Final Notes from Site Visit at Duke Energy’s M ia mi Fort Station

on March 1, 2010

EPA conducted a site visit at Duke Energy’s Miami Fort Station (Miami Fort) located in North Bend, OH on Monday

, March 1, 2010 to learn about the operations at the plant

, specifically the flue gas desulfurization (FGD) wastewater treatment system

. These notes describe the information collected during the site visit. Table 2 , located at the end of th ese notes , identifies the site visit participants. The presentation that the Duke Energy personnel gave during the site visit is provided as Attachment 1 to these notes and includes a FGD system process flow diagram, a simpli fi ed flow diagram of the FGD wastewater t reatment system , and detailed view of the DensaDeg® clarifier

. A more detailed process flow diagram of the FGD wastewater treatment system and a n aerial view of the plant are provided as Attachment s 2 and 3, respectively, to these notes

.

Plant Overview

• Miami Fort operates three coal

- fired steam electric generating units at the power plant. Unit 6, which began operation in 1960, has a generating capacity of 175 MW. Unit s 7 and 8
, which began operation in 1975 and 1978, respectively, each have a generating capacit y of 550 megawatts (MW). All three units are operated as baseload units. Table 1 contains some general information regarding the three generating units.

Table 1. Steam Electric Generating Unit Operations Summary

Unit Installation Date Gross Capacity

(MW) Particulate Control NOx Control SO 2 Control 6 1960 175 Electrostatic Precipitator (ESP) (cold

- side) Low

- NOx Burners None

7 1975 550 ESP (cold

side) Selective Catalytic Reduction (SCR) (2003) Wet FGD installed December 2007

8 1978 550 ESP (cold

side) SCR (2001) Wet FGD installed in April 2007

• Duke Energy is a partial owner of all the units at the plant. Miami Fort explained that a joint committee that meets regularly makes decisions regarding the units. It was also stated that both parties split the expenses and revenue of the units.

• Miami Fort retrofitted Units 7 and 8 in 2007 with FGD scrubber systems to control the sulfur dioxide (SO 2 ) releases from the plant. Unit 6 was not retrofitted with a scrubber system and Miami Fort does not have any plans for a retrofit.

• Miami Fort operates s el ective catalytic reduction ( SCR ) systems on Units 7 and 8, installed in 2003 and 2001, respectively. Miami Fort runs the SCRs year round. The plant has not yet performed a catalyst regeneration on either of the SCRs. ThePage 2

plant takes samples of fly ash every day and measures the amount of ammonia present. P lant personnel stated that more ammonia slip was noticed this year. Miami Fort is beginning to discuss the options for how to handle the SCR catalysts. Plant personnel explained that the y are consideri ng the following options:

o I nstall a new layer of catalyst ;

o R egenerate a n existing layer of catalyst; or

o R eplace an existing layer with a new layer of catalyst.

• Miami Fort stated that ash can build up on the catalysts in the SCR system, depending on the type of coal bur ned . Sonic horns are used to remove ash from the catalysts. The horns operate continuously based on a timer

. During quick outages, the plant uses vacuums to remove any remaining ash buildup. P ressure gauges exist to calculate the differential pressure across the catalyst, but are not used to activate the sonic horns.

• Miami Fort burns eastern bituminous coal in all three units . Miami Fort stated that the coal is delivered by barge from several different mines. Miami Fort explained that the source of the coal is a variable.

• Miami Fort stated that the sulfur content of the coal ranges from 2.5 to 7.5 pounds of sulfur per million BTU and that the chlorine content of the coal can range from 0.04 to 0.3 percent, depending on the source.

• Miami Fort previously had issues with blue plume from the stack, associated with sulfur trioxide emissions. The plant now injects lime into the flue gas between the air heater and the ESP to control the sulfur tri oxide emissions.

