[Effect of the Food to Mass Ratio and Hydraulic Retention Time on Hydrogen Production from Fruit and Vegetable Waste].

Semi-continuous biogas production from fruit and vegetable waste by medium temperature anaerobic fermentation was conducted. Hydrogen production under different food-microorganism ratios (F/M 0.5, 0.75, 1.0, 1.5) and hydraulic retention times (HRT) (2, 3, 4 d) were investigated. The results show that in the case of a smaller F/M values (0.5 and 0.75), not all HRT stages were conducive to the continuous production of hydrogen, however, they were conducive to producing methane, especially when HRT was 3 or 4 d. Continuous hydrogen production was viable when the F/M ration was relatively higher (1.0 and 1.5), however, this was not conducive to the production of methane, with almost no methane production detected in this process. A F/M of 1.0 and a HRT of 3 d provided the best conditions for continuous hydrogen production from fruit and vegetable waste. Meanwhile, the highest and average daily volume of hydrogen production were 451.2 mL·(L·d)-1 and (186±29) mL·(L·d)-1 respectively, whereas the highest and average hydrogen production rate of volatile solids were 133 mL·g-1 and (27±5) mL·g-1 respectively. The hydrogen content was 20%-30%.

Factors affecting the performance of a single-chamber microbial fuel cell-type biological oxygen demand sensor.

Microbial fuel cells (MFCs) are devices that exploit microorganisms as biocatalysts to degrade organic matter or sludge present in wastewater (WW), and thereby generate electricity. We developed a simple, low-cost single-chamber microbial fuel cell (SCMFC)-type biochemical oxygen demand (BOD) sensor using carbon felt (anode) and activated sludge, and demonstrated its feasibility in the construction of a real-time BOD measurement system. Further, the effects of anodic pH and organic concentration on SCMFC performance were examined, and the correlation between BOD concentration and its response time was analyzed. Our results demonstrated that the SCMFC exhibited a stable voltage after 132 min following the addition of synthetic WW (BOD concentration: 200 mg/L). Notably, the response signal increased with an increase in BOD concentration (range: 5-200 mg/L) and was found to be directly proportional to the substrate concentration. However, at higher BOD concentrations (>120 mg/L) the response signal remained unaltered. Furthermore, we optimized the SCMFC using synthetic WW, and tested it with real WW. Upon feeding real WW, the BOD values exhibited a standard deviation from 2.08 to 8.3% when compared to the standard BOD5 method, thus demonstrating the practical applicability of the developed system to real treatment effluents.