Coal

Zero Liquid Discharge for Coal-Fired Power Plants

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When environmental regulations for coal-fired power plants change, effluent treatment methods currently being used may not be able to meet the new standards. Many power plant operators find that one of the new factors they must face is the EPA’s revised Effluent Limitations Guidelines (ELGs), issued in September 2015.

Recently at a mine-mouth coal-fired plant with a nominal capacity of 1,600 megawatts (MW), designers had done what they thought necessary to comply with regulatory expectations – they designed for zero discharge of process water. For blowdown water from the cooling tower, they made plans to discharge in a way that would meet National Pollutant Discharge Elimination System (NPDES) limits for the permitted outfall.

Process water is recycled internally for other plant processes, including the air quality control system (AQCS), which incorporates the flue gas desulfurization (FGD) system. However, as the wastewater continuously cycles through the two FGD absorber units, a buildup of chlorides and other constituents occurs. The level of total dissolved solids (TDS) in the purge water is controlled by blowdowns triggered by the TDS levels, and makeup water is then added to the system.

The FGD wastewater can contain TDS in excess of 31,000 parts per million (ppm), total hardness of 30,000 ppm, chlorides of 20,000 ppm, and total suspended solids (TSS) of 10,000 ppm. The blowdown wastewater is purged from the system whenever the chloride concentration in the water exceeds 20,000 ppm of chlorides.

The purged high chloride FGD wastewater is then disposed of by mixing it with fly ash and gypsum coal combustion residual (CCR) material in a pug mill. That mixture was originally disposed of at an off-site landfill, located about 20 miles away.

One seemingly small change caused this design to tip off-balance: the decision by the power plant to start its own landfill on site for disposal of the fly ash mixture. This action opened up the plant to the responsibility of managing the landfill leachate – water from precipitation flowing through the landfill, picking up contaminants along the way. The plant’s operators began pumping the leachate from the on-site landfill back to the plant’s recycle basin for re-use as make-up water. However, they found that internal recycling of wastewater is not sustainable at that location, as it results in the cycling up of chlorides and other factors that increase pipeline corrosion.

As a result, from 2014 to 2015, the chloride concentration in the recycle basin increased to three times the previous year’s concentration. The design for chlorides concentration for the recycle basin was set at less than 500 mg/L, but the data show levels approaching 3,000 mg/L within two years. These concentrations seemed likely to go on increasing unless measures were taken to manage the problem.

Problems such as these have been found at many coal-fired power plants. At the root of the problem is the fact that the water-management systems were set up to support the efficient combustion of coal to produce power. However, environmental regulations concerning water use and disposal have become more restrictive. This change has put an increasing operational focus on efficient water management to lessen the discharge of water from the plant and reduce materials of concern in that wastewater.

Thus environmental regulations, such as those intended to support zero liquid discharge (ZLD), now have an increased effect on operations, moving water management up on the priority lists of power plant operators.

One of the most common issues at many coal-fired power plants is the one seen in the story above – that, in many cases, the plant’s operators do not have a comprehensive plan for water use. They lack detailed, accurate data on which parts of the plant use water, how much those parts use, and what constituents the processes add to that water.

Many plants combine their wastewater inputs into a central flow and then treat the water that comes from that single pipe. In such cases, a more focused and cost-effective plan could be developed by segregating flows so that each stream receives only the level of treatment it needs. Segregation of wastewaters can generate substantial opportunities for recycling part of that water flow and limiting the most costly treatment and disposal methods to only the streams that need it.

For example, consider pump seal water. Many plants use clean water around the outside of the seals to reduce the possibility of the pumped fluid escaping. The pump seal water that drips out is gathered and then generally is just placed into the plant’s overall wastewater flow. Since this water is virtually clean, it would make more sense to capture this water separately so it can be treated at low cost, rather than being part of the larger, more complex wastewater flow.

Comprehensive analysis of the many water flows within a plant may be able to point to similar opportunities to segregate wastewater streams so that not all water needs to be treated with expensive methods. Specific data on water use at various points within the plant can help guide the choice of treatment approaches. At the plant described above, an astute review of the wastewater components saved the owner millions of dollars that would have been required for a new treatment plant. Instead, the plant managers were advised to use low-cost techniques for reducing the chlorides in their wastewater flow.

It is important to remember that as the plant’s operations change, the effects on the wastewater stream must be considered. The above-mentioned power plant was impacted by just such a change – the new landfill’s leachate forming a new source of chlorides to be managed.