• Miami Fort operates dry fly ash handling systems on Units 7 and 8 and a wet fly ash handling system on Unit 6. The dry fly ash handling systems on Units 7 and 8 are separate systems and the ash from each unit is stored in a separate silo

. Wet fly ash from Unit 6 is sluiced to the plant’s ash pond.

• Miami Fort has both wet and dry fly ash loading capabilities for U nits 7 and 8

. Additionally, the plant has the capability to load rail cars from the Unit 7 silo.

• Miami Fort sells most of the ash to Ready M ix. Any fly ash that the plant cannot sell is transferred to their landfill located approximately three miles away

, which is owned and operated by Duke Energy. Miami Fort stated that if the ammonia in the fly ash exceeds 100 ppm, the ash is not able to be sold and is transferred to the landfill.

• Miami Fort operates wet bottom ash handling systems on all three units. A hydroveyor vacuum system sl uices the bottom ash to the ash pond

. Miam i Fort uses cooling tower blowdown as the source for the hydroveyor water. The fly ash and bottom ash from Unit 6 are sluiced together to the ash pond. The plant sluicesPage 3

pyrites separately to the ash pond to enable the plant to market some of the bot tom ash . Miami Fort previously had a contract with Home D epot to re use filtered bottom ash for cement board. The contract was dropped when the plant switched to a higher density coal. Miami Fort is currently not selling any bottom ash for reuse.

• Miami Fort operates an ash pond with two adjacent cells operated in series. The fly ash and bottom ash sluice streams are transferred to the first cell. Miami Fort adds p olymer to the ash pond near where the sluice pipes deposit the ash to improve solids removals. The plant operates the first cell using a rim ditch stacking method. This approach entails using equipment to maintain channels for the sluice water to move through the mass of ash solids collected in the pond. The plant removes the solids that settle out in the channels of the ash pond and stacks them in piles along the channels to allow the solids to dewater , while the water drains back into the pond.

• The plant hauls the dewatered ash from the pond to the landfill that is owned by Duke Energy for disposal. This ash is typically 18 percent moisture. Miami Fort stated that along with the fly ash, FGD gypsum wastes and FGD wastewater treatment solids are transferred to a landfill

. All off

- spec gypsum and waste water
treatm ent sludge is sent to an off

- site landfill

, either Duke Energy ’s East Bend or Zimmer Station l andfills.

• Miami Fort sends about 150,000 tons of ash to the pond per year . The plant estimates that the water in the ash pond has a three day retention time. The pond also receives the effluent from the FGD wastewater treatment system , which is transferred to the first cell (Pond A) after the stacking portion. The sumps from all three units are transferred directly to the second cell (Pond B). Coal pile runoff is also transferred to the ash pond, but it is collected in a smaller pond before being transferred to Pond A

.

• Miami Fort has the capability to add carbon dioxide to the ash pond wastewater as it flows from Pond A to Pond B. T he pH in the water flowing f rom P ond A to P ond B , is monitored daily. If the pH is greater than 8.5, carbon dioxide (CO 2 ) is added.

• Miami Fort discharges the ash pond effluent to the Ohio River via Outfall 002. The ash pond effluent flow rate is approximately 13 MGD.

• Leachate from the ash pond is collected in a dike along the outer edge of Pond B. The ash pond has 38 different drains that collect leachate and transfer it to the dike. The dike also collects rainfall and runoff from the ash pond berms. The removal of leachate from the ash pond keeps the pond from building too much pressure and makes the pond more stable. The leachate flows along the dike and is discharged to the Ohio River via a storm water outfall. Plant personnel stated that the combined flow from all 38 drains is about two gpm.Page 4

• Miami Fort has groundwater monitoring wells around the ash pond

. There are

seven monitoring wells adjacent to Pond A and B. One well is for water level only. O ne well

, MW

- 1
, is upgradient

. The remainder of the monitoring wells are downgradient. Water level, p H
, s pecific c onductance, arsenic

, b a rium

, ca d mium

, c a lcium

, iron

, lead

, magnesium

, manganese , potassium

, selenium

, sodium

, a lkalinity, chloride, s ulfate, a nd TDS are measured semi

- annually. All wells were installed in 2008. There is no background well other than MW

- 1.

