Document ID: EPA-HQ-OW-2009-0819-5628
Agency: epa
Document Type: Supporting & Related Material
Title: 
Posted Date: 2015-11-03T05:00Z

Notes from Site Visit at AEP's John E. Amos Plant on November 4, 2014

 EPA conducted a site visit at American Electric Power's (AEP's) John E. Amos Plant (Amos) located in Winfield, WV on November 4, 2014 to learn about the operations and wastewater treatment at the plant and to learn more about a pilot study conducted by AEP to evaluate treatment technologies for flue gas desulfurization (FGD) wastewater. EPA and ERG also received information about AEP's Mountaineer plant during the visit and that information is provided at the end of these site visit notes.

 Site Visit Attendee List

 Name
 Organization (Representing)
 Telephone
 E-mail
 Chuck Johnson
 AEP Amos
 304-759-3414
 cmjohnson2@aep.com
 Paul Massie
 AEP Amos
 304-759-3246
 pjmassie@aep.com
 RJ Roush
 AEP Amos
 304-759-3473
 rjroush@aep.com
 Jon P. Webster
 AEP Amos
 304-759-3246
 jpwebster@aep.com
 Dave Wickline
 AEP Amos
 304-759-3200

 Jason F. Baker
 AEPSC
 614-200-1845
 Jfbaker2@aep.com
 Tom Hart
 AEPSC
 614-716-3260
 tomlhart@aep.com
 Tim Lohner
 AEPSC
 614-716-1255
 twlohner@aep.com
 Steve Wells
 AEP - WERS
 614-716-2232
 sfwells@aep.com
 J.T. Massey-Norton
 AEP Geotechnical
 614-716-2924
 jtmasseynorton@aep.com
 Chuck Cunningham
 AEP Mountaineer
 304-882-4020
 cwcunningham@aep.com
 David Thompson
 AEP Mountaineer
 304-882-4023
 rdthompson1@aep.com
 James Covington
 EPA
 202-566-1034
 covington.james@epa.gov
 Phillip Flanders
 EPA
 202-566-8323
 flanders.phillip@epa.gov
 Jessica Hall
 EPA
 202-564-3376
 hall.jessica@epa.gov
 Ron Jordan
 EPA
 202-566-1003
 jordan.ronald@epa.gov
 Anna Dimling
 ERG
 703-633-1692
 anna.dimling@erg.com
 TJ Finseth
 ERG
 703-633-1698
 thomas.finseth@erg.com

 Plant Overview

 AEP's Amos plant is a coal-fired power plant with three stand-alone steam turbine generating units, and a total generating capacity of 2,932 MW. The units were brought online in 1971 (SE Unit-1), 1972 (SE Unit-2), and 1973 (SE Unit-3). Table 1 contains some general information on the three steam electric generating units at Amos.

                          Table 1. Amos Plant Summary

 Unit

                                     Fuel
  Capacity (MW)

   Fly Ash

 Bottom Ash

                                      FGD
 NOx Control

 FGMC
                                       1
 Coal: Bituminous Oil: No. 2 Fuel Oil
                                      816
 Dry conveyed
 Wet Handled
 Wet System
  SCR
  None
                                       2
 Coal: Bituminous Oil: No. 2 Fuel Oil
                                      816
 Dry conveyed
 Wet Handled
 Wet System
  SCR
  None
                                       3
 Coal: Bituminous Oil: No. 2 Fuel Oil
   1300
 Dry Conveyed
 Wet Handled
 Wet System
  SCR
  None

     On the day of the site visit, Unit 3 was not operating because of a tube leak.
    
        Amos uses No. 2 Fuel Oil in each of the three boilers during start-up periods and for load stabilization. For example, when the plant is increasing or decreasing the load on a unit, fuel oil may be used to help stabilize the unit loading during the transition if it requires a pulverizer to be placed into service.
    
