Fouling characteristics and cleaning strategies in a coagulation-microfiltration combination process for water purification Original Research Article

The membrane fouling characteristics and cleaning strategies in a coagulation-microfiltration combination process for purification of micro-polluted raw water were investigated. The microcosmic observation on the exterior and inner surfaces of the fouled membrane by Scanning Electronic Microscope (SEM) combined. with Energy Dispersive Spectrometer (EDS) revealed that the fouling on the exterior surface was an integrated effect of microorganisms, organic and inorganic matters, while that on the inner surface was mainly due to the bio-fouling. The investigation on the recovery of the membrane permeability with various cleaning methods showed that alkaline cleaning effectively removed most of the microorganisms and organic foulants formed on both the exterior and inner surfaces of the membrane, and acidic cleaning more effectively removed the inorganic scales. Based on the analysis of the extracted solution during chemical cleaning, it was found that the majority of soluble organic foulants were of low molecular weight, and Ca was the major inorganic element in the foulants.