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Questions Regarding the GE ABMet System

February 2014

The following are questions for GE regarding the operation and performance of the ABMet system for the 

treatment of FGD wastewater. These questions cover items raised as comments the proposed revisions to 

the Effluent Limitations Guidelines and Standards (ELGs) for the Steam Electric Power Generating Point 

Source Category.

Heat Exchanger

Question: Is there a need for heating or indoor treatment systems at plants located in colder 

climates? Does ABMet have any installations (full-scale or pilot systems) in any northern states (e.g., 

Maine, Michigan, Wisconsin, North/South Dakota, Montana) or Canada? These installations can be 

for treating FGD wastewater or for other applications, like mining.

At what temperature must the bugs be maintained to prevent them from dying off? How would 

GE propose to maintain this temperature in a cold climate during the winter if a plant was in a 

prolonged shut down (e.g., month-long) in which case warm FGD wastewater it not being transferred 

to the system?

If the system operated near the bottom of the temperature limit, how much additional retention 

time would be needed to compare with the retention time assumed for the cost estimate previously 

provided?

Background: Comments from EPRI cite the potential need for heat exchangers for winter 

operations in northern climates in order to maintain temperatures within the ideal range of 50°F105°F.

In previous contact with GE (2011), GE indicated that reduction in temperature will slow the 

biological kinetics resulting in a requirement for increased retention time in order to achieve the 

results specified in the design. Development and validation work conducted in 2009 have verified 

that the retention times used in the costing specified in the 2011 quote should be sufficient for 99%+ 

of the potential FGD installations in the US.

Ammonia Generation within the Biotreatment System

Question: Comments to the proposed ELGs and performance data from Belews Creek and Allen 

indicate ammonia generation across the biotreatment system. Has this been an issue with installed 

full-scale or pilot-scale systems in the past? Is GE aware of what mechanism is leading to this 

ammonia generation? Have you determined how much ammonia is typically generated in the system 

or a way to calculate how much would be generated?

Background: Performance data from EPA sampling and plant-provided data from Belews Creek 

and Allen show an average increase of approximately 66% in the ammonia concentration from 

biotreatment influent to biotreatment effluent.
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Requests for Additional Performance Data

Question: Does GE have any performance data for any of the pilot-scale installations of the 

ABMet system that could be provided to EPA? Comments to the proposed rule raise several 

concerns about the ability of the ABMet system to handle high influent concentrations, meeting the 

specified nitrate/nitrite limits, and demonstrating performance under a variety of nitrate, selenium, 

chloride concentrations and ORP ranges. We are particularly interested in any pilot-scale testing done 

on wastewaters containing the following characteristics: 

a) Demonstration of the ABMet system treating higher influent concentrations of chlorides, 

mercury, nitrate/nitrite, and selenium than those seen at Belews Creek and Allen and still 

meeting the proposed limitations. The maximum concentrations of these pollutants observed 

at Belews Creek and Allen are the following:

 Chlorides: 11,000 mg/L

 Mercury: 53,300 ng/L

 Nitrate/Nitrite: 39 mg/L

 Selenium: 2,940 ug/L

b) More data demonstrating that the proposed nitrate/nitrite limit (0.17 mg/L daily max and 0.13 

mg/L monthly average) and the proposed selenium limit (16 ug/L daily max and 10 ug/L 

monthly average) are achievable.

c) Data demonstrating the ABMet system is capable of treating a variety of chloride, 

nitrate/nitrite, and selenium concentrations. Values both above and below those specified in 

the design criteria. 

d) Does the ABMet system have a specific selenium loading limitation (e.g., can’t treat 

wastewater with selenium concentrations above a certain level)?

e) Data demonstrating the ABMet system is capable of treating wastewater at a variety of ORP 

levels.

f) Data demonstrating the ABMet system is capable of operating at chlorides concentrations at 

or above 35,000 ppm.

g) Data demonstrating that the ABMet system is capable of treating species of selenium other 

than selenite and selenate (e.g., selenocyanate and other species).

h) Data demonstrating that the ABMet system can meet the proposed limits immediately after an 

extended shutdown of the system (e.g., the plant has a 4-week outages where no FGD 

wastewater is transferred to the system and the plant can still meet limits after starting back 

up).

