Biological Sewage Treatment Stations
(capacity 50-100000 m³/day)

Combined installations and works (CW) are designed for biochemical purification of the sewage produced by settlements, towns and enterprises and characterized by impurity concentration BOD max. 1000 mg/L, suspended matters amount max. 700 mg/L.

After being mechanically processed, the sewage is discharged to mixing chamber 1 where it is mixed with the sludge mixture coming from settling aerotank 2. From chamber 1 the sewage and sludge mixture is driven by pump 3 to biofilter irrigation system 4 consisting of spouting chutes 5 with outlet pipes 6 and reflecting disks 7. The falling liquid jets are broken upon the disks thus irrigating the biofilter feed. The biofilter with the immobilized microflora is designed for sorption and oxidation of 50-70% organic impurities.
The existing CW use as their biofilter feed, corrugated asbestos boards which are hard and rough enough to hold microflora on their surface. Further on we plan to use flat feed from channeled CEF sheet of high specific surface.
Oxidization of the remaining impurities of up to 99% purification level is achieved with the help of the active sludge in settling tank 2. To saturate the sludge with additional oxygen and to stir the aerotank contents, water jet operation is applied. After the biofilter the liquid is driven by collecting tray 9 to air-spripping towers 10 into which air is sucked (0.6-0.9 m³ per 1 m³ of liquid) as a result of vortexes. The air-spripping towers distribute the air mixture over the aeration tank inside. Meanwhile 30-35% of the required oxygen get into the aerotank due to the air oxygen solution in the silt mixture, and 70-65% of oxygen due to the air bubbles lifting during the process of mass-transmission in the columns. Efficient stirring is provided in the aeration tank by the jets hitting on the aerotank bottom and gas-liquid flow movement. The sludge mixture displaced from the aeration zone is discharged through a slot to the settling zone where some part of it is compacted and driven back to the aeration zone, while the rest is making a suspended sludge layer.
CW excludes the possibility of untreated wastewater "breakthrough". The initial sewage first mix with sludge in the mixing chamber in proportion of 1:3-1:10, then come into contact with biofilters’ biocoenosis. After that it is evenly distributed in aeration area and finally it gets filtered through a layer of floating sludge in sedimentation areas. That’s why effectiveness of domestic waste water purification on the existing constructions within BOD id 5-10 mg/l, within suspended solids 5-10 mg/liter . CW operation in full oxidation mode, nitrifier and denitrifier bacteria biofilters availability in adherent micro flora layer ensures the developed process of removing nitrogen impurities.
While wastewater treatment with low contamination by BOD 50-100 mg/l a stable process of adsorption and oxidation of organic substances in CW biofilter (70-80%) occurs. Biomass coming off the biofilter loading adds to a layer of suspended sludge in aeropack, which makes it possible to bring the effect of cleaning up to 99%.