Insights into coconut shell incineration bottom ash mediated microbial hydrogen production from waste activated sludge

摘要

Previous studies reported that alkaline anaerobic fermentation was an efficient method for microbial hydrogen production from waste activated sludge (WAS) via inhibiting hydrogen-consuming microorganisms. However, the hydrogen production is still hindered by the low hydrolysis efficiency. This study proposed a new strategy to overcome this barrier by using coconut shell incineration bottom ash as mediator, which is a renewable waste and can be obtained for free from waste-to-electricity facilities. Experiment results showed that coconut shell ash (0.6, 0.9 and 1.2 g/g-Total Solids (TS)) remarkably enhanced microbial hydrogen productions from WAS in alkaline anaerobic fermentation, with the highest output being 3.2 times that without coconut shell ash mediating. Based on process modelling analysis, coconut shell ash promoted hydrogen production rate and potential of WAS by up to 7.9 and 3.0 times, and shortened the lag-phase time from 2.1 days to 0.1 day. A mechanistic study revealed that alkaline condition inhibited methonogenesis and homoacetogenesis processes for hydrogen consumption, and coconut shell ash as mediator enhanced WAS solubilization and hydrolysis that related to hydrogen generation. This was supported by microbial community analysis, which demonstrated that microbial community was changed to be favorable to hydrogen generation. This study provided an integrated waste-control paradigm by waste with more renewable energy production, achieving double benefits in sustainability and economy.