Events Calendar

Fecal pollution in urban streams: ecology, transport, and policy

Speaker: Stanley Grant, University of California, Irvine

Talk Title: Fecal pollution in urban streams: ecology, transport, and policy

Abstract: Fecal indicator bacteria (FIB) are the number one cause of river and stream impairment in the
United States. In this talk I describe field and modeling studies aimed at identifying dry weather
sources of FIB in the Santa Ana River, a wastewater effluent dominated stream in southern
California. Multiple lines of evidence support the hypothesis that FIB in this stream originate
primarily from in situ growth in streambed sediments. The measured flux of FIB from the
streambed is >10 times the flux predicted from prevailing models of interfacial mass transfer
across turbulent boundary layers, but similar to the flux of water between the stream and its
hyporheic zone estimated from dye injection experiments. Thus, hyporheic exchange appears
to control the trafficking of fecal bacteria, and perhaps other types of particulate organic
matter, across the sediment‐water interface. From a policy perspective, in situ growth of FIB in
riverbed sediments may lead to a decoupling of FIB and pathogen concentrations, and thus
limit the utility of FIB as an indicator of recreational waterborne illness in southern California’s
inland and coastal waters. These results also point to a possible environmental trade‐off
associated with hyporheic zone restoration, in which increased nutrient processing by riverbed
sediments is accompanied by increased flux of FIB to the overlying water column.

Biography: Dr. Stanley Grant is a Professor in the Departments of Chemical Engineering and Materials
Science (primary) and Civil and Environmental Engineering (courtesy) at the University of
California, Irvine. Dr. Grant also has a summertime appointment as a Visiting Chair of Hydrology
and Water Resources in the Department of Civil and Environmental Engineering at the
University of Melbourne (Australia). Dr. Grant received a B.S. in Geology from Stanford
University, and M.S. and Ph.D. in Environmental Engineering Science (minor in Applied Biology)
from the California Institute of Technology. His professional interests include coastal water
quality, environmental dispersion of pathogens, and fate and transport modeling. Professor
Grant served on the US EPA’s Science Advisory Board (Drinking Water Panel, Science and
Technological Achievement Awards Panel) from 2000 to 2009.

Host: Sonny Astani Dept. of Civil and Environmental Engineering

Location: Kaprielian Hall (KAP) - 209

Audiences: Everyone Is Invited

Contact: Erin Sigman