        Amos uses eastern bituminous coal from Ohio, West Virginia, Kentucky, and sometimes Pennsylvania (Pittsburgh) and usually has 8-10 coal suppliers at any one time. At the time of the site visit they indicated they were using approximately 9-12 coal suppliers. The coal fed into the boilers is a blend of low sulfur and high sulfur coal and is around 3 to 4 lbs SO2/million Btu for Units 1 and 2 and 4 to 4.5 lbs SO2/million Btu for SE Unit-3. The chlorine content of the coal used at Amos is approximately 0.01 percent.
    
        The limestone and coal are mostly delivered by barge because it is more economically favorable. It costs around $5 per ton of coal to deliver by barge and each barge can carry 5,000  -  15,000 tons of coal; whereas, rail cars can only carry around 500 tons of coal and cost significantly more per ton.

FGD Systems
       
        All three generating units at Amos have limestone forced oxidation FGD systems. The FGD systems were installed in the following timeframes:
                Unit 3: February 2009;
                Unit 2: February 2010; and
                Unit 1: January 2011.
       
        Units 1 and 2 are each serviced by one FGD absorber module, while Unit 3 is serviced by two absorber modules. The Unit 1 and 2 absorber modules are larger than the individual Unit 3 absorber modules.
       
        Each FGD absorber is a Babcock & Wilcox (B&W) Tray/Spray Tower. The Unit 1, 2 and 3 FGD absorber modules each have two levels of trays in the design of the absorber to increase contact with the FGD limestone slurry resulting in increased mass transfer, 75 L/G, and decreased FGD slurry flow rate. Units 1 and 2 have 2-1/2 levels of interstitial sprays; Unit 3 has 2 full levels of interstitial sprays.
       
        Amos operates three ball mills at the plant to generate the limestone slurry used in the FGD systems.  The plant targets a limestone slurry that is 30 percent solids. The limestone slurry is dumped into the FGD absorber module reaction tank to control the pH of the slurry. A number of variables establish sulfur dioxide removal, such as L/G, pH, vessel design, etc. Absorber slurry density is control by blowdown rate. Reaction tank level is controlled by the addition of reclaim/service water. 
    
        Amos uses service water as mist eliminator wash water, which is sprayed on the mist eliminators to keep them clean and falls into the FGD absorber module. Amos washes the mist eliminators for approximately 10-15 minutes every hour.
    
        The absorber recycle pumps move the slurry from the reaction tank supplying it to the spray headers near the top of the absorber modules. The plant intermittently blows down, or "bleeds the absorber", some of the FGD slurry from the reaction tank to control the approximately 20% density in the FGD system.  The blowdown from the FGD systems is transferred to the bleed tanks. Plant controls are set automatically to initiate blowdown when solids reach 21.5%. The blowdown will continue until the solids are lowered to 19.5%. 
    
        Each absorber module has agitators located around the walls of the reaction tank. Oxidation air is added in front of the agitators and mixed into the FGD slurry to oxidize the calcium sulfite to calcium sulfate (i.e., gypsum). Amos personnel stated that the plant uses two to three times more oxidation air than is theoretically needed to achieve full oxidation of the FGD material.
    
        Amos personnel stated that the FGD absorbers operate at an oxidation/reduction potential (ORP) between 100 to 300 mV.  Amos has been monitoring the ORP levels in the absorbers to try and optimize mercury removal, selenium removal, improve gypsum quality, and decrease manganese oxide scaling. Amos personnel noted that if the oxidation air feed is shut down it has a minimal effect on the ORP in the absorber. AEP has not determined a distinct correlation between FGD operating conditions and ORP levels within the absorbers.
    
        The absorber slurry (~20% solids) is pumped from the bleed tanks two miles and up a 350 foot elevation to the FGD dewatering system (specifically to the hydrocyclone feed tanks). Amos personnel noted that this required 14 miles of FRP piping; more specifically a total of 7 supply and return pipes that are two mile long each.
    
