Effect of coagulation pretreatment on membrane filtration performance

The effect of coagulation on microfiltration and ultrafiltration performance was evaluated in a recent laboratory study. The primary variables used in the study included source water, type of coagulant, coagulant dose, coagulation application conditions, and membrane material. Fouling was evaluated using flat sheet membranes in an unstirred filtration cell. As described in this article, a linear relationship between the removal of dissolved organic carbon (DOC), as measured by ultraviolet absorbance at 254 nanometres, and the reduction of fouling was observed. In addition, coagulation conditions appeared to influence the extent of fouling of the microfiltration membrane but had no effect on the ultrafiltration membranes. Low coagulant doses frequently caused greater fouling than no coagulation, but coagulant doses for enhanced coagulation always reduced fouling. Prefiltration was used to separate the effects of coagulation on particulate matter and DOC, and the results suggested that more than 80% of the fouling in these experiments was because of dissolved matter.