Comparative analysis of air scouring and unidirectional flushing of water distribution systems

Unidirectional flushing is a widely used method to remove sedimented particles from water distribution systems and prevent water discolouration events. However, it shows low efficiency in cases of high pressure losses, usually requires large volumes of water, and does not remove incrustations. Air scouring is known for being very effective in particle removal with minimal impacts from pressure loss, requiring little water and improving hydraulic capacities by removing soft incrustations. Flushing sequences of unidirectional flushing and air scouring were performed in similar conditions on 18 pipe sections from four water distribution networks located in the province of Quebec, Canada; unidirectional flushing was also performed on 14 additional pipe sections located in three other water distribution networks. Total suspended solid concentration, water flow and pressure of flushed water were recorded to estimate the amount of flushed particles, the required water volume and the evolution of hydraulic capacities. Within the studied networks, the water requirements for air scouring were approximately 8-fold less than for unidirectional flushing and did not significantly improve the hydraulic capacity of the cleaned pipes.