Sewage Treatment Systems

Why?

Why do we need to treat Sewage?

Treatment of sewage is essential to ensure that the receiving water into which the effluent is ultimately discharged is not significantly polluted. However, the degree of treatment required will vary according to the type of receiving water. Thus, a very high degree of treatment will be required if the effluent discharges to a fishery or upstream of an abstraction point for water supply. A lower level of treatment may be acceptable for discharges to coastal waters where there is rapid dilution and dispersion.

How ?

Sewage Treatment typically requires several treatment stages: Preliminary, Primary, Secondary and Tertiary.

Depending on the design criteria, several types of biological processes may be used. The technologies nowadays used are as mentioned below:

ASP

Activated Sludge Process is most commonly used suspended growth aerobic process. In this process, organic matter present in the wastewater is aerated so that micro-organisms metabolize the soluble and suspended organic matter. Part of the organic matter is synthesized and form new cells and part is oxidized into CO2 and water to derive energy. The new cells formed are removed in the settling tanks and part of this settled biomass is returned to the aeration tank. The remaining is removed as excess sludge.

MBBR

Moving Bed Biofilm Reactor (MBBR) technology is an attached growth aerobic process which is based on biofilm principle. Here the bacteria grow on plastic media carriers which are kept in suspension and in continuous movement with the help of aeration or mixing.

MBR

Membrane Bio Reactor is a combination of activated sludge biological process with a physical separation using membranes which are submerged into tank. This bioreactor incorporates activated sludge process and micro or ultrafiltration clarification based on membrane technology which produces treated water quality that can be utilized to reuse/recycle.

UASB

Anaerobic treatment is carried out in the absence of Oxygen which leads to conversion of organic matters into CH4 and end products like CO2 and NH3. Upflow Anaerobic Sludge Blanket (UASB) system uses granulated bacteria which are contacted to organic components present in the wastewater. Methane gas is produced due to decomposition of organic components. With the help of Gas liquid-solid separator (GLS), gas, liquid and granules are separated.

SBR

The Sequencing Batch Reactor (SBR) is a non-steady state activate sludge process which operates into batch mode with aeration and Sludge separation occuring in the same tank. This process does not require separate equalization and primary sedimentation basins.