Draft Notes from Site Visit at Detroit Edison’s Monroe Power Plant on September 23, 2009

EPA conducted a site visit at Detroit Edison’s Monroe Power Plant (Monroe) located in Monroe, MI on Wednesday, September 23, 2009 to learn about the operations at th e plant. Table 1, located at the end of this memorandum , identifies the site visit participants. Attachment 1 provides the presentation that the Monroe personnel gave during the site visit.

This memorandum describes the information collected during the site visit.

Plant Overview

**•** Monroe is owned by Detroit Edison Company, a subsidiary of DTE Energy. Detroit Edison was founded in 1903. It is the ninth largest electric utility in the United States with 2.1 million customers and over 11,000 MW of electri c power generating capacity, primarily coal
fired. Detroit Edison owns one nuclear plant (Fermi 2).

**•** The Monroe plant covers 1,200 acres and is surrounded by Lake Erie and the Raisin River.
The Monroe

- related property is split into three sections, includ ing the Monroe plant property, the dry fly ash loading area, and the fly ash basin, including the 200 acres of land south of the fly ash basin. Monroe purchased the 200 acres south of the fly ash basin for possible future use if the basin needed to be exp anded. An aerial view of the Monroe plant property is provided as A ttachment 2 to this memorandum.

**•** Monroe employs more than 400 permanent employees and 100 long term contract employees. Monroe also employs about 500

- 800 temporary construction employees f or various construction projects, including the Environmental Project.

**•** Monroe produces about 35 percent of DTE Energy’s electrical power and 44 percent of its fossil power. Monroe has a net winter electric generating capacity of 3,135 MW, and the net

sum mer capacity is typically about 3,115 MW. The plant’s auxiliary power requirement is about 5 percent parasitic load without the flue gas desulfurization (FGD) operation. With the added FGD operation, the auxiliary power requirement increases to about 6.2 percent. The plant generates about 16 to 18 million MWs per year. The table below contains some general information for each electric generating unit.

Unit Installation

Date Capacity (MW) a Fly Ash Handling

System Particulate
Control NOx
Control SO 2

1 Co ntrol

1971 817 Dry and wet systems in operation Cold

- side
electrostatic precipitator (ESP) Low

- NOx burners;

SCR FGD
scrubber planned to
be installed by 2015.

2 1972 823 Wet system in operation; Dry system
installed projected operation in Cold

- side

ESP Low

- NOx burners;

SCR planned to
be installed FGD
scrubber planned to
be installed by 2015.Page 2

Unit Installation

Date Capacity (MW) a Fly Ash Handling

System Particulate
Control NOx
Control SO 2

Fall 2009. (UPDATE: in operation since Sept.
2009 ) Co ntrol

3 1973 823 Wet system in operation; Dry system planned to be
installed in

2013 Cold

- side

ESP

b Low

- NOx
burner s; SCR Limestone
forced
oxidation (LSFO)
FGD
scrubber planned to
be operational
in Nov 2009

4 1974 817 Wet system in operation; Dry system planned to be
installed in

2013 Cold

- side

ESP

b Low

- NOx burners;

SCR LSFO FGD
scrubber operational
in June
2009

a

– Capacities from the 2005 EIA database. These capacities will be updated with further information from the facility.
b

– Although the company signed an agreement that allows a 3 rd party to install a dry system, as of this date the company cannot state that there is a likelihood that a dry system will be installed. Among other things, such an installation by a 3 rd party is predicated on the company not electing to burn pet

- coke in this unit. As of this date the company has not decided whether it will burn or not burn pet coke in this unit.

**•** Monroe operates low

- NO X burners on each of the coal

- fired units (Units 1, 2, 3, and 4). Additionally, Monroe operates SCRs on Units 1, 3, and 4. Plant personnel stated that they are planning to install an SCR on Unit 2 i n the future. The SCRs on Units 1, 3, and 4 each have four catalyst layers available, but there are typically less than four layers that are loaded

. When necessary, these catalyst layers are replaced and are not regenerated on site.

