1
Under the 2015 Effluent Limit Guidelines (ELGs) Rule enacted by the U.S. Environmental Protection Agency (EPA), existing producers of FGD wastewater need to limit the concentrations of mercury, arsenic, selenium and nitrite/nitrate in their discharged FGD streams (Table 1). Although EPA has postponed the original compliance date of November 1, 2018, they will propose a new revised Rule with a projected compliance date of November 1, 2020 1 . As such, many facilities will still need to address this compliance issue by implementing an economic and efficient treatment process to prepare for the release of the new ELGs NEED INTRODUCTION Jinjian Wu 1 , Joon Min 1,a , Young Chul Choi 2 b , Nishil Mohammed 2 1 ES Engineering Services, LLC, a subsidiary of Montrose Enironmental Group, Inc. 2 Southern Research a Principal Investigator, TEL: 949-400-3458, Email: [email protected] b co-Principal Investigator, Email: [email protected] REFERENCES 1. https://www.epa.gov/eg/steam-electric-power-generating-effluent-guidelines-2015-final-rule 2. https://www.federalregister.gov/documents/2015/11/03/2015-25663/effluent-limitations-guidelines- and-standards-for-the-steam-electric-power-generating-point-source 3. Min, J.H., Zhang, J.Z., Tasser, C., Crozes, G.F., Hering, J.G., “Development and application of low-cost biopolymer-based adsorptive media for arsenic, chromium, and selenium removal.” Paper at the KSEA Western Regional Technology Conference “Green Earth and Beyond”, Caltech, Pasadena, CA, Feb 9, 2008. 2019 Crosscutting Annual Review Meeting Pittsburgh April 10 th , 2019, Pennsylvania PROJECT PROGRESS BENFITS AND FUTURE WORK Current treatment methods for selenium in FGD wastewater include biological reduction, adsorption, and membrane processes. Biological reduction converts Se 6 and Se 4 to Se 0 . 2 Although effective, it has limitations including: Long retention time, which requires larger footprint and higher capital costs Requires frequent handling of biological sludge/backwash waste High food source (electron donor) consumption to achieve complete reduction to Se 0 Next Steps: APPROACH Contaminants Unit Daily Maximum Monthly Average Arsenic μg/L 11 8 Mercury ng/L 788 365 Selenium μg/L 23 12 Total Nitrogen (NO 3 /NO 2 -N) mg/L 17 4.4 Table 1. Proposed ELG limits for FGD wastewater discharge 2 Schedule and Progress: In this project, a novel hybrid process is proposed to remove selenium and other key contaminants in FGD wastewater. The hybrid process combines chemical and biological processes to achieve selenium removal. The process has advantages including: Reduction on overall reaction time for selenium removal; smaller footprint Membrane processes such as RO is able to reject Se 6 and Se 4 . However limitations exists for membrane treatment of FGD wastewater including: High fouling/scaling potential Requires concentrate management and disposal High capital and O&M cost Capturing selenium, arsenic in solid media phase, rather than in backwash stream, achieving better waste management 3 Spent media volume reduction by dewatering naturally to achieve volume reduction for disposal cost reduction 3 Meeting TCLP leaching test of the spent media Technology Energy Requirements Water Requirements Treatment Process Backwash / reject rate Startup wash water Biological Treatment - Influent pumping - Chemical feed - 5 ~10% - ~Daily backwash to remove selenium solids - Start up rinse water to wash out fine media due to attrition for carbon based media Conventional Media Adsorption - Influent pumping - 0% - Start up rinse water Conventional Ion Exchange (regenerable) - Influent pumping - ~ 5 % - Daily regeneration with brine and rinse cycle - Start up rinse water Membrane (RO) - High pressure influent pumping - Inter-stage pumping - Chemical feed - 15~20 % - Continuous reject stream due to RO recovery limit - Membrane conditioning water - Regular membrane cleaning water Hybrid Process - Influent pumping - Chemical feed ~2~3% - Start up rinse water Future Work Scale-up production in treatment system Integration of treatment system in existing FGD management Potential Benefits: Lower capital and O&M costs compared with existing treatment processes Lower energy consumption Low wastewater generation and easier management

PROJECT PROGRESS NEED · PROJECT PROGRESS BENFITS AND FUTURE WORK Current treatment methods for selenium in FGD wastewater include biological reduction, adsorption, and membrane processes

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Page 1: PROJECT PROGRESS NEED · PROJECT PROGRESS BENFITS AND FUTURE WORK Current treatment methods for selenium in FGD wastewater include biological reduction, adsorption, and membrane processes

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