Biological stability of water in water distribution systems. The effect of water treatment trials

Research into the removal efficiency of biogenic substances, necessary for the growth of heterotrophic microorganisms, was carried out for the following water treatment trials: surface water, infiltrative water and mixed surface water after microsieving with aerated underground water. The results have shown that the efficiency of removal of organic substances, independently of the type of treated water, increased along with the organic carbon concentrations in raw water. The average effectiveness of phosphate removal was: 92.1%, 88.8% and 83.7% for surface, infiltrative and mixed water, respectively. In all analyzed systems, presence of phosphates was an limiting factor for the regrowth of microorganisms in the distribution system. In none of the water treatment trials, effective removal of inorganic nitrogen has been recorded.