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