The project provides for the repair of the digester-clarifier No. 9 of the treatment facilities. For settling wastewater, fermentation and compaction of the precipitated sediment, the treatment facilities use clarifiers-digesters, in which wastewater after the grates and sand traps is fed through distribution chambers through trays into the central pipe of the clarifier-digester. The water pressure (0.4-0.6 m) created by the difference in liquid levels above the pipe entrance and in the clarifier, provides a wastewater velocity in the central pipe of 0.5-0.7 m/sec, necessary for the suction of air from the atmosphere into the liquid. The wastewater saturated with air is directed from the central pipe by a reflecting shield into the flocculation chamber, where mixing and enlargement of suspension particles in the wastewater occurs for 20 minutes. After that, the wastewater enters the settling chamber, where a layer of sediment is formed. The duration of the liquid in the settling chamber is at least 40 minutes. The clarified liquid is collected by a peripheral tray and discharged through a pipe to the next stage of purification. The sediment that has fallen to the bottom of the clarifier is sent through a pipe under hydrostatic pressure to the receiving tank of the sludge pumping station, from where it is fed by a pump through a pressure pipe to the upper zone of the digester (evenly around the circumference), where it undergoes fermentation. The fermented sediment is discharged through a sludge pipe after 7-10 days. The relative location of the clarifier and digester (the clarifier tank is located in the center of the digester tank) allows the sediment to be isolated from direct contact with the clarified liquid and to use the heat of wastewater during sludge fermentation, which is carried out without artificial heating. At the moment: metal trays that feed wastewater from the distribution chamber to the central clarifier pipe, the central clarifier pipe, the reflecting shield, the flocculation chamber, the clarified wastewater outlet pipe have become completely unusable. The listed equipment needs to be replaced. The sludge supply pipeline to the digester from the sludge pumping station is in a condition suitable for further operation after being fixed to the newly installed clarifier-digester fence. The equipment must be installed in accordance with DSTU-N B V.2.5-68:2012 "Guidelines for the construction, installation and quality control of pipelines of external water supply and sewage networks". The operating mode of the treatment plants is 24 hours a day, all year round.