In this study, methanethiol(MT)-degradation bacteria were cultivated by using MT, methanol and trimethylamine as carbon sources under anaerobic conditions. It was found that the batch bacteria used MT and metha- nol...In this study, methanethiol(MT)-degradation bacteria were cultivated by using MT, methanol and trimethylamine as carbon sources under anaerobic conditions. It was found that the batch bacteria used MT and metha- nol as carbon sources grew faster than those used trimethylamine. The enriched bacteria used MT and methanol as the carbon sources were respectively inoculated in different biotrickling filters. The biological conversion performance ot MT under anaerobic conditions was investigated in biotrickling filters. The results showed that the performance of the biotrickling filter inoculated with the bacteria enriched using MT was better than that inoculated with the bacteria en- riched using methanol. When the inlet concentration of MT was 0.005vo1% (50 ppm), the empty bed residence time was 50 s, pH value was 8.0, and the flow rate of the nutrient solution was 10 L/h, the removal efficiency of MT reached 95.3%. Adding methanol stimulated the growth of the biomass and the degradation of MT, but caused that some bacteria only degrading methanol outcompeted the bacteria only degrading MT. The concentration of sodium bicarbonate in the nutrient solution needed to be controlled lower than 30 g/L, otherwise, it would be harmful to the degradation of MT.展开更多
An anaerobic digestion unit for producing biogas from cow dung in the rural communities was designed, fabricated and tested for performance, durability and throughput. The major components of the digester included the...An anaerobic digestion unit for producing biogas from cow dung in the rural communities was designed, fabricated and tested for performance, durability and throughput. The major components of the digester included the substrate holding tank, tank cover, agitator, debris collector, inlet and outlet pipes, gas reception tank, hose and heat source. The digester is a vertical cylindrical tank with an inlet pipe for the introduction of substrate and an outlet pipe to collect the digested substrate. An agitator is incorporated inside the digester to break scum on the substrate and create uniform temperature profile in the digester while a pressure gauge was fitted to the gas outlet valve to measure the gas pressure in the tank. The agitator shaft is extended outside to be driven by an electric motor through belt and pulley system. The criteria considered in the design of the digester included air tightness of the system, mesophilic and thermophilic temperature, nature and type of substrate used, substrate retention period, number of crank turns per minute and volumetric capacity of the digestion tank. Other considerations included the desire to make the digestion tank and gas reception tank of galvanized steel to ensure good quality of the product and the need for a strong structural support to ensure structural stability of the system. After construction and assembly, the biogas digestion unit was tested with 40 kg of cow dung diluted with 80 kg of water and subjected to a retention period to make a substrate (slurry) of 10 % total solid (TS). Daily gas yield was determined; gas pressure in the tank was measured by the pressure gauge, while the ambient temperature was taken at five hours interval. Results showed that a cumulative gas yield of 0.415 litres after 22 d retention period at average substrate temperature and pH of 29 ℃ and 6.2, respectively. The digester has a substrate holding capacity of 330.8 litres and a production cost of $375 with all the construction materials being available locally.展开更多
Anaerobic digestion of Chinese cabbage waste was investigated through a pilot-scale two-stage digester at a mesophilic temperature of 37 ℃. In the acidification digester, the main product was acetic acid, with the ma...Anaerobic digestion of Chinese cabbage waste was investigated through a pilot-scale two-stage digester at a mesophilic temperature of 37 ℃. In the acidification digester, the main product was acetic acid, with the maxi- mum concentration of 4289 mg·L^-1 on the fourth day, accounting for 50.32% of total volatile fatty acids. The oxidation reduction potential (ORP) and NH^+-N level decreased gradually with hydraulic retention time (HRT) of acidification. In the second digestion phase, the maximum methanogenic bacterial concentration reached 9.6 × 10^10ml^-1 at the organic loading rate (OLR) of 3.5-4 kg VS·m^-3, with corresponding HRT of 12-16 days. Accordingly, the optimal biogas production was 0.62 m^3· (kg VS)^-1, with methane content of 65%-68%;. ORP and NH4^+-N levels in the methanizer remained between -500 and -560 mV and 2000-4500mg· L^-1, respec- tively. Methanococcus and Methanosarcina served as the main methanogens in the anaerobic digester.展开更多
