[Comparative Study on Pretreatment Process of Ultrafiltration: Chemical Coagulation and Electrocoagulation]

The ultrafiltration membrane response mechanism and the effect on the membrane fouling under dead end filtration were comparatively investigated in ultrafiltration pretreatment processes using chemical coagulation (CC) and electrocoagulation (EC). The effects of Al³⁺ dosage on the flux of the membrane,the properties of the floc (particle size, strength coefficient, recovery coefficient, fractal dimension) and the properties of the cake layer were studied. The results showed that taking EC as a pretreatment method, the flocs were stronger and more compact, the cake layer deposited on the surface was porous and higly hydrophilic; while in CC pretreatment, the flocs were loose and had low strength, which would be compacted and crushed easily by the pressure in membrane filtration process, resulting in relatively dense cake layer and low hydrophilicity. Therefore, EC was the most effective pretreatment process to alleviate membrane fouling during operation, which could maintain a flux that was about 5.57% higher than CC.