Hydraulic backwashing for low-pressure membranes in drinking water treatment: A review

Conventional drinking water treatment processes have faced several obstacles that are severely affected by water pollution and shortage, which makes it difficult to produce potable water effectively. Low-pressure membrane filtration, which includes ultrafiltration (UF) and microfiltration (MF), is one of the most promising treatment technologies for improving water quality. Periodic hydraulic backwashing is a necessity for the routine operation of UF/MF membranes, but only sparse data are available regarding the optimization of backwashing procedures, while more attention has been directed toward membrane fouling and cleaning. In the current work, we critically review the backwashing parameters of UF/MF membranes used in municipal water supplies. These parameters include pressure, flux, permeability (or resistance), mass balance, and membrane characterization techniques. The factors affecting backwash performance, which include membrane properties, feed water properties and operating conditions, are discussed in detail. The pretreatments of feed water, such as peroxidation, adsorption, coagulation and filtration influence the performance of UF/MF membranes to varying extents. The impacts of the backwash interval, backwash duration, backwash strength, air-assisted backwashing, chemically enhanced backwashing, and backwash water quality on backwash performance are summarized to provide more comprehensive data, which can improve backwash performance in full-scale drinking water and water reuse treatment plants.