Final Notes from Site Visit at American Electric Power’s Cardinal Steam Electric Plant on 

February 2, 2010

EPA conducted a site visit at American Electric Power’s Cardinal Steam Electric Plant

(Cardinal) located in Brilliant, OH on Tuesday, February 2, 2010 to learn about the operations at 

the plant, including the operation of the flue gas desulfurization (FGD) wastewater treatment 

system. Table 1 identifies the site visit participants. The presentation Cardinal gave during the 

site visit is included as Attachment 1.

Plant Overview

• Cardinal operates three coal-fired electric generating units. American Electric 

Power (AEP) owns Unit 1 and operates the facility. Buckeye Power owns Units 2

and 3. The table below contains some general information on the current 

operation of each steam electric generating unit.

Unit

Installation 

Date

Gross Net

Capacity 

(MW)

Particulate 

Control

NOx 

Control SO2 Control

1 1967 600 ESP (Electrostatic 

precipitator) (coldside)

SCR 

(2001)

Wet FGD (March 2008)

2 1967 600 ESP (cold-side) SCR 

(2001)

Wet FGD (December 

2007)

3 1977 630 ESP (hot-side) SCR 

(2001)

Wet FGD (Planned for 

2012)

• Cardinal burns 4.5 million tons of coal annually. Units 1 and 2 burn only 

bituminous coal. Unit 3 burns 80% low sulfur coal and 20% Powder River Basin 

(PRB) coal. After Cardinal completes the FGD scrubber on Unit 3, the plant plans 

on switching coals to burn a coal with a higher sulfur content (or whatever coal is 

cheapest). The FGD systems on Unit 1 and 2 were originally designed for a coal 

with 7.5 lbs sulfur dioxide (SO2) per mmbtu. However, starting in 2001 during 

NOx season, the sulfur in the coal was reduced to 2.5 lbs SO2 per mmbtu to reduce

sulfur trioxide (SO3) formation. 

• Cardinal receives coal for Units 1 and 2 via truck; whereas, coal for Unit 3 is 

received via barge. The plant stores approximately 30-60 days’ supply of coal on

site.

• Units 1 and 2 use the following air pollution control technologies in the following 

order: low NOx burners, SCR system, ESP, and FGD absorber. Unit 3 operates

the same order of air pollution control technologies; however, the FGD absorber 

has not yet been installed. 

• Cardinal does not regenerate the SCR catalysts on site.
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• Cardinal operates an on-site landfill that receives a portion of the FGD gypsum

(the majority of the gypsum is used in wallboard manufacturing). The landfill has 

a leachate collection system. The leachate collected from the system has an 

internal outfall (Outfall 602) and is ultimately discharged via final Outfall 019. 

Cardinal is required to monitor at internal Outfall 602 for flow, dissolved solids, 

fluoride, boron, mercury, and selenium. 

Flue Gas Desulfurization System

• Units 1 and 2 both have wet FGD systems. Cardinal is in the process of adding an

FGD system to Unit 3. The FGD system for Unit 3 will be designed similarly to 

Units 1 and 2; however, Cardinal is not installing a stack for Unit 3. Instead the 

flue gas will be inserted into the center of the cooling tower. This will lead to 

better dispersion and additional droplet removal within the cooling tower.

Placement of the stack in the cooling tower, where it will be clear of the cooling 

tower plume impingement and the unsafe conditions created when it freezes on 

the stack shell, is less expensive than building a free-standing stack. Cardinal 

states that a stack can cost up to 30 million dollars to install. Although this 

technology is commonly used in Europe, Cardinal is the first US plant to build 

one.

• Units 1 and 2 both have 95% SO2 removal capability using high sulfur coal (7.5 lb 

S/mmbtu). Additionally, both units have a trona injection system for SO3

mitigation. 

