Pollution Solutions
In-situ and passive techniques

FORAGER® Sponge Type M (for metals absorption) and bioremediation are 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 industrial effluents, landfill leachates and various kinds of non-point pollution involving unattended gravity flow. In such 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 may be needed.

A typical example of a passive, gravity-flow installation for treating an industrial discharge is shown in the drawing. In such installation, a pivoted section of pipe provided with a downstream retaining grate holds a Sponge absorption unit. This type of installation is well suited for the “polishing” of an effluent stream to remove pollutants that have survived conventional upstream remediation treatments.

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 Type M FORAGER® Sponge can hold about 190 grams of lead at saturation. If an industrial discharge, or 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 the 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 for handling 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 (Type M) 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.

In certain applications, it is possible to desorb the pollutants and re-use the Sponge.