Each coal-fired plant is different – the type of coal, equipment, and other factors such as local geology – so the following steps may be useful in finding an appropriate solution:

Analyze the current situation: One of the first steps for preparing for the new ELGs is to collect data on the flow and composition of wastewater streams and characterize typical wastewater flows.

Develop plans: Review various limiting strategies, such as reusing wastewater to reduce discharges, and then use mass balance and chemistry modeling tools to evaluate reuse, treatment, and discharge strategies to meet these new limits.

Choose management options: The choice for selecting the appropriate management tool depends on yet another wide range of factors that are better understood after carrying out the first two steps. The toolbox can include:

  • Discharge to a Publicly Owned Treatment Works (POTW)
  • Evaporation Ponds
  • Flue Gas Injection
  • Fixation
  • Deep Well Injection (depending on factors such as geology – experience has found that the tight rock formations of Pennsylvania, for example, are less useable for this purpose than the more appropriate geologic formations of other locations, such as Florida)
  • FGD wastewater treatment system (WWTS) Effluent Reuse/Recycle
  • Settling Ponds
  • Constructed Wetlands, Phytoremediation, and other Natural Based Systems
  • Vapor-Compression Evaporation
  • Physical/Chemical Treatment
  • Physical/Chemical with Added Biological Treatment
  • All the above can be components of a Zero Discharge approach

Other approaches utilities should consider include measures such as using existing evaporation (from cooling towers and FGD absorbers), using blowdown water for conditioning of fly ash, and other water reuse and conservation measures to reduce the amount of wastewater requiring treatment.
Working with a qualified professional with experience in each of these technologies can lead to wiser choices around which systems may be best, given the site-specific factors.

If you have any questions regarding your plant, please contact the post author, Ivan A. Cooper, P.E., BCEE, a principal based in CEC’s Charlotte, N.C., office, at icooper@cecinc.com; (704) 226-8074.

Illinois Governor Quinn issuing Emergency Regulations on Coke and Coal Storage

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Update 2/17/2014:   In addition to regulatory initiatives by the City of Chicago and the IEPA, the Illinois Attorney General’s office has introduced, HB 5939 (Currie, D-Chicago), which amends the Environmental Protection Act, creating a new title in the law concerning the regulation of coal and coke storage, processing, and transloading. The bill provides for minimum setbacks for coal and coke facilities, sets limits for quantities of fugitive dust permitted from facilities, establishes specified requirements for storage of coal and coke products, requires permits for construction and operation of facilities, regulates the loading and unloading, paving, and cleaning of facilities. The bill also requires monitoring and testing, record keeping, and reporting to the IEPA. View the bill here.

Update: On January 23, 2014, the IPCB met and ruled 4-0 that IEPA had not demonstrated the filing qualified for treatment under Emergency Rule making provisions of IAPA and the Environmental Protection Act. The Board did not further comment or clarify the bases for their determination or what would have been acceptable to them. The Chairperson voiced a willingness to pursue with the proposal under General Rule making.

 The IEPA response to comments did not attempt to justify the request by citing precedents from prior IPCB and IACA cases. The footnote of their Statement of Reasons noted that there is no requirement for the Board or IEPA present a Statement of Reasons. They further noted that regulations for emergency rule makings are unclear and do not appear to be tailored to the purpose and intent of an emergency rule making. The IEPA Statement of Reasons ignored several commenters who cited precedents for acceptance and denial of emergency rule makings.

 In the morning public comment session, comments were submitted and summarized by the Illinois Chamber on behave of a coalition of industry trade associations, KCBX and the Environmental Law Policy Center.

 Newly issued Illinois emergency regulations will require total enclosure of all coke and coal storage, handling, and transfer activities. These emergency regulations call for plans to be due in 45 days and construction completed within two years. Regulations will also address dust suppression, storm water controls, elimination of fugitives, street sweeping, setbacks, height restrictions, record keeping and reporting. These requirements may cause costs to rise to the point of forcing closings of some coke and coal storage and handling activities.

