The activated sludge is one of the most common methods of sewage treatment , which has been studied through to find the relation between sedimentation properties and the performance of aeration units. sedimentation experiments were applied on a highl
y- aerated activated sludge experimental treatment plant .Also, another experiments were applied on Marj Maerban treatment plant which is operated using the extended aeration method in order to find the Factors influencing the settling of activated sludge . These experiments were done using the Sludge volume index (SVI) ,the maximum velocity sedimentation rate (UMAX) and the time corresponding to the maximum velocity of sedimentation (TUMAX).In experimental treatment plant. We found that the sedimentation experimental parameters (Vo, n) are very sensitive and can be changed significantly with changing the values of suspended solids (MLSS) in the aeration tank. The mathematical relationships can be used to predict the value of (Vo, n) as well as designing and selecting the operating system of sludge without resorting to a conventional sedimentation tests . We also found in the extended aeration the maximum velocity sedimentation rate (UMAX) is the most important in settling process as we got some good correlation coefficients (R2) between UMAX and (TUMAX, MLSS, SVI) was at a temperature (20OC) were respectively (98, 96,98%), and when the temperature (17 OC) respectively (97,96,97%) which is almost the same values. We noticed that the sludge volume index (SVI) is closely associated with the settling parameters (UMAX, TUMAX) with the correlation coefficients were respectively (98,99%) on the temperature of (20OC) and (98,97%) on the temperature of (17OC) . Velocity sedimentation rate (UMAX) was the largest and deposition time (TUMAX) was smaller on the temperature of (20OC) Indicating an improved sedimentation with higher temperatures . Subsequently, temperature is an influential factor on deposition and It is necessary to be taken into account in the design and operation of activated sludge treatment plan.
