Transport of E. coli colloids and surrogate microspheres in the filtration process: Effects of flow rate, media size, and media species

Drinking water safety risks caused by bacterial contamination from Escherichia coli (E. coli) have aroused widespread concern. Filtration is crucial to drinking water treatment and can effectively capture and remove E. coli colloids without producing toxic by-products. This work systematically simulated the operating conditions of filtration by determining the transport behavior of E. coli colloids in lab-scale columns. Microspheres were used as surrogates of bio-colloids and breakthrough curves were drawn and analyzed at different flow rates, media sizes, and media species. The impact of media species on colloidal retention might be underestimated in the filtration process, and the removal efficiency of E. coli colloids varied by more than 59% between different media. From the point of interface interaction, excellent removal efficiency may be due to the strong attractive force caused by more positive zeta potential on the media surface. The results indicated that there were differences in transport behavior and environmental sensitivity between the E. coli colloids and surrogates. The DLVO theory cannot analyze the transport behavior between different colloids in media with opposite charges, and it is not easy to quantify the contribution of media species accurately. The study focuses on the adjustable parameters of the filtration process and provides new insights for ensuring the safety of drinking water.