        The FGD slurry is then pumped through one of the three sets of hydrocyclones, which operate around 35 psi. The underflow from the hydrocyclones is 50-55% solids. The hydrocyclones operate 36 hours/day collectively (e.g., 24 hours for one set of hydrocyclones and 12 hours for another set of hydrocyclones).
    
        The hydrocyclone overflow (3-5% solids) is pumped at an average flow rate of 400 gpm (800 gpm maximum design flow rate; 500 gpm average design flow rate) to the equalization tanks in the chemical precipitation system. Amos runs two 100% capacity trains at all times.
       
        The underflow from the hydrocyclones is fed by gravity to one of the vacuum belt filters (Amos maintains 3 vacuum belt filters). The vacuum belt filters dewater the gypsum material to a moisture content around 10-15 % moisture. The dewatered gypsum is then conveyed out of the building on a belt and deposited on the ground for truck transport to the FGD landfill.
    
        Service water is used to wash the vacuum belts and is mixed with the filtrate from the vacuum belt filters.
    
        The facility does not market their gypsum due to economic and logistic considerations. Major cities and companies that could potentially utilize the Amos gypsum do not like the wallboard to be shipped by train or barge; however, those transportation methods are the best available shipping methods from Amos.
      
FGD Wastewater Treatment (WWT) Design

        Amos previously used Lamella separators as the secondary clarification step in the FGD wastewater treatment; however, the facility experienced a number of issues and could not optimize the system. According to plant personnel, the FGD by-product was the consistency of jelly and the Lamella plates would get clogged and the Lamella clarifiers needed weekly maintenance. Amos ended up dismantling the system and sending it to another plant for handling coal ash.
     
        Amos started a project to replace the Lamella separators with secondary clarifiers in November 2011. The total cost for that project was around $4 million. That project had a long start-up period due to the time required for determining the dosage rates, injection locations, polymer vendors, and water sources.
     
        The current FGD chemical precipitation system consists of the following equipment (see DCN SE05645A1 for process flow diagram):   
             [Redacted]
             Sludge holding tank
 20  -  25 % solids
             Filter Presses (five)
 Batch process, about 2-4 batches per day
                  	+65% solids
 Replace filter cloths every 500 runs
 Wash every 12 runs and wash water is sent to wastewater collection sump and back to the beginning the process
 Filter cake is discharged through bomb bay doors and trucked to a landfill
             Wastewater Collection Sump
 Pumped back to FGD absorbers
             Clear Water Sump
 Discharged via Outfall 003

      Dosage Rates for the FGD wastewater treatment system:
             [Redacted]

        AEP stated that General Electric (GE-Betz) still visits the plant every Monday to assist the plant with the performance of the chemical feed systems.
     
        The facility did not indicate organosulfide as a chemical in their 2010 Steam Electric Questionnaire. Amos indicated that they started to add organosulfide into the system around November 2010. [Redacted]
     
        Amos monitors the FGD wastewater treatment system daily by observing the turbidity in the primary and secondary clarifiers from grab samples and checking that the feed pumps are operating correctly. The facility indicated that they are looking into installing a continuous sample monitoring system.
     
        The clarifiers are treated once a year for algae. Additionally, once every three years, the facility drains the entire clarifier tank for a thorough cleaning.

 FGD WWT Sampling Results

        The following AEP plants are associated with the data provided in the AEP presentation (DCN: SE05645A1)
             Plant A  -  John E. Amos Plant
             Plant B  -  Cardinal
             Plant C  -  Conesville
             Plant D  -  Mitchell Plant
             Plant E  -  Mountaineer Plant

 AEP eliminated statistical errors and outliers from the graphs provided in the presentation. Data used to create the graphs are a mix of monthly and weekly samples; however, samples were usually taken about one time a month or once every two months. AEP indicated that the samples were taken over the course of 2+ years.

