### Site Visit Notes: Duke Energy Carolinas’
Belews Creek Steam Stati on (March 12, 2008)

EPA conducted a site visit at Duke Ener gy Carolinas’ Belews Creek Steam Station located in Belews Creek, NC on Wednesd ay, March 12, 2008 to learn about the operations at the plant, specifically the F GD wastewater treatment system. Table 1,
located at the end of th is summary, identifies the site visit participants.

This summary describes the information collect ed during the site visit and the pre-site visit phone call, which was held on February 1, 2008.

Plant Overview

• Belews Creek operates two generating units at the power plant. It is a baseload plant with a total generating capacity of 2,400 MW The table below contains some general information for each unit.

Unit Installation
Date Capacity (MW) Particulate
Control NOx Control SO 2 Control 1 1974 1,200 Cold-side
ESP SCR installed
8/2003 Wet FGD – 2/2008

2 1975 1,200 Cold-side
ESP SCR installed
2/2004 Wet FGD – 5/2008

• Both Units 1 and 2 have cold-side ESPs, which achieve approximately 99.9 percent removal of fly as h and other particulates.

• The SCRs have been operati ng year-round since January 1, 2007.

• Belews Creek began operating a we t limestone forced oxidation FGD scrubber on Unit 1 in February 2008. Belews will begin operating a wet
limestone forced oxidation FGD scr ubber on Unit 2 in early May 2008. The plant currently receives four 60-car trains of limestone each month.

• Belews Creek burns eastern bituminous coal in both units. Belews Creek burns approximately 19,000 tons of coal per day and receives two 100-car trains each day. Belews Creek stores approximately a 30-day supply of
coal on site.

• Belews Creek is located adjacent to Belews Lake, which is approximately 3,863 acres with 88 miles of shore line. Belews Creek owns 7,000 acres adjacent to the lake. The plant operates once-through cooling systems for each unit and withdraws approximately one million gallons of water from the lake per minute. The plant discha rges the cooling water back to the Belews Lake after it passes through the condensers.Page 2 • Belews Creek has 180 employees.

Ash Handling

• Belews Creek stated that they have th e capability to sluice the fly ash with a wet system, but the plant primarily uses a dry fly ash handling system. Belews Creek stated that they onl y occasionally use the wet fly ash handling system, and when it is used, th e fly ash sluice water is transferred
to the ash basin.

• Belews Creek stated that they convert ed to a dry fly ash handling system because of selenium toxicity issues in Belews Lake which were identified in 1976. In addition to converting the fly ash system, the plant rerouted the discharge point for bottom ash wastewater from Belews Lake to the
Dan River.

• The fly ash collected by the ESPs is transferred to silos for temporary storage and then trucked to an on-site fly ash landfill. The fly ash landfill is also permitted to receive solid waste from the FGD wastewater treatment plant.

• Belews Creek handles the bottom ash using a wet sluicing system.

• Belews Creek stated that they have a mesh screen to segregate the bottom
ash solids from the ash sluice water prior to entering the ash basin. Belews Creek described the mesh screen operation as similar to a vibrating sieve, and that the plant is classifying the bottom ash into different size particles.

• The ash basin also receives the e ffluent from the FGD wastewater
treatment system; storm water runo ff from fields surrounding the plant; coal pile runoff; runoff from the fly ash landfill, gypsum landfill, and limestone handling area; and effluent from the sewage treatment lagoon.

• The ash basin discharges to the Dan River.

FGD Scrubber

• Belews Creek uses ball mills to crush limestone to make limestone slurry
which is used as the so rbent in the scrubber.

• Each of the scrubbers is designed with four recirculation pumps and four spray levels. In Unit 1, the plant has been achieving a 95 percent removal
of SO 2 using only three of the spray leve ls; therefore, the plant is only operating three spray levels. Belews Cr eek alternates the spray levels that are used to keep all of the pumps operating.Page 3 • Belews Creek stated that it took so me time before they started sending
wastewater from the FGD scrubbers to the FGD wastewater treatment system because they had to cycle the FGD slurry in the system to build up the solids. The plant operates the scrubber at approxima tely 15% solids.

• Belews Creek stated that the desi gn maximum chlorides level in the scrubbers is 12,000 ppm. Belews Creek stated that they are operating the system between 8,000 and 10,000 ppm.

• Belews Creek stated that the design co al for the plant has a sulfur content
of 2.4 lbs SO 2 /MBTU. The percent sulfur of the coal is 1.5 percent.

• Belews Creek stated that they will have the capability to add DBA to the FGD scrubbers, but they have no plans of using DBA in the near future, other than for performance testing, wh ich will be conducted in July 2008. The plant does not plan to use DBA fo r 2009 because it is not currently in their budget.

