抄録
Constant rate microfiltration experiments were conducted in purification of sewage secondary effluent pretreated with polyaluminum chloride (PAC). Monolithic ceramic membrane having a nominal pore size of 0.1 µm with 19 tubular channels is used as a filter medium. The system is capable of selecting the required mode of membrane cleaning, i.e., physical backwashing or chemically enhanced backwashing, based on the set value of the operating parameters. It was found that the physical backwashing and the chemically enhanced backwashing were effective in reducing the flow resistances resulted from the formation of the filter cake and irreversible pore blocking, respectively. Sodium hypochlorite is used as the cleaning agent in the chemically enhanced backwash mode and it is injected automatically when initial pressure drop reaches the preset value. The fully automatic system was found to be stable and the effluent quality meets the target quality and was independent of the influent quality variation. The system was tested even at the higher flux of 4.0 m/d for a relatively long period of time. The filtrate is free from E. Coli etc. and can be reused as reclaimed water for toilet flushing, car washing, etc. Furthermore, the results obtained under various operating conditions indicated that the effective flux, concentration of coagulant and the amount of cleaning agent used per net filtrate volume should be considered for process optimisation
