_O & M MANUAL - WEST LANE MOBILE HOME PARK

Home Browse Search

A. Trash Accumulators- A small primary tank designed to trap large solids such as rags, leaves, sticks and greases which could be detrimental to the system. B. Bar Screen- A series of bars with approximately one inch spacing designed to screen out the larger solids. C. Comminutor- A mechanical grinder device designed to cut and/or shred large solids into smaller particles that can more readily be digested by the bacteria in the aeration chamber. 2. Aeration From the screening device the sewage flows into the aeration chamber. In this chamber sewage is decomposed by the action of aerobic bacteria and other microorganisms in the presence of air. In a properly operating plant, these microorganisms (sometimes referred to as the "bugs') will form a dark brown mass called activated sludge floc. This floc is mixed with the incoming sewage by introducing air along on one side of the tank near the bottom through air diffusers, which caused mixing currents within the liquid. An adequate air supply is maintained to allow the organisms to decompose the sewage into carbon dioxide, water and ash. Blowers provide the air, and are either mounted on top of the plant, or directly adjacent to the aeration chamber, the air is piped through a box beam manifold through the diffusers at the bottom of the tank. A second blower for stand-by service is usually provided. Each blower is equipped with a fifteen-minute interval timer to control the run time of the blower and air to the aeration tank. The aeration tank is usually designed to provide a volume equal to the twenty-four hour flow, unless otherwise required by authorities due to unusual peak flow conditions. Sometimes a spray system to retard foam created by the mixing action is provided in the aeration tank. This consists of a submersible pump mounted in the clarifier which discharges clarified liquid through spray nozzles places longitudinally along the aeration tank on the side opposite the diffusers. 3. Settling From the aeration chamber the treated sewage mixed with the activated sludge floc passes though a port in the wall into the settling tank (clarifier). In the clarifiers the heavy activated sludge flow settles to the bottom of the clarifier, and the clear liquid flow to the outlet weir trough. Adequate volurne is provided in this chamber to retain the sewage for approximately a four-hour period, depending on flow conditions. The settled Sludge is returned back to the aeration chamber by the airlift sludge return pump to decompose more incoming sewage. This system consists of a vertical pipe extending down into the clarifier hopper along with an air supply line that injects air near the bottom of this pipe. As the air rises, the sludge is drawn into the pipe and lifted into the horizontal sludge return pipe which pumps the liquid into the inlet end of the aeration tank where it is mixed with more incoming sewage. An airlift type skimming device is also mounted in the clarifier and operates on the same principle. It is used to remove floating solids back to the aeration tank. gcs-0&M-intro-1-3