• Miami Fort was recently issued a new NPDES permit on July 1, 2009. Miami Fort will provide EPA with an electronic copy of the permit. [NOTE: Miami Fort sent EPA the new NPDES permit on March 5, 2010.]

FGD System

• Miami Fort operates two limestone forced oxidation FGD systems (one each on Units 7 and 8).

• The FGD systems have three spray levels ; however, the plant typically only operates two of the spray levels at one time. The FGD systems are also equipped with dual flow trays

.

• River water is used as the source of makeup water to the FGD system. The plant does not use organic acids in the FGD systems

.

• Miami Fort maintains the solids concentration in the FGD system between 21 and 24 percent solids. According to plant staff, absorber chlorides are typically maintained at approximately 5,000

- 10,000 ppm

. The FGD systems have a design maximum chlorides limit of 12,000 ppm. The plant blows down from the absorbers in batches, depending on the chlorides and solids concentrations in the absorber. The FGD system operates at a pH of 5 S.U.

• The blowdown for each FGD system is transferred to its primary hydrocyclone

. Each FGD system has a d edicated hydrocyclone. The gypsum from the each primary hydrocyclone is sent to its own vacuum belt filter for fu r ther dewatering. The overflow from each primary hydrocyclone is transferred to its own secondary hydrocyclone

. The underflow from the secondar y hydrocyclone s is sent to the reclaim tank , which is shared between the two units, and reused in the FGD system as make

- up water

. The overflow from the secondary hydrocyclone s , which contains between 2.5 and 3.0 percent suspended solids, is sent to the FGD wastewater treatment system.

• As the gypsum slurry is applied to the vacuum belt filter s, Miami Fort washes the gypsum with service water to reduce the chlorides in the gypsum to less than 10 0 ppm. The vacuum belt filter s dry the gypsu m to a moisture content of approximately nine percent. The gypsum product produced at the plant is marketed to Lafarge , a wallboard manufacturer . If the gypsum is off

- spec or Lafarge refuses the product , the gypsum is sold f o r agricultural use

.Page 5

• The fil trate from the vacuum belt filters is collected in the reclaim tank and transferred back to the FGD system

. Each unit has its own reclaim tank.

• Miami Fort’s third party contractor, Synmat , operates the entire FGD system, including reagent preparation, gypsum dewatering and marketing, laboratory, and wastewater treatment and solids handling.

FGD Wastewater Treatment System

• The FGD wastewater treatment system , which was designed by Infilc o Degremont
, is a chemical precipitation system that uses hydroxide and sulfide precipitation to remove metals and suspended solids from the wastewater . Ferric chloride and polymer are also added to enhance pollutant removals. The maximum design flow rate for the system is 200 gpm, but the average flow rate into the FGD wastewater treatment system is 150 gpm.

• Secondary hydrocyclone overflow from the scrubber is transferred directly to the equalization tank. Miami Fort adds lime to the equalization tank to raise the pH of the wastewater from approximately 5 S.U. to between 8.4 and 8.6 S.U. The equalization tank also receives wastewat er from the wastewater treatment building sump, which consists of filter press filtrate.

• From the equalization tank, the FGD w astewater flows to the coagulation tank, where Miami Fort adds organosulfide and ferric chloride to the wastewater

. The ferric c hloride is used to assist in the coagulation of the solids precipitated in the equalization tank, as well as promote iron coprecipitation of some residual metals in the wastewater. The organosulfide is added to precipitate residual metals as sulfide comple xes.

• Flow from the coagulation tank splits into two parallel streams that flow to two DensaDeg ® clarifier s

. The DensaDeg® clarifier has an initial reactor section, where p olymer is added for coagulation and flocculation to improve solids removals. From the reactor section, the wastewater enters the clarification/thickening section of the clarifier, where the solids settle out of the wastewater. The sludge is transferred to the sludge holding tank and then processed through the filter presses. The filtrat e from the filter presses is collected in the wastewater treatment building sump and recycled to the equalization tank. The sludge from the filter presses is hauled off site for disposal at a landfill

.

