POLYURETHANE FOAM FILTRATION
Ronald J. Romagnoli, Environmental Engineer
Ronald L. Berglund, Environmental Engineer
Union Carbide Corporation
Research and Development Department
South Charleston, West Virginia 25303
INTRODUCTION
Filtration, as a tertiary suspended solids removal technique, has recently gained importance with the advent of more stringent effluent guidelines for municipal and
industrial biological treatment facilities. Most of the previous studies using sand or
multimedia gravity filters on various secondary effluents from Union Carbide Corporation (UCC) petrochemical facilities have been characterized by surface filtration (using
only the upper few inches of the filter bed), short run times, rapid head loss buildup,
low media loadings, high backwash requirements and restrictive capital and operating
costs.
Two primary obstacles: (a) achieving effective depth filtration, and (b) removing
small colloidal particles, have prevented rapid deep-bed filtration from being economically applied to remove suspended solids from UCC's petrochemical effluents. Several
studies [1,2,3]  have shown that the particle size of secondary effluents follows a bi-
modal distribution with means at 3.5 and 85 microns. Such a distribution enhances
these obstacles because the larger particles would be removed at a filter's surface, while
the smaller particles pass through the entire filter bed. Studies were initiated to develop
a deep-bed filter that would overcome these obstacles and attempt to solve UCC's filtration problems.
This paper discusses the research efforts, through laboratory and pilot plant studies,
that developed a novel deep bed filtration process that:
• utilizes polyurethane foam as the filter media
• overcame the various obstacles
• solved many of UCC's problems, and
• has a potential to be applied to several additional applications.
A patent application for this process was submitted to the U. S. Patent and Trademark Office in 1977.
PROCESS DESCRIPTION
The Polyurethane Foam Filter is a rapid-deep bed filtration process whereby water,
containing suspended solids is passed through the filter bed. The solids are removed
from the liquid and retained by discontinuous, reticulated polyurethane foam particles
within the filter vessel. The primary physical characteristic variables for the media
include:
• cellular density (cells/linear cm)
• true density (kilograms/m )
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