### Site Visit Notes: Progress Energy Carolinas’ Roxboro Steam Electric Plant (March 11, 2008)

EPA conducted a site visit at Progress Energy Ca rolinas’ Roxboro Steam Electric Plant located in Semora, NC on Tuesday, March 11, 2008 to l earn about the operations at the plant, specifically the FGD wastewater tr eatment system. Table 1, located at the end of this summary, identifies the site visit participants.

This summary describes the information collected during the site visit and the pre-site visit phone call, which was held on February 5, 2008.

Plant Overview

• Roxboro operates four generating units at the power plant. It is a baseload plant, generating a total of 2,557 MW. The table below contains some general information about the units.

Unit Installation Date Capacity (MW) Particulate Control NOx Control SO 2 Control 1 1966 410 Cold-side ESP SCR; lowNOx burner Wet FGD planned for 12/2008 2 1968 657 Cold-side ESP SCR; lowNOx burner Wet FGD – 4/2007

3 1973 745 Cold-side ESP SCR; lowNOx burner Wet FGD planned for 5/2008 4 1980 745 Hot-side ESP SCR; lowNOx burner Wet FGD – 12/2007

• The North Carolina Power Agency owns 16.7% of Unit 4.

• In 1995, Roxboro began working on an upgrade to the boilers to install low-NOx burners to reduce the amount of NOx gene rated in the boilers. According to Roxboro personnel, this installation resu lted in a 50 – 65% reduction in NOx.

• In 2001, Roxboro began installing SCRs to all four units. The final SCR began operating in 2005. According to Roxbor o personnel, the SCR installation achieves an additional 80 – 90% reducti on in NOx. The SCRs are scheduled to operate year-round.

• Roxboro burns eastern bituminous coal in all four units. Roxboro stated that they are currently burning coal with a sulfur content of 1.6 to 2.0 lbs sulfur/MBTU (0.69-1.11 percent sulfur). Roxboro stated th at they plan to in crease the sulfur content of the coal as the scrubbers c ontinue to operate and as they bring additional scrubbers on line. Roxboro st ated they are evaluating the optimum sulfur content that can be used in the boilers. Roxboro noted that there can beslag issues in the boiler when burning higher sulfur coal. Roxboro is currently only increasing the sulfur cont en t of the coa l f o r Unit 4.

• Roxboro stated that they burn approx im ately 6 to 7 m illion to ns of coal per year. Roxboro stores a 35-day supply of coal on site for units 1, 2, and 3, and a 28-day supply of coal for Unit 4.

• Coal pile runoff is collected in a se ttling pond and the overf low from the pond is discharged directly to Hyco Lake.

• Units 1 and 2 have once-through cooling sy stem s that withdraw and discharge to Hyco Lake. Unit 3 has a once-through and a cooling tower system . However, the Unit 3 cooling tower is a once-through cooling tower (help e r tower) th at is operated seasonally (May 1 – October 15) . The plant operates the Unit 3 oncethrough cooling system for the rest of the year. Unit 4 has a recirculated cooling tower system that is operated year round.

• Roxboro has 255 em ployees.

Ash Handling

• Roxboro stated that they have the capability to handle fly ash with a wet system

, but they predom inantly operate a dry fl y ash handling system (about 95% of the tim e). W h en the plan t u s es the wet s l uice system , they typ i ca lly ope rate it f o r less than a day ; however, if there is an extended m a intenance outage, they could operate it for a week. When the wet fly ash handling system is used, the sluice water is transferre d to the ash pond.

• Roxboro stated that they converted to a dry fly ash handling system in the 1980s because the fly ash sluice was causin g sele n i um t oxicity issu es in Hyco Lake. Roxboro stated that they are still m o nito ring the selenium levels in the lake. Roxboro stated that the plant sp ent appr oxim a tely $20 m illio n to convert all four units to a dry fly ash system

.

