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 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 causes of death of people during a fire, as well as the effect of toxic combustion products on the human body are analyzed. It was found out that the main problem of unhindered evacuation of people from the building is blocking the evacuation routes by smoke. Methods of fighting smoke in a fire are considered and their advantages and disadvantages are determined. One of the ways to solve this problem is ultrasonic coagulation of aerosols with subsequent precipitation. Effective coagulation of smoke in a fire can be provided by a piezoelectric ultrasonic oscillatory system.

Keywords: fire, fire safety, multi-storey public building, toxic combustion products, smoke removal, smoke deposition, high intensity ultrasonic vibrations, ultrasonic radiation, acoustic radiator, piezoelectric ultrasonic oscillatory system

There were considered the processes of electrochemical coagulation and contact filtration for clarification, bleaching and disinfection of the Don River. There were made the experiments to compare electrochemical coagulation to chemical treatment of water with different reagents in conditions of contact filtration. There were defined feculence change, water chromaticity depending on reagent dose and the changе of the total microbial number.

Keywords: Extraordinary situations, water-supply, coagulation, clarification, bleaching, filtration, purification effect.