MEMORANDUM

TO: Ron Jordan, EPA 

FROM: TJ Finseth, ERG 

 

DATE: 24 May 2007 

SUBJECT: Notes from Site Visit at Tampa Electric Company’s Big Bend Station on 

April 27, 2007 

EPA conducted a site visit at Tampa Electric Company’s Big Bend power plant on Friday, April 

27, 2007 to learn about the operations at the plant and determine where and how samples would 

be collected if the plant was selected for sampling. Table 2, at the end of this memorandum, 

identifies the participants at the site visit. 

This memorandum summarizes the information collected during the site visit and the pre-site 

visit phone call, which was held on April 23, 2007. 

Plant Study 

Plant personnel noted that they are in the process of installing SCRs on each of the four units 

over the next few years; the SCR on Unit 4 begins operation in the next couple of weeks. As 

part of their NPDES permit modification, they will be conducting a study over the next nine 

months to assess the impact of the installation of the Unit 4 SCR on wastewater characteristics. 

The plant will collect wastewater samples at several points throughout the process including the 

FGD make-up water, FGD blowdown prior to treatment, FGD wastewater treatment effluent, 

and intake cooling water. The plant will analyze the waste streams for nitrogen, ammonia, 

mercury (low-level), and flow. Table 1 below shows which anlaytes will be analyzed at each 

sampling point. 

Table 1. Sampling Points and Analytes for the Big Bend Wastewater Study 

Parameter 

FGD 

Make-up 

FGD Blowdown 

Prior to Treatment 

FGD Wastewater 

Treatment Effluent 

Intake Cooling 

Water 

Ammonia (as N) X X 

Nitrogen, Total (as N) X X 

Mercury, Total X X X 

Flow X X 

Although ammonia is added to the SCR, the plant theorizes that nitrogen loads in the FGD 

wastewater drop when an SCR is operating (from about 400 mg/L without the SCR in operation 

to 100 mg/L with the SCR in operation). However, because some of the sulfur dioxide in the 

flue gas is converted to sulfur trioxide in the SCR, the plant intends to inject ammonia into the 

flue gas downstream of the SCR and upstream of the air preheater, ESP, and FGD. In fact, the 
May 24, 2007 

Page 2 

plant intends to add excess ammonia to the flue gas. The ammonia and sulfur trioxide will react 

to form ammonium sulfate. Althought the plant expects the majority of the ammonium sulfate to 

be removed by the ESP, they expect that some of the ammonium sulfate will pass through the 

ESP and be transferred to the wastewater in the FGD system. The study will determine the 

resulting wastewater characteristics associated with operation of the SCR and determine the 

nitrogen species present. If possible, they will determine if denitrification will be necessary. 

The plant stated that they could provide the study data to EPA in lieu of EPA sampling the plant. 

EPA stated that there could be some issues with the timing of the plant’s study and when EPA 

would need the results to make decisions for the detailed study. In addition, the plant’s study 

may not cover all the analytes and waste streams that EPA intends to sample. 

Plant Overview 

• There are 4 units at the Big Bend plant. Unit 1 began operation in 1970, Unit 2 in 

1973, Unit 3 in 1976, and Unit 4 in January of 1985. Units 1 and 2 are each rated 

at 445 MW, Unit 3 is rated at 465 MW, and Unit 4 is rated at 485 MW. 

• All 4 units have ESPs. 

• Each of the 4 units is scrubbed, by one of two FGD systems. The plant has one 

FGD scrubber system for Units 1 and 2 (began operation 1/1/2000), and one FGD 

scrubber system for Units 3 and 4 (began scrubbing Unit 4 in 1985 and Unit 3 in 

1995). 

• Currently none of the units have SCRs operating, but the plant will begin 

operating the Unit 4 SCR within the next couple weeks. The plant intends to 

install one new SCR each year until all four units have SCRs. All of the SCR 

units, once installed, will operate year-round. The plant estimates that the NOx

emissions will be reduced by approximately 89% (based on 1998 levels) once all 

four are operating. 

