Influence of phosphate on bacterial adhesion onto iron oxyhydroxide in drinking water

The transport and storage of drinking water in water distribution systems can modify its initial composition and properties. The accumulation of bacteria on corroded pipes is prejudicial and may lower the microbiological quality of the water. Previous results have shown that when pipes are highly corroded, the addition of phosphate, used as an anticorrosion treatment, decreases the bacterial concentration in the water. We studied the possibility of using phosphate to reverse the surface charge of iron oxyhydroxide (FeOOH) to limit bacterial adhesion. Iron oxyhydroxide (IOH) particles and Escherichia coli SH 702 were used as models of corrosion products and bacterial contamination, respectively. Electrophoresis was used to characterize the initial surface charges of both types of particles and the modifications that occurred after the addition of phosphate anions. Flow cytometry and adhesion assays were used to build adsorption isotherms of bacteria on IOH versus (phosphated-) IOH. X-ray photoelectron spectroscopy permitted to determine the chemical composition of the E. coli envelope and to discuss on functional groups responsible for bacterial surface properties. In the present conditions, adding phosphate to water allowed a decrease of 75% of the bacteria adhering to IOH.