**•** Monroe’s current p lan for reduction of mercury emissions includes the operation of SCR and FGD systems. Monroe estimates that an SCR and FGD scrubber installed in series controls is expected to typically reduce about 80 percent of mercury emissions.

**•** DTE Energy/Monroe pa rticipated in a DOE

- co

- funded pilot study for activated carbon injection (ACI) at Monroe. All of the equipment was removed once the study was finished. Monroe stated that injecting activated carbon upstream of the ESP would preclude the sale of fly ash due to high carbon content, and specifically, high activated carbon content. Monroe stated that if they implemented ACI downstream of the ESP to keep the dry fly ash marketable, a baghouse would have to be installed. [QUESTION FOR MONROE: Have any other optio ns, additional to ACI, been considered for mercury control?] Fuel additives andPage 3

FGD slurry additives would be considered if additional mercury oxidation is required or re

emissions from the FGD became an issue. No additives are used currently.

**•** The plan t has three coal piles; one contains low

- sulfur Powder River Basin (PRB) coal (0.2 to 0.5 percent sulfur); one contains mid

- sulfur eastern bituminous coal (1.2 to 1.6 percent sulfur); and one contains a blend of coal (60 to 70 percent PRB and 30 to 40 perc ent eastern bituminous). Monroe estimated that this year they have burned closer to 70 percent PRB and 30 percent eastern bituminous coal because recently the total cost for obtaining PRB coal is
less than that for eastern bituminous coal. All coal arrive s by rail or lake vessel. At full load, the plant consumes about 32,000 tons of coal per day and on an average year, burns 8

- 9
million tons of coal.

**•** Monroe’s coal pile runoff is not acidic due to the significant amount of PRB coal burned.
The runoff is typically between 7 and 8 S.U. (a recent measurement was 7.76 S.U.). Monroe sends the coal pile runoff to a small basin and then to the bottom ash basin.

**•** Plant personnel estimated that the distribution of ash generated from the generating units,
calcu lated based on coal consumption, is approximately 20 percent bottom ash, 80 percent fly ash and 1 percent economizer ash. The plant has no means of measuring any of these ash steams and the above numbers are estimates based on literature review of compara ble units.

A sh Ponds

**•** Monroe has two ash ponds, the bottom ash basin (Area 15) and the fly ash basin. Originally, the plant’s fly ash pond and bottom ash pond were both located in Area 15. These ash ponds were filled with all ash produced at the Monroe site since it began operation in 1971. When the plant personnel determined that the area/ponds would soon reach its limits, it was converted to the bottom ash pond only. Area 15 was only used for fly ash disposal as an interim measure in the early 1970’s , while the fly ash basin was being built. Area 15 has never reached its limits and continues to be used as a bottom ash pond. There are no chemical additions to the ponds.

**•** The bottom ash basin receives bottom ash sluice , coal pile runoff, effluent fr om the FGD
wastewater treatment system , and low volume wastes. The bottom ash is sluiced to the basin and then dredged and sold or used for roadbed. Bottom ash sales are infrequent. Effluent from the bottom ash basin is discharged via Outfall 001B to th e main discharge cooling canal, and then discharged to Lake Erie via Outfall 001.

**•** The Monroe constructed the 410

- acre fly ash basin was constructed in 1974. The ash basin has never been expanded and is currently at about 2/3 of its volume capacity. The bottom of the basin is about 5 to 10 feet below ground level, and the highest point of the berm is about 35 feet above ground level. Monroe fills about 5 to 10 acres of the pond each year with fly
ash. The estimated end of life for the ash basin is abou t 20 years from the time of the site
visit. This could be extended if more dry fly ash can be sold or decreased if the plant is no longer able to sell ash or gypsum. The fly ash basin is licensed/permitted by the state as a
landfill under the solid waste program

.Page 4

**•** Compacted “Lake Erie” clay, the naturally

- occurring clay in the area, was used to construct the berm of the fly ash basin

. and is the main component of the bottom of the ash basin. The basin is not lined. Monroe stated that the permeability o f the clay, 10E