• Belews Creek stated that the de sign purge flow rate to the FGD wastewater treatment system is 600 gpm (300 gpm for each unit), but Belews Creek is estimating that th e flow will be approximately 350 gpm (for both units combined). On average, Belews Creek now estimates the purge flow rate is between 400 and 450 gpm during operation.

• Belews Creek operates a two-stage h ydroclone system to dewater the gypsum prior to sending it to vacuum filter belts for final dewatering. The
blowdown from the scrubbers is sent di rectly to the primary hydroclones. The underflow from the primary hydroclone s is sent to the filter feed tank,
which is then transferred to the vacuum filter belts. The overflow from the primary hydroclones is sent to a hold ing tank and then to the secondary hydroclones. The underflow from the secondary hydroclones is returned
to the scrubber or sent to the filter feed tank. The filter feed tank forwards the underflow to vacuum filter belts for dewater the gypsum. The overflow from the secondary hydroclone s is sent to the purge tank and then to the FGD wastewater treatment system.

• Belews Creek washes the gypsum with se rvice water as it is applied to the
vacuum filter belts. The vacuum filter belts dry the gypsum to approximately 10 percent moisture.

• Belews Creek transfers the dry gyps um to an uncovered gypsum storage
area. Belews Creek then trucks th e gypsum to a wallboard manufacturer in Mount Holly, NC.

• Belews Creek has a lined landfill for disposal of off-spec gypsum, or for gypsum the wallboard manufact urer does not want.Page 4 • Belews Creek is expecting to produce approximately 250,000 tons of gypsum during 2008. Note that neither of the scrubbers will have been operating for the entire 2008 calendar year.

FGD Wastewater Treatment System

• The FGD wastewater treatment system at Belews Creek consists of three processes: physical/chemical se paration (hydroxide and sulfide precipitation), biological treatm ent, and constructed wetlands.

• [CBI information has been removed from this document.]

• The FGD wastewater treatment system at Belews Creek starts with the physical/chemical separati on. Figure 1, at the en d of this memorandum, presents a process flow diagram for the physical/chemical separation portion of the wastewater treatment system.

• The secondary hydroclone overflow from the scrubbers is transferred to a purge tank and sent to th e equalization tank at the start of the wastewater treatment system. Belews Creek stat ed that the equalization tank also receives water from the filtrate sump (which includes filter press filtrate), gravity filter backwash reject, backflush waste from the biological treatment system, and off-specifica tion biological treatment effluent.

• From the equalization tank, the wastewat er enters three reaction tanks in series: reaction tank 1 in which lime is added to increase the pH to between 8.5 and 9.2 (target 8.8); reaction tank 2 in which organosulfide is added; and reaction tank 3 in which fe rric chloride is added. A portion of the clarifier sludge is also recycled to reaction tank 1. The wastewater flows from reaction tank 3 to a mix chamber where polymer is added.

• From the mix chamber, the wastewater is split and enters two clarifiers in parallel. The clarifiers are solids co ntact clarifiers th at contain a sludge
bed which attracts the solids in the wastewater. Each of the clarifiers is capable of handling 100 percent of the waste stream capacity. The
overflow from the clarifie rs is split and sent through three sand filters in parallel. Each of the sand filters can handle 75 percent of the waste stream capacity. From the sand filters the wa stewater enters a feed tank where hydrochloric acid is added to reduce the pH prior to the biological treatment system. The target maximum TSS level for the sand filter effluent is 50 ppm; however, the plan ts tries to keep TSS below 20 ppm.
The sand filters are continuous back wash gravity filters. The filter backwash is sent to a sump, then transferred to the equalization tank.

• The sludge from the clarifiers is tran sferred to a sludge tank and then to a filter press for dewatering. Belews Creek achieves a solids concentration of 15 percent in the sludge tank, wh ich is higher than the designed percentage, because it forms a better cak e in the press. The filter pressPage 5 cake is landfilled in the fly ash landfill and the filtrate is sent to the filtrate sump. Each filter press operati on produces 28,000-30,000 lbs of filter cake. When both FGDs are fully operating, Belews Creek anticipates there will be 10 filter press operations per week. Currently, there are approximately 5 filter press operations per day.

• The biological treatment system consis ts of 16 biological cells, shown in Figure 2, at the end of this memorandum. Belews Creek treats the wastewater in two stages. Each st age contains eight biological cells operated in parallel. Each cell contai ns an activated carbon bed. Within the activated carbon bed, specialized microbes fill the voided areas to reduce the nitrogen and metals, specifi cally selenium, in the wastewater.

• The wastewater from the sand filters is transferred to a holding tank prior to entering a heat exchanger to reduce the temperature to 95 o F. Belews Creek adds nutrients (molasses-based) to the wastewater as it flows from the heat exchanger to the biological system. The nutrients provide a
source of carbon to feed the bacteria. The wastewater is divided evenly among the eight first stage cells. The flow to each cell is sent to 16 distribution pipes to create an even distribution of flow into the top of the
cell. The water level in the cells is approximate ly three feet above the
activated carbon bed.

