AWWA JAW60488

Tanks and reservoirs have typically been designed and operated to satisfy hydraulic purposes, such as emergency storage, with water quality issues having largely been ignored. But water quality issues are actually important considerations in the design and operation of distribution system tanks and reservoirs. Mixing and aging, for example, are two related phenomena that can affect water quality-long residence times depress disinfectant residuals and can promote bacterial regrowth, and uneven mixing can result in zones of older water. Minimizing detention time and avoiding parcels of water that remain in the storage facility for long periods of time should therefore be implicit objectives in the design and operation of distribution system storage facilities. Monitoring techniques and models are available that can help to assess the potential for water quality problems in tanks and reservoirs, and relatively straightforward designs, retrofits, and operational solutions exist to help eliminate or reduce the potential for water quality problems in the distribution system. This study resulted in practical solutions that, in many cases, can easily be implemented to reduce problems with water quality and protect public health. Includes 20 references, figures.