- 8 UNITS , makes it an ideal component for the bottom and berm of the ash pond. [QUESTION FOR MONROE: Please confirm the clay permeability and provide the measurement units.] Permeability
coefficient of the ash basin embankment soils strata ranges from 1.30 X 10(

- 7) to 2.37 X 10(

- 8) cm/sec. Permeability coefficient of the ash basin site soils strata ranges from 1.0 to 2.0 X10(

- 8) cm/sec. This data is based on soil test results from a 1986 ash basin embankment soils investigation and 1995 ash basin site soils investigation. Clay is not the main component of the bottom ash basin. Clay was the only component used to build the fly ash basin. Permeability verification documents were provided to GZA: the other EPA contractor reviewing ash basin c onstruction.

**•** The fly ash basin effluent is currently monitored for total suspended solids (TSS), oil and grease with grab samples taken at the end of a discharge canal. Flow is also recorded. The water from the fly ash basin is discharged with an under flow/overflow weir that is controlled by gates. The water flows underground to one of three upwellings and then flows to the monitoring point. The fly ash basin effluent is discharged via Outfall 001F to the main discharge cooling canal, and then discharge d to Lake Erie via Outfall 001. An aerial view of the fly ash basin, with monitoring points and discharges identified, and a plant water bal ance are provided as Attachment 3 to this memorandum.

**•** There is an air quality monitor located near the ash basin that continually monitors for fugitive dust.

**•** An engineering study of the fly ash basin was conducted in 2008 (prior to the TVA ash spill), during which the structural integrity of the pond was analyzed. The 2008 study was focused on the design of a re pair plan for the surficial sloughs that have occurred on the exterior of the basin. The 2008 plan was not focused on the stability of the core of the dike. After the TVA ash spill occurred, Monroe obtained a second opinion, and it was determined that th e embankment slope needed to be modified. The second opinion was again focused on the

su r ficial sloughs and identified a number of remedial options. The company could have maintained the existing slopes, but recognized that there would be less maintenan ce with a flatter slope. Ultimately the company chose to modify the embankment slope to both repair surficial sloughs and incur less O & M expense in the future. Monroe operators perform weekly inspections of the fly ash basin to look for any visual diff erences concerning the ash
basin. DTE Surveyors also use inclinometers and dike movement indicators to inspect the fly ash basin. Every two years, Monroe hires a private contractor to survey the ash basin and observe/record any location and depth changes.

A sh Handling

Overview

**•** Monroe operates wet fly ash and wet bottom ash handling systems on Units 1, 2, 3, and 4. Recently, Headwaters Resources (Headwaters) built a dry fly ash handling system on Units 1 and 2. The dry fly ash handling system is current ly in operation on Unit 1. Monroe stated that Unit 2 should be in operation by the end of September 2009. As currently planned, Units 3 and 4 will have dry fly ash handling systems installed and operated by 2013. HeadwatersPage 5

may build a dry fly ash handlin g system on one or both of the remaining Units (units 3 & 4), but will not build a dry system on any unit bur n ing petroleum (pet) coke. The company is currently entertaining a request that it burn pet coke.

**•** The bottom ash is sluiced to Area 15. Mill rej ects are collected and sluiced with the bottom ash. The bottom ash is dredged and sometimes used or sold for roadbed.

**•** Headwaters owns and operates the dry fly ash handling system at Monroe. Headwaters markets the ash to the cement/concrete industry for us e in ready mix and concrete pipe. Headwaters has been in the business of marketing fly ash since the late 1980’s.

**•** As the fly ash handling system is currently set up for Units 1 and 2, Monroe has the ability to handle fly ash wet or dry. The dry fly ash h andling system was not intended to be a complete

wet

- to

- dry conversion. The current system lacks redundancy and capacity to handle 100 percent of the fly ash dry. Monroe was able to install and bring the dry fly ash handling system on line without any add itional outages, outside of those regularly scheduled. The dry fly ash handling system was first installed parallel to the wet fly ash handling system, and then connected to the wet fly ash handling system during a regularly scheduled outage.

