Comprehensive biotechnology of livestock farm wastewater purification

The environmental situation in the country, domestic and foreign experience of biologisation of agriculture indicate the need to develop and implement post-industrial bioconversion technologies and their integrated use. Currently, the problem of treating concentrated wastewater, which also includes livestock farm wastewater, is becoming increasingly important in addressing environmental issues. The use of livestock wastewater on irrigation fields and composting does not allow for the full range of organic matter available in them. On the other hand, the current methods of treating and disinfecting these wastewaters do not provide the required degree of purification. Insufficiently purified wastewater (the degree of purification during aerobic treatment is 55–60% in terms of biochemical oxygen consumption), emergency discharges from manure storage facilities, storm water discharges from the complex’s territories, and excessive irrigation rates all cause soil and water pollution, which is why improved purification technologies are needed. The most promising from an environmental point of view is a comprehensive technology for the purification of concentrated wastewater from livestock farms and complexes using anaerobic (methane) fermentation at the preliminary stage of purification followed by aerobic purification, as well as the use of a biofilter and hydroponic installation. The research was conducted on the manure wastewater of a dairy cattle farm. For their purifica tion, a plant consisting of an anaerobic-aerobic fer menter, a biofilter, a block of containers, heat supply and aeration systems was used. The liquid fraction of manure effluents was subjected to biological purification on a mock-up sample of the technological line after settling in the block of containers. Methane fermentation of the effluent was carried out in a methane tank. The fermentation exposure was 5 days at a temperature regime (process temperature 40...45 °C). The fermented effluent entered the aeration tank, where it was aerated with compressed air for 2,5 days. The pre-purified effluent was subjected to further purification on a biofilter, then – on hydroponic equipment, the crop was barley, the seeding rate was 5 kg/m2, the duration of growing hydroponic green fodder was 7 days. As a result of the purification of livestock farm wastewater using biological treatment using anaerobic and aerobic aeration and a biofilter, as well as hydroponic equipment, the pH value decreased from 8,61 to 7,6, the COD decreased from 3282 mg/l to 746 mg/l, the BOD5 decreased from 2177 mg/l to 96 mg/l, the nitrogen content decreased from 955 mg/l to 152 mg/l), the phosphorus content decreased from 180 mg/l to 7 mg/l. As a result of the use of the biofilter, the suspended solids content decreased from 1520 mg/l to 70 mg/l. The purified wastewater from the livestock farm after growing hydroponic green fodder can be used for technical purposes and cannot be used for direct discharge into water bodies. It was established that the obtained feed corresponds in chemical composition to the GZK, which was grown on an artificially prepared base solution, and the optimal duration of cultivation is 7 days at an optimal seeding rate – 5 kg/m2. The obtained research results give grounds to conclude that it is expedient to use combined technologies that include the processes of microbiological non-sterile fermentation and phytopurification. The resulting biomass can be used as hydroponic green fodder. Key words: waste disposal, microbiological fermentation, phytoremediation, hydroponic green fodder, livestock effluents.