Aerobic Treatment
Aerobic treatment is a proven and widely adopted biological wastewater treatment process in which aerobic microorganisms degrade organic pollutants in the presence of oxygen. Depending on wastewater characteristics, organic loading, and the feasibility of anaerobic treatment, aerobic systems are implemented in various configurations to achieve the desired treatment objective.
Aeration System :
In aerobic treatment systems, oxygen is supplied through external aeration equipment to sustain microbial activity. Commonly adopted aeration methods include:
Surface Aerators – These supply oxygen by agitating the wastewater surface. Surface aerators are available in floating and fixed configurations, with fixed aerators remains the preferred option.
Diffused Aeration Systems – In these systems, air is delivered by external blowers and introduced into the Aeration tank through submerged diffusers. The diffusers are typically classified as coarse-bubble and fine-bubble types, depending on oxygen transfer efficiency requirements. The diffusers can be either fixed or retrievable type.
Aerobic Treatment Process Flow :
An aerobic treatment system typically comprises an aeration tank followed by a clarifier (settling unit) or Membrane Bio Reactor ( MBR).
Microorganisms in the aeration tank metabolize organic matter and generate biological sludge. The mixed liquor then flows to the clarifier, where the biomass settles under quiescent conditions.
While with Aeration Tank & MBR combination, The waste water is taken to MBR tank where submerged membranes acts as advanced clarifier. Using vacuum, good quality water is filtered through membranes.
A portion of the settled sludge from clarifier and separated sludge from MBR, is recycled to the aeration tank to maintain the desired Mixed Liquor Suspended Solids (MLSS) concentration, while excess sludge is withdrawn and conveyed to sludge handling and dewatering systems for further processing.
Sludge Handling & dewatering :
Sludge generated from aerobic treatment processes is dewatered using mechanical equipment such as filter presses, decanters, belt presses, and screw presses. The dewatered sludge cake is disposed of in a safe and environmentally compliant manner, while the filtrate is returned to the Effluent Treatment Plant (ETP) for further treatment.
Alternatively, Sludge Drying Beds (SDBs) may be employed where mechanical dewatering systems are not preferred. However, SDBs require large land areas and are generally unsuitable during the monsoon season due to operational limitations.