**•** Monroe prod uces a class of dry fly ash that is between “C” and “F”. Plant personnel stated that there is high demand for their fly ash. Plant personnel stated that the loss on ignition (LOI) of their fly ash is typically 1.5 percent.

**•** The piping of the dry fly ash handling system is routed to pneumatically transfer fly ash to a Headwaters owned and operated 4,000 ton storage silo, which is 3,100 ft away from the ash silos at the Monroe plant.

**•** Headwaters operates the dry fly ash truck loading area with four on

- site employees. Two Headwaters employees, Mr. Mike Dunlap and Mr. Lance Staron, spoke with EPA during the Monroe site visit. The dry fly ash truck loading area is currently only able to handle/load “bone dry” (less than one percent moisture) fly ash for sale. It is not set up to moisture

condition the fly ash, as would be done for landfilling. Headwaters has sold about 4,000 tons of Monroe’s fly ash from August 6, 2009 to the time of the site visit; local market demand has driven when Unit 1 fly ash has been handled dry. Similarly, market demand will determine whether Unit 2 fly ash will be handled dry. The demand for dry fly ash will likely increase next summer. Headwaters intends to stock pile the dry fly ash this winter for the
demand next season.

**•** Headwat ers has a rail network across the country for selling/transporting dry fly ash and they network locally by truck. The company strategically placed ash storage silos across the country where ash demand is high. Headwaters looks to expand the dry fly ash sal es at Monroe. Rail would allow Headwaters to market the fly ash where demand is high year

round. Rail loading equipment is already installed at the Monroe plant. To begin operation, this rail loading equipment would need to be connected and track would need to be installed. Rail loading would increase the staff requirements at the loading facility.

Detailed Fly Ash Handling OperationPage 6

**•** The fly ash from Monroe’s Unit 1 is collected dry in two rows of precipitator hoppers (upper and lower).

**•** When Monr oe operates the wet fly ash handling system, economizer and fly ash are pulled dry by a vacuum (using a water ejector/eductor) through a set of pipes that split from the pipes used for the dry fly ash handling system. The ash is then introduced to water fo r sluicing in slurry tanks. The ash sluice is then pumped from the slurry tanks to the fly ash basin located approximately 3,500 ft from the precipitator.

**•** When Monroe operates the dry fly ash handling system, only fly ash (no economizer ash) is pulled by vacuum, using mechanical exhausters, from the precipitator hoppers to two filter/separators. The filter/separators separate the fly ash from the transfer air, which is exhausted. The fly ash is then dropped into a 150

- ton, air

- locked transfer hopper. The ash is then introduced to the compressed air pressure system that pushes it to the storage silo at the Headwaters loading site. The timed, air

- locked transfer hopper allows the system to switch between the negative and positive air pressure used to transp ort the ash.

**•** The dry fly ash is transported 3,100 ft to the Headwaters loading site. With the current system at Monroe, 3,100 ft is probably the farthest distance that the ash can be efficiently transported pneumatically. Options to improve the system in clude larger blowers or a booster system. With a booster system, bursts of air are strategically placed along the pipe to enhance air flow. Headwaters stated that 4,000 ft is about the maximum distance that ash can be transferred pneumatically.

**•** Headwate rs stated that there are two ways to transfer fly ash pneumatically. The first is called a dilute system, in which there is a small amount of ash relative to air in the pipe. This system, which is operated at Monroe, offers less risk of clogging. The other type of system operates with higher amounts of ash relative to air in the pipe. Although the system ideally transfers more ash through the pipe than the dilute system, it is usually more expensive, slower, less reliable, and not cost effective.

**•** From the 4,000

- ton storage silo, the ash is pneumatically transferred to a 200

- ton loading silo by an air slide and bucket conveyor. The air slide, located at the bottom of the storage silo, is a long piece of fabric membrane, positioned at a specific gradient with air jets underneath that float and move the ash “down the slide”. From the slide, the ash is filled into the bucket conveyor, which can load the silo at 200 tons per hour if necessary. Both the air slide and bucket conveyor are operated under a vacuum sys tem. Any fugitive dust is pulled back into either the main storage silo or the loading silo and collected in a baghouse at the top of each silo. There are induced air fans that pull air out of the silos through the filter bags. An air quality monitor is l ocated in the loading area that continually monitors for fugitive dust.