• [CBI information has been removed from this document.]

• Because the first stage bi oreactor cells denitrify the waste stream, they produce nitrogen and carbon dioxide gas. To remove the gas from the cells, the plant occasionally performs a degassing operation where water is sent backwards through the cells, like a backflush, but the flush is only long enough for the gas to “burp” out of the system.

• The effluent from the first stage bioreactor cells is transferred to the first stage effluent storage area. The efflue nt from all eight first stage cells is commingled in the storage area. The wa stewater is then transferred to the second stage of eight parallel cells. Nu trients are added to the wastewater
as feed for the microbes as the wastewat er is transferred. As in the first stage, the wastewater is divided ev enly among the eight second stage cells and each cell has 16 distributor pipes to evenly distribute the flow into the
cell.

• The second stage bioreactor cells are primarily anoxic and therefore do not produce as much gas as the first st age cells. The second stage cells remove the metals remaining in the wastewater.

• Occasionally the bioreactor cells will need to be backflushed to remove the solids that have built up in the system. Belews Creek will send service water backwards through each cell, st arting at the bottom and pushing the solids upward. The cells have a spi ll over area to collect the backflushPage 6 water which is then sent to the equalization tank at the start of the FGD
wastewater treatment system.

• From the second stage of the biological treatment system, the wastewater enters the wetland supply tank, where cooling water is added to the wastewater to reduce the temperatur e and chlorides level. The plant dilutes the wastewater with the cooling water from the heat exchanger prior to the biological system at a ra tio of 1:1, but they can increase to a 2:1 ratio (cooling water: FGD wastewater) to keep the chlorides level around 4,000 ppm. From the wetlands supply tank, the wastewater enters the constructed wetland system. Figur e 3, at the end of the memorandum, presents a simplified process flow diagram of the constructed wetlands
treatment system.

• The first stage of the constructed we tlands consists of two equalization tanks which allow further cooling of the wastewater. The wastewater is then split to enter two identical constructed wetland treatment trains in parallel. The first and second cell of each train (1A, 1B, 2A, 2B) contain
bulrush. The wastewater then flow s over cascading rocks (3A, 3B) and enters the third cell containing cattails (4A, 4B). After the cattail cell, the
wastewater flows over another cascad e of rocks (5A, 5B) and then the
wastewater from the two trains are commingled and discharged to the ash
basin.

• Each of the constructed wetlands ce lls has a geosynthetic clay liner.

• The first two constructed wetland ce lls provide a reduced environment
with anoxic conditions which allow fo r removal of selenium and mercury.

• In fall of 2006, Belews Creek planted th e plants in the constructed wetland cells, but the plants did not take. Th erefore, Belews Creek replanted the cells. Belews Creek is looking to repl ant the cells again soon because the plants are still not taking in the cells.

• Belews Creek stated that they ar e having issues planting the bulrush because the plants will not spread throughout the cell. The plant is considering adding cattails to the first and second cells because they have
had better luck with the cattails. Bele ws Creek stated that if they do plant cattails in the cells, then the cattails w ill probably take over the entire cell pushing out the bulrush. Belews Creek stated that this should not make much difference because the main purpose of the plants is to produce organic matter.

• Each constructed wetland cell is ap proximately 2.5 acres and Belews Creek planted 13,000 plants in each of the cells. The plants prevent the wastewater from channeling through th e cells, provide organic material, and also provide oxygen to the wastewat er. Belews Creek stated that it will take several years for the cells to reach full maturity.Page 7 • Belews Creek estimated the retention time for the constructed wetland system is six to seven days.

• Belews Creek stated that the redox potential in the constructed wetland cells is controlled by the water level. The higher the water level in the cells, the more anoxic the conditions. Belews Creek controls the water level by adding or removing wooden pl anks to the overflow weir. The water level in the cells is appr oximately 12 to 15 inches deep.

• Belews Creek stated that they do not expect the mercury in the wastewater to convert to methylmercury because the mercury is present at such low concentrations. Belews Creek will not be monitoring the constructed wetlands effluent for methylmercury.

• Belews Creek stated that they ar e achieving good removals of mercury from the constructed wetlands, but the selenium removals have not been as good as they expected.

• Belews Creek stated that there is not much nitrogen reduction in the
constructed wetlands because most of the nitrogen reduction is accomplished in the biological system.

• Belews Creek does not have limits for metals from the constructed
wetlands because it is an internal outfall.

• Belews Creek stated that they decide d to have an extensive wastewater treatment system because the plant want ed to reach the selenium limit of 26 ppb for the ash basin effluent prior to the wastewater entering the ash
basin at the end of the constructed wetland system. Belews Creek stated
that took a conservative approach and the system ensures that they will
meet the limit.

