An assessment of the oxidizing ability of activated sludge used in the process of biological wastewater treatment was carried out when it was treated with a direct electric current on an electrohydrodynamic device. The efficiency of biological wastewater treatment is analyzed when the DC voltage changes, the sign of polarization of the electrode, as well as the values of the Camp criterion. It is shown that the electrotreatment of activated sludge leads to an increase in the efficiency of biological wastewater treatment, determined by the indicator of chemical oxygen consumption. A relationship has been established between the intensity of sludge treatment and the magnitude of the zeta potential of activated sludge at the outlet of the aeration tank.

Keywords: wastewater, biological treatment, activated sludge, electrohydrodynamic device, zeta potential, chemical oxygen consumption

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

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

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 factors influencing the process of flocculation during aeration are analyzed. It is determined that the effect is due to the damping of small-scale pulsations of water during mixing, accelerated formation of nuclei of solid phases of coagulant hydrolysis products on the surface of air bubbles due to electrostatic and surface forces, as well as the release of excess amounts of carbon dioxide from the water. Theoretical dependences have been obtained showing that the dose of coagulant injected into the mixer with simultaneous aeration of water is proportional to the concentration of heterophase impurities and inversely proportional to the average particle size of contaminants, the gas saturation of the resulting water-air mixture and the velocity gradient.

Keywords: natural water, coagulant, mixer, aeration, coagulant dose, velocity gradient

The parameters of the mixers widely used in the practice of water treatment are given. A fundamentally new design of the mixing unit is proposed, which provides a process of rapid and complete mixing of reagents in a thin layer of a rotating flow of a pre-created water-air mixture using the method of concentrated coagulation. At the same time dispersion of air bubbles is carried out. A detailed description of the design, operating principle and basic design parameters of the mixer used in the mixing unit.

Keywords: natural water, coagulant, mixer, concentrated coagulation, aeration, velocity gradient, rotational motion

The method of calculating the coagulant dose using the technology of concentrated coagulation with the addition of air is given. The paper considers the peculiarities of using aluminum sulphate and aluminum polyoxychloride as a coagulant in different periods of the year, taking into account seasonal changes in water quality. Recommended values of parameters used in calculations of the coagulant dose during the year are given. The refined method of calculating the coagulant dose allows determining the weight dose of the reagent, including the mixed coagulant, taking into account the required air saturation of water, as well as the optimal volume of the so-called auxiliary water flow sent for concentrated coagulation.

Keywords: coagulant dose, aluminum sulphate, aluminum polyoxychloride, air saturation, concentrated coagulation, auxiliary flow, mixed coagulant

The features of natural water reagent treatment are considered. The evaluation of the efficiency of coagulants, the most frequently used in the Russian Federation, rational methods of their introduction into the treated water is given. A method of water treatment is proposed, which allows to use the advantages and minimize the disadvantages of mineral coagulants. Experimental data confirming the effectiveness of the proposed method of concentrated coagulation using a mixed coagulant are presented.

Keywords: water of superficial sources, coagulant, sulfate aluminum, aluminum polyoxychloride, the concentrated input of a coagulant

The work of the sensors of passenger traffic control in conditions of a dense stream of people in the controlled section of the doorway was conducted. The results showed the possibility of determining the direction of movement of a person due to a change in the distance between the sensor and the moving person. The interference due to the high density of passenger traffic, which, however, does not lead, however, to the development of the corresponding algorithms, to false alarms of the sensors is detected. However, additional field studies are required on the vehicle of the passenger counting device based on ultrasonic distance measurement sensors

Keywords: passenger, ultrasound, passenger transport, road transport, distance sensor, Arduino, bus

The field studies of the device in a controlled section of the doorway of the trolleybus were carried out. Studies have shown the operability of the device with the appropriate information processing algorithm, which allows to extract an information signal from short-term interference. It is necessary to carry out on the vehicle additional field studies of the passenger counting device based on ultrasonic proximity sensors aimed at eliminating the reflection of interference from the walls and, accordingly, improving the accuracy of counting the number of incoming and outgoing passengers.

Keywords: passenger, ultrasound, passenger transport, road transport, distance sensor, Arduino, trolleybus