| Microbial electrolysis cell（MECs） was developed by the microbial fuel cell with the following advantages: low energy input（compared with electrolytic hydrogen） and high hydrogen yield. MECs were used to produce hydrogen with acetate, but how to treat actual waste materials in MECs to achieve the hydrogen gas was still limited in the MECs producing hydrogen process. Waste sludge treatment and disposal was an important problem in the sewage treatment plant. Using the waste sludge to produce the hydrogen directly in MECs was high energy consumption, low energy recovery and hydrogen production rate. Volatil e fatty acids（VFAs） could be produced by the sludge fermentation, which was used as substrate in many bioprogress. Hydrogen production could be obtained in MECs with sludge fermentation liquid, which made the waste sludge disposed.In this study, the key parameters of hydrogen production in MECs reactor were optimized and ascertained. Bovine serum albumin（BSA） was better than the peptone for MECs to produce the hydrogen. The maximum value of hydrogen yield was 0.3 ± 0.015 m L/mg COD when the concentration of the BSA was 800 mg/L. Butyric acid accumulation could promote the hydrogen production in MECs, rather than propionic acid, the rate of the energy recovery was 117.1 ± 0.08%. The optiminized conditons were as following: the original value of p H was 6.5, additional voltage was 0.8 V and electrical conductivity was 8. The hydrogen was decreased, while the methane was increased when the shock of acid was happened to the MECs. Diversity of the microbial community was increased. However, the relative bacteria group of the C gene was recoveried faster after the MECs were shocked by the acid. In addition, the carbon utilization function gene of the bacteria was related to the degradation of the simple carbon source, which was the most affected by the acid shock in the MECs.The three sludge pretreatment methods was compared and studied in this study, including heat-preated sludge, alkaline-pretreated sludge and heat-alkaline pretreated sludge. It was found that the more VFAs were released from the sludge after heat-alkaline pretreatment. Compared with filteration, centrifugating the sludge fermentation liquid was better for hydrogen production in MECs. Further analysis showed that the hydrogen production and energy recovery efficiency achieved the maximum in the the MECs innoculating the heat-alkaline pretreated sludge fermentation liquid. The hydrogen yield was 34.4 ± 4.1 m L H2/g VSS, and 19.3 ± 2.3 m L H2/d. Based on the efficiency of hydrogen production in MECs, heatalkaline pretreatment>heat pretreatment>alkaline pretreatment>non-pretreatment.The initial micro-oxygen condition of the MECs was performed by air exposure in order to inhibit methane and stimulate hydrogen production. Micro oxygen condition could promote the hydrogen production in MECs. It was found that micro-oxygen fermentation was better than anaerobic sludge degradation for SCOD production. According to the SCOD concentration, the performance of sludge pretreatment was as following: micro-aerobic heat-alkaline > heat-alkaline > micro-aerobic heat > alkaline. Compared with the strictly anaerobic fermentation, micro aerobic fermentation facilitated the total volatile fatty acids（TVFAs） accumulation. The best concentration of the sludge fermentation liquid and reaction time were assured when the MECs were inoculated with the different sludge fermentation liquid. Additonally, the microbial community structure was analyzed in MECs inoculating sludge fermentation liquid with micro-oxygen-heat-alkaline pretreatment. The dominated species were β-Proteobacteria, Legionella and Clostridium. Clostridium was increased from 4.1% to 19.3%, while Solobacterium was increased to 10.5%. β-Proteobacteria was 21.3% when the highest hydrogen production efficiency was observed. |
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