**•** According to Headwaters, capacity at storage silo is enough to handle about 4 days of ash production at the plant.

**•** Dry fly ash is transferred from the loading silo to the trucks pneu matically with a double annular spout. A vacuum is pulled through the outer annulus of the spout, creating a tight seal with the truck. Ash is delivered through the inner annulus of the spout into the truck. ThePage 7

vacuum captures any fugitive dust and pulls it through the loading silo to the baghouse. It takes about 1 or 2 minutes for the ash to settle in the trucks before the spout is pulled away.

**•** Headwaters frequently tests the moisture content of the dry fly ash being loaded. Plant personnel stated that is the fly ash usually contains less that 1 percent moisture.

**•** The amount of ash that is transferred to the trucks is determined by weight. Trucks in Michigan are permitted to haul up to 50 tons. Headwaters estimated that they can load about
25 tons of as h into a truck in 10 minutes, and can load 200 tons from the loading silo into eight trucks.

**•** Monroe stated that a complete conversion from the current wet/dry fly ash handling system
to a moisture

- conditioned dry fly ash handling system (suitable for lan dfilling the dry fly ash) would require the following major changes:

**•** The 150

- ton silos that collect the dry fly ash from the precipitator hoppers
would need to be converted to 500

- ton silos to support a completely dry
system.

**•** Modifying the silo and lo ading area for moisture

- conditioning would also be expensive. This modification would include adding an exhaust system and doors to the loading area that will provide enclosure to the transfer space. Additionally, Monroe stated that because they burn 70 pe rcent PRB coal, any moisture conditioning would cause the ash to become cement i tious in the bottom of the storage silo.

**•** Transfer of the moisture

- conditioned ash to the basin/landfill would be a potential issue. Suggested options include truck, pneumatic t ransfer, or conveyors. State and township permits would be developed to control any fugitive dust and the infrastructure (new roads or piping) used for transport.

**•** Monroe would also have to develop another ash handling system specifically
for economizer as h. The economizer ash cannot be handled with marketable fly ash because the larger size of the economizer ash particles would make the ash unmarketable to the cement/concrete industry. Economizer ash also
cannot be handled with bottom ash because the trac e metals it contains would
not allow Monroe’s bottom ash to meet certain state standards. The bottom ash is currently considered by the Michigan Department of Environmental Quality (MDEQ) to be inert and not a solid waste (i.e., does not leach any pollutan ts above drinking water standards).

FGD System

**•** Monroe operates one limestone forced oxidation (LSFO) FGD scrubber system that services
Unit 4

. An identical FGD scrubber system has been installed to service Unit 3 (planned to be in operation Nov 2009). (UPDATE: Unit 3 FGD was placed in operation in November 2009. ) [QUESTION FOR MONROE: Is this FGD scrubber system currently operating?] Monroe is currently considering constructing/installing two additional LSFO FGD scrubbers that will
service Units 1 and 2 by 2015, depending on the outcome of the CAIR rule and economicPage 8

factors. Plant personnel estimate that it takes about 30 months to construct, install, and bring an FGD scrubber system on line. It took about two weeks from the time Monroe began operating the Unit 4 FGD system to the time it was at steady state and Monroe could begin sending wastewater to the FGD wastewater treatment system. It took about 10 days from that point to “fill” the FGD wastewater treatment system with wastewater.

**•** The Unit 4 FGD system has four absorber recycle pumps and four sets of spray headers.
Three of the four are typically operated. The absorber has two trays. Process flow diagrams of the Unit 3 and 4 FGD systems are included in Attachment 4 of this memorandum.

**•** T he Unit 4 FGD absorber is constructed of concrete block and lined with Stebbins, semplate tile. It is a B&W design.

