Draft Notes from Site Visit at Constell ation 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 bituminuous coal;

o Unit 3: 359 MW - Eastern bituminuous coal;

o Unit 4: 415 MW - Fuel oil and natural gas) ;

o Once through cooling;

o No FGD systems;

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

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

o Dry fly ash: trucked off-site 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 2010 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 and conditioned and disposed of in an off-site landfill

. [ QUESTION FOR BRANDON SHORES: Ho w does the plant dispose of th e PAC material? ] 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 wast ewater treatment plant is MP 601. The FGD wastewater treatment system has an internal outfall ( Outfall MP 801). There is a combined NPDES outfall (001) which receives all the Brandon Shores wastewaters as well as wastewater from the three four units at Wagner. This outfall discharges to saline (brackish) water.

 Brandon Shores uses effluent from the Anne Arundel County Cox Creek Water Reclamation Facility as the source for its intake FGD make-up 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 Shores uses the ball mills to crush the limestone and create the limestone slurry used in the FGD system. The FGD systems can remove up to 98% of th e sulfur dioxide, but typically achieves 95% removal of sulfur dioxide.

 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 the pH of 5.85

.

 The FGD systems are still in the commissioning phase. Brandon Shores has been tuning the systems for three and a half months and expects that adjustments will continue for another three months.

 At this time, the plant is maintaining the chlorides level in the FGD systems between 10 8 ,000 to 1 2 0 ,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 ; however, not all of the gypsum is currently committed to contract

.

 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 landfill, which is not 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 900 gpm the equalization tank effluet between two treatment trains. A block flow diagram for the treatment trains is included as attachment 2.

 The temperature of the water coming in to the equalization tank is approximately 112°F to 115°F varies. The secondary hydro cy clone overflow temperature is approximately 112°F to 115°F

, ; however, but the filtrate water from the wastewater filtrate sumps is not as warm and reduces the wastewater temperature to approximately 90°F.

 The primary flocculation clarifier can receive s 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 (one of which is in the commissioni ng phase)

.

 From the equalization than tank , the wastewater is pum ped to reaction tank 1

, where Brandon shores adds for lime slurry (calcium oxide hydrate) addition. The system also can add an d organosulfide (TMT-15) at this point . The lime increases the pH to 8.6 to 9.2 S.U. Metal hydroxides ar e generated and precipitated.

 Water flows by gravity to reaction tank 2, where Brandon Shores adds ferric chloride is added to the wastewater. Iron hydroxides ar e generated and other metal hydroxides are co-precipitated.

 After leaving reaction tank 2, Brandon Shores adds a flocculating polymer is added to the stream, which is transferred to a solids contact ing clarifier. Some 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.

 Brandon Shores adds h H ydrochloric acid is added to the clarifier overflow

, to adjust the pH to between 6 and 6.8 S.U., as it is being transferred 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 were was more effective when added prior to ferric chloride.

Sequencing Batch Reactors

 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 if for dilution is needed and/or cooling . The optimal temperature for the SBR is 85 75 °F with a maximum temperature of 95°F. At the time of the site visit, Brandon Shores had not needed to use either of these streams to reduce th e temperature prior to the SBRs; therefore, t he physical/chemical treatment efflue nt makes up nearly 100% of the SBR influent. These d ilution water streams are sent to the sludge holding tank if not needed

. The SBR’s also receive a carbon s ource addition with each batch cycle.

 In the SBR influent equalization tank , Brandon Shores adds sodium bisulfite and a carbon source . 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 become s anaerobic. During this process, denitrification occurs, where the microorganisms convert the nitrates to nitrogen gas.

 The SBR system can is designed to handle a maximum of 290 ppm total nitrogen and is designed to 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 influent nitrogen concentration is composed of 60 to 70 ppm nitrates, less than 10 ppm TKN (primarily ammonia), and an insignificant concentr ation of nitrites. Phosphorus control may is also be required eventually

.

 After the wastewater is denitrified, the wastewater is settled and decanted. The decanted water goes to the S BR 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 contact ing clarifier s in the physical/che mical portion of thetreatment 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 can be added 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 efflue nt storage tank and is then either recycled back to the equalization tank or transferred to the outfall fo r 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.

Solids Handling

 The sludge from the primary flocculati on clarifier, physical/chemical solids
contact ing 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 the equalization tank via the filtrate sump

.

 The dewatered solids are hauled via dump trunk to an off-site landfill.Table 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