基金Supported by the National Natural Science Foundation of China(No.21106098)
文摘In this study, methanethiol(MT)-degradation bacteria were cultivated by using MT, methanol and trimethylamine as carbon sources under anaerobic conditions. It was found that the batch bacteria used MT and metha- nol as carbon sources grew faster than those used trimethylamine. The enriched bacteria used MT and methanol as the carbon sources were respectively inoculated in different biotrickling filters. The biological conversion performance ot MT under anaerobic conditions was investigated in biotrickling filters. The results showed that the performance of the biotrickling filter inoculated with the bacteria enriched using MT was better than that inoculated with the bacteria en- riched using methanol. When the inlet concentration of MT was 0.005vo1% (50 ppm), the empty bed residence time was 50 s, pH value was 8.0, and the flow rate of the nutrient solution was 10 L/h, the removal efficiency of MT reached 95.3%. Adding methanol stimulated the growth of the biomass and the degradation of MT, but caused that some bacteria only degrading methanol outcompeted the bacteria only degrading MT. The concentration of sodium bicarbonate in the nutrient solution needed to be controlled lower than 30 g/L, otherwise, it would be harmful to the degradation of MT.
文摘An anaerobic digestion unit for producing biogas from cow dung in the rural communities was designed, fabricated and tested for performance, durability and throughput. The major components of the digester included the substrate holding tank, tank cover, agitator, debris collector, inlet and outlet pipes, gas reception tank, hose and heat source. The digester is a vertical cylindrical tank with an inlet pipe for the introduction of substrate and an outlet pipe to collect the digested substrate. An agitator is incorporated inside the digester to break scum on the substrate and create uniform temperature profile in the digester while a pressure gauge was fitted to the gas outlet valve to measure the gas pressure in the tank. The agitator shaft is extended outside to be driven by an electric motor through belt and pulley system. The criteria considered in the design of the digester included air tightness of the system, mesophilic and thermophilic temperature, nature and type of substrate used, substrate retention period, number of crank turns per minute and volumetric capacity of the digestion tank. Other considerations included the desire to make the digestion tank and gas reception tank of galvanized steel to ensure good quality of the product and the need for a strong structural support to ensure structural stability of the system. After construction and assembly, the biogas digestion unit was tested with 40 kg of cow dung diluted with 80 kg of water and subjected to a retention period to make a substrate (slurry) of 10 % total solid (TS). Daily gas yield was determined; gas pressure in the tank was measured by the pressure gauge, while the ambient temperature was taken at five hours interval. Results showed that a cumulative gas yield of 0.415 litres after 22 d retention period at average substrate temperature and pH of 29 ℃ and 6.2, respectively. The digester has a substrate holding capacity of 330.8 litres and a production cost of $375 with all the construction materials being available locally.
基金the National Science-Technology Support Plan of China(2014BAD02B04)
文摘Anaerobic digestion of Chinese cabbage waste was investigated through a pilot-scale two-stage digester at a mesophilic temperature of 37 ℃. In the acidification digester, the main product was acetic acid, with the maxi- mum concentration of 4289 mg·L^-1 on the fourth day, accounting for 50.32% of total volatile fatty acids. The oxidation reduction potential (ORP) and NH^+-N level decreased gradually with hydraulic retention time (HRT) of acidification. In the second digestion phase, the maximum methanogenic bacterial concentration reached 9.6 × 10^10ml^-1 at the organic loading rate (OLR) of 3.5-4 kg VS·m^-3, with corresponding HRT of 12-16 days. Accordingly, the optimal biogas production was 0.62 m^3· (kg VS)^-1, with methane content of 65%-68%;. ORP and NH4^+-N levels in the methanizer remained between -500 and -560 mV and 2000-4500mg· L^-1, respec- tively. Methanococcus and Methanosarcina served as the main methanogens in the anaerobic digester.