The effectiveness of various inorganic coagulants based on aluminum and iron was evaluated. Based on a review of the literature data, as well as experimental studies, the advantages and disadvantages of a number of coagulants based on aluminum and iron have been identified. Aluminum sulfate, iron sulfate, as well as polyoxychloride and aluminum oxychloride were studied. Based on the results of evaluating the effectiveness of inorganic coagulants in terms of turbidity, chromaticity, residual aluminum, permanganate oxidability, recommendations for their separate and joint use are given.

Keywords: coagulant, aluminum, iron, turbidity, chromaticity, permanganate oxidability, residual aluminum

The article provides an analysis of technological schemes for the reuse of contaminated water obtained after washing the rapid filters of water treatment plants. The advantages and disadvantages of existing options for reuse and disposal of purified and untreated wash water are shown. A new water treatment technology has been proposed, which involves pre-treatment of wash water with an organic coagulant, followed by mixing it with river water and subsequent reagent purification of the resulting mixture by settling and filtration.

Keywords: water treatment, filter wash water, coagulation, aluminum sulfate, organic coagulant, clarification

The problem of energy efficiency and rational use of energy resources in housing and utilities sector remains relevant over the past years. In this regard, the reduction of heating and hot water costs remains under continuous review of specialists all over the world. The article discusses the issues of using low potential thermal energy of domestic wastewater for hot water heating. Data on wastewater temperature in various locations are presented. The main designs of wastewater heat recovery units and the features of their application are considered. It is shown that the temperature parameters of residential building wastewaters differ significantly and depend not only on the climatic zone, but also on the regional features of water consumption. It is concluded that in process of wastewater heat recovery it is possible to reduce wastewater temperature at least by 5 ºС, and in hot season ‒ by 10-15 ºС. The analysis of literature data lead to the conclusion that wastewater heat recovery units are more promising and viable at building level as well as sewer or wastewater treatment plant level. For these cases, greater efficiency can be reached by using heat recovery facilities with a heat pumps.

Keywords: hot water supply, sewage, low potential heat, wastewater temperature, heat pump, heat exchanger, waste water heat recovery, energy saving

Experimental studies have been carried out to determine the sludge index of activated sludge used in the process of biological wastewater treatment on aerotanks at various doses of sludge. The possibility of changing the sedimentation properties of activated sludge when using its electrical treatment is analyzed. It is shown that the electrotreatment of returnable activated sludge together with aeration leads to a decrease in the value of the sludge index, as well as an improvement in the quality of the treated water after settling. pretreatment of activated sludge in an electrolyzer with aeration allows biological wastewater treatment in an aerotank with increased doses, as well as to increase the flocculating properties of sludge in relation to suspended solids.

Keywords: household waste water, biological treatment, activated sludge, aerotank, sedimentation, sludge index, electrical treatment, aeration

The article presents the results of experimental studies on the study of changes in the concentration of active chlorine in water treated with sodium hypochlorite when exposed to UV radiation and its contact with the concrete surface. The obtained research results are aimed at studying and solving the problem of the absence of residual active chlorine in the most remote points of water sampling in large cities with a large length of water distribution networks.

Keywords: disinfection of water, sodium hypochlorite, chlorination, disinfection, residual active chlorine

The paper presents the results of experimental studies on the effectiveness of complex electrochemical treatment using hydrogen peroxide for water disinfection. The effectiveness of the method for sanitary-indicative microorganisms has been confirmed. The most significant parameters for the disinfection process have been identified and a mathematical model has been developed based on them, which makes it possible to design industrial disinfection devices that are separate modules.

Keywords: disinfection of water, electrochemical methods, hydrogen peroxide, bactericidal effect, disinfection

The technical solution for the construction of local treatment of return drainage flow from an irrigated area, based on the use of ion-exchange filter materials, is proposed. It has been established that the concentration of chemicals in the water of the drainage well is 1/3 lower than in the open collector, where the drainage flow is diverted. Therefore, the localization of the technological unit for the treatment of drainage water relative to the drainage well is a reasonable decision, since it will reduce the financial costs of filter media and the frequency of their replacement. The technological scheme of the treatment plant based on the block principle is described: by disconnecting or connecting individual blocks, it is possible to respond flexibly to changing needs in the quality and degree of drainage water treatment.

Keywords: technical solution, water treatment, ion exchange, drainage flow, block approach, drainage well, water quality, chemical analysis, land reclamation, irrigation system

Issues of high-quality and reliable water supply are closely related to automation and management of engineering systems for stormwater and wastewater treatment. Options for managing continuous technological processes formulate different goals. Different control algorithms correspond to different variants, and, consequently, different methods of algorithmic support systems and control system structures. The expediency of dividing the general task of sorption purification control into several subtasks of a smaller dimension is shown where the control system acquires a hierarchical structure: at the lower level, the task of separate adsorption tanks controlling is solved, at the upper level, the task of controlling the entire purification plant as a whole. The criterion of operational management is provided. The scheme of adaptive control of continuous sorption purification systems is given.

Keywords: stormwater and wastewater, automation and control, continuous operation systems, sorption purification, control algorithms, mathematical model, optimality criterion, autonomous and dispatcher modes, hierarchical control system

Liquid pumping processes which require flow variations over a wide range are often equipped with centrifugal pumps connected in parallel. In such pumping systems, speed control enables the required capacity to be achieved with different numbers of pump units running and the selected speed values. The information required for modeling such systems, such as wastewater treatment and various cooling and water supply tasks, can be scarce, and the lack of real-time monitoring of operating points often sets limitations for precise optimization of energy efficiency. Consequently, easily implementable control strategies that can be adopted with minimal system data are needed, requiring adaptive methods. A significant part of pumping stations operate in conditions when the flow rate and the required pressure vary widely, which can lead to a decrease in the efficiency of their management and, as a consequence, a decrease in energy efficiency. Therefore, it should be noted that the task of choosing the optimal strategy for controlling pumping units during their parallel operation is very relevant.

Keywords: pumping units, energy efficiency, modeling, rotation speed, speed control

Experimental studies of the effect of the intensity of mixing of mineral coagulants with water on the efficiency of water treatment in different periods of the year have been carried out. The studies were conducted in June-August - low-turbidity water with relatively low color and high temperature; November-December - low-turbidity and low-color water with low temperature; flood in April-May - increased turbidity and color of water with low temperature and alkalinity. The results obtained allow us to evaluate the effectiveness of the use of concentrated coagulation, high-gradient mixing in water purification with mineral coagulants. The possibility of separate and joint use of mineral coagulants in different periods of the year was assessed.

Keywords: natural water, coagulant, concentrated coagulation, high gradient mixing, mixed coagulant, velocity gradient

The paper presents the results of experimental studies on increasing the settling rate and reducing the solid phase in the clarified layer during settling of a solution of sulfuric acid leaching of heavy metals from galvanic sludge. For this purpose, it is proposed to use a monoethanolamine vinyl ester copolymer with sodium or potassium methacrylate as a flocculant. This flocculant works well in a wide range of pH of the solution medium, unlike the well-known and widely used polyacrylamide flocculant. The increase in the efficiency of settling is achieved due to the fact that the flocculant in question makes it possible to simultaneously flocculate positively and negatively charged particles due to the presence of various functional groups in its composition. The use of the proposed flocculant will ensure a more complete extraction of heavy metals from galvanic sludge, which reduces the risk of environmental pollution and their reuse in industry.

Keywords: galvanic sludge, heavy metals, leaching, flocculant, settling, suspended solids