different coals fo r business reasons and boiler

needs.

 Brandon Shores keeps approximately 40 to 50 da ys of coal on site. Coal is delivered by barge.

 Both units operate hot-side ESPs which remove 99% of the fly ash.

 Brandon Shores injects Powdered Activat ed Carbon (PAC) downstream of the ESP and upstream of the FGD system for incr eased mercury removal. Brandon Shores installed a baghouse immediately downstream of the PAC addition to capture the mercury-impregnated PAC material. The sy stem is a pulse jet baghouse. The PAC material is collected in hoppers, conditioned and disposed of in an off-site landfill. This material is handled separately fro m the fly ash collected in the ESPs.

 Brandon Shores injects hydrated lime downs tream of the hot-side ESP and upstream

of the FGDs for sulfur trioxide removal. Th e presence of sulfur tr ioxide inhibits the Powdered Activated Carbon’s ability to remove Hg.

 The outfall of the existing wastewater treatment plant is MP601. The FGD wastewater treatment system has an intern al outfall (MP801). There is a combined NPDES outfall (001) which receives all the Brandon Shores wastew aters as well as wastewater from the four units at Wagner. Th is outfall discharges to saline (brackish)

water.

FGD System

 Both units operate limestone forced oxi dation wet FGD systems. A process flow diagram for the FGD system is included as an attachment 1. Both FGD systems have a dual flow tray/perforated plate.

 Brandon Shores receives its limestone vi a barge. The limestone is moved via conveyor and transferred to the on-site ball mills. Brandon Shores uses the ball mills

to crush the limestone and create the lim estone slurry used in the FGD system.

 Brandon Shores uses effluent from th e Anne Arundel County Cox Creek Water Reclamation Facility as the source for its FGD make-up water.

 The FGD systems can remove up to 98% of th e sulfur dioxide, but typically achieves

95% removal of sulfur dioxide.Page 3

 The FGD systems have a pH set point of between 5 and 6 S.U., depending on the operating conditions. The limestone slurry is used to maintain a pH of 5.85 S.U.

 At this time, the plant is maintaining the chlorides level in the FGD systems between 8,000 to 12,000 ppm.

 The plant blows down from the FGD system when the absorber reaches a density between 1.07 and 1.16, which at the time of the site visit, could be every day or every four days. The blowdown will last 4 to 12 hours depending on the size of the particles.

 The blowdown from the system is transfe rred to the primary hydrocyclones (one per unit with common spare). The underflow from the primary hydrocyclones is

transferred to the vacuum belt filer for dewatering. Brandon Shores washes the gypsum as it is applied to the belt to reduce the chlorides in the gypsum. Brandon Shores has several contracts to sell the gypsum.

 The plant can store some gypsum on site for a temporary period to wait for the market to need the gypsum. However, if a buyer cannot be found in a certain time frame, the gypsum is disposed in an off-site landf ill, which is owned by Constellation Energy.

 The filtrate from the vacuum belt filter s is transferred to the reclaim tank.

 The overflow from the primary hydrocyclones can be returned to the absorber or transferred to the secondary hydrocyclones (one per unit with common spare). The underflow from the secondary hydrocyclones is transferred to the reclaim tank, which

is returned to the absorber. The overfl ow from the secondary hydrocyclones is transferred to the purge tank and then pu mped to the FGD wastewater treatment
system.

FGD Wastewater Treatment System

 Brandon Shores operates the FGD wastewater treatment system 24 hours a day, 7 days a week.

 The secondary hydrocyclone overflow collected in the purge tank is transferred to the FGD wastewater treatment system.

 From the purge tank, the FGD wastewater is pumped to the equalization tank. Wastewater forwarding pumps then split the equalization tank effluent between two treatment trains. A block flow diagram for the treatment trains is included as

attachment 2.Page 4

 The temperature of the water coming into the equalization tank is approximately 112°F to 115°F; however, the filtrate water fr om the wastewater filtrate sumps is not

as warm and reduces the wastewater temperature to approximately 90°F.

 The primary flocculation clarifier can r eceive 600 of the 900 gpm. The clarifier removes the fines, which make up the bulk of the solids. The effluent from the clarifier is approximately 50-100 ppm TSS, which equates for approximately 95-98%

solids removal. The clarifie r underflow is transferred to the sludge holding tank.

Clarifier overflow is sent back to either the water reclaim ta nk (for reuse in the scrubber) or to the FGD wastew ater treatment equalization tank.

Physical/Chemical Treatment

 The FGD wastewater treatment system receives 300 of the 900 gpm. The system consists of a physical/chemical treatmen t train (which began operating in early December 2009) and three sequencing batch reactors.

 From the equalization tank, the wastewater is pumped to reaction tank 1, where the plant adds lime slurry (calcium oxide hydrate). The system can also add an organosulfide (TMT-15) at this point. The lime increases the pH to 8.6 to 9.2 S.U. Metal hydroxides are genera ted and precipitated.

 Water flows by gravity to reaction tank 2, wh ere Brandon Shores adds ferric chloride to the wastewater. Iron hydr oxides are generated and ot her metal hydroxides are coprecipitated.