        The data from the Conesville plant showed a significantly higher arsenic concentration in the FGD wastewater. AEP stated that the Conesville plant has an older particulate removal system (ESP) and a larger portion of fly ash carries over into the wastewater treatment influent. Therefore, that facility uses their jet bubbling reactor (JBR) also as a polishing device for the particulate control.

 Currently, Amos takes a composite sample at the beginning of the month for the Department of Environmental Protection (DEP) at Outfall 003. The permit limit for mercury at Outfall 003 are an average monthly limit of 229 ppt and daily maximum limit of 624 ppt. Amos also has a report only NPDES internal limit for the FGD wastewater (Outfall 203) that will be renewed in 2018. The NPDES requirements for Outfall 203 include monitoring once per month for the following parameters:
                Flow  -  24 hour total;
                Nitrogen nitrate  -  24 hour composite;
                Nitrogen nitrite  -  24 hour composite;
                Total mercury  -  Grab;
                Total recoverable selenium  -  24 hour composite; and
                Total recoverable arsenic  -  24 hour composite. 

 Amos uses a diffuser in the Kanawha River to establish a mixing zone at their Outfall 003.

 Ash Handling

 AEP sluices bottom ash from Units 1, 2, and 3 to a pond system prior to discharge via Outfall 003.

        AEP previously sluiced the fly ash from Unit 3 to a fly ash pond and discharged the fly ash transport water via Outfall 001; however, the system has been retrofitted to a dry system. Although the Unit 3 fly ash is now dry handled and most of the wet system was dismantled, some of the piping out to the fly ash pond still exists. Currently, no fly ash transport water is sluiced to the pond and the facility is in the process of closing the fly ash pond permanently (a 4-5 year project). Amos also indicated no additional workers were needed for retrofitting the wet fly ash system to a dry handling system.

 All of the fly ash at Amos is dry handled and sent to silos (2 per unit) for temporary storage. Each silo [Redacted]. From the silo the fly ash is transferred to the pugmill for wetting and then trucked to a landfill or marketed to concrete customers. The fly ash trucks are weighed to keep track of the amount that is landfilled versus the amount that is marketed. AEP noted that only a small amount is marketed for sale. Between 2013 and 2015 roughly [Redacted] was marketed. AEP noted that if the fly ash has a high loss of ignition (LOI), which is an indicator of the carbon content, it is not suitable for sale. In addition, Amos has found that dry loading and trucking the fly ash is difficult.

 Amos indicated that the fly ash lines, silos, and vacuum pumps have redundant components. Each generating unit is serviced by two fly ash silos, with one silo normally operating and the other acting as a spare. Fly ash lines to each silo are the same, with a primary line and a backup. There are five pumps in the vacuum system and the facility can operate the ash handling system with only four without shutting down the system. See DCN SE05664A2 for a diagram of the fly ash and bottom ash handling systems.

 Landfills and Pond Systems

        The bottom ash pond system consists of Bottom Ash Pond A, Bottom Ash Pond B, Recirculation Pond, and Clear Water Pond. Approximately 12,600 gpm of water from the recirculation pond is reused as seal water for the boilers and water for the ash handling system. AEP adds polymer in both Bottom Ash Pond A and B for coagulation and settling. Clear Water Pond receives all the wastewater from the pond system and discharges via Outfall 003. AEP identified the small size of the Clear Water Pond as a driving factor in the wastewater treatment improvements (e.g. installation and updates to chemical precipitation system) because a shorter residence time leads to less solids settling before discharge.
        
 Bottom Ash Pond A was out of service during the site visit and bottom ash was being excavated from the pond to be transferred to the landfill or beneficially reused (i.e., used in roads and chimney drain in landfill).AEP indicated that they anticipate Bottom Ash Pond A to be back in service by early next year (January or February 2015). AEP also indicated that they close one of the bottom ash ponds about every 6 months for excavation and all bottom ash transport water is directed to the other operating pond during that time.

