Application of Pellet Fluidized Bed Process in Ferric Flocs Sludge Conditioning

In this paper, a dynamic experimental study was carried out on concentrating ferric floes sludge by pellet fluidized bed process with scale of 1.3~5.4 m
³
/h and outlet turbidity less than 5NTU. The pilot experiment aimed to optimize the conditioning system and determine the operational parameters. The experimental results showed that the static mixer, being used as pre-coagulation process to control the growth of primary pellets, achieved better pre-conditioning effect than any other mixing device for its sufficiency mixing and moderate pellets size. Under the raw water concentration of 103~1154 mg/L, PAC dosage of 5.1~15.3 mg/L accompanied with PAM (molecular weight of 10~12 million) dosage of 0.3~2.7 mg/L could achieve ideal conditioning effect with optimal rotating rate of 10 rad/min and water up-flow rate of 30~80 cm/min. The moisture content of the thicken sludge could be reduced below 97%. Moreover, the pellet floes was characterized with fine sedimentability with settling velocity of more than 10 mm/s. accompanied with the increasing of raw sludge concentration, the optimum dosage of PAM increased synchronously, while accompanied with the increasing of raw sludge concentration, the maximum up-flow rate would decreased linearly.