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Wahaso - First Flush Or rainwater Pre-Filtration System
The first step is to remove as much debris as possible from the rainwater before it enters the system. A first flush sequence can be programmed into the control system that senses a rain event and diverts the first few minutes of rainfall to the stormwater system. This is an effective way of minimizing debris and contaminants in the water but also wastes many gallons.
A high-capacity vortex filter uses the pressure of water coming off a roof or parking lot to spin it in a centrifugal manner and then force it through a cleaning screen. Debris drops through the center and to the stormwater system while clean water exits out the sides. We like this method because it is 95% efficient when screening large quantities of water and requires minimal cleaning or maintenance. Vortex filters can be located above ground or below ground.
For higher capacity systems, we like to use commercial-grade cascade filters and nutrient separating baffle boxes (NSBB). These systems effectively filter several cubic feet of rainwater and stormwater per second, separating oils and suspended solids before the water is sent to the cistern.