Collection & Equalization Tank: The equalization tank overcomes this by collecting and storing the waste, allowing it to mix and become a regular quality before it is pumped to the treatment units at a constant rate. To determine the required volume of equalization tank the hourly variation of flow needs to be determined.
From the screen chamber water should be come in the collection tank, where water will be equalized by air purging grid system. Effluent / Sewage liquor is run into deep tanks with diffuser grid aeration systems that are attached to the floor. These are like the diffused air stone used in tropical fish tanks but on a much larger scale. Air is pumped through the blocks and the curtain of bubbles formed both oxygenates the liquor and also provides the necessary mixing action. Where capacity is limited or the sewage is unusually strong or difficult to treat, oxygen may be used instead of air. Typically, the air is generated by some type of blower or compressor.