Chemical and microbial composition of loose deposits in drinking water distribution systems

Processes occurring in drinking water distribution system can form mineral and biological materials. These materials are present in the distribution systems as loose deposits. Origin of the mineral sediments in water networks is often linked to an insufficient treatment process or corrosion of distribution system pipes. The bacterial regrowth processes associated with biofilm formation may originate within these loose deposits. Sudden changes in hydraulic conditions may resettle the loose deposits leading to increase in turbidity or deterioration of microbiological water quality at the consumer tap, which in some circumstances can cause health risk. This paper reviews current literature for composition of loose deposits and presents a simple operational method for removal of loose deposits from drinking water distribution system using unidirectional flushing (velocity 1.5 m/s, clear water front, 2 pipe turnovers). This method for effective loose deposit removal can be used to evaluate chemical and microbial status of a drinking water distribution system.