The article analyzes the ways to improve the water supply system at agro-industrial enterprises. It is stated that the Institute of Water Problems and Land Reclamation of NAAS proposed to improve closed water supply systems at these enterprises to spend water and energy rationally and economically by developing highly efficient wastewater treatment technology to reuse wastewater and its sediments for technological needs. During the work, the main tasks to be solved were the analysis of the reasons of unsatisfactory operation of traditional wastewater treatment plants and their current quality indicators and improvement of the rational technological scheme of closed water supply at the agro-industrial enterprises. Scientific and practical results were obtained by analyzing the operation of wastewater treatment plants of industrial enterprises dealing with agricultural products processing, their quality indicators and known methods of improving technological schemes of biological wastewater treatment. It was specified that traditional technology of biological wastewater treatment do not ensure the proper treatment quality, as the quality of wastewater from enterprises has significantly deteriorated due to the inflow of harmful impurities (xenobiotics, heavy metal ions, etc.) and high concentrations of organic matter, the content of which amount to: suspended solids> 1000 mg/dm3, COC> 10000 mgO2/dm3, BOC5> 6000 mgO2/dm3, BOCcomplete> 2000 mgO2/dm3, nitrogen and phosphorus ≤50 mg/dm3, which prevents the effective operation of aeration tanks. The practicability of improving the "bioconveyor" technology by downward filtration through fibrous loading in bioreactors and upward filtration through floating filter loading in contact and clarifying filters to increase the efficiency of wastewater treatment was scientifically substantiated. It was proved that this method provides high efficiency of biological wastewater treatment by reducing the amount of sediment and the absence of reverse activated sludge, and thus reducing capital and operating costs. Natural mechanisms of household sewage treatment with reuse of water and sediments when cultivating agricultural crops are used as much as possible are used in the specified system of water supply at agro-industrial enterprises. The optimal design and technological parameters of these structures are determined using the recommendations developed on the basis of our experimental research. The proposed technology of closed water supply at agro-industrial enterprises provides for the separation of water supplied to consumers into technical and drinking one, as well as supplements of sewage treatment plants with bioreactors and contact-clarifying filters. Such systems ensure a minimum intake of water from natural water sources having its preliminary treatment directly in water reservoir, maximum use of treated wastewater and protection of the environment against wastewater pollution.