Effluent Limitation Guidelines (ELGs) under the Clean Water Act set technology-based discharge standards for Steam Electric Power Generators. Recent regulatory updates and proposed deadline extensions have increased the complexity of achieving compliance for flue gas desulfurization (FGD), bottom ash (BA), combustion residual leachate (CRL), and legacy wastewaters. These changes in the regulatory landscape have prompted generators to evaluate alternative technologies to achieve compliance in a cost-effective and timely manner.
Deep well injection, regulated under the EPA’s Underground Injection Control (UIC) program, offers a potential solution for wastewater disposal by removing and isolating wastewater from the surface hydrologic cycle. Groundwater protection is assured through rigorous demonstration of geologic containment and well construction standards. However, there are additional operational considerations for deep well injection, particularly for pretreatment design.
Pretreatment design bases are directed towards maintaining the deep well’s operability and injectivity. Geochemical modeling is essential for identifying and defining mineral scaling and corrosion potentials in the subsurface, thereby establishing pretreatment design targets. Process design modeling can then optimize flowsheets that evaluate potential solutions towards achieving the pretreatment design targets.
Learn more at The World of Coal Ash (WOCA) 2026, May 4 – May 7
The World of Coal Ash – affectionately called WOCA – is the premier international conference on the science, application, and sustainability of coal combustion products. WOCA is hosted by the American Coal Ash Association (ACAA) and the University of Kentucky Center for Applied Energy Research (UK CAER).
Our Author, John Yang, will present a session titled “Managing Pretreatment Design, Injectivity, and Cost Through Modeling.” In his presentation, SCS will detail the workflow for establishing pretreatment design basis for two representative scenarios – a sulfate-rich contact water and an FGD wastewater currently undergoing heavy metal removal for indirect discharge. Jon discusses the geochemical basis for selecting pretreatment operations and high-level budgetary considerations. A combined geochemical and process modeling approach for deep well injection helps operators with vetting all potential options for achieving ELG compliance.
Jon Yang, PhD, is an engineering-focused geochemist with extensive experience serving industries for critical minerals and rare earth elements, industrial wastewater management, contamination, carbon capture and sequestration, and environmental services. He holds a Doctorate in Ocean, Earth, and Atmospheric Science from Oregon State University and a Bachelor of Science in Chemical Engineering from the University of Arizona. Dr. Yang’s background combines fundamental geoscience with applied engineering and has broad applicability to service areas such as deep-well injection, electric utilities, mining, and wastewater treatment.
Dr. Yang has previously led critical mineral and rare-earth element (REE) resource assessments at the National Energy Technology Laboratory for unconventional geologic feedstocks, including coal-related materials, shale, and ultramafic rocks. His experience includes advanced geochemical modeling of extractive processes, detailed lithologic and geochemical evaluation of core samples, and interpretation of depth-dependent compositional changes. He has designed and advanced novel extraction and geochemical process workflows, contributing to patented technologies and federally funded research programs designed to further the critical mineral supply chain in the U.S. Dr. Yang’s work has advanced research from early technology readiness levels along pathways for potential commercialization and/or technological transfer. He has served in professional capacities, providing technological due diligence on emerging technologies.
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