• The FGD systems are wet limestone forced oxidation jet bubbling reactors (JBR)

designed by Black and Veatch. Service water and JBR slurry is used to cool the 

flue gas from 300°F to 126°F. Once cooled, the flue gas enters the JBR and is 

bubbled into the JBR slurry. In the slurry, air is injected to supply oxygen to form 

a sulfate product. The SO2 reacts with limestone (CaCO3) and oxygen to form 

gypsum (calcium sulfate), water, and carbon dioxide (CO2). The pH in the 

absorber is maintained at approximately 4.8 S.U. Limestone is more easily 

dissolved at a lower pH, so with this low pH, the plant does not have to grind the 

limestone as much as other plants. The vapor pressure of the slurry affects the 

SO2 absorption in the liquid phase, forming a weak acid. Subsequent 

neutralization, precipitation, and oxidation steps convert the weak acid to calcium 

sulfate.

• Cardinal receives limestone at the plant via barge. Cardinal operates an on-site 

ball mill to crush the limestone. The limestone slurry formed in this process is 

sent to a hydrocyclone. Oversized material is returned to the ball miss grinding 

circuit via the hydrocyclone underflow. The correctly sized material 

(hydrocyclone overflow) is used to replenish the JBR slurry; it is approximately 

30% solids by weight. 

• The blowdown rate from the JBR varies to maintain a 20 percent solids 

concentration in the JBR, which results in a chlorides concentration of around 

4,000 to 5,000 ppm, depending on the chloride in the coal. The system is designed 
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to have a limit of 12,000 ppm of chlorides; however, Cardinal has found that the 

FGD scrubber system operates best if the chlorides concentration does not go

above 4,000-5,000 ppm.

• Blowdown from the FGD scrubber is continuous and goes to the Hydroclone Feed 

Tanks. Blowdown from the hydroclone feed tanks is pumped to a set of primary 

hydrocyclones.

• The underflow from the primary hydrocyclones is transferred to vacuum belt 

filters to dewater the gypsum. Cardinal washes the gypsum as it is applied to the 

vacuum belt filters to reduce the chlorides in the gypsum. Filtrate from the 

vacuum belt filters is sent to the reclaim tank. Wastewater in the reclaim tank is 

either recycled back to the JBR or sent to the wastewater treatment system.

• The dewatered gypsum contains 95% solids and less than 10 ppm of chlorides.

The gypsum must have less than 10% moisture for Cardinal to be able to sell it to 

wallboard manufacturers. Cardinal sells approximately 50% of the gypsum to 

Serpentine. All gypsum that is not sold is transported to an on-site landfill.

• The overflow from the primary hydrocyclones is transferred to the wastewater 

treatment system. This waste stream contains approximately two percent solids. 

Cardinal also blows down from the reclaim tank. 

• Cardinal only has one set of primary hydrocyclones per dewatering train. 

Personnel state that the plant only needs primary hydrocyclones because the 

hydrocyclones are sized correctly to feed the vacuum filters.

FGD Wastewater Treatment System

• A process flow diagram for the FGD wastewater treatment system at Cardinal is

included as Attachment 2.

• Cardinal began sending FGD wastewater to the wastewater treatment plant in 

January 2008. According to plant personnel, it took two to three weeks for the 

treatment system to fill up with water.

• The hydrocyclone overflow and reclaim water are both transferred to the FGD

wastewater treatment system. The plant has a sample point for the combination of 

the two streams before they enter the wastewater treatment system, but there is 

not a sample point for the individual streams. 

• The FGD wastewater is first combined in two equilization (EQ) tanks. The EQ

tanks main purpose is to help the system maintain a steady flow rate. Mainly, the 

EQ tanks contain hydrocyclone overflow and wastewater from the reclaim water 

tank. Sumps from the wastewater treatment building are also transferred to the EQ 

tank. If the effluent from the FGD wastewater treatment system does not meet the 

specifications for discharge, the plant can pump the effluent back to the EQ tank.
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• The wastewater from the two EQ tanks is combined and then split to enter either 

of two trains of the FGD wastewater treatment system, which operate in parallel. 

The wastewater first enters the desaturation tanks. Cardinal adds lime to the 

desaturation tanks to maintain a pH of plus 9.0 S.U. Cardinal personnel stated that 

lime is not added to target any specific metals. In the desaturation tanks, the water 

is softened, reducing the potential for scaling downstream.

