Does your plant use coal to generate electricity? If so, it is essential that you are aware of these proposed revisions.
By Bill Kennedy
If you are the owner or operator of a plant that uses steam to generate electricity—such as coal, gas, or nuclear systems—then you are likely aware of the proposed revisions to the steam electric power generating effluent limitation guidelines (ELGs).
This November, the United States Environmental Protection Agency (EPA) published proposed revisions to the ELGs related to flue gas desulfurization (FGD) and bottom ash (BA) transport water effluent limits. These industry-specific guidelines are mandated under the Clean Water Act. They are US standards for wastewater discharges to surface waters.
Does this apply to your plant? If so, there are a few things you may need to consider in order to meet these proposed regulations.
Flue gas desulfurization wastewater is the liquid waste stream generated from the scrubbing, or removal, of acid gasses, from the flue gas of most coal burning power plants.
Subject to comment
It is important to note that these proposed changes are subject to comment and further review. There is a chance that the changes may be revised further before they become formal regulations.
_q_tweetable:A more creative evaluation of your treatment approaches may be necessary._q_As I mentioned above, the proposed revision applies to FGD and BA transport waters, which are the two largest volume effluents typically found with coal-fired power generation.
FGD wastewater is the liquid waste stream generated from the scrubbing, or removal, of acid gasses, specifically sulfur dioxide, from the flue gas of most coal burning power plants. The process produces gypsum, a solid product used in drywall. But the process also captures a range of elements found in coal that are either dissolved or suspended in the wastewater. Many of these elements must then be removed from the water, allowing for the safe and compliant discharge to surface waters.
BA transport water is what has historically been used to convey the heavier ash that drops to the bottom of the boiler during combustion. The water cools and then conveys the ash to a location that enables the separation of the solid ash from the water. Under previous regulations, this water would typically have been returned to a pond and then to surface waters. But, with the 2015 ELGs, this water must now be largely recycled.
It is worth noting how certain limitations for FGD and BA transport water have changed. You need to be aware of what concentrations of these constituents of concern will be allowed under the proposed new guidelines.
For FGD, the limits on arsenic have been increased slightly, and the limits for nitrates/nitrites have been decreased slightly. When it comes to mercury, however, the EPA has decreased the limits by over an order of magnitude. The limits for selenium have also increased, from 12 to 31 parts per billion (ppb).
For BA transport water, the proposed changes include a possible easing of the requirement to recycle 100 percent of the system water.
If you’re the owner or operator of a plant, it’s essential to be aware of these proposed changes. Failure to comply by the proposed deadlines may result in a violation with subsequent consequences.
Belews Creek Wastewater Treatment Station, which author Bill Kennedy commissioned. He also supported operations of the station, which was identified by the Environmental Protection Agency as best available technology (BAT) for selenium removal.
How you can deal with these changes
It is important to bring in experts to help you comply with these proposed new limits. It is interesting how the limits interact and what solutions they can inspire.
While selenium limits are being eased, the new mercury limits have made treatment more challenging, so it may be necessary to look at the holistic operation of your facility. A more creative evaluation of treatment approaches may also be necessary, so you can provide the most economical solution to meet these proposed limits.
Exceptions to the rule
There are exceptions to the FGD limits. These include low-utilization boilers, high-flow facilities, early unit retirements (which eliminate selenium and nitrate/nitrite limits), and a membrane-based voluntary incentive program (which extends the compliance deadline). BA transport water discharge exceptions are also proposed for low-utilization boilers and early unit retirements, but with several caveats.
With the risk of noncompliance, it is critical to have a plan to meet these regulatory changes. Wading through the regulatory documents can be cumbersome and time-consuming. If you would like to get a more complete summary of the proposed changes and details on the exceptions, attend our webinar on Tuesday, December 3 at 2 p.m. Eastern Time. Click here to register.
About the author
Bill Kennedy is a senior principal based in Charlotte, North Carolina, with more than three decades of experience providing solutions to the chemical, polymer, pharmaceutical, and electric power industries. He’s actively engaged in advancing treatment technologies, and he’s passionate about training the next generation of engineers.