Comparison of performances of mechanical flocculation and grid flocculation treating low turbidity source water by pilot-scale experiment

In view of the third-stage project construction of the third waterworks of a city, pilot-scale experiment was used to select mode for the flocculation. The results of the test showed that, sedimentation effect with grid flocculation was better than that with mechanical flocculation under the same condition of source water, dosage and influent water quantity. With the increasing of the PAC dosage, the effluent turbidity after the sendimentation and the number of granules with diameter greater than 2 μm were on a downward tendency. Source water quality and flocculant dosage were indicated to be the most important factors affecting the effluent water quality from the sedimentation tank, the optimal dosage was within the range of 21 mg/L to 28 mg/L.