**•** The Unit 4 FGD system achieves a sulfur dioxide removal of greater than 97 percent. After passing through the Unit 4 FGD system, flue ga s exits through a dual flue chimney stack, which will also service the Unit 3 FGD system when it is operational.

**•** Monroe receives limestone by boat . The limestone is conveyed to a storage pile. Limestone for the Units 3 and 4 FGD systems is then conveyed to a silo with an 890 ton capacity.

**•** Monroe has two ball mills on site to crush limestone to the correct size for use in the limestone slurry. At the time of the site visit, one was in operation and the other was being prepped for operation. The ball mill crushes 43 tons of limestone per hour.

**•** The limestone slurry from the ball mill is transferred to a classifier to remove the large limestone particles before the slurry is transferred to the limestone storage tank. The large limestone particles are recyc led back to the ball mill for additional processing.

**•** Monroe has a 600,000 gallon FGD make

- up water tank that holds filtered plant service water. Plant service water, which is intake water from the surrounding Lake Erie (note that this is
not Raisin Rive r water due to a reversal of water flow), is filtered through six multimedia filters to remove any unwanted debris (e.g., stones, zebra mussel larvae). Backwash from these multimedia filters (“FGD pretreatment backwash”) is sent to the bottom ash basin. T he filtered water is used for the limestone slurry, the FGD absorber mist eliminators, and the vacuum belt filter,

**•** Monroe maintains a pH of approximately 5 to 6 S.U. in the Unit 4 FGD absorber.

**•** Monroe does not add any acid additives to the Unit 4 FGD sc rubber system.

**•** Monroe blows down from the Unit 4 FGD absorber when the solids concentration in the absorber reaches 21 percent (by weight). This blowdown occurs about three times per day for approximately one to one and a half hours. The typical solids c oncentration in the FGD absorber is 19 to 21 percent and the typical chlorides concentration is 9,000 to 12,000 ppm (and always maintained below 12,000 ppm). Plant personnel stated that 15,000 ppm is the maximum allowable chlorides concentration according to the design specifications of the
FGD scrubber.Page 9

**•** The blowdown from the FGD system is transferred to the primary hydroclones for initial solids separation. Four sets of hydroclones are currently in place that can service all four FGD systems, when operat ional. If the overflow from the primary hydroclones is between 11,000 and 12,000 ppm chlorides, it is sent to the chloride purge tank. If the overflow from the primary hydroclones is between 9,000 and 10,000 ppm chlorides, it is recycled back to
the r eclaim water tank, from which water is recycled back to the absorber. The underflow from the primary hydroclones, which is approximately 55 percent solids (by weight), is
transferred to filter feed tanks and then to the vacuum belt filter.

**•** Monroe uses a vacuum belt filter to dewater the gypsum into a saleable byproduct. The vacuum used is created with a 500 horsepower pump. Monroe washes the gypsum with filtered plant service water as the gypsum is applied to the belt filter to reduce chlorides. The
mois ture content of the dewatered gypsum is about seven to eight percent. The filtrate from
the vacuum belt filter is transferred to the reclaim tank.

**•** Monroe markets the gypsum product and they are currently looking to improve their current

contract. Monroe anticipates that the gypsum specifications will be less than ten percent moisture and less than 100 ppm chlorides in order for the gypsum to be used for wallboard. The gypsum produced at Monroe typically contains about 30 ppm chlorides. The gypsum
from the vacuum belt filter is transferred to a gypsum storage building. The gypsum is either sold (Monroe is currently holding some saleable gypsum) or trucked to an offsite landfill at the Sibley Quarry, which is owned by Monroe. Typically, Monroe sends about f our truckloads of gypsum per day to the Sibley Quarry. The Sibley Quarry landfill is not lined. Groundwater monitoring wells are located around this landfill. Landfill l eachate is collected.

**•** The water in the chloride purge tank is transferred to the se condary hydroclones for additional solids separation. The underflow from the secondary hydroclones is transferred to
the reclaim tank and the overflow is transferred to the wastewater treatment tank. Monroe
sends wastewater from the wastewater treatment ta nk to the FGD wastewater treatment system once every three days for approximately two hours.

