Performance And Efficient Of CSTR And ABR For Hydrogen And Methane Production By Organic Wastewater Fermentation

Anaerobic fermentation technology is an important route to solve environmental pollution and resources problems. In this paper, the theoretical and technical characteristics of CSTR and ABR (anaerobic baffled reactor) during fermentation hydrogen production and methane fermentation were explored, and the adjustment of fermentation hydrogen-methane production was researched. Furthermore, the simultaneous hydrogen-methane production was tested and optimized.The CSTR fermentation hydrogen production system was initialed using aerobic sludge, and different anaerobic microorganisms were cultured to achieve propionic acid type fermentation, butyric acid type fermentation, and ethanol type fermentation. Ethanol type fermentation was the optimum one among all these types; the specific hydrogen production efficiency was 2.89 mol/kgMLVSS·d, 4 times that of butyric acid type fermentation and 148 times that of propionic acid type fermentation. In CSTR, the hydrogen production mechanisms included pyruvate decarboxylation hydrogen production and coenzymeⅠhydrogen redox balance adjustment, and their contributions were 82% and 18% respectively. Hydrogen-producing acetogens did not work. Lower sludge loading rate was beneficial to the formation of ethanol-type fermentation. It took 30 days to achieve stable ethanol-type fermentation when the sludge load was 0.99 kgCOD/kgMLVSS·d during start-up or 16 days when the load was 0.64 kgCOD/kgMLVSS·d.Results showed that ABR was an ideal facility for hydrogen production from organic wastewater fermentation. It had higher efficiency and lower energy consumption comparing with CSTR. ABR achieved stable ethanol type fermentation within 26 d with HRT of 13.5 h, 35℃and initial COD of 5000 mg/L, and the specific hydrogen production rate was 0.13 L/gMLVSS·d while that of CSTR under the same conditions was 0.06 L/gMLVSS·d.Both CSTR and ABR could establish complete methane fermentation microbial systems under certain controlled conditions. With an influent COD concentration of 4000 mg/L and HRT of 24 h, CSTR could form a suspended anaerobic sludge system with complete methane fermentation process within 73 d and the COD removal ratio was around 70%. Under the same conditions, ABR could achieve 74% COD removal within 17 d, and further improved to 90% COD removal with an organic load of 4 kg/m3·d.Based on above findings, simultaneous hydrogen-methane fermentation was proposed and realized in the ABR system. The first two compartments functioned as hydrogen production, while the last ones acted as methane production. When influent COD was 6000 mg/L and ALK was 1900 mg/L, COD removal ratio reached 62%, hydrogen production capacity reached 0.37 m~3/m~3·d, and methane production capacity was 1.66 m~3/m~3·d. Alkalinity adjustment could stimulate the proliferation and methanogenic activity of sludge in the back compartment'but inhibited the hydrogen production in front compartments. Trace element addition, on the other hand, stimulated the activity of all types of microorganisms, enhanced the bio-diversity of ABR, but did not change the amount of biomass. The influent COD change, alkalinity adjustment, and trace element addition caused succession of the microorganism communities in ABR. Accordingly, the microbial communities'formation in each compartment presented a regular variation.A novel method was built to measure the activity of hydrogen production hydrogenase. The hydrogenase activity measured using this method was highly relevant with the specific hydrogen production efficiency of the ABR, and, thus, could be used to evaluate the performance of ABR.