• The plant estimates that the improvements to the scrubber, ESPs, and the addition 

of the SCRs will reduce the SO2 emissions by 89%, the particulate matter 

emissions by 72%, and the mercury emissions by 78% (all based on 1998 levels). 

• The plant burns approximately 4 to 5 million tons of coal per year. The coal is 

eastern bituminous and comes from Kentucky. The coal used in Unit 4 is Illinois 

Number 6. The coal contains approximately 5 pounds of SO2 per million BTU. 

The plant is permitted to blend 20 percent petroleum coke with the coal; however, 

they typically burn around 1 to 2 percent petroleum coke, with a maximum of 5 

percent petroleum coke. 

• According to the plant, the use of anhydrous ammonia to control SO3 emissions 

(originating from SCR operation) is not typical of the industry. Most plants do 

not use ammonia because it sticks to the fly ash and therefore, the fly ash cannot 

be sold. The Big Bend plant is planning to build a fly ash beneficiation plant that 

will strip the ammonia from the fly ash and return it back to the plant. In 

addition, the remaining carbon in the fly ash will be stripped from the fly ash 

inerts. The resulting fly ash inerts will be marketable. 
May 24, 2007 

Page 3 

• The plant operates a dry fly ash handling system and currently sells approximately 

99 percent of the fly ash produced. 

• Unit 4 has a dry bottom boiler. The bottom ash from the other units is sent to the 

bottom ash ponds. The plant sells the slag and bottom ash from the plant. 

• The plant has installed hydrobins to separate the bottom ash from the sluice water; 

however, they are not currently operating. The plant intends to begin operating 

them in the next 4 to 6 months. The plant stated that most of the water will be 

reused for sluicing and some may go the plant’s pond system. 

• All four units generating units have a once-through cooling water system. The 

plant uses approximately 1,300 MGD of cooling water combined for all four 

units. The plant pulls cooling water from the intake canal, uses it to condense 

steam, and discharges it to the discharge canal. The plant does not perform any 

type of biofouling control. 

• The Tampa Bay Desalination plant is located next door to the power plant. The 

desalination plant pulls water from Big Bend’s intake canal and discharges to Big 

Bend’s discharge canal. The discharge is downstream of the Big Bend’s 

monitoring location. 

• The plant is currently working on several projects to improve the environmental 

impacts from the plant. As mentioned previously, the plant has installed 

hydrobins and will begin operating them in Fall 2007. The current slag pond will 

be used for stormwater collection. The plant is also working to line the existing 

unlined ponds. In addition, the plant is upgrading the gypsum storage area. 

FGD System and Wastewater Treatment System 

• The scrubber system for Units 3 and 4 was initially designed only for Unit 4 for 

compliance with NSPS. It is a limestone, forced oxidation system. The scrubber 

design is old and consists of a double loop, spray/tray tower and is not typical of 

the newer scrubbers being installed. The scrubber was modified to be used for 

both Units 3 and 4, including the use of DBA as an additive. There are four 

individual scrubber towers for the system. When the scrubber was initially 

designed only three of the four towers were intended to operate at one time (with 

the fourth used as a spare), but when Unit 3 started being scrubbed in the system, 

all four towers needed to operate. 

• The plant installed a single scrubber for Units 1 and 2 that began operating on 

January 1, 2000. The scrubber is approximately 60 feet in diameter and 60 feet 

tall. The scrubber holds approximately 1.3 million gallons of water. The 

scrubber is a limestone, forced oxidation system and the plant uses DBA as an 

additive. The scrubber system contains a single tower and is one of the largest 

scrubbers in the United States. 

• Approximately 1.25 gpm/MW of water evaporates in the scrubber, which exits 

out the stack 

• The limestone used in the scrubbers is sent to three individual day silos for 

storage, which feed the three ball mills. The ball mills pulverize the limestone, 

but it is a rougher pulverization than most plants because of the initial design of 
May 24, 2007 

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the Unit 4 scrubber. The limestone feed rate to the scrubbers is based on the pH 

in the scrubber. 