• The clarified wastewater from the two DensaDeg® clar i fiers is combined in the effluent tank

. The wastewater is pumped to the ash pond and discharged via Outfall 002. The transfers to the ash pond are based on level control within the effluent tank; therefore, the transfers are not continuous.

• Miami Fort d oes not have discharge limits for the effluent from FGD wastewater treatment system.Page 6

• During the time of the site visit, Miami Fort was testing the use of Nalmet® 1689 as the organosulfide in the FGD wastewater treatment system instead of TMT 15®, which was used by the plant when the FGD wastewater treatment system began operation. The plant was testing the effectiveness of Nalmet® 1689 by adjusting its feed rate, as well as the feed rates of the other FGD wastewater treatment additives (i.e., polymer, fe rric chloride). Miami Fort personnel stated that the Nalmet® 1689 results look promising and that it has been effective in lowering mercury levels.

• Miami Fort is also planning to test a General Electric organosulfide product in the summer using a slip st ream. However, n o formal plans have been developed.

• EPA stated that regardless of the testing being conducted in the FGD wastewater treatment system, EPA would like the plant to operate the FGD wastewater treatment system at stable operating conditions during EPA’s planned sampling episode.

• The plant stated that mercury data are available for the inlet and outlet of the FGD wastewater treatment system, Outfalls 601 and 608, respectively. EPA stated that these data would be helpful to review. Plant personnel stated that the data would be sent electronically to EPA. [NOTE: Miami Fort sent EPA the data on March 5, 2010 .]

Information for Sampling

• EPA identified the FGD wastewater treatment system influent sampling point as the tap off the secondary h ydrocyclone flowing to the equalization tank.

• EPA identified the FGD wastewater treatment system effluent sampling point as a tap on the pump discharge off the effluent tank. Miami Fort stated that they could install a smaller hose barb on the tap to acco mmodate the sample collection. Miami Fort also stated that EPA can us e a small tap off the effluent tank (drain line) to a sump , so that they can get continuous flow for the sampling event or EPA can pull a sample from the DensaDeg® overflows which is cont inuous and gravity fed into the effluent tank.

• There is p lenty of table and cooler storage space near the sample point in the FGD
wastewater treatment building

.

• Plant personnel stated that all EPA/ERG sampling personnel would be required to go through a 4 5 minute health and safety orientation prior to the sample collection

.

• Plant personnel also stated that there is a first responder team on site and ERG would have access to the team in case of emergency.Page 7

Table 2

. Site Visit Attendees

Name Organization (Representing) Telephone E

- mail
Pat Coyle Duke Energy 513

- 287

- 2268 pat.coyle@duke

- energy.com

Brian Huddleston Duke Energy 217

- 218

- 2985 huddlebj@muohio.edu
Joseph G. Potts Duke Energy 513

- 287

- 2609 joseph.potts@duke

- energy.com

Jim Stieritz Duke Energy 513

- 287

- 2269 jim.stieritz@duke

- energy.com

Tara Thomas Duke Energy 513

- 467

- 4950 Tara.thomas @duke

- energy.com

JR Wood Duke Energy 513

- 467

- 4886 jr.wood@duke

- energy.com

Donna B. Hill Southern Company/UWAG 205

- 587

- 4846 dbhill@southernco.com

Jezebele Alicea US EPA 202

- 566

- 1755 alicea.jezebele@epa.gov

Ron Jordan US EPA 202

- 566

- 1003 jordan.ronald@epa.gov

TJ Finseth ERG 703

- 633

- 1698 thomas.finseth@erg.com

Elizabeth Sabol ERG 703

- 633

- 1659 elizabeth.sabol@erg.com