Biofilter media performance updates for WinSLAMM

Bob Pitt, Shirley Clark, Redahegn Sileshi,and John Voorhees


This paper focuses on specific information needed to model the various parts of the pollutant retention processes in biofilters. The updates currently being incorporated in WinSLAMM are building on expanded data from laboratory and field research mostly conducted by Pitt’s research group at the University of Alabama and by Dr. Shirley Clark’s research group at Penn State – Harrisburg. These tests were conducted to provide the details needed for modeling the performance of biofilters, specifically focusing on methods to predict treatment flow rates through the media, particulate retention by particle sizes, and retention of filterable pollutants. These tests also addressed issues not routinely described in the biofilter performance literature, such as maintenance issues associated with particulate clogging and breakthrough of pollutants, failure due to excessive salt loadings on media having large amounts of fines, problems associated with compaction of the media, and leaching of material from the media. Most of the data supporting these model enhancements are associated with several studies:

  • Clark’s master thesis and dissertation research using laboratory and pilot-scale field testing of different media (Clark 1996 and 2000; Clark and Pitt 1996).
  • Pitt and Clark’s research for the Boeing Co to develop biofilter media mixtures suitable for a wide range of pollutants at an industrial site being restored to open space use (Pitt and Clark 2010).
  • Sileshi’s dissertation on soil and sand media for biofilter treatment flow rates, underdrain design, and retention of particulate sizes (Sileshi 2013).

In addition, several full-scale biofilter monitoring projects also contained useful information and data for this summary. The Wisconsin DNR and USGS have been monitoring test biofilters to compare the performance of various media mixtures (Bannerman, personal communication). The Kansas City Demonstration Project of Green Infrastructure in Areas served by Combined Sewer (Pitt, et al. 2014) included monitoring of many biofilters throughout a large area and examined their benefit at a large scale.

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