Effects of operating conditions on biofouling in crossflow ultrafiltration membrane processes

We evaluated the effects of operating conditions on the biofouling behaviors in ultrafiltration (UF) membrane processes with respect to biofilm formation and decrease in permeate flux. The biofouling experiment was performed by filtering nutrient-containing feed water with a crossflow membrane cell through a regenerated cellulose UF membrane consisting of pre-adhered bacteria. The nutrient concentration, initial permeate flux, flow rate of feed water, and trans-membrane pressure (TMP) were controlled as the operating conditions. The permeate flux was monitored during the filtration, and the adhesion of bacteria and extracellular polymeric substances (EPS) to the membrane surfaces was observed using confocal laser scanning microscope. The increase in the medium concentration and initial permeate flux facilitated both the decline of the permeate flux and the biofilm formation by causing concentration polarization of the medium. The TMP and flow rate of the feed water also affected the permeate flux and bacterial adhesion. The biofilm thickness on the membrane surface after the biofouling tests was positively related to the decline ratio of the permeate flux.