Evaluating the potential of biofilm control in water supply systems by removal of phosphorus from drinking water

Effect of microbially available phosphorus (MAP) on biofilm development in drinking water systems was investigated at the pilot-scale experiments over 3 years. Completely mixed biofilm reactors Propella® (water detention time 24 h, flow rate 0.25 m s^-1, PVC pipe coupons) were used as water distribution network models. Four experimental runs were carried out with water containing different levels of phosphorus which was limiting nutrient for bacterial growth. Positive correlation between MAP in the inlet water and heterotrophic plate count (correlation coefficient 0.95) in biofilm, as well as for the total bacteria number (correlation coefficient 0.71), was observed. However, our experiments showed that removal of phosphorus down to very low levels (below detection limits of chemical method and MAP < 1 μg L^-1) was not an efficient strategy to eliminate bacterial regrowth and biofilm formation (<51,00,000 cells/cm²) in drinking water supply systems.