Increased Costs for Different Influents

Question: Would increased influent nitrate/nitrite and/or selenium concentrations result in any 

design changes to the biological treatment system? If so, how would these design changes affect the

cost of the system? Comments specifically cite nitrate/nitrite levels greater than 100ppm in the 

influent to the ABMet system. 

Background: The cost request sent to GE cites a maximum design nitrate/nitrite concentration of 

160 mg/L (or ppm). Pleasant Prairie sampling data includes nitrate/nitrate concentrations as high as 

220 mg/L (at least 3 results are at or above the design concentration).
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Comments from We Energies cite a paper presented by GE at the 2010 IWC which specify a 

maximum design nitrate/nitrite concentration of 100 ppm.

Capital and O&M Costs

Question: ERG would like to clarify whether specific cost elements are included or not included 

in the cost estimates provided in previous correspondence.

1. Does the cost estimate include any costs for site prep work? These would be costs for 

any site preparation work needed at the construction site, work such as clearing land or 

structural reinforcement needed to support the ABMet system.

2. Does the cost estimate include costs for system start-up and operator training? If so, how 

much support is provided by GE (e.g., how long will GE work with the plant on start-up 

and training)?

3. Does the cost estimate include any additional margin to account for bonding and 

insurance and a margin for GE’s profit?

4. Are electrical costs included in the cost estimate? Costs to wire and connect any 

instruments or equipment requiring electricity within the ABMet system.

5. Does the cost estimate include costs for the control equipment for the ‘island,’ such that 

all FGD wastewater treatment equipment can be controlled from the control room?

Background: In previous contact with GE (April 2011), a list of cost assumptions was provided 

along with the cost curves for equipment and installation costs. The costs provided by GE include the 

following items:

 Assume unionized contractor labor is utilized,

 Assume no special seismic criteria is incorporated into construction or design,

 Costs are based on executing project structure as a consortium between GE and 

contractor with a balance of plant engineering as a sub-contractor,

 Costs assume the ABMet system is an ‘island’ with integration into the full power plant 

system not being included (e.g. DCS interfaces, tie-in with existing plant, etc. omitted),

 Costs assume integration of ABMet following conventional physical/chemical treatment 

with ABMet backwash waste recycled to conventional solids removal system, and

 Equipment and installation costs include costs to purchase and install the following 

elements:

o All process pumps, valves, and instruments,

o Process and instrument compressed air system, valves and lines,

o Nutrient system, storage tank, and pumping,

o All process piping and supports within the ABMet ‘island,’

o Building for all process equipment with HVAC (concrete floor, block structure 

with steel roof),

o Concrete bioreactor tank walls and floor with epoxy-coated rebar and epoxy 

flake-glass coating,

o Concrete backwash supply and backwash waste tank walls and floor with epoxycoated rebar and epoxy flake-glass coating,

o Concrete process and utility sump with pumps,

o Support steel, access stairs, walkways, grating, and handrails,
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o Engineering, commissioning, and project management labor for ABMet ‘island,’ 

and

o Construction equipment, materials and labor for ABMet ‘island.’

The ABMet correspondence also calls out several items that are not included in the cost curves 

provided by GE. The following items are listed as being omitted from the cost estimate;

 Utility overhead and labor,

 Plant tie-in/integration (e.g. DCS interface, feed water, effluent water line to discharge, etc.),

 Pilings, caissons, etc,

 Permitting,

 Financing charges,

 Other wastewater processes such as pre- or post-treatment, dewatering, and 

 Backwash waste disposal/solids handling.