Apparatus and method for treating storm water runoff

Abstract

Apparatus and for the treatment of storm water runoff to remove contaminants that accumulate in the storm water when it flows over paved surfaces in urban areas. The apparatus includes a basket that has an outer surrounding water-permeable wall, and an inner water-permeable wall, spaced from and surrounded by the outer wall. A bed of an absorbent, able to absorb contaminants in the storm water, is disposed in the space between the outer and inner walls, while allowing fluid communication between the walls. An inner drainage space is defined by the inner wall and is in fluid communication with the absorbent. During operation, storm water flows through the outer permeable wall, into the bed where it is treated; and treated water flows from the bed through the inner wall into the inner drainage space. Treated water then flows from the drainage space, in some embodiments under a siphon-effect, into a treated water drainage conduit for disposal. The absorbent may be selected from compost, vermiculite, activated carbon, peat, ion exchangers, clays, and the like, and may be in the form of pellets or particulates. The baskets are of modular construction so that the beds are in containers that may be removed and replaced, with minimal labor. Moreover, the baskets may be backflushed to remove particulates and debris that clog the beds and retard the treatment rate.