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South Clarifier Hopper <br /> Skimmer Inlet <br /> South Hopper Skimmer <br /> Discharge in Aeration Tank <br /> I <br /> I <br /> I <br /> I <br /> RAS Valve Adjustment <br /> �h <br /> South RAS Discharge <br /> South Skimmer <br /> F — Discharge Piping <br /> Clarifier South Hopper RAS and Skimmer <br /> Return Activated Sludge <br /> The bacteria which have settled to the bottom of the clarifier, near the opening of the return <br /> sludge pipe, are lifted up and returned to the aeration tank, by the air-lift pumps. This process is <br /> referred to as Return Activated Sludge or RAS. There is a RAS line in each of the two clarifier <br /> hoppers. <br /> Visual Observations <br /> • Verify that the RAS pump is operating. RAS pump discharge in the aeration tank should <br /> be brown and should be a full pipe flow when discharging. <br /> • If RAS is not operating well the piping or the "straw" may need to be cleaned. <br /> • Discharge may be adjusted by slightly turning the gate valve handle at the end of the <br /> discharge pipe, but this is not often done, as reduced flow can lead to a plug in the line. <br /> • Clarifier hopper walls need to be squeegeed daily in the summer and the winter <br />