Pollution Solutions
Storm Water

FORAGER® Sponge Type M (for metals absorption) is available in the form of half inch cubes. A multitude of the cubes, confined within a conduit, presents extremely little impedance to flow of water through the conduit, and will not become clogged by suspended solids. The cubes can even be confined within elongated fishnet bags which become giant “tea bag” absorption units that can be easily emplaced within, and removed from conduits.

Such characteristics of the FORAGER® Sponge products make them well suited for the interception and remediation of storm water. In some storm water treatment installations, little or no capital investment is required beyond the cost of a conduit of suitable diameter, and connecting fittings.

In order to optimize the absorption of trace pollutants flowing through the absorption unit, it is desirable to present a geometrical configuration which maximizes contact time of the water with the Sponge. This is generally done by causing the water to flow through a long path length of the Sponge cubes within a conduit. Although the aggregation of cubes presents little impedance to flow, such impedance is a factor which must be taken into consideration. If the impedance is too high for a given path length, a larger cross-sectional area of the path length should be employed.

It is preferable to utilize an up flow system configured somewhat similar to a classic “plumber’s elbow”, or a U-tube wherein the water enters one leg of the U, and exits the second leg which contains the absorption unit. Examples of suitable equipment employing an up flow principle are shown in Figures A and B. In such system, a clean-out catchment basin is disposed below the absorption unit for retaining debris that would otherwise clog the absorption unit. Storm water that is allowed to remain in stagnant contact with the Sponge in the U-tube will undergo 100% remediation in view of the long contact time. A vertical orientation of the conduit which holds the absorption unit facilitates installation and removal of the absorption unit.

The operational lifetime of an absorption unit depends upon a number of factors such as : size of the unit, cumulative flow volume through the unit, concentration of absorbable pollutant, and the absorption efficiency of the unit in the specific configuration of your treatment system. For example, a cubic foot of FORAGER® Sponge can hold about 190 grams of lead at saturation. If the storm water contains 1 ppm of lead, and the unit is achieving 100% removal of the lead and is not absorbing anything else, then one cubic foot of Sponge can treat 50,160 gallons of storm water. If the flow rate through the unit averages 1000 gal/week, then one cubic foot will last almost a year.

The saturated Sponge may be disposed of by way of compaction into a small volume which can be handled as hazardous waste. Alternatively, a fixation treatment might be applied to the Sponge to render the absorbed species non-hazardous. The metal-absorbing grade of Sponge can be incinerated because its combustion products are relatively innocuous. However, appropriate consideration must be given to the combustion products of the absorbed metal species.