Increasing of efficiency of fermentation process of organic substrates for intensification of methanogeneration

Abstract

The prospects of increasing the efficiency of fermentation process of organic substrates to ensure the maximum yield of biogas and increase the economic efficiency of processing of organic sewage sludge are considered. Biogas, as an analogue of natural gas, is used in production of thermal and electrical energy, as transport motor fuel, as a raw material for chemical industry.
 An analysis of trends in intensification of methane fermentation processes was carried out. A promising way to increase productivity of methane generation process during processing of organic matter is to increase the energy saturation of an organic substrate and its preliminary treatment. One of the approaches aimed at intensifying methane generation is use of organic waste as an auxiliary substrate for fermentation of sewage sludge – a process known as co-fermentation.
 The sediments of primary and secondary settling tanks of the biological wastewater treatment complex were studied. According to results of tests, it was noted that ratio of carbon and nitrogen in the studied excess activated sludge is 4–5, in the mixture of primary and secondary sediment – 5–6, in sediment from sludge sites – 6–10, which is significantly less than desired ratio of 20:1, which limits the negative impact of increased nitrogen content in the organic substrate for methane fermentation. According to obtained data, it can be predicted that nitrogen-containing compounds present in sewage sludge will contribute to a microbiological process of formation of nitrogen-containing reduced products, which reduce output of methane during methanogenesis.
 The expediency of enriching the inoculated biocenosis with hydrolytic enzyme preparations or microorganisms with high hydrolytic activity is shown, given the fact that activated sludge has a lower hydrolytic activity than enzyme preparations isolated from the same sludge, as well as than some bacteria, and even more so microscopic fungi. This was caused by presence of inert organic and inorganic mass, dead microorganisms and those with low hydrolytic activity in the sludge biomass. It is also possible to increase speed of the first phase of sediment fermentation due to alkaline pretreatment of the substrate mixture.