Effect of dead cells on biofouling in the reverse osmosis process

Biofilm formation in membrane processes causes a flux decline, pressure drop increase, and other adverse effects. Understanding the mechanisms of fouling, control, and cleaning are important in order to resolve fouling problems. In this paper, the effect of cell viability on biofouling was studied via a feed water analysis and membrane autopsy. Pseudomonas aeruginosa PAO1 was used as the model bacteria. Biofouling tests were divided into two parts: live cells and dead cells (autoclaved cells). The feed water was periodically collected every 3 h to analyze the total direct counts (TDCs), heterotrophic plate counts (HPCs), and extracellular polymeric substances (EPS). A membrane autopsy was performed to characterize the fouled membrane through TDCs and EPS. When dead cells were inoculated into the feed water, low concentrations of TDCs and EPS were measured in both the feed water and fouled membrane. As a result, it was determined that initial flux decline by biofouling can be reduced if feedwater is disinfected before the reverse osmosis process.