DEFINING INDICATORS FOR THE ANAEROBIC FERMENTATION PROCESS OF AQUACULTURE WASTEWATER SEDIMENTS

Abstract

The object of this study is the process of anaerobic fermentation of wastewater sludge from aquaculture. It was established that the exponential dependence adequately describes the experimental data on the change in the level of decomposition of dry organic matter (DOM) and the specific yield of biomethane per unit of decomposed DOM of aquaculture wastewater sediment depending on the time of anaerobic fermentation. The maximum level of DOM decomposition during anaerobic fermentation achieved in 38 days was 0.74 relative units at a process speed of 0.108 relative units per day. The integrated level of DOM decomposition over 21 days of anaerobic fermentation can reach only 0.43 relative units, and the integrated level of DOM decomposition is set at the level of 0.033 relative units per day. The output of biogas and biomethane during anaerobic fermentation over 21 days of anaerobic fermentation reached 4.083 and 2.627 l, respectively. At the same time, the concentration of biomethane in biogas on day 7 of fermentation reached 74–75 % and remained at this level until day 21. The maximum level of specific yield of biomethane during anaerobic fermentation reached on day 38 was 803.936 ml in terms of normal conditions per gram of decomposed DOM with a rate of change of the specific yield of biomethane of 0.207 ml in terms of normal conditions per gram of decomposed DOM per day. The integrated specific yield of biomethane over 21 days of anaerobic fermentation could reach 580–590 ml in terms of normal conditions per gram of decomposed DOM. With a fermentation time of 21 days, the specific output of biomethane has an optimal value depending on the periodicity of loading the reactor, which is 1.48–1.49 m3 of biomethane per one m3 of biomass in the reactor in one day with a periodicity of loading the reactor once per time from 4.5 to 6 days. The research results could be used to determine the volume of biomethane production and electricity based on it during the anaerobic fermentation of aquaculture wastewater sludge