The principle image of activated sludge method: The microorganism "eats" the organic matter in the sewage, so the sewage becomes clean water. It is essentially similar to the natural water purification process, but it is strengthened by artificial, and the effect of purifying sewage is better.
After the activated sludge purification of the mixture into the two sedimentation tank, the mixture of suspended activated sludge and other solid substances here to precipitate down and water separation, clarified sewage as a treatment of water discharge system. The sediment-enriched sludge is discharged from the bottom of the sedimentation tank, most of which are discharged from the sludge to the aeration tank to ensure the concentration of suspended solids and microbial concentrations in the aeration tank; the proliferation of microorganisms is expelled from the system, known as "residual sludge". In fact, pollutants are largely transferred from sewage to the remaining sludge.
In the second stage, microbes absorb these organics and decompose them to form carbon dioxide and water, and partly to provide their own multiplication and reproduction. As a result of activated sludge reaction, the organic pollutant in wastewater was degraded and the activated sludge was multiplied and the sewage was purified and treated.