• The plant s t ores the fly ash in silos a nd sells approxim a tely one-third of the

am ount generated for use in concrete m a nuf acturing. Any fly ash that is not sold is sent to an on-site landf ill.

• Roxboro handles the bottom ash at the plant with a wet sluicing system . Roxboro uses intake water from Hyco Lake as the source water for bottom ash sluicing for Units 1, 2, and 3. Roxboro uses the Unit 4 cooling tower blowdown as the source for bottom a s h sluicing for Unit 4.

• Roxboro stated that all of the bottom ash sl uice water is sent directly to the ash pond.

2• Roxboro excavates the bottom ash from the ash pond using backhoes and other

m achinery. The bottom ash that is re moved is sold for use in concrete

m a nufacturing. Roxboro stated that they are rem oving ash from the pond as needed, which is alm o st every day.

• The ash pond effluent is discharged to Hy co Lake. Roxboro stated that the ash pond retention tim e is approxim a tely 10 to 11 days. Ash pond effluent is not reused with in the plan t.

• Prior to discharging the ash pond effluent, Roxboro uses a skimm e r to prevent the discharge of cenospheres to Hyco Lake. Roxboro has a contractor who collects the cenospheres from the pond and hauls them off site.

FGD System

• Roxboro stated that the Unit 2 and Unit 4 FGD scrubbers began operation in April and Decem ber 2007, respectiv ely. T h e plant exp ects to begin operating th e Unit 3 and Unit 1 FGD scrubbers in May an d Decem ber 2008, respectively. (Note: Unit 3 scrubber began comm e r cial operation on May 6, 2008.)

• Roxboro stated that they will even tu ally be capable of addin g DBA to the scrubbers, but currently only spray nozzl es are installed in the scrubbers. Theref ore, a ll of the oth e r f eed equip m ent will need to be in stalled b e f o re the plant could begin using DBA.

• Roxboro installed Babcock and W ilcox lim estone, forced oxidation, tray-tower scrubbers. The scrubbers on Units 2, 3, a nd 4 have five recirculation pumps and three spray levels. The Unit 1 scrubber has three recirculation pum p s and two spray lev e ls.

• Roxboro uses horizon tal ball m ills to crush lim e stone to m a ke the lim e stone slurry that is the sorbent in the scrubbers.

• Roxboro stated that the design m a ximum ch loride level in the scrubbers is 20,000
ppm , but the plant is operating the sc rubbers at a level less than 10,000 ppm (typically between 5,000 and 8,000 ppm ) . R oxboro stated that they think the actual m a ximum chloride level for th e scrubber m a terial is around 12,000 ppm

, which is why they are o p erating at the lo wer ch loride level. Operation a lly, the plant is using a 10,000 ppm setpoint as th e m a ximum allowable level to protect

m e tallurgy. Roxboro is currently operating at a lower chloride level to m a intain sufficient margin to prevent exceedin g 10,000 ppm while changing the coal used for Unit 4.

3• Roxboro operates two-stages of hydroclones and a vacuum be lt filter to dewater the gypsum produced in the scrubbers. E ach of the scrubbers has an individual set of hydro c lones and a vacuum belt filte r. The blowdown from the scrubbers is continuously sent to the prim ary hydrocl one. The prim ary hydroclone underflow can either be return ed to the scrubb er s or sent to the vacuum filters for dewatering. The prim ary hydroclone overflo w is sent to a holding tank and then transferred to the secondar y hydroclones. The secondary hydroclone underflow is returned to the scrubbers and the secondary hydroclone overflow is transferred to the blowdo wn tanks an d then to the FGD settlin g pond.

• Roxboro stated that the blowdown from the scrubbers is continuous and the flow to the blowdown tanks is continuous. Th e wastewater from the blowdown tanks flows interm ittently to the settling pond; however, Roxboro stated that when all of the FGD scrubbers are operating, the flow to the settling pond could be continuous.

