CH2Mers to share their expertise addressing wastewater treatment issues facing Coal Fired Power Plants during the Engineer’s Society of Western Pennsylvania International Water Conference, November 6 – 10 in San Antonio, Texas. The conference presents the latest in scientific advances and practical applications in the field of water, cutting across a wide range of industries, technologies and functional areas.
Coal combustion residuals (CCRs), commonly known as coal ash, are created when coal is burned by power plants to produce electricity. According to the Environmental Protection Agency (EPA), coal ash is one of the largest types of industrial waste generated in the United States. In 2012, 470 coal-fired electric utilities generated nearly 110 million tons of coal ash. To address this issue, the EPA is promoting environmentally sound coal ash recycling and has developed regulations for the safe disposal of coal ash in landfills and surface impoundments.
As part of this mitigation, the EPA has placed significant requirements on existing and new wastewater treatment ponds that contain CCRs and is implementing new rules and regulations to address CCRs. Traditionally, coal-fired power plants manage their wastewater in large earthen basin ponds. The CCR Rule requires that ponds be closed or lined if they contain CCRs. Additionally, the EPA has revised the Effluent Limitation Guidelines (ELGs) for the steam-electric power generating category, which severely limits Flue Gas Desulfurization (FGD) wastewater and ash transport water. These new regulations change current operations of coal-fired power plants in terms of ash transport and water management. Thus, many plants are required to close their previously accepted treatment and water and solids management vehicles (i.e., ponds) and implement other ways of treating FGD wastewater.
Because utilities in regulated states typically cannot recover costs for treatment systems that are not required by current permits, they are limited to building treatment systems to meet current, but not necessarily future limits. Those facilities will benefit if these systems are easily adaptable to meet the CCR Rule and ELG requirements. During the IWC, we will discuss the various ways we are working with clients to address treating FGD wastewater, as this has become the largest cost to electric utilities in complying with the ELGs.
CH2M IWC Presentations:
Monday, Nov. 7; 1:15 to 5:00pm
IWC 16-17: Innovative Solids Separation and Dewatering Reduces Cost of Flue Gas Desulfurization (FGD) Wastewater Treatment Thomas Higgins, Reston, VA; Dennis Fink, Oakland, CA; Jeffrey Tudini, Atlanta, GA; CH2M Simply focusing on flow reduction to reduce FGD wastewater treatment costs can minimize savings and environmental benefit; a significant cost of physical/chemical treatment stems from solids handling/dewatering. We present a pretreatment solids separation and dewatering system that separates larger FGD wastewater solids for direct landfilling. Fine solids are settled and dewatered in a reduced-size system. We show field testing and economic analysis comparing cost savings of flow reduction, this technology, and conventional solids-dewatering systems.
Tuesday, Nov. 8; 8:00am to noon
IWC 16-33: Overcoming Challenges in Getting to Zero with Flue Gas Desulfurization (FGD) Wastewater Krystal Perez, CH2M, Bellevue, WA; Thomas Higgins, CH2M, Reston, VA; Dennis Fink, CH2M, Oakland CA
We use a chemistry and mass balance modeling tool to develop a zero liquid discharge method to meet water quality–based standards and ELGs. The method combines FGD system evaporation; fines removal to reduce wastewater flow; wastewater recycling; lime softening to remove magnesium, sulfate, fluoride, and boron; and mixing brine with fly ash to produce disposable solid material. We present a successful example and review factors influencing wastewater quality and quantity.
Tuesday, Nov. 8; 8:00am to noon
IWC 16-44: Wet Flue Gas Desulfurization (WFGD) Wastewater Treatment Systems—Mechanical Design Tips Thomas Higgins, CH2M, Reston, VA; Dennis Fink, CH2M, Oakland, CA; Brian Choi, CH2M, Atlanta, GA We identify mechanical aspects key to ensuring that effluent complies with recent ELGs. We present equipment choices (mixers, etc.) that promote precipitation/adsorption of metals and growth of sturdy particles while minimizing shear. Our closed-loop sludge wasting and recycle design maintains scour velocity in piping, minimizing plugging of FGD solids and the need for flush water. We discuss designs to minimize variability in biological treatment parameters, promote ease of O&M, and provide adaptability for future changes.