About the Surface Sand Filter
General Information Performance Data Water Quality Treatment Process Design


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Water Quality Treatment Process

1. Runoff flows into a sedimentation forebay or other pretreatment chamber. Low-flows are metered out slowly through the standpipe into the filter basin. When the forebay’s capacity is reached, the overflow spills across a weir into the sand filter basin.

2. As the stormwater permeates the filter bed, the contaminants it contains are both physically filtered by sand particles and chemically sorbed to particle surfaces.

3. If located in suitable soils, such as those belonging to groups A and B, the treated runoff is allowed to infiltrate into the subsurface beneath the system. Otherwise, it is collected in a perforated subdrain and returned to a storm drain system or discharged to the surface.