• Effluent from the constructed wetlan ds is sent to the ash pond where it joins with other wastestreams (appr oximately 5:1 dilution of the FGD wastewater occurs here, in addition to the dilution water added at the wetlands supply tanks). The ash pond di scharges to the Dan River (outfall 003).

FGD Wastewater Treatment Data

• Belews Creek stated that they have NPDES monitoring locations at the end of the constructed wetlands syst em and the discharge from the ash
basin. Belews Creek stated that they are required by their permit to
monitor for 10 metals at these locations.

• Belews Creek is also currently coll ecting wastewater samples from the following sample points:Page 8 o FGD purge;

o Equalization tank effluent;

o FGD clarifier influent;

o FGD clarifier effluent;

o Gravity filter effluent/influent to bioreactors;

o First stage bioreactor effluent;

o Second stage bioreact or effluent; and

o Constructed wetland effluent.

• Since the time of the site visit, Belews Creek reports that samples are now being collected within th e wetland treatment system.

• Belews Creek stated that they also pl an to begin collecting samples of the
influent to the constructed wetlands and the effluent from each of the
individual cells.

• Belews Creek has been analyzing th e samples collected from the above sample points for the following analytes:

o Alkalinity;

o Chloride;

o Ammonia;

o Nitrate/nitrite;

o Total phosphorus;

o TSS;

o Oil and Grease;

o Total Metals (Hg, B, As, Ag, Cd, Cr , Ni, Se (total and dissolved), and Zn); and

o Selenium speciation (selenite and selenate).

• The total metals samples have been analyzed using the 200-series methods
and not the 1600-series low-level methods . Belews Creek plans to collect these samples daily for three to six months and then reevaluate sampling frequency.

• Belews Creek stated that monito ring results have shown the FGD wastewater treatment system is not removing chlorides or boron.

• Belews Creek stated that the perfor mance testing for the system will be conducted in July 2008.

FGD Wastewater Treatment Cost Information

• Belews Creek stated that the treatment vendors are sensitiv e about the cost information associated with their systems because of the competing
vendors. Belews Creek stated that th e costs of their systems will not be finalized until September 2008.Page 9 • EPA stated that all information can be handled as confidential business
information if Belews Creek would like . EPA also stated that they would appreciate if Belews Creek could sepa rate the cost of the FGD wastewater treatment system into the physic al/chemical portion, the ABMet® biological treatment portion, and the constructed wetlands portion. In addition, EPA stated that Belews Creek does not need to provide the final cost values, estimates of the total cost will be sufficient.

• Belews Creek stated that they will co llect the cost information for EPA but
it will be claimed as Confidential Business Information.Table 1. Site Visit AttendeesNameOrganization (Representing)TelephoneE-mailJon Arterburn Duke Energy (704)382-0966 jrarterburn@duke-energy.comJeff Blackwood Duke Energy (336)445-0504 jkblackw@duke-energy.comBill Kennedy Duke Energy (980) 721-7626 wkennedy@duke-energy.comMelonie Martin Duke Energy (336)445-0610 mymartin@duke-energy.comDebbie Nispel Duke Energy (317)838-1957 dnispel@duke-energy.comJay Perkins Duke Energy (704)875-5348 jperkins@duke-energy.comShannon Todd Duke Energy (336) 445-0428 stodd@duke-energy.comRobert Wylie Duke Energy (704) 382-4669 rrwylie@duke-energy.comDonna Hill Southern Company (205) 257-5234 dbhill@southernco.comKarrie-Jo Shell EPA/Region 4 (404)562-9308 shell.karrie-jo@epa.govJosh Hall EPA/Office of Water (202) 566-1002 hall.josh@epa.govRon Jordan EPA/Office of Water(202) 566-1003 jordan.ronald@epa.govT.J. Finseth ERG (Contractor to EPA) (703) 994-7130 thomas.finseth@erg.comPage 11Figure 1. Process Flow Diagram for Physical/Chemical Separation Portion of FGD Wastewater Treatment SystemFGDPurgeEQ TankLimeLandfillSludgeTankBioReactorsSand FilterClarifierFilterPressSulfideFerricPolymerAcidPage 12Figure 2. Process Flow Diagram for BiologicalPortion of FGD Wastewater Treatment SystemSand filterEffluentFirstStageSecondStageCooling WaterCooling WaterWetlandSupplyTankCWTSFirstStageRecycleSecondStageRecycleNutrientNutrientPage 13Figure 3. Process Flow Diagram for Constructed Wetland Portion of FGD Wastewater Treatment SystemEQ AEQ B1B 2B 3B 4B 5B1A 2A 3A 4A 5A002WetlandSupplyTankAshPond