Kaspars Neilands

Interpretation of Loose Deposits Motion in Drinking Water Distribution Network

The present study was designed to describe the turbidity curve obtained during planned unidirectional flushing in drinking water distribution system of a diameter 100-300 mm. The online measurements of flow and turbidity for cast iron (n=16), polyethylene (PE, n=7) and polyvinylchloride (PVC, n=4) pipe sections and calculations of hydraulic values indicated that the turbidity curve peaks appeared at the locations of bends, tees, narrow parts of the pipes etc viz. where increased hydraulic drops take place. The application of on-line measurements during the wash-out of loose deposits in both cases from one and two hydrants simultaneously, the calculations of average velocity (0.72 m/s, n=22) and shear stress (2.05 N/ m 2 , n=29) on pipe walls showed that the loose deposits in the pipes move according to plug-flow principle in a turbulent regime. The granulometric analysis of loose deposits showed that the average diameter ranged from <1-558.4 µm (n=16) and did not correspond to the cohesive nature and average surface area of loose deposits which was 48.864 m2/g (n=17) with lowest values for samples of PE and PVC pipe sections (1.684 m 2 /g) and highest for CI sections -148.991 m 2 /g. The analysis of X-ray crystalline phases of loose deposits indicated the predominance of goethite and quartz. The observations of peaks from turbidity curves fitted for junctions of pipe network are significant for modeling of loose deposit discoloration events in distribution network.