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Wastewater from human settlements contains a significant amount of organic and biogenic substances. Insufficiently treated wastewater enters surface water and leads to their eutrophication. The usage of microalgae in wastewater treatment has significant advantages in comparison with other methods of removing biogenic substances. Namely: effective and simultaneous removal of nitrogen and phosphorus without reagents management facilities, oxygen formation. Using microalgae in wastewater treatment is a new environmentally friendly biotechnological method. Microalgae grow well in wastewater, from which they absorb pollutants. The purpose of the study is to analyze the work and determine the possibility of intensification of sewage treatment plants in the western region of Ukraine with a population of about 18,900 inhabitants. Productivity of treatment plant is 3400 m3/day. Experimental investigation consisted in adding a concentrate of a living microalgae strain of the species Chlorella vulgaris to the wastewater that was entered to the treatment plant during May-September 2019. During the research, the results of wastewater analyzes conducted by the chemical laboratory of the municipal water supply and sewerage company were used. The results of the survey and analysis of the city's treatment plant indicate an insufficient degree of wastewater treatment. The effectiveness of Chlorella vulgaris at the treatment plant has been experimentally proven. Mathematical dependences of the effect of wastewater treatment (using Chlorella vulgaris) on their temperature according to the indicators: BOD5, COD, concentration of ammonium nitrogen, phosphates and suspended solids were obtained. Dependencies are described by a linear function that characterizes the general behavior of the obtained data. The obtained results made it possible to significantly reduce the negative impact of treatment plants on the environment.

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The concentration of total iron is one of the main physicochemical indicators of the safety and quality of tap water. The standard amount of the concentration of common iron in tap water is not more than 0.2 mg/dm 3. In some cases, due to specific natural conditions and technology for drinking water preparation/treatment, this number may be increased to 1.0 mg/dm 3. Excess iron concentration in the water adversely affects the skin, blood composition, etc. Prolonged consumption of water with high iron concentration leads to liver disease, causes allergic reactions, etc. The analysis of groundwater quality in the territory of the Lviv region shows the increased total iron concentration in water of some water intakes. However, even relatively normal spring water quality and satisfactory operation of pipe water treatment plants, cannot prevent it from secondary pollution in the distribution networks of the water supply system. The Residents of Ukraine use household filters for additional purification of drinking water, including cartridge type. The purpose of the study was to compare the effectiveness of the iron removal from drinking water with household filters of the brands Nasha Voda (Ukraine), BRITA (Germany) and Aquafor (Russia). An experimental research of the filters was performed to determine the dependence of the iron concentration in the filtrate on the volume of the filtered model solution. During the preparation of the model solution, water was used from the water supply system of the city of Lviv, selected in the area of S. Bandera street with a starting iron concentration amount of 0.02-0.3 mg/dm 3. After being passed through 15, 15 and 2.5 dm 3 of the filtrate, for the filters Nasha Voda, BRITA and Aquafor respectively in the beginning of the experiment, the concentration of iron in the filtrate decreased and reached the normative value of 0.2 mg/dm 3. The filtrate volumes passed through Our Water, Nasha Voda, BRITA and Aquafor filters were 210, 350 and 80 dm 3 respectively. The slow filtration rate of the water through the Aquafor filter made it impossible to carry out the experiment after filtering 80 dm 3 of the model solution. Tested filters have shown positive results in reducing the total iron concentration in water. However, it is recommended to apply the known methods of ironing on water treatment plants of settlements for iron removal from drinking water, particularly from tap water.

The presented materials describe the technical condition of sewage networks in Ukraine for 2021. The reasons for malfunctioning of sewage networks are outlined. The mechanism of concrete corrosion of sewage collectors is described. On the basis of a visua