| Abstract: | In the circular economy, waste-to-energy (WTE) technologies are essential to minimize waste and pollution, reduce dependency on fossil fuels, and combat climate change. The carboxylate platform is a promising approach to sustainably produce valuable bio-derived chemicals and fuels from low- and negative-value waste streams. A novel integrated treatment process based on the carboxylate platform was developed to valorize high-strength wastewater (HSW). The process enables simultaneous HSW treatment and carboxylate production via high-rate methane-arrested anaerobic digestion (MAAD). The objectives of this study include: (1) establishment of a tailored microbial consortia for high-efficiency HSW treatment and high-titer carboxylate production, (2) development of MAAD using dairy and brewery wastewater, (3) development of MAAD kinetic model, and (4) separation of MAAD broth via in-situ and downstream techniques. The links between wastewater characteristics, microbial community structure, digester operation mode (batch and semi-continuous), and operating conditions (e.g., temperature, substrate, and pH) of MAAD digesters were investigated at small scale (500-mL). The process was then developed and optimized at bench-scale (14-L), and the most stable condition of hydraulic residence time (HRT) 3 days, pH 6.0, and 40 ℗ʻC was selected for further scale-up. Semi-continuous pilot-scale MAAD (100-gal) produced a total acid concentration of 40.6 g/L. A kinetic model developed using batch MAAD experimental datasets was successfully selected and applied to predict total acid production in semi-continuous MAADs. A modified bench-scale MAAD configuration employing an anaerobic submerged membrane digester (SubMBR) was developed to enhance volatile fatty acid (VFA) production. This configuration achieved a high VFA productivity (11.3 g/(Lliq⁾́⁵d)). In-situ product separation using Resin Wafer Electrodeionization was integrated into the SubMBR, resulting in enhanced HSW treatment efficiency and a peak total VFA concentration of 113.7 g/L. Widespread implementation of the carboxylate platform requires efficient and cost-effective separation methods to isolate VFAs. Five strong- and weak-base anion-exchange resins and five nanofiltration (NF) and reverse osmosis (RO) membranes were used to evaluate the removal efficiency of acetic acid in aqueous solution. At pH 6.3, the strong-base IX resin IRN-78 achieved 95.1% acetate removal. For membrane separation, RO achieved 98.6% acetate rejection, whereas NF achieved the best permeate flux (105 L/(h℗ʺm℗ø)) and acetate rejection (83.1%). The electronic version of this dissertation is accessible from https://hdl.handle.net/1969.1/197818 |
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