• The gypsum from the prim ary hydroclone underflow is washed with service water that ha s bee n f ilter e d an d heated a s it is app lied to the vacuu m f ilter belts

. The f iltra t e and the wash water f r om the v acuum f

ilte r belts is returned to the scrubbers or used for the preparation of the lim estone slurry.

• The gypsum from the vacuum filter belts is trans f erred via a conveyor sy stem to an uncovered gypsum st orage pad. Based on the design coal for the system , the plant estim ates th at th ey will produ ce 600,000 tons of gypsum per year.

• Roxboro stated that they have a contr act in place for a com p a ny to buy the
gypsum from the plant; however, they do not think any transactions have occurred yet. Roxboro stated that the buyer is planning to use the gypsum to produce wallboard. The gypsum produced by Roxboro must have a chlorides concentration less than 100 ppm and less th an 10 percen t m o isture to m eet the
term s of the contract. R oxboro stated that the gypsum buyer plans to build a plant next door to the power plant.

FGD Wastew a ter Treatment System

• Roxboro’s FGD wastewater treatm ent syst em consists of a settling pond followed by an biological treatm ent system fo r treatm ent of nitrogen compounds and

m e tals. W a stewater then flows from the bioreactor to the ash pond discharge canal, which comm ingles with the co o ling water discharge canal, and is discharged to Hyco Lake.

• Roxboro stated that they have been tran sferring water to th e settling pond since the Unit 2 F GD system began operation in April 2007; however, Roxboro only began transferring wastewater to the bioreactor on Febr uary 27 (two weeks prior

4to the s ite v i sit). Acco rd ing to plant st aff, the bio r eactor is ex pected to reach steady state operation approxim a te ly 2-4 weeks after startup.

• The design flow rate for the FGD wa stew ater treatm ent system is 1,269 gpm (for all four units com b ined). At the tim e of the visit, the aver age flow rate through the system was 540 gpm (only Units 2 and 4 currently operating). The plant is estim ating that the total flow rate from all four scrubbers will be approxim a tely 1,000 gpm ; however, the Unit 4 coal change could affect this estim ate.

• Roxboro stated that the s e ttling pond was built sp ecifically for FGD wastewater
treatm ent and it has a sy nthetic liner. Roxboro stated th at th e pond was built to have a 10-year life. At the end of the 10 years, the plant can either build a new pond next to the existing one or dredge the settling pond.

• Roxboro stated that the goal for the sett ling pond is to reduce the wastewater
tem p erature to less than 105 o F and reduce the TS S for optim a l operation of the bioreactor. Roxboro personnel did not know the target TSS level.

• Roxboro stated that the plant operate s the settling pond below the m a xi mum capacity so they can hold an additional m onths worth of wastew ater in the pond if there is an F GD system upset. The extr a capacity allows the plant to avoid sending the wastewater through th e bioreactor if there are issues with the system

. Roxboro also stated that the settling pond has an em ergency overflow to transfer wastewater to the ash pond instead of discharging it to the ash pond discharge canal.

• The bioreactor at Roxboro has four parallel trains that each have two biological cells in series. The wastewater en ters at th e top o f the first cell in th e series and flows downward through activated carbon charcoal m a terial. The charcoal

m a terial con t ains m i crob es to redu ce the m e tals p r esent in th e wastewate r to the i r elem ental state. The effluent from the fi rst cell is pum p ed to the top of the second cell in the series. The effluent from each of the four trains is com b ined and discharged to the ash pond canal. O u tfa ll 010 is an internal monitoring point for the FGD effl uent prior to it entering th e Ash Pond Discharge Canal. Outfall 010 enters the A s h Pond Discharge Cana l downstream of outfall 002 (ash pond discharge to the Ash Pond Discharge Ca nal), but upstream of outfall 003 (Heated W a ter Disch a rge Canal).

