Impact of mixing phenomenon at cross junctions on the variation of total coliform and E. coli in water distribution systems: experimental study

This study investigates factors that influence the growth and diffusion of microorganism especially total coliform and Escherichia coli (E. coli) in water distribution networks. The experiments were carried out in a laboratory distribution network where different flow directions at junctions, varying inlet flow rates, initial chlorine doses and natural organic matter were studied. Depending on the incoming flow directions, two hydraulic behaviors were observed at cross junctions: (i) incomplete mixing and (ii) perfect mixing of the fluid stream. The study shed light in to how concentration of microorganism (total coliform and E. coli) can vary greatly in the same water network system due to the impact of the mixing of water with different physicochemical characteristic. The results also indicate that pipe material was the main factor that influenced bacteria growth in a water distribution system.