[Enhanced Mitigation of Membrane Fouling by Regulations on Floc Morphology in Electrocoagulation].

In this study, the electro chemical parameters were regulated to control the floc morphology in order to mitigate membrane fouling. The main effects of current density, initial pH and conductivity on the floc characteristics and flux were studied, and the mechanisms of interaction between flocs with different morphology structures and ultrafiltration membranes were analyzed. The results showed that the key to mitigate the membrane fouling by electrocoagulation was to form a loose and porous cake layer on the membrane surface. The electrocoagulation-ultrafiltration (EC-UF) technology could not only effectively mitigate the membrane fouling, but also greatly enhance the water quality of the effluent. By increasing the current density and keeping water quality conditions at neutral pH, the EC-UF technology could maintain a higher flux. Under conditions of j=20 A·m-2, initial pH=7 and initial conductivity=1000 µS·cm-1, the removal rate of humic acid (HA) was 97%, and the normalized specific flux of J/J0 was 81%.

[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.