Simulating the impact of suppression of methanogenesis in continuous flow biohydrogen reactors

Abstract

A calibrated model of the patent-pending integrated biohydrogen reactor clarifier system (IBRCS) using BioWin was used to evaluate the impact of sludge and/or feedstock pre-treatment for methanogens inhibition in a dynamic simulation for 90 days with and without methanogens suppression. Dynamic simulations at four different OLRs ranging from 6.5 to 103 gCOD/L-d have shown that without any pre-treatment, the system was capable of washing out methanogens and enriching hydrogen producers. The average methane gas content in the reactor’s headspace was 4% after 7 days of continuous operation, decreasing sharply to less than 0.5%, while the maximum reduction in hydrogen gas was <10%. The hydrogen gas content in the headspace ranged from 65% to 72%. Simulating the impact of extended SRT ranging from 3 days to 20 days on the performance of the IBRCS revealed that up to an SRT of 5 days hydrogen production was predominant with a reasonable deterioration in the production rate by 20%. Biomass distribution showed that at SRTs up to 20 days, acetoclastic methanogens were naturally eliminated. However, hydrogenotrophic methanogens had a significant impact on the overall hydrogen production rate where most of the hydrogen gas produced was consumed at SRTs of 10 days and 20 days.