Aerobic Wastewater Treatment

Aerobic technology (biological wastewater treatment) is the most widely used type of industrial effluent treatment.

Contrary to other types biological wastewater treatment uses bacteria and other microorganisms to remove or decompose organic contaminants. The dissolved oxygen as well as water effluent, containing carbon, nitrogen, and phosphorus contaminants is conveyed into a biological reactor, which contains relatively large numbers of bacteria. In the presence of dissolved oxygen, the bacteria degrade the carbonaceous, nitrogenous and phosphorus wastes. The oxidation of wastes by the bacteria (in a biological reactor) results in the growth of bacterial population. The water effluent oxidated by the bacteria is the substrate used to obtain carbon and energy.

Solids contained in the aeration tank are referred to as sludge. Because the sludge is aerated, and bacteria become very active, the term «activated biomass» is used to describe the phenomenon of the wastewater being purified within the aeration tank. Since the bacteria in aeration tank age, numerous bacteria stick together, forming the floc or large suspended particles. These particles contain a large number of diverse bacteria, which purify and treat the wastes in aeration tank. When suspended particles flow into the secondary clarifier, they settle to the clarifier’s bottom as a sludge. Then, it is conveyed to the sludge basin with a radial or chain sludge scraper, and the clearly purified water develops above the settled solids. The purified water is then discharged to the receiving basin for futher conveyance as a treated waste.

Image 4. Example of accomplished installation of aerobic reactor at the dairy plant in the town of Illintsi, Vinnytsia region, Lustdorf, LLC

We offer systemic configuration that combines the process of denitrification and nitrification. A small cylindrical tank unit is used as a denitrification tank. It is assembled and installed directly inside of another cylindrical tank of large diameter. The outer circle shape part is closed with a baffle plate placed between two cylindrical parts and is used as a nitrification tank.

This configuration ensures a stable and efficient process under the least possible pressure on the sludge when discharged from aeration. It is important to conform to the maximum rates of effluent standards, especially the maximum level for the COD concentration rate. Besides, the sludge developed during the treatment process has a sludge volume index <120 ml /g.

Denitrification

The process of denitrification allows to convert nitrates (NO3) contained in the wastewater fed for denitrification into the pure nitrogen (N2). This is a microbially facilitated process of dissimilatory nitrate reduction that can result in ultimately occurring molecular nitrogen (N2) through a sequential series of intermediate gaseous nitrogen oxide products. This process is performed primarily by heterotrophic bacteria (such as Paracoccus denitrificans and various pseudomonads).

Denitrification mainly proceeds through combination of the following intermediate products:

NO3- ? NO2- ? NO + N2O ? N2

The process of denitrification allows to use the wastewater organic matter BOD5 as a resource of carbon, which is required for biological process.

Nitrification

In the nitrification tank, the ammonium (NH4) is oxidated to nitrates (NO3) and the remaining COD and BOD concentration is removed.
The required amount of oxygen is fed and distributed through “Aerofit-V” medium-size bubble aeration system to the bottom of reactor. The compressed air is fed into the system through air blowers.

Coagulants * flocculants * caustic * industrial effluents * raw wastewater pumping room * mechanical treatment * averaging tank * pumping room * DAF * pumping room * denitrification * nitrification * secondary clarifier * discharge into receiving water * pumping room * flotation sludge pumping room * excess biomass * sludge collector * filtering press * organic and mineral fertilizer * fields

The scheme of aerobic (biological) wastewater treatment facilities.

The wastewaters clarification (separation) from activated sludge takes place in secondary clarifier, where activated sludge recycles in reactor up to 140 %..

Secondary clarifiers in rectangular and radial shape.

Sand filters (self-cleaning) at the final stage of pre-clean.