Sustainable Wastewater Management Decision-Making Process and Its Application to Water Resource Recovery Facilities

Abstract

Water Resource Recovery Facilities (WRRFs) are facing various unprecedented environmental demands; they must reduce greenhouse gas (GHG) emissions, manage emerging pollutants like Per- and PolyFluoroAlkyl Substances (PFAS) and microplastics, and protect aquatic ecosystems. Additionally, facilities must consider their relationship with neighboring communities. WRRFs must balance environmental and social needs with economic feasibility while also complying with legal requirements. Decision-making in WRRFs should address these challenges, yet the process itself is complex and requires the participation of various stakeholders and the assistance of experts. This dissertation proposes a framework to systematically address complex decision-making in WRRFs and evaluates its applicability in two actual decisions at a large WRRF related to: (1) biosolid management (strategic management decision) (2) bar rack and grit chamber (operational planning decision). To achieve environmental, economic, and social sustainability and enhance stakeholders’ participation in the decision-making process and assessment of alternatives in WRRFs, several outstanding knowledge gaps must be addressed: inadequate systematic decision-making process applicable to WRRFs and limited research on plant-wide assessment and framing issues in WRRF’s decision. 1) Wastewater management decisions are complex due to regulatory challenges, conflicting stakeholder expectations, and constraints like technology, regulations, and consumer affordability. Over 200 papers were reviewed to propose a structured decision-making process that is science-based, sustainability-focused, clear, transparent, inclusive, objective-oriented, scalable, repeatable, and efficient. Stakeholder engagement, combined with data-driven analyses, was emphasized as essential for effective and widely supported decisions. 2) Limited research has been conducted specifically considering the interactions between the liquid and sludge streams of WRRFs to evaluate the technical and environmental impacts of biosolid management. This dissertation applied process modeling and Life Cycle Assessment (LCA) to assess the overall technical and environmental performance of biosolid management alternatives at a large WRRF. All alternatives, including composting and four anaerobic digestion options, achieved the following key goals: addressing aging infrastructure, reducing landfill biosolids, and lowering greenhouse gas emissions. Anaerobic digestion options demonstrated greater environmental impact reductions. 3) There has been a limited systematic approach for identifying stakeholders and establishing a decision hierarchy in WRRF decisions. Preliminary results were produced through interviews with internal staff; decision-makers and stakeholders were identified, and a decision hierarchy was proposed for biosolid management in a large WRRF. 4) The use of Multiple Criteria Decision Analysis (MCDA) WRRF decisions has increased among practitioners and researchers in the last two decades, but this analysis becomes more complex when considering numerous alternatives. This complexity was addressed in a bar racks and grit chambers decision at a large WRRF by applying a structured framework combining Data Envelopment Analysis (DEA) for initial screening with MCDA. The methodology effectively identified top-ranked alternatives, and improved decision efficiency. Stakeholder engagement and sensitivity analysis can help integrate diverse values and preferences to achieve well-informed, implementable, and adaptive decisions. When these methods are applied in the decision-making process, the outcome has a higher likelihood of being accepted by the relevant parties, thereby reducing social conflicts and the associated costs.