• Each of the four treatm e n t trains is desi gned for a four-hour retention time (based on all four units operating FGDs and all four treatm ent trai ns operating). The design flow rate through all f our trains is 700 gpm (175 gpm e a ch). At the tim e of the visit, each train had an 8 hour retenti on tim e . At the tim e of the visit, Roxboro was operating all four bioreactor trains even though only two FGD scrubbers were operating. Therefore, each bioreactor train was processing wastewater at approxim a tely 50 percent of design fl owrate, doubling th e re tention tim e.

5• Roxboro stated that the bioreactor needs to be flushed periodically to remove solids from the system . Roxboro estim a ted that each cell will need to b e backflushed twice per year. The source of water f o r the b l ackf l ush is the F GD settling pond and the flow rate is estim at ed to be 6,280 gpm (per unit). B ackflush wastewater will be trans f erred to the flus h pond, which is lo cated directly next to the settling pond. Roxboro stated that they expect m o st of the water in the flush pond to evaporate, o t herwise, if the fl ush pond o v erflows, it will flow into the settling pond.

• Three weeks prior to the site visit, th ere was a breach in the flush pond that caused a crack to form i n the stru cture of the pond. The start up and

comm issioning water that had been sent to the flush pond leaked out of the pond and into the ash pond. The settling p ond also had som e leaking issues, bu t the settling pon d has not yet breached. Roxbor o stated that both of the ponds will need to be fixed. At this point, Roxboro is determ ining the cause the problem s and potential solutions. Roxboro is s till sending FGD scrubber purge to the settling pond. The plant is also pum ping som e of the water from the FGD settling pond to the ash pond to keep the le v e ls in the settling pond lo w.

• Roxboro added one new chem .-tech to th e plant staff to oversee bioreactor operation. S t aff present at the visit s uggested that the workload would support adding another 0.5 FTE. Total staffing to operate the FGD system (not the
wastewater treatm e nt portion) is approxim a tely 20 operators.

FGD Waste w a ter Treatment Syste m Data

• Roxboro stated that they have a new perm itted ou tfall (Outfall 010) for the effluent from the bioreactor system

, prior to comm ingling in the ash pond discharge canal. Roxboro stat ed that they are required to m o nitor for beryllium and m e rcury weekly and to m onitor for an tim ony, selenium , silver, and vanadium quarterly. R oxboro stated th at the metals do not need to be analyzed using lowlevel m e thods.

• Roxboro stated that they plan to co llect add ition a l perform a nce sam p les (e.g., FGD purge and FGD settling pond effluent sam p les); however, they hav e not

m a de f i nal decis i ons reg a rding whic h sam p les will b e collec ted and the f r e quency of sa m p ling.

• Roxboro stated that although the biological treatm ent system is only in the startup phase, it has shown good rem ovals for m e rcury and selenium . Roxbor o stated that they need to decreas e the oxid a tion -reduction num b ers in the system , increas e the tem p erature of the wastewater, and incr ease the flow rate through the system

. Roxboro thinks that thes e changes w ill im prove the system perform a nce.

• Roxboro stated that they are cons idering using a chem ical additiv e (polym er) in the settling pond to im prove m e rcury rem ovals.

6• Roxboro provided the following results from sa mpling conducted on March 4, 2008. The influent sample was collected from a common he ader entering the system and the effluent was collected from the effluent pipes from the two operating tre a tm ent train s . Please no te tha t th is is sam p ling f o r the initial s t ar t up of the system and m a y not re present long-term results. According to plant staff, TSS into the bioreactor (settling pon d effluent) is approxim a tely 5 m g /L.

