The drinking water safety has been paid close attention, and the water purification development and distribution cleaning have been widely studied. To meet stricter water quality regulations and fight new emerging pollutants, upgrading treatment processes to improve treated water quality has become common practices worldwide. However, the quality improved drinking water still needs to be delivered by the old distribution system with harboured material which may cause serious water quality deterioration during the shifting of supply water quality. Until now, the accompanying transition effects within distribution networks caused by changes of water quality or hydraulic condition have been poorly documented. These irregular operations will impact water quality
negatively through the associated physiochemical and microbiological destabilization of accumulated materials such as loose deposits resuspension and biofilm detachment.
The destabilized materials would be released as suspended solids into bulk water and travel throughout distribution networks. Therefore, the investigation on changes of suspended solids characteristics is the key to understand transition effects. To study the transition effects through suspended solids, there are challenges: 1) suspended solids are diluted in the big volume of water, resulting in low concentration if take water samples; 2) the detection limit of regular parameters makes the changes hard to be noticed; 3) the
release of suspended particles is non-periodicity, which leads to the difficulty of catching the moment.
In my studies, the online particle sampling system (OPSS) was applied in three distribution systems to collect and monitor suspended solids, which successfully overcame all of the three challenges mentioned above. The main objective of this report is to study water quality changes under regular operations, and transition effects under irregular operations such as the upgraded treatment and pipe cleaning by using OPSS. At the end of the report, the problems were diagnosed and the management strategies were proposed for different systems.