• The DBA for the Unit 3 and 4 scrubber is added to the limestone reagent, 

therefore all the limestone that is added contains DBA. The DBA for the Unit 1 

and 2 scrubber is added to the reaction tank in the scrubber. 

• Both of the scrubbers produce commercial grade gypsum for use in wallboard 

manufacturing. National Gypsum built a wallboard manufacturing plant near the 

power plant. The Big Bend plant produces 650,000 to 900,000 tons of gypsum 

per year, which is transported to National Gypsum. 

• The gypsum slurry from the Unit 1 and 2 scrubber is pumped directly to primary 

hydroclones. The gypsum slurry from the Unit 3 and 4 scrubber is pumped to 

quencher blowdown tanks and then pumped to a separate set of primary 

hydroclones. The underflow from both of the primary hydroclones is 

approximately 50 to 55% solids and is combined and sent to rotary drum vacuum 

filters. The overflow from both primary hydroclones is approximately 6% solids 

and is combined in the chloride purge feed tank. Most of the primary hydroclone 

overflow is transferred from the chloride purge feed tank to the return water tank 

and recycled back to the Unit 1 and 2 scrubber. The remaining primary 

hydroclone overflow is sent to a secondary hydroclone. The overflow from the 

secondary hydroclone is between 1 and 2 % solids and flows to the wastewater 

equalization tank (the beginning of the FGD wastewater treatment system). The 

underflow from the secondary hydroclone is returned to the Unit 1 and 2 scrubber. 

The blowdown to the equalization tank represents the purge stream from all four 

units and it is fairly continuous at a flow rate of approximately 230 gpm. The 

chlorides concentration is about 30,000 mg/L. 

• The rotary drum vacuum filters dry the 50% solids underflow from both primary 

hydroclones into a 90% solids gypsum product. The plant washes the gypsum 

with Sun City Center Sewage effluent. The gypsum produced by the plant is 

transported to the National Gypsum plant next door. Any off-spec gypsum is 

piled on-site and allowed to sit. The rain rinses the chlorides out of the gypsum 

and the product is later sold to the National Gypsum plant. 

• The make-up water for the FGD system is taken from a series of ponds on site 

that have a 70 million gallon water storage capacity. The plant pulls additional 

water (about 3.5 MGD) into the pond system from the Sun City Center Sewage 

Treatment Plant effluent discharge. The plant washes the gypsum cake with fresh 

Sun City Center Sewage Treatment Plant effluent to remove the chlorides from 

the gypsum. The plant is capable of using potable water for the FGD make-up, 

but avoids using it unless absolutely necessary. 

• The FGD wastewater treatment system began operation in January 2000, but the 

plant immediately had issues with settling the calcium sulfate. The clarifiers were 

unable to settle the solids. Therefore, the plant redesigned the treatment system. 

The plant initially had a primary clarifier for initial solids settling and secondary 

clarifier after solids conditioning. In the redesign, the plant built a larger clarifier 

that was capable of handling all of the wastewater after the solids conditioning. 

The original primary and secondary clarifiers are now used in parallel with the 
May 24, 2007 

Page 5 

new primary clarifier after solids conditioning. The plant no longer has an initial 

solids settling clarifier. 

Current FGD Wastewater Treatment System: 

• The equalization tank recieves wastewater from the secondary hydroclones, offspecifiation effluent from the treatment system, and wastewater from the filtrate 

sump, which includes filter backwash and filter press filtrate. 

• From the equalization tank the water is transferred to a reaction tank where lime is 

added to adjust the pH. The water is then transferred to a second reaction tank 

where ferric chloride is added for coagulation. Then the wastewater is sent to a 

third reaction tank where the water is gently mixed to create a denser floc. From 

the third reaction tank, a polymer is added as the wastewater flows to the 

clarifiers. The plant is not sure what polymer is used. 

