Resilient Biosolids Management Planning in Southern California

Introduction Eastern Municipal Water District (District) operates four Regional Water Reclamation Facilities (RWRFs) in Southern California that collectively treat an average flow of 48.7 million gallons per day and generate about 173 wet tons per day (wt/d) of digested, dewatered Class B biosolids, which are hauled to Arizona for land application. Rising hauling costs, potential regulatory changes, aging infrastructure, and new statewide requirements have increased the risk of depending on a single biosolids management outlet. To address these challenges, the District prepared a Biosolids Master Plan that provides a coordinated strategy for the next twenty years. The plan evaluates regional market opportunities, identifies near term and long-term needs, and examines the feasibility of future Class A biosolids product. The following sections summarize the key findings and present a roadmap to future biosolids management decisions. Background The District currently hauls all Class B biosolids to Arizona, but rising costs, per- and polyfluoroalkyl substances (PFAS)-related regulations, and legislation such as Arizona's House Bill 2669 have revealed the risks of relying on a single outlet. This prompted the need to reassess solids processing, address aging infrastructure, and plan for a more resilient long term approach. The Biosolids Master Plan evaluates each RWRF and compares solids handling technologies to support a diversified strategy that strengthens the District's goals across the near, mid, and long term. Biosolids Market Opportunities Biosolids management represents one of the most significant risks faced by a utility, which is why the Biosolids Master Plan began by evaluating feasible markets for both current Class B material and potential future products. The assessment focused on technologies that could produce products accepted by regional end users and examined California's beneficial use opportunities along with the regulatory and market conditions that shape what the District can successfully produce and distribute, as shown in Table 1. Although many biosolids products are viable in California, practical implementation depends on capital cost, program needs, and operational considerations. Immediate Needs An evaluation of solids handling systems at each facility identified capacity and performance limitations, including an immediate need for additional digestion capacity that will be added to the District's capital improvement program (CIP). Several thickening and digestion alternatives were compared, and the selected option provided the lowest overall cost, allowed a single near term construction effort, and avoided the limited value of rebuilding aging infrastructure. Class A Post-Dewatering Facility Challenges The Biosolids Master Plan evaluated regional post dewatering technologies, including belt drying, drum drying, and composting, and compared their layouts, capital and operating costs, net present costs, and overall performance. The assessment found that developing a regional post-dewatering Class A facility would require substantial capital investment (as shown in Figure 1) that significantly increases cost per wet ton and does not offer an economic benefit over continuing to haul dewatered cake to Arizona. These results indicate that decisions on future biosolids management should also weigh non-cost factors to better understand risk, long term sustainability, and opportunities to diversify end uses. Roadmap Increasing regulatory uncertainty, especially around PFAS, is making biosolids management more complex. In response, an adaptable implementation roadmap was developed in the Biosolids Master Plan and is a key to low-risk and economical long-term biosolids management with built-in diversification. The roadmap in Figure 1 outlines treatment technologies, end use markets, and the decision points that determine when actions should move forward, and it is fully integrated with the 20-year CIP to align investments with anticipated costs, risks, and regulatory conditions. It also expands opportunities for the District's Class B biosolids by incorporating new contracts and technologies that strengthen program resilience and open access to emerging markets. Audience Takeaways Effective biosolids planning starts with understanding the intended end-use, which drives technology selection and long term program success. The market assessment showed that California can accommodate many biosolids products, but implementation depends on capital cost, operational needs, and program requirements. The planning process was critical for identifying near term capacity needs. Although a post dewatering Class A regional facility is not economically competitive with hauling Class B material to Arizona, long term decisions should consider non cost factors such as risk, sustainability, and opportunities to diversify outlets. The implementation roadmap brings these elements together by outlining viable technologies and markets and defining the decision points that guide future actions.