Evaluation of Innovative Biosolids Management Strategies with Considerations of Circular Water Economy

The circular water economy optimizes water resources and minimizes waste and emissions by recycling, recovering and regeneration. Biosolids, an organic and nutrient-rich byproduct of wastewater treatment, are an important and valuable resource that can be beneficially used to support improvements to the circular water economy. However, growing challenges associated with greenhouse gas emissions, limited land and resources, contaminants of emerging concerns (CECs), such as PFAS and microplastics, have begun to threaten the beneficial use of biosolids. In response to the rising challenges, a plethora of innovative biosolids management alternatives have been emerging, providing utilities new perspectives on biosolids treatment, end-use, and pathways to advance the circular water economy via beneficial co-product(s) generation, emissions control/capture, and cost reduction. To comprehensively understand the potential of innovative biosolids management alternatives in addressing these challenges, a holistic evaluation framework (Fig. 1) was developed. The framework encompasses environmental impacts, social impacts, cost-effectiveness, as well as integrability into the circular water economy through the sustainable management of end-products. This presentation will provide valuable and practical information to utilities including: 1) definition, function, and level of readiness of innovative biosolids treatment technologies and 2) a holistic evaluation framework developed to screen innovative technologies for implementation, featuring end-product evaluations. The presentation will inform utilities of innovative solutions to rising wastewater treatment challenges, offer insights to different end-products from innovative technologies, and provide an adaptable tool that utilities can use to select suitable, practical, and sustainable innovative technology(ies) for implementation. This project is funded by the Water Research Foundation (WRF 5169). Innovative Biosolids Treatment Technologies The comprehensive evaluation gathered information from 140 references, including published literature (focused on peer-reviewed literature), gray literature (information from vendors, including WRF's TechLink), information from associations, and responses from a distributed online survey. Technologies captured from the comprehensive search were required to provide at least one of the following benefits compared to established technologies to be considered as 'innovative technology': - Reduce biosolids quantity. - Improve end-product quality. - Enhance energy generation. - Reduce GHG emissions. - Address concerns on emerging contaminants. The findings from this initial evaluation were screened to determine whether the technology is classified as 'innovative,' in alignment with the definition developed by the EPA (2006), where at least one of the following categories must be met by the technology: - Tested at a full-scale demonstration site in this country. - Available and implemented in the United States (U.S.) for less than 5 years. - There is some degree of initial use. - Established technologies overseas with some degree of initial use in the U.S. Within the technology capture, there were 36 innovative treatment technologies identified. The technologies are grouped under several unit operations; thermal conversions, stabilization, thickening, dewatering, drying, and other innovative processes. The results from this evaluation will be presented on an interactive dashboard accessible to utilities and other interested parties. Holistic Evaluation Framework for Innovative Treatment Technologies The framework embraces end-product evaluation, technical capabilities, operation and maintenance requirements, social impacts, regulatory performance, and environmental impacts. The viability of end product biosolids and their co-products, such as energy content, plays a key role in closing the unsustainable loop of resource release to the environment. To this end, end-products are evaluated through the lenses of waste diversion, materials cycling and their benefit predominantly in the natural environment in comparison to the traditional management of biosolids. Key considerations of end-product evaluation are their inherent values, cost recovery potential, market viability, and destruction of CECs. Inherent value reflects the value of constituents in the end-products, such as nutrients and organic matter, and the indirect value of their use (e.g. energy content, carbon offset generation potential). Aggregated inherent values are not indicative of the market value of residuals, but are rather an indication of potential market access and suitability for beneficial use. Management fees and potential market values present opportunities for cost recovery which is typically not available to the baseline product of dewatered biosolids. The values are estimated based on the project team's experience, reports from US contractors, reports from technology vendors, or professional opinion. Figures 2 and 3 present an example result of inherent value and cost recovery potential of the end-products of innovative thermal conversion technologies. The range of beneficial constituents inherent within these residuals will influence market access. Residual products are assessed for their suitability for a range of traditional and innovative markets. Market suitability was assessed on a scale of 0-1 (with 0 being no suitability/access and 1 being full access) based on the project team's experience, industry knowledge, and academic trials and reporting. The environmental impacts of innovative technologies are quantified through energy demand and the greenhouse gas emission during the operation of technology as well as the application of its end-products. Technical performance, operational and maintenance requirements provide information on the robustness, consistency, and scaling flexibility of innovative technologies, helping utilities assess the potential staffing and operating requirements. Social impacts are also included in the evaluation framework, accounting for public opinion and nuisance risks such as odor and noise. The weights of evaluation categories and criteria represent the relative importance of each one and serve as channels to incorporate stakeholders' opinion. The weights are determined based on utilities, project advisory committee, and other stakeholders. Conclusion This project aims to assist utilities in understanding the cross-section and applicability of innovative and sustainable technologies that can fit into a circular water economy, while also meeting the current pressures being faced by the biosolids management community. This presentation will provide practical information on emerging solutions to the challenges in biosolids management and share tools that utilities can use to select options to meet their unique needs.