Winter Recycled Water – Maintaining Quality During Low Demand

The Dublin San Ramon Services District has experienced difficulties maintaining a chlorine residual in its recycled water distribution system during the winter wet season months when irrigation demand is low. The District is concerned about potential water quality issues such as slime growth and odors, and suspects that nitrification is occurring in the system due to high winter water age and causing the inability to maintain a residual. Water modeling confirmed that portions of the distribution system have a very high water age during the low demand months. The District explored but was ultimately unable to significantly reduce winter storage tank levels to reduce water age. While this may be a viable strategy in the future, the District is currently focusing on annual system flushing to mitigate potential water quality issues due to low winter demand.