The Great Lakes Water Authority (GLWA) is a regional water authority in the U.S. state of Michigan. It provides drinking water and sewer services for the Southeast Michigan communities, including Wayne, Oakland, and Macomb counties, among others.S.
Anaerobic digestion (AD) is a key technology for energy recovery in wastewater treatment plants, converting organic matter into methane-rich biogas. However, its efficiency is constrained by slow reaction rates, particularly during hydrolysis and methanogenesis, necessitating large reactor footprints for effective sludge digestion. Alternative AD configurations for process intensification present a promising solution to address these limitations by altering the design and operational setup of the AD process. In this review, key configuration-based AD intensification strategies were systematically analyzed, including recuperative thickening, single-stage thermophilic AD, acid/gas two-stage AD, temperature-phased AD, and multi-stage AD systems. The mechanisms, governing factors, efficiency gains, and scalability of these technologies were critically examined. These configurations demonstrated substantial improvements in methane production rates, process intensification, and the removal of solids and organics. Single-stage thermophilic and cascade AD technologies showed the highest potential for full-scale implementation, supported by successful real-world applications. Conversely, recuperative thickening exhibited promising results at lab and pilot scales but remains limited by its lower technology readiness level. Furthermore, the integration potential of such alternative systems with other intensification technologies was explored, highlighting synergistic opportunities for further optimization. This review provides critical insights into means to intensify AD process through alternative process configurations, offering a comprehensive guide for their application in biogas upgrading. It also identifies key challenges and outlines actionable steps to advance these systems toward widespread adoption in full-scale AD operations.
Performic acid (PFA) has emerged as a promising disinfectant for wastewater effluents and combined sewer overflows (CSOs), offering strong microbial inactivation with minimal formation of harmful disinfection byproducts (DBPs). This review systematically evaluates existing research on PFA performance across primary effluent, CSOs, and secondary effluent, emphasizing microbial inactivation kinetics, exposure modeling, DBP formation, and toxicity, while identifying knowledge gaps. Compared with traditional disinfectants such as free chlorine, chlorine dioxide, chloramines, and peracetic acid, PFA demonstrates comparable or superior bacterial inactivation while generating substantially lower concentrations of regulated halogenated DBPs. PFA also generates diverse oxygenated and nitrogen-containing transformation products, with PAA behaving similarly, whereas chlorine and chloramines form more persistent halogenated and nitrogenous byproducts. Disinfection efficacy of PFA varies across microbial groups, with enterococci, spores, and protozoan cysts demonstrating greater resistance, consistent with patterns observed for other disinfectants. However, PFA achieves faster inactivation at equivalent doses. Studies indicate that integral CT (ICT)-based models more accurately describe PFA inactivation under real wastewater conditions by capturing disinfectant decay and non-ideal hydraulics. DBP formation during PFA disinfection remains low, with halogenated DBPs detected only at high PFA concentrations (≥30 mg/L), and no nitrosamine formation reported. Acute toxicity assays show low ecotoxicity, although responses differ among species. Despite these promising findings, research gaps remain regarding PFA reactivity with complex wastewater matrices, inactivation of human enteric viruses and resistant bacterial spores, environmental fate of transformation products, and long-term ecological impacts. Overall, this review highlights PFA’s strong potential as a safer, effective disinfectant for wastewater treatment and identifies critical areas for future investigation to support full-scale implementation.
Although hydrothermal liquefaction (HTL) is the leading technology in converting wet biomass into bioenergy, the treatment of its toxic-laden aqueous phase wastewater presents a major challenge on its path toward commercial viability. This study presents the first-ever assessment of sewage sludge-fed HTL wastewater (SS-HTLWW) treatment and toxic compound removal using municipal activated sludge (AS) by optimizing its cultivation condition. It was found that AS with optimized pretreatment can remove up to 91.2% of the soluble chemical oxygen demand (sCOD) in SS-HTLWW, of which up to 82% can be attributed to biological mineralization and adsorption of sCOD by AS. Conventional bioprocess optimization techniques, including overliming, elevated temperatures, and nutrient supplementation, were found to raise the maximum rate of sCOD utilization (Rm) of AS treatment by 44%, 67%, and 45%, respectively. The variation in the maximum degradation potential (Dmax) after 23 days of treatment across all groups was negligible. Adjusting the SS-HTLWW dilution factor from 20× to 10× resulted in no significant difference in Rm or Dmax values due to the counteracting effects of high substrate and inhibitor concentrations. Additionally, AS was able to eliminate almost all N-heterocycles, phenolic compounds, and organic acids found in SS-HTLWW. This suggested that AS can both survive in and mitigate the high level of toxicity associated with SS-HTLWW; however, the high levels of recalcitrant COD after treatment may require further attention before it can be adequately discharged. The insights gained from this study are poised to interest engineers and treatment plant operators in search of efficient strategies for SS-HTLWW management and the broader application of HTL.
