Evaluating Innovative and Sustainable Treatment Options for Biosolids (WRF Project No. 5169)

Introduction: Biosolids are an organic and nutrient-rich product that are an important and valuable resource than can be used beneficially to support the advancement of the circular water economy. However, the market for the beneficial use of biosolids has been increasing challenged by concerns regarding high cost and limited land application opportunities, public perception, and contaminants of emerging concerns (CECs), such as per- and polyfluoroalkyl acids (PFAS) and microplastics. In response to these rising challenges, a range of innovative biosolids management alternatives have been emerging that can help utilities overcome some of these challenges. To comprehensively understand the potential of innovative biosolids management alternatives to address these challenges, a holistic evaluation framework (Figure 1) was developed.

Objective: The information presented provides valuable and practical information to utilities including: 1) definition, function, and level of readiness of innovative biosolids treatment technologies and 2) a market assessment and value of the various end products identified through the technology screening. The proposed presentation will inform utilities of emerging technologies to address specific challenges, offer insight to different end-products from innovative technologies, and provide an update on the project. At the time of presentation most of the project should be completed. Status:The project is funded by the Water Research Foundation (WRF 5169) and will produce an adaptable tool that utilities can use to select suitable, practical, and sustainable innovative technologies for implementation. The project is ongoing and will be completed the second half of 2025, and includes the following tasks:
Task 1: Technology Capture and Identification of Innovative Technologies
Task 2: End Product Evaluation
Task 3: Technology Screening
Task 4: Case Studies and Life Cycle Analysis

Emerging Opportunities add-on Project: The add-on project extends the scope of the project to perform a comparative life cycle analysis (LCA) of biosolids management via conventional anaerobic digestion and emerging/innovative biosolids treatment technologies. The objective of the add-on project is to understand the benefits and trade-offs associated with innovative technologies in comparison to conventional biosolids treatment.

Methodology: The comprehensive technology review and evaluation gathered information from more than 140 references, including published literature (focused on peer-reviewed literature), gray literature (information from vendors, including WRF's TechLink), information from various associations, and responses from an online survey. Once the initial number of innovative technologies was compiled, several screenings were conducted to determine applicability and if it would advance to further evaluation. 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.'

The innovative biosolids management technologies identified produce a variety of valuable products. To assess the markets for these products, an evaluation was conducted comparing the value of these end products to a standard of Class A/EQ dewatered cake. The suite of end products evaluated is presented in Table 1. Information was gathered from various sources including scientific journal articles, industry reports, technology vendors, characterization data, and professional experience. End-products, including a baseline product of Class A/EQ dewatered cake, were assessed for various categories.

Findings Following the initial screening 35 technologies met the defined criteria for innovation, seen in Table 2. The results from this evaluation will be presented on an accessible interactive dashboard for utilities and other interested parties (Figure 2). The presented information will include definitions, fact sheets, benefits to existing technologies and more. The innovative technologies identified resulted in a variety of end products that were further evaluated in the context of the existing market.

Technology Screening (Task 3) aims to shortlist technologies identified in Task 1 for detailed case studies. Previously, the team developed an approach that utilize a muti-criteria decision making support tool and a comprehensive set of screening criteria that encompassed technical and regulatory performance, operation and maintenance, sustainability, social impacts, and end-product evaluation. The task approach workflow is shown in Figure 3.

The level of implementation includes bench-scale, small pilot scale, large pilot scale, and full scale. Technologies that have been implemented at large pilot or full scale. Table 4 shows the applicability of the four criteria to different technology categories, and three key parameters — product solids content, volatile solids reduction (VSR), and end-product evaluation, were selected to evaluate the performance. Regulatory resilience refers to a technology's ability to meet future regulations such as PFAS limits in biosolids and diversion of biosolids from landfill.

The five technologies recommended for case studies are summarized in Table 5.