SBR type STP works on the principle of batch treatment of the sewage. Sewage is collected & fed to the reactor in 4 or 5 batches. Air is supplied & the completed aerobic process takes 2 hrs per batch. Once aeration is finished, the sewage comes to a stand-still position so that all suspended solids settle at the bottom thus clarifying the water. Clarified water is then decanted out to be collected in the clarified water tank. This water is further disinfected, filtered & stored or drained.