In the dry heat of August 2013, fugitive coke dust from bulk storage along Illinois’ Calumet River migrated into residential neighborhoods and led to complaints. The Chicago Tribune published a series of articles in the fall and environmental groups found traction criticizing petroleum refiners, Canadian crude and byproduct coke. By December, the City adapted petroleum coke and coal storage regulations from the South Coast Air Quality Management District and extended them to ores. The day of the City’s public meeting the Governor and IEPA Director Lisa Bonnett visited the area and announced emergency regulations affecting all coal and coke storage and handling operations within Illinois. Proposed regulations will be filed this week and will be subject to public comment and approval by the Illinois Pollution Control Board, but some go into effect immediately upon filing. Major time lines and provisions that would be effective upon official adoption include:

  • Within five days, a facility must install equipment to monitor wind speed.
  • Within 30 days, a facility must install dust suppression systems along conveyor systems and any piles that are not totally enclosed.
  • Within 30 days, a facility must submit applications for necessary permits and a comprehensive wastewater and stormwater runoff plan to IEPA that ensures that runoff that has come into contact with the piles is prevented from entering the waters of the state and complete it within 60 days of approval.
  • Within 45 days, a facility must submit a plan to IEPA for total enclosure of all coke and coal piles, transfer points, loading and unloading areas, screening areas, crushing and sizing areas to be completed within two years of these rules being adopted. Enclosure structures must be equipped with air pollution systems at all vents and entrances and exits for material and vehicles as well as an impermeable base to guard against ground seepage.
  • Within 45 days, a facility must submit a plan to IEPA to minimize the impact of truck traffic on residential areas near the source. All petcoke loading and transport must be done in vehicles sufficiently covered to guard against fugitive dust emissions.
  • With 45 days, a facility must submit a plan to IEPA for coke and coal fugitive dust that must adhere to requirements in the Illinois Environmental Protection Act and must be updated at least semi-annually or within 30 days of a major equipment or control change.
  • Within 60 days, a facility must remove all petcoke and coal that has been at the source for more than one year.
  • Within 60 days, a facility must locate any piles, loading operations, transfer or emission points that are not totally enclosed to at least 200 feet inside the property line of the source, a minimum of 200 feet from all waters of the United States, all public water supply reservoirs and intakes and all potable wells and onto impenetrable bases or pads.
  • Within 60 days, no pile may exceed 30 feet in height. Visible height markers must also be installed.
  • A least once per calendar week, a facility must measure moisture content of representative samples and adjust dust suppression measures so as to meet certain standards and inspect all dust suppression equipment so as to ensure adequate operations.
  • At least monthly, a facility must certify the operation of all dust suppression systems at all times during the processing of coal and coke and submit records to IEPA showing the types and quantities of materials delivered to and transported from the source, and data reflecting cleaning, street-sweeping and equipment maintenance frequency.

If you have questions on these proposed City or State emergency regulations, please contact CEC’s Chicago office at 630-963-6026.

More information:

Clean Water Act, Section 308 Requests for Information

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So…you have received a Request for Information from the US Environmental Protection Agency (USEPA) pursuant to Section 308 of the federal Clean Water Act. A Section 308 request is done when the agency has reason to think that your facilities are not in total compliance with their NPDES permit limits. No need to panic – just start compiling the needed information.

Often the first thing that companies do after receiving a Section 308 letter is to call an experienced environmental attorney to get some assistance in working through this process. Odds are you wouldn’t have received this letter if you did not have some exceedances of NPDES permit limits, so the attorney can help you work through usually inevitable enforcement discussions with the USEPA.

Here are the types of information that the USEPA will typically ask for in Section 308 letters. You will need to pull this information together into one location so it can be copied and shipped to the USEPA:

  1. A list of all of your facilities by name, location, NPDES and mining permit numbers.
  2. Copies of each NPDES permit and permit applications for each identified facility.
  3. NPDES data for the past five years (or more), including your Discharge Monitoring Reports (DMR’s) and, often, the lab sheets upon which the DMR’s were based.
  4. You will need to summarize the information from items #1 through #3 (and any additional requested information) into an Excel spreadsheet(s).

Mining facilities with NPDES permits that have discharge violations of metals, chloride, TDS, TSS, pH, etc. may be faced with hefty fines, as well as corrective measures to address and eliminate non-compliant discharges. These corrective measures typically include additional monitoring and reporting, implementing an electronic environmental database management software, implementing an environmental compliance management system, developing a response plan for eliminating effluent limit violations, and conducting internal and/or third-party environmental audits. Depending on the parameters in question, expensive treatment (or pre-treatment) systems may need to be installed.

Known recent civil penalties have ranged from $4 million to $20 million, which doesn’t include costs for corrective measures. Given the amount of money at stake, it is crucial to go into meetings with USEPA as prepared as possible.

If you have questions about the Section 308 process as it relates to mining companies, please contact Jonathan Pachter in our Pittsburgh office at 1-800-365-2324 or jpachter@cecinc.com. Additional information regarding EPA Section 308 matters can be found at the EPA’s website.