TREATMENT AND DISPOSAL OF WASTEWATER FROM LIVESTOCK COMPLEXES IN AGRO-ECOSYTEMS

Abstract

According to the Ukrainian-Canadian cooperation program for the improvement of the Dnipro River basin, a comparative assessment of the effectiveness, cost-effectiveness and profitability of methods for cleaning and recycling waste from livestock complexes in Canada and Ukraine was carried out. According to the method of Canadian farmers, liquid waste is accumulated with its subsequent mechanized application under plowing with control of the content of mineral phosphorus in the soil. In Ukraine, large livestock complexes practice cleaning the liquid fraction of wastewater in biological structures (aerotanks) with subsequent accumulation of treated water in settling tanks until the temperature rises in the spring-summer period with subsequent cleaning in algae-crustacean ponds and the use of grown zooplankton biomass for feeding carp fry, and the treated water is supplied for irrigation and stabilization on a bioplateau before being released into the river network. The development of livestock farming is a necessary condition for supplying the population with protein (meat and dairy products), using about 30% of the gross harvest of feed grain during grazing. In modern conditions, the main direction of its development in Ukraine is stall keeping, which requires the use of significant areas of land for growing agricultural crops. However, the implementation of this program requires solving the problem of waste disposal, especially when creating large livestock complexes. In world practice, providing the population with protein of animal origin is implemented by the principle of keeping cattle in regulated stall conditions with a ratio of one head of cattle to an area equivalent to 1 hectare of agricultural land. Waste is accumulated in containers and applied in the spring under arable land during plowing as organic fertilizers, which is typical for farm livestock in Canada. In Ukraine, the creation of large livestock complexes with hydraulic waste removal, their accumulation in settling tanks and purification in the system of algae-crustacean ponds is used, which creates additional problems with land drainage and surface water pollution. When wastewater is purified in such a system, it is fed to the utilization of biomass of live feed in fish farming or for irrigation of agricultural lands. In case of excess of such water, it is fed to the bioplateau and subsequently to the river network. To activate the processes of biological purification of wastewater, brood ponds with introduced cultures of microalgae Chlorella and zooplankton (Daphnia) are used. Taking into account the possibility of the presence of pathogenic microorganisms, viruses and helminth eggs in the discharge waters, it is recommended to use them for irrigation of agricultural crops in hydraulic methods of wastewater disposal. This will once again contribute to the compensation of water content in the river network with increased water evaporation. However, in small farms, direct application of liquid waste under plowing is historically justified, which reduces the impact on the aquatic environment. In modern conditions of depletion of the natural food base of flowing river systems due to flow regulation and channel straightening, the use of algae-crustacean ponds for wastewater treatment is a promising direction for the revival of species diversity of populations and productivity of aboriginal ichthyofauna. At the same time, harmful impurities and biogenic compounds as causes of eutrophication of surface waters will be removed from the aquatic environment.