Accumulation of Loose Deposits in Pipe Segments

Abstract

Loose deposits in drinking water distribution systems (WDS) on nowadays cause serious problem causing accumulation of bacteria and discoloration. The present study was designed to calculate amount of loose deposits accumulated in WDS of cast iron, polyethylene and polyvinylchloride pipes. The loose deposits were resuspended and collected during planned unidirectional flushing of isolated pipe segments. The flow (Siemens Sitrans FM MAG 8000 (Siemens Energy & Automation Inc., Germany)) and turbidity (Hach 2100P, Dr. Bruno Lange GmbH&Co, Düsselfdorf, Germany) during flushing was measured with online instruments. The average velocities of flushing ranged from 0.2-2.34 m/s and shear stress 0.43N/m2 -2.05N/m2 acting on pipe walls. The calculations of hydraulic values indicated that the different types of pipes has various potential of particles and new polyethylene pipes sometimes has even more deposits than old cast iron pipes. The concentrations of loose deposits per meter of pipe were observed from 0.05kg/m till 2.4kg/m. Results showed that flow velocity of flushing and daily hydraulic regime are the key factors for accumulation of loose deposit amount in pipe segments. Dead-end treads has more loose deposits than transit without influence of pipe material. More attention should be paid for model validations, so the daily flow regime could indicate critical pipe segments, where most of sediments are settled