Full Scale Evaluation on Ferric Flocs Sludge Treatment with Pelleting Flocculation Blanket Process

The Pelleting Flocculation Blanket (PFB) process is a newly developed technology for high concentration suspensions removal characterized by high surface loading solid-liquid separation. In this paper, by using the PFB process, a pilot-scale experimental study was carried out on concentrating ferric flocs sludge with a full scale of 19~38 m3/H. The investigation aimed to optimize the operational conditions. Under the raw sludge concentration of 103~1154 mg/L, the system could achieve ideal conditioning effect with PAM (polyacrylamide) dosage of 0.3~2.7 mg/L, agitation speed of 3 rpm, and water up-flow rate of 19~38 m/H. Under the experimental conditions, the increase of polymer dosage would improve outlet turbidity and pellets settling behavior. The moderate up-flow rate had no marked effect on treatment results, while too large surface loading could worsen the outlet turbidity. The experimental results also revealed that there exists an approximately linear relationship between raw sludge concentration and optimum PAM dosage, that is, the optimum dosage of PAM increased synchronously with the increasing raw sludge concentration. While the relationship between raw sludge concentration and maximum up-flow rate reflected negatively linear dependence, the maximum up-flow rate would decreased linearly with the increasing raw sludge concentration.