• The wastewater travels from each desaturation tanks to a primary clarifier (i.e., 

desaturation tank A flows into primary clarifier A; and desaturation tank B flows 

into primary clarifier B). The sludge from each primary clarifier is pumped to the 

sludge holding tanks.

• The overflow from each primary clarifier is transferred to the coagulant mix 

tanks. Cardinal adds ferric chloride and sulfuric acid to each of the coagulant mix 

tanks. The sulfuric acid is added to lower the pH to 8.0-8.3 S.U. Cardinal

determined that ferric chloride forms a precipitate better at this pH set point.

Cardinal is also planning to add organosulfide to each mix tank by December 

2010. Cardinal is adding organosulfide to specifically target mercury removal. 

The organosulfide storage tank has not been built yet.

• After the coagulant mix tanks, the wastewater is transferred to the secondary 

clarifiers, where Cardinal adds anionic polymer. The secondary clarifiers are 

solids contact clarifiers. The sludge from each secondary clarifier is either 

recycled back to the desaturation tank to act as seed crystals or sent to one of the 

sludge holding tanks.

• The sludge in each of the two sludge holding tanks is dewatered using one of four 

filter presses. The filtrate from the dewatering process is sent to the filtrate 

equalization tank and returned to the secondary clarifiers. Cardinal personnel 

stated that the filtrate goes to the secondary clarifier rather than back to the EQ 

tank because the wastewater has already been processed so there is no need for it 

to go through the entire process all over again.

• The dewatered solids from the filter presses are trucked to the Cardinal FAR1 

Residual waste landfill.

• The overflow from the secondary clarifiers is transferred to the effluent storage 

tanks. Although Cardinal had planned to install gravity filters after the effluent 

tanks as shown in the process flow diagram for the wastewater treatment system, 

they decided not to add these units. Cardinal personnel state that the floc is too 

fine for the gravity filters to function efficiently. Furthermore, they stated that it

would be impossible to add ultrafiltration or microfiltration at the end of the 

process because of scaling/plugging problems.

• Cardinal has limits for the discharge of effluent from the FGD wastewater 

treatment system (internal outfall 601) for pH and suspended solids. Additionally, 

the plant must monitor the following pollutants: flow, temperature, specific 

conductance, dissolved solids, alkalinity, chlorides, fluorides, sulfate, arsenic, 
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barium, boron, cadmium, chromium, copper, iron, lead, mercury, nickel, 

selenium, and zinc. 

• There is a sample point for the effluent where the plant does compliance 

monitoring. Cardinal takes 24-hour composite samples at the location. The flow 

rate of the effluent is around 645-700 gpm; however, the effluent is not 

necessarily continuous over the entire day and depends largely on the amount of 

wastewater recirculating through the system. FGD wastewater still flows through 

the sample point even when wastewater is being recirculated in the system.

• Effluent from the FGD wastewater treatment system is discharged to the river at 

the same location where once-through cooling water is discharged at final outfall 

001. Twenty feet below the surface of the river there is a 20-foot long header 

which disperses the release of the treated wastewater.
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Table 1. Site Visit Attendees

Name Organization (Representing) Telephone E-mail

Tom Hart AEPSC 614-716-3260 tomlhart@AEP.com

Deanna King AEPSC 614-716-1234 djking@aep.com

JR Holland AEP – Cardinal 740-598-6806 JRholland@aep.com

Bernie Lombard AEP - Cardinal 740-598-6514 BLombard@AEP.com

Tom Kaufmann AEP – Cardinal 740-598-6511 Tdkaufmann@aep.com

Donna Hill Southern Company, UWAG 205-257-5234 dbhill@southernco.com

Josh Hall EPA 202-566-1002 hall.josh@epa.gov

TJ Finseth Eastern Research Group 703-633-1698 thomas.finseth@erg.com

Becky Schwantes Eastern Research Group 703-633-1715 becky.schwantes@erg.com