New approaches to FGD Wastewater Treatment unveiled at Hot Topic Webinar Yesterday

“Control and Treatment Technology for FGD Wastewater” was the Hot Topic on Thursday, August 15. There are State rules in place which are requiring significant investment in treatment. The new MATS rule will add pollutants to the waste stream, so every FGD system purchaser should be carefully examining his treatment options.

On April 19, 2013, EPA proposed revisions to the effluent limitations, guidelines and standards that would strengthen the existing controls on water discharges from steam electric power plants. The rules would require power plants to install pollution control technology and implement waste-treatment procedures in a phased approach between 2017 and 2022. The EPA must finalize the rules by May 22, 2014. The rules apply to all water discharged from steam power plants, but a particular concern is FGD wastewater. The pollutants of concern include mercury, arsenic, selenium, nitrogen and total dissolved solids. Since some States already have rules regarding discharges, many of the operators will be needing to comply with requirements much sooner. So utilities will be glad to hear that suppliers are developing solutions which are lower in cost but accomplish the needed reductions

Paul Chu, Project Manager at the Electric Power Research Institute (EPRI), presented the work EPRI has been doing to evaluate wastewater treatment options. EPRI has been conducting treatment evaluation studies in the laboratory, pilot and full-scale. EPRI’s work has focused upon physical/chemical precipitation and adsorption-based technologies as well as biological reduction approaches. Paul pointed to the severity of the proposed standards which apply just to the FGD waste stream.

State requirements for total wastewater discharges may even be tougher to meet. Paul explained that where the conventional physical/chemical/biological process are not sufficient, it may be necessary to also incorporate polishing adsorption. Paul emphasized that each power plant must be analyzed individually.

A question was asked as to the impact of halogenated compounds in the air stream and chemicals to prevent re-emissions in the scrubbing solution. Paul said that EPRI was looking at the impacts but they may not be significant in changing process requirements.

Norikazu Inaba, Manager of Process Engineering at MHIA /Advatech (a URS & MHIA Company), discussed “Simple Zero Liquid Discharge System for FGD Wastewater.”  MHI has developed low CAPEX/OPEX technology for truly achieving zero liquid discharge (ZLD) from wet FGD to meet the stringent effluent limits. The Wastewater Spray Dryer (WSD) that eliminates a purge stream from the wet FGD process is easy to retrofit and requires no chemicals and significantly less energy than the conventional brine evaporator.

The advantages of the WSD are

• Low capital and operating cost
• No chemical or biological treatment required
• Small footprint (easy to retrofit)
• Does not need to operate continuously
• Fully isolatable for easy maintenance
• Handles wide range of dissolved solids content
• Dissolved solids and trace elements captured in existing solid waste stream

Disadvantages are

• Slight impact on heat rate (around 0.5 percent)
• Slight increase to PM loading on particulate control device (<5 percent)
• May limit the volume of water that can be treated.

Gordon Maller, Principal Project Manager and Business Development Manager for URS Corporation – Process Technologies Office, discussed the non thermal ZLD process.

It is a version of the original chemical fixation processes used with the inhibited magnesium lime FGD systems built in the 1970s. URS has found that the fixation process works with gypsum as well as with the calcium sulfite mixture of the early systems. With the correct blends of flyash, gypsum and lime mixed with the wastewater, a very stable product is created.  It is a low cost option.  Some flyash is needed for the process but many power plants are now landfilling both gypsum and flyash, so for these plants the system should be a clear winner.

Gordon was asked whether this development would encourage operators without FGD to consider the inhibited oxidation magnesium lime systems in lieu of forced oxidation limestone. The capital cost with a smaller scrubber and no oxidation blower would be less. Gordon agreed but emphasized that the near term goal was to focus on the gypsum producers who have the wastewater problems now.

William A. Shaw, Senior Process Engineer for HPD^® Evaporators and Crystallizers at Veolia Water Solutions & Technologies North America, observed that ZLD systems can be very expensive from both a capital and operational perspective. New approaches to evaporator system design, especially the recently patented CoLD^® crystallization technology, provide additional options to power plants which are looking for methods to effectively and economically reduce or eliminate their water discharges from FGD scrubbers.  

The low operating temperature lowers the solubility of the high solubility dissolved salts, so they crystallize at a much lower concentration. Softening equipment, chemicals and resulting sludge disposal costs are eliminated.

Bios, Abstracts and Photos can be seen BIOS, ABSTRACTS, PHOTOS 8-15-13.htm

The individual presentations are as follows:

• Control and Treatment Technology for FGD Wastewater Webinar - Hot Topic Hour August 15, 2013  (Webinar Recording  Dated:  8/15/2013)

• The Wastewater Spray Dryer, "The Simple Solution to Zero Liquid Discharge" by Norikazu Inaba, Advatech - Hot Topic Hour August 15, 2013  (Presentation  Dated:  8/15/2013)
• FGD Wastewater Treatment Evaluation by Paul Chu, EPRI - Hot Topic Hour August 15, 2013  (Presentation  Dated:  8/15/2013)
• The CoLD Crystallization Process by William Shaw, Veolia - Hot Topic Hour August 15, 2013.  (Presentation  Dated:  8/15/2013)
• Wastewater Treatment and Xero Liquid Discharge Technologies: Overview and New Developments by Gordon Maller, URS Corp. - Hot Topic Hour August 15, 2013  (Presentation  Dated:  8/15/2013)