Spatial and Temporal Scaling of Biofilter Media Performance Data and Updates to WinSLAMM


Robert Pitt, Emeritus Professor of Urban Water Systems, The Department of Civil, Construction, and Environmental Engineering, The University of Alabama

Thursday, October 21, 2021 - 10:00am


There are many publications reporting the performance of isolated stormwater controls, but relatively few that have examined how the use of many of these controls function at larger scales and for long periods of time. Researchers, stormwater managers and regulators need to know answers to such questions as:

  • Are source area distributed controls effective in reducing outfall discharges?
  • Can results from small-scale laboratory and pilot-scale field experiments be up-scaled to large, long-term installations?
  • How robust are stormwater controls for extended periods?
  • How do local groundwater conditions affect bioretention performance, and what is the potential for groundwater contamination?

This presentation summarizes the results from several research projects that I and my students have been involved with that address scaling issues and these questions. Specifically, we have found that carefully conducted small-scale and short-term laboratory and pilot-scale tests can be useful when extrapolated to full-scale installations. These tests need to use actual stormwater and the tests need to be conducted in a manner that accurately represent expected conditions. Obviously, scaling up these results are also highly dependent on the amount of the stormwater directed to the controls. Small “hot spots” need priority treatment, but since they usually only represent small runoff amounts, moderately contaminated areas representing greater amounts of the runoff are also usually needed for effective watershed-scale benefits. Also, unintended consequences of large-scale implementation of infiltration may adversely affect the local groundwater, and/or poorly understood local soil and groundwater conditions may adversely affect the performance of the stormwater controls.

These projects have primarily used media treatment and infiltrating stormwater controls (usually in conjunction with other supporting unit processes). These data have been used to support on-going updates to WinSLAMM, the Source Loading and Management Model. Example production functions developed using WinSLAMM are also presented indicating how these design curves can be used for preliminary sizing of media treatment controls for local conditions.

bob pitt

Speaker bio: Bob Pitt is the Emeritus Cudworth Professor of Urban Water Systems in the Department of Civil, Construction, and Environmental Engineering at the University of Alabama. Prior to his academic career, Pitt was a senior engineer in industry and government. He has conducted research concerning the effects, sources, and control of urban runoff and has written more than 100 publications, including journal articles, book chapters, research reports, and several books. He is a registered Engineer (WI), a Board-Certified Environmental Engineer by the American Academy of Environmental Engineers, and a Diplomate of the American Academy of Water Resources Engineers. He has served on numerous professional committees in the U.S. and abroad. He and his graduate students have conducted research on integrating green infrastructure controls in combined sewer areas; construction site erosion characterization and control, characterization and treatment of emerging contaminants in wet weather flows; stormwater treatment using media filtration; urban PAH sources and fates in marine waters; heavy metal releases from drainage system components; groundwater impacts from stormwater infiltration; beneficial uses of stormwater in times of changing weather; sources and fate of indicator bacteria in urban areas; and continued work on enhancements to the Source Loading and Management Model (WinSLAMM).