**•** Monroe takes grab samples of the influent to the FGD wastewater treatment system from the top of the open wastewater treatment tank using a bucket.

FGD Wastew ater Treatment System

**•** The FGD wastewater treatment system operated at Monroe was designed by Siemens. Monroe monitors the wastewater treatment system at various points (effluent of equalization tank, reaction tank #1, effluent of the clarifier, and the fi nal wastewater treatment system effluent) to ensure that it is achieving metals removal according to Siemens’ design specifications. Monroe sends the FGD wastewater treatment samples to a lab for analysis of metals that include, but are not limited to, alu minum, antimony, arsenic, copper, lead, mercury, and selenium.

**•** The two

- train FGD wastewater treatment system operated at Monroe was designed to handle
wastewater from all four FGD systems, when installed/operating. When operating at full capacity, Monroe projects that FGD wastewater will be treated 7 days a week and sludge will be treated 5 days a week. Currently, Monroe operates the FGD wastewater treatment system as a batch process. Each train of the wastewater treatment system was designed to treat 60 0Page 10

gpm of FGD wastewater (each clarifier can handle 1,200 gpm). The current, typical flow rate through the wastewater treatment system is 550 gpm. A process flow diagram of the FGD wastewater treatment system is included in Attachment 5 o f this memorandum

.

**•** The FGD scrubber purge (from the wastewater treatment tank) is transferred to the equalization tank of the FGD wastewater treatment system. The equalization tank also
receives the filtrate from the wastewater treatment filter press, off

- spec treated ef fluent, and water collected from the sumps of the wastewater treatment system building. [QUESTION FOR MONROE: At what flow rate is the FGD wastewater transferred to the equalization tank? What is the residence time of the wastewater in the equalization t ank?] The influent
flow rate to the Equalization tank is 1200 gpm. The residence time in the equalization tank depends on the flow rate that the WWT plant is processing. At a flow rate of 600 gpm the
residence time is approximately 12 h ou rs.

**•** The wastew ater treatment system includes a maintenance tank in case the equalization tank or sludge holding tank is out of service.

**•** The wastewater from the equalization tank is transferred to reaction tank #1 (the wastewater treatment system includes two of these tanks) where lime slurry is added to adjust the pH of the wastewater. Organosulfide is added to target the removal of certain metals, such as mercury. The target pH in reaction tank #1 is between 8 and 9 S.U.

**•** The FGD wastewater gravity drains to react ion tank #2 (the wastewater treatment system includes two of these tanks) where ferric chloride is added.

**•** From reaction tank #2, the wastewater gravity drains to the clarifiers (the wastewater treatment system includes two clarifiers). As the water is tra nsferred, AcuTreat® 4355 polymer is added. The total retention time in the clarifiers is about 6 hours.

**•** From the clarifier, the wastewater gravity drains into one of five sand gravity filters (continuous backwash). Hydrochloric acid is used to adjust the pH of the wastewater to
between 6 and 8 S.U. as the water is transferred to the sand filters.

**•** From the sand filters, the water is transferred to the treated wastewater storage tanks (there are two of these tanks) and is sent to the bottom ash basin (Ar ea 15). [QUESTION FOR
MONROE: How often is this treat ed effluent sent to the bottom ash basin, for how long, and at what flow rate?] On average Monroe’s WWT Plant will discharge to the bottom ash basin

14 h ou rs a day at a flow rate of 275 GPM. This depen ds upon the pH falling within a range
of 6.5 to 9.0 and how much waste water is being sent to the WWT Plant from the FGD
system

. This effluent is monitored for pH and turbidity. Off

- spec treated wastewater is recycled to the equalization tank.

**•** Monroe takes grab samples of the treated wastewater downstream of the treated wastewater storage tank on the suction side of the treated wastewater discharge pumps from a fiberglass reinforced plastic (RFP) pipe tap.

**•** Monroe estimated that the total retention tim e for the entire wastewater treatment process is approximately 12 hours. The residence time of the wastewater depends on the flow rate thatPage 11

the WWT facility is processing. At a flow rate of 600 gpm the residence time is approximately 20 h ou rs.

