Biological Treatment
The most common method of biological treatment is an aeration tank or a bioreactor, in which wastewater is treated with active sludge. The second most popular bioreactor is biofilters, which use biofilm as a special biomass - a community of microorganisms attached to the surface. As such a surface, special carriers of the attached microflora are used.
In aeration tanks, wastewater is mixed with active sludge, which performs the purification process. Depending on the impurities and the purification process itself (nitrification, denitrification, oxidation of organic impurities), oxidative and reducing reactions are distinguished.
Reducing reactions occur in anoxic and anaerobic zones. To ensure normal activity of the active sludge these zones are equipped with a special immersion equipment – mixers and pumps. For their maintenance, hoisting devices are used, mounted on the surface of the aeration tank.
the water, are installed on the bottom of the aeration tank. The aeration system consists of air distribution pipes and diffusers – aerators. Depending on the type, the aerators can be disc, tubular and toroidal.
Also, air is used for pumping sewage and active sludge by means of devices called airlifts. The use of airlifts instead of pumps is often justified due to their low cost, ease of operation and simple design.