Laserfiche WebLink
Plant Loading <br /> Relative <br /> Air Supply <br /> Tu. Wed. Thur. Fri. Sat. Sun. Mon. <br /> Figure 1.1 — Typical Aeration Cycle <br /> Procedures for Wasting Sludge <br /> The following procedures should be followed when wasting sludge to the sludge holding <br /> tank. <br /> 1 . At least one hour before wasting sludge, close the air valve to the diffusers in the <br /> sludge holding tank. This will allow the sludge already in the tank to settle, <br /> leaving a clearer liquid (supernatant) on top. The clearer liquid is returned to the <br /> aeration chamber through the supernatant pipe when sludge is wasted to the <br /> tank. If the diffusers are not turned off, the same amount of sludge that entered <br /> the tank will leave the tank. The settleable solids test in the aeration chamber <br /> would then show no reduction in solids. Do not begin wasting sludge until the <br /> sludge in the sludge holding tank has settled enough to make room for the <br /> new sludge. <br /> 2. Run a thirty minute settleable solids test on the mixed liquor solids. Remember, <br /> only 10% of that reading is to be wasted. Be sure the blower has been on <br /> long enough to completely re-suspend the aeration chamber contents. For <br /> example, if settleability tests routinely show 50% solids, then the amount of <br /> sludge to be wasted is 10% * 50% or 5%, and the settleability test after <br /> wasting should show 50% - 5% = 45%. To achieve 20% wasting for the week, <br /> another settleable solids test is run approximately three days later. Then, 10% of <br /> that reading would be wasted. This procedure exchanges the mixed liquor every <br /> 35 days. <br /> 3. Open the valve on waste sludge line that leads to the sludge holding tank and <br /> then close the valve on the return sludge line leading to the aeration chamber. <br /> Valves must be operated in this order, or the clarifier could be back flushed <br /> if the blower were operating. <br /> 4. Waste sludge for approximately 15 minutes. This is an arbitrary time: with <br /> experience, the proper wasting time for the treatment plant can be decided. <br /> 5. Open valve on the return sludge line leading to the aeration chamber and then <br /> close the valve on the waste line that leads to the sludge holding tank. <br /> 6. Open air valve to the diffusers in the sludge holding tank to obtain good mixing. <br /> Once a good rolling action has been established, do not open the air valve any <br /> pcsr'ol :n- raeea-ProcesscontrolEc-I <br />