 After leaving reaction tank 2, Brandon Shores adds a flocculating polymer to the stream, which is transferred to a solids c ontacting clarifier. So me of the underflow from the clarifier is recycl ed to reaction tank 1 to act as seed crystals to help precipitate out the solids. Depending on the blanket level, the remainder of the underflow sludge is transferre d to the sludge holding tank.

 The plant adds hydrochloric acid to the clarif ier overflow to adjust the pH to between 6 and 6.8 S.U., as it is being transferre d to the sequencing batch reactor (SBR) influent equalization tank.

 Brandon Shores adds the chemicals in the order described to maximize the amount of solids in the system prior to building floc. Additionally, bench scale tests showed that organosulfide was more effective when added prior to ferric chloride.

Sequencing Batch Reactors (SBR)

 The SBRs receive the physical/chemical tr eatment effluent and may also receive

overflow from the service tank or backwash reject off the tertiary sand filter for dilution and/or cooling. The optimal te mperature for the SBR is 75°F with aPage 5

maximum temperature of 95°F. The S BR’s also receive a carbon source addition with each batch cycle.

 In the SBR influent equalization tank, Br andon Shores adds sodium bisulfite. A defoaming agent can also be added if the plant starts noticing foaming in the SBRs.

 Sodium bisulfite eliminates free chlorine. The maximum chlorides concentration that can be handled by the SBR is 15,000 ppm. The TDS concentration is approximately 45,000 to 50,000 ppm.

 The system includes three SBRs, designed to operate two at a time each at 50% capacity in batch mode. The SBR tanks are not covered.

 The first step in the SBR process is the fill, feed, and aerate step. The wastewater is fed into the tank along with a carbon source and the water is aerated. During this process, nitrification occurs, where the mi croorganisms convert ammonia present into nitrates. In the second step of the SBR pr ocess, the aeration is stopped and the tank becomes anaerobic. During this proce ss, denitrification occurs, where the microorganisms convert the nitrates to nitrogen gas.

 The SBR system is designed to handle a maximum of 290 ppm total nitrogen and get to 4 ppm (not including TKN). The permit limit requires and annual net zero nitrogen load. Monitoring is conducted every week using a 24-hour composite at the influent and the internal outfall. The expected influe nt nitrogen concentra tion is composed of 60 to 70 ppm nitrates, less than 10 pp m TKN (primarily ammonia), and an insignificant concentration of nitrites. Phosphorus control is also required.

 After the wastewater is denitrified, the wastewater is settled and decanted. The decanted water goes to the SBR effluent equalization tank, which is shared by all

three SBRs.

 Some of the sludge from the SBRs is wa sted to the sludge ho lding tank (same one used for the solids contacting clarifiers in the physical/chemical portion of the treatment system). However, most of the sludge remains in the SBRs to retain the microorganisms in the system.

 After the SBR effluent equalization tank, Brandon Shores adds ferric chloride and polyaluminum chloride to the wastewater as it is being transferred to the continuous backwash gravity filters, as a polishing step. The filtered water is collected in the treated effluent storage tank a nd is then either recycled back to the equalization tank or transferred to the outfall for discharge.

 The effluent flow rate is not continuous. It depends on the purge, water source, limestone source, station load (varie s seasonally), scrubber performance and

turndown rate.Page 6

Solids Handling

 The sludge from the primary flocculati on clarifier, physical/chemical solids contacting clarifier, and the SBR underflow are collected in the sludge holding tank.

 The sludge is pumped through plate and fram e filter presses operated in batch mode.

 The filtrate is transferred back to th e equalization tank via the filtrate sump.

 The dewatered solids are hauled via dump trunk to an off-site landfill.Page 7Table 1. Site Visit AttendeesNameOrganization (Representing)TelephoneE-mailTerry Murphy Constellation Energy Generation Group (410) 787-6971 terry.murphy@constellation.comDavid MayConstellation Energy Generation Group(410) 787-6936david.l.may@constellation.comCatherine StewartConstellation Energy Generation Group(410) 787-5782catherine.stewart@constellation.comAmy HetheringtonConstellation Energy Generation Group(410) 787-9093amy.m.hetherington@constellation.comJim BalikConstellation Energy Generation Group(410) 787-6514james.balik@constellation.comGrace Counts-Smith Constellation Energy Generation Group (410) 787-5588grace.a.counts-smith@constellation.comEd MuchConstellation Energy Generation Group(410) 787-9073edwin.much@constellation.comJack KustererConstellation Energy Generation Group(410) 787-6928john.n.kusterer@constellation.comMark De VriesConstellation Energy Generation Group(410) 787-5443mark.a.devries@constellation.comHeather LentzConstellation Energy Generation Group(410) 917-3209heather.m.lentz@constellation.comBill KennedyOrion Engineering/Constellation EnergyGeneration Group(980) 721-7626b.kennedy@orionengr.comDonna HillSouthern Company/UWAG(205) 587-4846 dbhill@southernco.comJosh Hall EPA/Office of Water (202) 566-1002 hall.josh@epa.govRon Jordan EPA/Office of Water(202) 566-1003 jordan.ronald@epa.govDeb Bartram ERG (Contractor to EPA)(703) 633-1669 deborah.bartram@erg.comT.J. Finseth ERG (Contractor to EPA)(703) 633-1698 thomas.finseth@erg.comKavya Kasturi ERG (Contractor to EPA) (703) 633-1701 kavya.kasturi@erg.com