Coagulation as pretreatment for improving ultrafiltration performance in water and wastewater treatment.

摘要

Addition of a coagulant prior to membrane filtration has been suggested to enhance the membrane permeate flux and improve the contaminant removal in natural river water and pulp mill wastewater treatment. Various process and operating conditions affecting the coagulation and membrane filtration were examined with a flat sheet, crossflow ultrafiltration membrane filtration apparatus: coagulant type and dosage, pH, ionic strength, membrane material, crossflow velocity and transmembrane pressure. Jar tests were carried out to investigate the enhanced coagulation efficiency at the controlled condition. The results showed that membrane permeability and permeate water quality are enhanced by coagulation pretreatment. However, in some cases, coagulation pretreatment increased the extent of membrane fouling. The membrane operating conditions, transmembrane pressure and crossflow velocity, had a relatively small effect in improving membrane performance. Thus, coagulation pretreatment conditions were more important than physical operating parameters in determining the process performance of a coagulation-ultrafiltration system, highlighting the importance of the proper selection of coagulation pretreatment conditions.