 AEP's FGD landfill was evaluated in 2013 to assess the available space; it was determined that 19-20 years of space was still available. The FGD landfill contains FGD wastes, mostly in the form of gypsum. The Quarrier landfill is located about four miles down the road from the FGD landfill and contains bottom ash and fly ash solids. Leachate is collected from both landfills and sent to Bottom Ash Ponds A and/or B.

 FGD Wastewater Pilot Study

        Amos was looking for a polishing step that would aid in consistently meeting the proposed ELG limits for mercury. The facility later decided to also focus on other pollutants such as selenium and nitrate-nitrite; therefore, they reached out to the Electric Power Research Institute (EPRI) and used vendors to test five technologies, four vendors on a small pilot scale basis (3-4 month and 7 month studies). The studies evaluated treating the treated chloride effluent at a flow rate of 1-2 gpm per process. Amos also wanted to gather information on installation, regeneration, maintenance (O&M), and life cycle costs for the technologies.
          During the site visit, Amos facility personnel provided data from the pilot studies, but noted that they do not own any of the pilot study data; EPRI, technology vendors and the jointly sponsoring utilities own the data.

       At the time of the site visit, Amos had not yet received a draft of the pilot studies from EPRI.

 Amos personnel indicated that it was their professional opinion that none of the technologies tested were ready to scale up to commercial operation. In addition, AEP personnel noted that the technologies work at a low pH in the initial steps and need a higher pH for subsequent steps, which necessitates greater chemical use and increased costs. One of the technologies is designed to remove only dissolved constituents; given that the majority of the mercury in the FGD blowdown water is in the non-dissolved form, this technology would be of little value in meeting limits based on total mercury in this application. Amos stated that the best design they could consider is having a slip stream polishing step where a smaller side stream is redirected and treated from the CP effluent to bring down the pollutant averages in the effluent.

          Amos personnel noted that the ZVI technology (Liberty Hydro) had trouble with fines (colloidal particles) that pass through the dewatering step. They experimented with different kinds of filters but found that they plugged up and did not function. Amos personnel also noted that the ZVI technology had issues with nitrates/nitrites affecting the efficiency of the system.

   Mountaineer Plant Information

 AEP's Mountaineer Plant, located in New Haven, WV, is a coal-fired power plant with one stand-alone steam turbine generating unit, and a total generating capacity of 1,300 MW. Table 2 contains some general information on the steam electric generating unit at Mountaineer. AEP reported that the unit operated 341 days in 2009.

                       Table 2. Mountaineer Plant Summary

 Unit

                                     Fuel
  Capacity (MW)

   Fly Ash

 Bottom Ash

                                      FGD
 NOx Control

 FGMC
                                       1
 Coal: Bituminous Oil: No. 2 Fuel Oil
   1300
 Dry conveyed
 Wet Handled
 Wet System
  SCR
  None

 EPA conducted a site visit at the Mountaineer plant in New Haven, WV, see DCN SE02070 for the site visit notes.  Since that site visit, AEP has installed an ABMet biological treatment system which began operating in November of 2011, to further treat the FGD wastewater prior to discharge (FGD wastewater treatment previously consisted of only chemical precipitation treatment). In addition to receiving the FGD wastewater after the chemical precipitation system, the ABMet system also treats the combustion residual leachate that is generated at the plant.

 The lined leachate surge pond was designed to hold two consecutive 25-year rain events and represented about 33 percent of the cost of the ABMet system (which includes piping and pumps from the pond to the treatment system). AEP indicated that the logistics, lining, issues (problems with liner floating), fencing (deer falling in and unable to get out), dual pumps (for redundancy), controls/blending, and piping were all issues they addressed in the design of the pond. The pond has a capacity of around 5 million gallons and is blended into the FGD treatment system after the CP system and before the ABMet system at a ratio between 50/50 and 60/40 for FGD CP Effluent/Leachate pond water.

