The object of the study was water samples, cultures of green microalgae <i>Parachlorella kessleri</i> U1 and <i>Chlorella vulgaris</i> I2, Maybalyk Lake (Astana). The aim and objectives of the study were to study the bioremediation potential of a consortium of two strains of microalgae <i>Parachlorella kessleri</i> U1 + <i>Chlorella vulgaris</i> I2 (hereinafter U1+I2) through the algolization of Lake Maibalyk according to microbiological and hydrochemical indicators. This lake is a large lake in Astana with fishery importance. The state of the reservoir is reflected in the state of the capital's air basin. A study of the water quality of Lake Maibalyk was conducted on the main morphometric, hydrochemical and hydrobiological indicators in May and June of 2020. To study the effect and determine the efficiency of using microalgae, preliminary biomass production and algolization of the U1 + I2 consortium were carried out. The introduction of a consortium of microalgae showed an improvement in the sanitary and microbiological indicators of the reservoir after just one month, due to its high antimicrobial properties and a decrease in such groups of bacteria as ammonifiers, coliforms, heterotrophic bacteria, coli group bacteria, pseudomonas, wax bacilli, staphylococcus, enterococci, enterobacteria, salmonella, fungi and yeast. After algolization for 30 days by the consortium I2+U1, an improvement was recorded not only in the organoleptic characteristics of water, but also in a number of hydrochemical parameters, including a decrease in COD, suspended solids, iron, SSAA and phosphates. . An increase in transparency, a decrease in water color and the absence of a specific odor were also noted. It was found that, although the content of BOD₅, nitrates, sulfates in the original sample did not exceed the MРC values, the introduction of microalgae had a positive effect on reducing the concentration of these substances, which significantly affected the quality of the water in the reservoir. The results obtained can serve as a basis for developing environmentally friendly biotechnologies to improve water quality. In the future, it is necessary to conduct studies in triplicate, which will increase the reliability and quality of the data obtained, which will allow more effective assessment of the state of the ecosystem of the reservoir and ensure the safety of water use.