Description
Modular or monolithic prefabricated first flush tanks are used to collect the first 5 mm of runoff water uniformly distributed over the surface. The function of these tanks is to store polluted water and prevent it from being conveyed directly to the discharge system.
The water stored in the tanks is disposed of by means of a discharge pump to the municipal sewer system, or treated according to the pollutants it contains in dedicated systems such as oil separators and/or physico-chemical plants in the case of waters containing mineral oils, surfactants, settleable solids, heavy metals, etc.
The discharge of first flush water into municipal treatment systems should take place within 24-48 hours after the end of the rainfall event, and in any case according to the requirements of the authority managing the sewer and treatment plant. This is because municipal treatment plants, during rainfall, already have to process water from combined sewers and would therefore have to treat enormous quantities beyond their treatment capacity.
This system consists of a modular or monolithic prefabricated tank internally divided by a wall and, if necessary, by subsequent storage tanks of the same size, until the required storage volume is reached.
The main module is equipped with electronic equipment installed at the inlet that detects the start and end of the rainfall event and, after a preset time from the beginning of rainfall, activates a pump to discharge the water stored up to that point, sending it to the sewer or to any treatment system.