 AEP constructed the ABMet system over an approximate one year time period. In addition, the commissioning period was on the order of a couple months.

 The physical / chemical system consists of the following equipment:
             Desaturation tanks (with lime and organosulfide addition)
 Note: The Mountaineer treatment system has an opposite order of treatment system than that at Amos since the desaturation tank is before the equalization tank; however the order of the chemical addition remains the same.
             Primary clarifier (with primary polymer addition)
 Only the sludge from the primary clarifier is sent to a sludge feed tank located upstream of the filter presses; the sludge from the secondary clarifier is sent back to the beginning of the system (desaturation tanks) to be removed in the primary clarifier.
             Equalization tank (with organosulfide addition)
                Ferric Mix Tanks (these tanks are out of service and bypassed; the facility does not add ferric chloride any longer)
             Secondary Clarifier (with secondary polymer addition)
             Sludge Feed Tank
             Filter Presses (2)
 Larger than the filter presses at Amos
             Effluent Storage Feed Tank

         The influent to the biological treatment system is made up of about 50 percent CP effluent and 50 percent leachate with a design flow rate of around 600 gpm and an average flow rate of 500 GPM. The ORP of the comingled influent is around 200  -  300 mV (aim for 150  -  200 mV), the TSS is about 200ppm, and the pH is around 8-8.4 S.U. (adjusted to 7-7.5 S.U. using sulfuric acid).

 The ABMet biological treatment system consists of the following equipment and took around 18 months to construct: (includes the leachate surge pond discussed above)
             First stage feed tank (with sulfuric acid (93%) addition)
 pH monitored
             First stage reactors (with molasses-based nutrient addition; includes 6 reactors)
 ORP and pH monitored at each reactor cell
 The first stage removed the nitrate-nitrite and a portion of the selenium.
             Second stage feed tank
 pH monitored
             Second stage reactors (with molasses-based nutrient addition; includes 6 reactors)
 ORP and pH monitored at each reactor cell
 Use of the second stage achieves another order of magnitude reduction of selenium, which is sufficient to achieve compliance with the proposed ELG limits.
             Effluent tank

 During the ABMet biological treatment system start-up period, Bill Kennedy of Duke Energy worked on-site to help with getting the biological treatment system up and running. AEP stated that there were large swings in the ORP during this period. AEP also noted that the start-up period lasted a few months.

 AEP noted that the FGD treatment system takes a lot of manpower. AEP estimated that, on average, the physical/chemical system requires one full-time operator and the CP plus biological treatment system requires two full-time operators.

         The molasses-based nutrient contains trace metals (including selenium and aluminum) so that if the unit to which it is being added is offline, the microbes will stay alive. In addition, there is a filter for the nutrient feed system to prevent clogging of the feed system.  The rate that the nutrient is fed into the system is based off of the ORP measured in the reactor cells.

 The biological system is automatically degassed when trapped nitrogen and some hydrogen sulfide gases build-up within the system from microbial metabolism.  If the system is degassed twice in one day the system is flushed and the flush water is sent back to the beginning of the physical / chemical system.

 AEP indicated that temperature is often an issue with the biological treatment system and needs to be monitored daily to make sure that the temperature does not exceed 105°F or dip below 50°F. While AEP indicated that the treatment system sometimes reaches temperatures around/above 105°F (maximum observed was 106°F before comingling with leachate), the                temperature after commingling with the leachate remains below 105°F. A low treatment system temperature is of particular concern during the winter months when the water being pumped from the leachate surge pond is significantly below 50°F.

 AEP noted that the total arsenic spike attributed to start-up conditions (1,000 ppb) in the WWT plant influent increased the average in the bar graph of all five plants (average arsenic in the influent is 199 ppb).

 The selenium limits for AEP's current NPDES permit are 83 ppb daily and 33 ppb monthly average at the final outfall.