Roxboro Sampling Results: March 4, 2008

Analyte Sample Influent to the Bio System (ug/L) Effluent fro m the Bio System (ug/L) Percent Removal (% ) 1 0

. 5 1 1 0

. 0 2 3 9 5

. 5 Mercury 2 0

. 5 1 1 < 0

. 0 1 9 > 9 6

. 3 1 1 8 4 0 4 7 9 7

. 4 Selenium 2 1 8 4 0 3 9 4 7 8

• Because of the leak ing is sues with th e FGD settling pond, the state of North Carolina is requiring Roxboro to collect weekly grab sam p les from the FGD
wastewater treatm e nt sys t em until 90 days after th e problem is fixed. Roxboro will be required to sam p le f o r a range of m e tals a nd other an a l ytes f r om the f

o llowing f i ve sam p le location s :

o FGD purge water, before settling pond;

o Settling pond effluent (i nf luent to bioreac tor) ;

o Effluent from bioreacto r (this is s i m ilar to NPDES outfall 01 0);

o Outfall 002 (discharge from ash pond in to the Ash Pond Discharge Canal); and

o Outfall 003 (discharge from Heated Water Discharge Canal to Hyco Lake).

• Roxboro will be requ ired to subm it a report of th e sam p ling results to the s t ate of North Carolina each m o nth. Roxboro agreed to su pply Ron Jordan, EPA, with the report as we ll.

FGD Waste w a ter Treatment Cost I n formation

• EPA stated that they were interested in receiving cost inform ation from Roxboro regarding the FGD wastewater trea tm ent system. Roxboro provided the f

o llowing ca pita l cost inf o rm ation:

o Blowdown line $1.258 m illion

o Settling pon d $7.571 m illion

o Flush pond $2.534 m illion

o Bioreactor s y stem $22.43 m illion

78 • Roxboro stated that they do not have the operating and maintenance costs yet because the system is not yet operati ng. Roxboro did state, that it costs approximately $200,000 to inoculate the micr obes for the bioreactor, which would be a significant expense if the microbes are killed.

• EPA stated that they would be interest ed in any projected O&M costs that the plant can estimate.

Progress Energy’s Mayo Plant

• Progress Energy also operates the Mayo Steam Electric Plant, located in Person County, NC. The Mayo plant will soon st art operating an FGD scrubber. The FGD wastewater treatment system will be similar to the Roxboro treatment system (settling pond plus bioreactor), ex cept that Mayo’s bior eactor is designed for an 8-hour retention time at full flow , rather than the 4- hour design retention time for Roxboro. The FGD wastewater tr eatment system is scheduled to begin operating in spring 2009.Table 1. Site Visit AttendeesNameOrganization (Representing)TelephoneE-mailRobin BrysonProgress Energy(919)546-3962robin.bryson@pgnmail.comTom CopoloProgress Energy(336)597-6193tom.copolo@pgnmail.comJodirah GreenProgress Energy(336) 598-4068jodirah.green@pgnmail.comFred HoltProgress Energy(919) 546-5286fred.holt@pgnmail.comDanny JohnsonProgress Energy(919) 546-7724danny.johnson@pgnmail.comShannon LangleyProgress Energy(919)546-2439shannon.langley@pgnmail.comBilly MilamProgress Energy(336) 597-6284william.milam@pgnmail.comIssa ZarzarProgress Energy(919)546-3962issa.zarzar@pgnmail.comDonna HillSouthern Company(205) 257-5234dbhill@southernco.comSergei ChernikovNorth Carolina Department of Environmentand Natural Resources (DENR)(919) 387-8044ext. 594sergei.chernikov@ncmail.netAutumn HobanNorth Carolina DENR(919) 791-4247autumn.hoban@ncmail.netVicki WebbNorth Carolina DENR(919) 791-4256vicki.webb@ncmail.netKarrie-Jo ShellEPA/Region 4(404)562-9308shell.karrie-jo@epa.govJosh HallEPA/Office of Water(202) 566-1002hall.josh@epa.govRon JordanEPA/Office of Water(202) 566-1003jordan.ronald@epa.govT.J. FinsethERG (Contractor to EPA)(703) 994-7130thomas.finseth@erg.com