The Operational Research Of Two-phase "CSTR-UASB" Anaerobic System For Coproduction Of Hydrogen And Methane

With the rapid development of economic and technology, the overuse of fossil fuels has caused many environmental problems. It has become the energy strategy policy all over the world to seek clean energy instead of fossil fuels. Hydrogen has attracted a great deal of attentions of researchers due to its interests such as environmental kindness and renewable. Anaerobic fermentation biological hydrogen production has board development respects, but low production efficiency is the major obstacle which limits its industrial application. However, according to the characteristics of microorganisms, the effluents from biological hydrogen production can continue to be used to produce methane. This can both reduce the environmental damage of organic waste and recover simultaneously hydrogen and methane to improve energy recovery efficiency.In this study, a two-phase anaerobic system composed of continuous stirred tank reactor (CSTR) as acidogenic phase and up-flow anaerobic sludge bed (UASB) as methanogenic phase was established to realize the coproduction of hydrogen and methane. Experiment firstly studied the influence of hydraulic retention time (HRT) on acidogenic phase and methanogenic phase, so as to determine the optimal operation condition. Results show that:the optimal HRT condition for acidogenic phase was5h and under this condition, hydrogen production rate of8.31(±0.11) mmol L-11h-1and content of59.0(±1.69)%was obtained; the optimal HRT condition for methanogenic phase was18h and under this condition, methane production rate of2.14(±0.05) mmol L-11h-1and content of75.5(±1.19)%was obtained.With optimal operation condition of acidogenic phase and methanogenic phase, the two-phase anaerobic system for the coproduction of hydrogen and methane was established and the influence of organic loading rate (OLR) on system energy recovery efficiency was investigated. Results show that:at OLR16g COD L-1d-1, the maximum energy recovery efficiency of73.1%was obtained, at which about16.6%and56.5%of COD was resealed in the form of hydrogen and methane, respectively. Compared with single phase anaerobic system, the two-phase anaerobic system can greatly improve energy recovery efficiency. In addition, regardless of different OLR, this system indicated s strong removal ability of organic substances.Though the highest COD removal efficiency was obtained at OLR24g COD L-1d-1, from perspective of energy recovery, the OLR of16g COD L-1d-1was more suitable for the operation of two-phase anaerobic system. Experimental data revealed that two-phase anaerobic system is the effective combination of wastewater treatment and energy recovery, but further research was deserved in this system especially the acidogenic phase.