**•** Some of t he sludge from the clarifiers is recycled to reaction tank #1 for seeding. The rest of the sludge is transferred to the sludge holding tank and then to the sludge conditioning tanks. Monroe dewaters the sludge from the sludge conditioning tanks using fou r belt filter presses. As the sludge is loaded onto the belt press

, AcuTreat® 4355 polymer is added. The press sandwiches the sludge between two rollers to remove moisture. The filtrate from the belt presses is recycled to the equalization tank. The dewate red sludge, which is typically about 35 percent moisture, is transferred to four sludge hoppers and trucked off site to a landfill

.

Metal Cleaning Wastes

**•** Monroe cleans each of their four boilers about once every ten years. Monroe uses an acid
wash to cl ean the boiler tubes. The wastewater from cleaning the boilers is sent to a 6.5 million gallon, open storage tank. Monroe ’s past practice was to send water from the storage tank to the Unit 4 boiler, where it was evaporate d . There is currently no discharg e of metal cleaning wastes. [QUESTION FOR MONROE: What type of acid is used to clean the boiler
tubes? The two acids used to clean the boiler tubes are 4% hydroxyacetic acid and 2% formic
acid. How much wash water is generated and transferred to the stor age tank with each cleaning (for each boiler)? The typical boiler volume is approximately 105,500 gallons. Unit 3 was cleaned in November 2009 and generated approximately 2.2 million gallons of wastewater, including wash water and rinse water. Unit 2 wa s cleaned in May 2010 and generated approximately 1.7 million gallons of wastewater, including wash water and rinse water. Exact volumes of metal cleaning wastewaters are not known for earlier cleanings, but are likely between about 1.7 million gallons an d 2.5 million gallons. How often is water transferred from the storage tank to Unit 4 for evaporation? Between 1994 and 2001, the plant evaporated chemical metal cleaning wastewater in the Unit 4 boiler. However, Monroe will no longer be evaporating me tal cleaning wastes, because it will poison the SCR catalyst and possibly the FGD. The current practice is to adjust the wastewater to a pH of 10 using
lime

, and then agitating it with oxygen in order to meet the NPDES permit requirements prior
to dischar ge under the NPDES permit. EPA noted a significant volume of water in the storage tank

– are other cleaning waters sent to this tank? Only chemical metal cleaning wastes are sent to this tank. Because it is an open tank, storm water may also enter the t ank.

**•** Monroe stated that they only use water to clean the air heaters. No chemicals are added to the water during this process. The water is sent to the bottom ash basin (Area 15).Table 1. Site Visit Attendees

Name Organization (Representing) Telephon e E

- mail

Mary Hana Environmental Management and

Resources (313) 235

- 8704 hanamj@dteenergy.com

Chuck Larlham Environmental Management and
Resources /Monroe Power Plant (734) 384

- 2560 larlhamr@dteenergy.com

Claire Jennings Environmental Management and
Resources /Monroe Power Plant (734) 384

- 2562 jenningsc@dteenergy.com

Dan Casey Monroe Power Plant (734) 384

- 2371 caseyd@dteenergy.com

Dennis Leonard Environmental Management and

Resources (313) 235

- 8714 leonardd@dteenergy.com

Brett Mac Intyre Environmental Management and

Resources (31 3) 235

- 6922 macintyreb@dteenergy.com

Paul Tracy Monroe Power Plant (734) 384

- 6812 tracyp@dteenergy.com

Donna Hill UWAG/Southern Co. (205) 257

- 5234 dbh ill@southernco.com

Ron Jordan EPA/Office of Water (202) 566

- 1003 jordan.ronald@epa.gov

Jezebele Alicea

Virella EPA/Office of Water ( 202 ) 566

- 1755 alicea.jezebele@epa.gov

Sarah Holman ERG (Contractor to EPA) (703) 633

- 1661 sarah.holman@erg.com

Elizabeth Sabol ERG (Contractor to EPA) (703) 633

- 1659 elizabeth.sabol@erg.com