A detention tank is an artificial flow-control structure that is used to contain stormwater and wastewater for a limited period of a time.
The detention tank can be incorporated into the sewer network system at the wastewater treatment plant or at factories.
A detention tank in the sewer network is used to even out peak flows in the system. This helps to avoid overflow into the recipient, protecting downstream areas. It also helps to prevent hydraulic overload of downstream sewers and wastewater treatment plants.
At the wastewater treatment plant the detention basin is used to even out fluctuations in the wastewater inflow to ensure an even flow throughout the process tanks at the plant. This is necessary to keep the treatment processes operating in an optimal way, to maintain discharge requirements and to avoid sludge drift.
Factory detention tanks (more commonly equalisation tanks) are also used to even out peak flows. Additionally, they are used to stabilise batch volumes of process water with regard to pH or chemical substances before discharge into the sewer system.