In the present work, the effect of 2-chlorophenol and 2,4,6-trichlorophenol on the performance of a sequencing batch reactor operated with suspended municipal recycle activated sludge (RAS) in terms of total carbon and total nitrogen removal is presented. The total carbon removal achieved ranged in 80-100% and total nitrogen removal in 10-84%. The results showed that chlorophenols did not inhibit either the activated sludge growth or the total carbon removal significantly. However, inhibition is observed in total nitrogen removal. 2-chlorophenol inhibited the ammonium oxidation (nitrification) while such an effect was not observed in the case of 2,4,6trichlorophenol indicating that the later inhibits the ammonification step. Furthermore, under the experimental conditions examined, complete removal of both chlorophenols was observed after few days of operation.

"For the majority of Kazakhstan sewage treatment plants, the issues of modernization and construction of new blocks of wastewater treatment facilities are very relevant, the solution of which involves a comprehensive engineering and technological approach. This article analyzes the level of automation and disadvantages of the project of the second stage of sewage treatment plants (STP) of the State Enterprise «Astana SU Arnasy». The project of biological treatment on the aeration tanks of the second stage of (STP) does not provide for deep cleaning for biogenic pollutants, namely the internal recycling of activated sludge. The volume of the anoxic zone is 18 %, which is not enough for the process of biological dephosphotation. Thus, in order to more effectively achieve high-quality cleaning indicators, it is necessary to provide for a denitrification zone of at least 30 % of the total volume of the aeration tank. Analysis of the main causes of inefficient removal of phosphates at the stage of biological purification showed: insufficient concentration of biological oxygen consumption in incoming wastewater, absence of denitrification process, dephosphotation in the design of the second stage aerotanks and insufficient volume of the anaerobic zone, which is 18 % of the volume of the aerotank. The problems of inefficiency of technological wastewater treatment from phosphates at (STP) in Astana are primarily related to design errors and the impossibility of effective operation of wastewater treatment facilities associated with insufficient automation. Thus, in order to increase the efficiency of the biological treatment facilities of the second stage, it is necessary to carry out a new calculation of the facilities taking into account the processes of nitri-denitrification and biological removal of phosphates, additionally equip with equipment to ensure internal recycling with the allocation of intermediate zones and in the process of retrofitting to provide greater automation to minimize manual labor. "