Waste-to-energy (WTE) technologies are essential to minimize waste and pollution, reduce dependency on fossil fuels, and combat climate change. With the growth of global economy, large quantities of high-strength wastewater (HSW) are discharged into the environment, resulting in severe problems. When treating HSW, traditional treatment processes are hindered by low treatment efficiency or high operation costs. Thus, a new cost-effective HSW treatment process based on methane-arrested anaerobic digestion (MAAD) was developed to efficiently convert HSW to valuable bio-derived carboxylic acids.<br/>To achieve high waste conversion and acid productivity, a robust microbial consortium with high salt toxicity tolerance was selectively established and enriched. A blend stream of dairy and brewery wastewater with elevated chemical oxygen demand (COD) concentration (&gt;70 g/L) was used as the feed HSW. Specifically, the effects of wastewater characteristics, microbial consortia structure, digester operation mode (batch and semi-continuous), and operating conditions (e.g., temperature, substrate concentration, and pH) on MAAD performance were investigated at bench scale (500-mL). The process was then developed and optimized at lab-scale (14-L), and the most stable condition of hydraulic residence time (HRT) 3 days, pH 6.0, and 40 °C was selected for further scale-up. Semi-continuous pilot-scale MAAD (100-gal) produced a total acid concentration of 40.6 g/L with COD conversion greater than 70%. A new kinetic model was developed to predict the total acid productivity in semi-continuous MAADs. Different cost-effective separation methods (e.g., membrane, adsorption, electrodeionization) were evaluated to determine the most suitable approach to harvest carboxylic acids from MAAD broth. The results show that the newly developed process has the potential for large-scale application and is a successful example of the WTE technologies to transform low- or negative-value waste streams into high-value bioproducts.

Valorizing high-strength industrial wastewater to bioproducts via methane-arrested anaerobic digestion

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ACS Fall 2022

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