Application of unidirectional flushing in water distribution pipes

Abstract

In this study unidirectional flushing (UDF) was conducted to improve the effectiveness of deposit removal from internal pipe walls and to provide information on pipe networks to enable operators to implement flushing in field. Four ductile cast iron pipes with epoxy-lined and cement-lined were selected for the practice of UDF. Water pressure was measured using a data logger equipped with a pressure gauge. The normal flow velocities of the networks were found to be 0.12 m/sec or below in the study area. Flushing velocities ranged from 1.07 m/sec to 2.78 m/sec by using a blow-off valve for discharge. The discharged water was taken in five-minute intervals to measure water quality parameters: turbidity, residual chlorine, pH, temperature and conductivity in the field; metals, inorganic ions, total suspended solids and heterotrophic plate count bacteria in the laboratory. The practice of periodic UDF as preventive maintenance is expected to contribute to enhancement of safety and stability of the water supply. It was indicated that part of the biofilm could be removed with the sediments in the pipe by UDF since the removal of HPC bacteria was correlated with total suspended solids (TSS) (R 2 ¼ 0.90). The coefficient of determination (R 2 ) between turbidity and TSS is 0.90 except for one outlier. Sediment removal could be estimated from the turbidity data of flushed water in the field using the equation of the relationship between turbidity and TSS.

Comparison of Modern Drinking Water Network Maintenance Methods: Evaluation of Removed Deposits in the Form of Total Suspended Solids (TSS)

“…Even in this case, it was appropriate to end the cleaning by conventional flushing, to re-settle the incrustations in the pipe and flush out any accumulated air. According to [ 43 ], the daily flow rate in the water supply system was found to be ≤ 0.12 m·s −1 , therefore, it is advisable to flush at this flow velocity or lower. The flow velocity used in the given experiments corresponded to v = 0.066 m·s −1 .…”

Designing Isolation Valve System to Prevent Unexpected Water Quality Incident

“…On the other hand, changes in flow direction have a higher likelihood of causing water quality incidents compared to velocity criteria, as reported in the literature [24,25,27,36]. For instance, studies by Ahn et al [36] and Armand et al [37] indicated that backward flows are more efficient in suspending deposits or cleaning pipes compared to simple velocity changes. Similarly, when there is a change in flow direction within the pipe, it directly affects the detachment of previously stabilized scale [24,33].…”