An integrated system for hydrogen and methane production during landfill leachate treatment

Abstract: The patent-pending integrated waste-to-energy system comprises both a novel biohydrogen reactor with a gravity settler (Biohydrogenator), followed by a second stage conventional anaerobic digester for the production of methane gas. This chemical-free process has been tested with a synthetic wastewater/leachate solution, and was operated at 37°C for 45d. The biohydrogenator (system (A), stage 1) steadily produced hydrogen with no methane during the experimental period. The maximum hydrogen yield was 400mL H2/g glucose with an average of 345mL H2/g glucose, as compared to 141 and 118mL H2/g glucose for two consecutive runs done in parallel using a conventional continuously stirred tank reactor (CSTR, System (B)). Decoupling of the solids retention time (SRT) from the hydraulic retention time (HRT) using the gravity settler showed a marked improvement in performance, with the maximum and average hydrogen production rates in system (A) of 22 and 19L H2/d, as compared with 2–7L H2/d in the CSTR resulting in a maximum yield of 2.8mol H2/mol glucose much higher than the 1.1–1.3mol H2/mol glucose observed in the CSTR. Furthermore, while the CSTR collapsed in 10–15d due to biomass washout, the biohydrogenator continued stable operation for the 45d reported here and beyond. The methane yield for the second stage in system (A) approached a maximum value of 426mL CH4/gCOD removed, while an overall chemical oxygen demand (COD) removal efficiency of 94% was achieved in system (A). [Copyright &y& Elsevier]