Algal fouling control in low-pressure membrane systems by pre-adsorption: Influencing factors and mechanisms

A series of filtration experiments were designed and implemented to compare the roles of adsorbent properties, membrane pore size, and permeate flux on algal fouling control by pre-deposited and pre-mixed adsorbents using Microcystis aeruginosa suspension as feed water. The results demonstrated that the pre-mixed powdered activated carbons mitigated the fouling, and the fouling control efficiency increased with the increase in powdered activated carbon size and with the decrease in membrane pore size and permeate flux. In comparison to the gradually formed cake layer in the conventional dosing mode, the pre-deposited layer on the membrane surface exhibited significantly more complicated reactions to these parameters. The interactions between pre-deposited powdered activated carbons and algal foulants changed from synergistic fouling to buffering effects that were highly associated with the storage capacity of the pre-deposited layer and cell rearrangement through the depth of the layer. Thus, contrary to the pre-mixed powdered activated carbons, the pre-deposited powdered activated carbons reduced the fouling resistance under high permeate drag force because of the limited algal cell transference into the powdered activated carbon layer caused by the increasing compactness of the initially formed foulant layer. This study demonstrated the feasibility of controlling fouling through pre-deposited powdered activated carbons and benefitted the selection of the optimal adsorbent dosing mode based on operational conditions.