• The wastewater treatment plant has three clarifiers; one primary clarifier that can 

treat all of the wastewater and two secondary clarifiers that can each treat 50% of 

the wastewater. All three clarifiers operate in parallel. In the retrofit design, the 

plant intended to only use the secondary clarifiers as back-ups, but the plant 

typically operates all three of the clarifiers. 

• The overflow from all three clarifiers is combined and sent to the filtration 

system. From the filters, the wastewater is sent to the treated water transfer tank, 

which is where the plant collects its NPDES monitoring samples, and then is 

discharged to the Tampa Bay. 

• The underflow from the clarifiers is sent to the sludge storage tank and goes 

through one of two filter presses to dewater the sludge. 

FGD Wastewater Treatment Data 

• The plant stated that they have had some issues analyzing the FGD wastewater 

treatment effluent samples using clean methods for mercury. The plant stated that 

they have also had issues analyzing for arsenic, chromium, lead, nickel, and 

selenium using the 200 series method because of the dilution needed for the 

matrix. 

• The plant monitors the FGD treatment system effluent quarterly for TSS, oil and 

grease, arsenic, chromium, copper, lead, mercury, nickel, selenium, gross alpha, 

combined radium 226 and 228, and pH. Note: All metals are total recoverable 

and all are low-level, except mercury. The plant provided EPA with the data 

collected since 2000. 

• The plant does not have data for the influent to the FGD treatment system. 

Sampling Information 

• The sampling points are located outside; therefore, we will need to prepare to any 

rainfall that may occur. 
May 24, 2007 

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• The influent to the FGD treatment system could be collected from the 

equalization tank effluent. There is a valve and sample tap located on the pipe 

exiting the tank where the samples could be collected. This point is where the 

plant will be collecting the influent to treatment samples for their study. The 

plant monitors the flow from the tank. Figure 1 presents a picture of where the 

sample could be collected. 

• The effluent from the FGD treatment system could be collected from the sample 

collection tap for the plant’s monitoring location I-130. The FGD effluent sample 

piping is next to the filter press filtrate piping; however, the filter press filtrate 

discharge can be shut off. The plant monitors the flow rate for I-130. Figure 2 

presents a picture of where the sample could be collected. 

• The intake canal only provides water for the cooling systems. The intake for the 

process comes from the recycle pond system. Therefore, the intake water sample 

would be collected from the recycle pond. The plant has a sample tap from the 

pump that transports water from the recycle ponds back to the plant operations. 

The plant monitors the flow rate of the water back to the system. Figure 3 

presents a picture of the sample tap for the recycle pond water. 

• The plant has an on-site nurse for minor injuries. The nearest hospital is Sun City 

Center Hospital. The plant would require all samplers to complete a 4-hour health 

and safety training course. The course could be completed the day before 

sampling, or on-line. 

• The plant has a lab in the FGD area that we could use as the staging area. 
May 24, 2007 

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Figure 1. Sampling Location for FGD Influent to Treatment 
May 24, 2007 

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Figure 2. Sampling Location for Effluent from FGD Treatment 
May 24, 2007 

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Figure 3. Sampling Point for Process Intake Water
Table 1. List of Attendees 

Name Organization (Representing) Telephone ELaura Crouch Tampa Electric Company (813) 228-4104 lrcrouch@Tara Crews Tampa Electric Company (813) 228-4740 tncrews@John Smolenski Tampa Electric Company (813) 228-1456 jusmolensKaren Zwolak Tampa Electric Company (813) 630-6968 kozwolakDonna Hill Southern Company (205) 257-5234 dbhill@soJosh Hall EPA/Office of Water (202) 566-1002 hall.josh@Ron Jordan EPA/Office of Water (202) 566-1003 jordan.ronT.J. Finseth ERG (Contractor to EPA) (703) 633-1698 thomas.fi