Hydrogen production in the anaerobic treatment of domestic-grade synthetic wastewater

Abstract

The aim of this study was to evaluate the potential of domestic wastewater for anaerobic hydrogen production. High-strength and ordinary-strength organic loadings of synthetic wastewater, i.e., real-time domestic wastewater with and without a mixture of food waste, were tested. During operation at a high strength loading, the initial pH was maintained at 7 and then gradually decreased, and a pH of 5-5.5 was observed as the best experimental condition. A pH of 5-5.5 was controlled during the operation at an ordinary-strength loading. Maximum hydrogen yields of 1.125 mol H2/mol glucose and 1.01 mol H2/mol glucose were observed during operation at high (48 g COD/L·day) and ordinary (3 g COD/L·day) strength loadings in terms of chemical oxygen demand (COD), respectively, with hydrogen contents of 42%-53%. The operating environment of the hydrogen production system was found to be very crucial because the metabolic pathway of the microorganism and production of intermediates were found to be dynamic with the controlled environment. Smaller COD removals of 30% and 26% were observed in high-strength and ordinarystrength loadings, respectively. Organic mass balance in terms of COD described the distribution of organics in the system via reactor byproducts. The findings of this study can be applied during the design of onsite domestic wastewater and energy recovery systems.