Seminar on Potential of Riverbank Filtration for Water Supply in the United States
Date: 15 May, 2013 (Wednesday)
Time: 13:00-14:30hrs
Venue: E220
By:
Chittaranjan Ray
Professor of Civil & Environmental Engineering
Interim Director, Water Resources Research Center
University of Hawaii, Honolulu, Hawaii, USA
e-mail: cray@hawaii.edu
Abstract:
Riverbank filtration (RBF) is a low-cost drinking water treatment technology that has been used
for over a century in Europe and more than 50 years in the United States. The RBF systems use a
combination of vertical and horizontal wells, located on riverbanks, to induce the river water to
flow towards them. The pumped water is a mixture of infiltrated river water and ground water
present in the alluvial aquifer. The quantity of surface water that infiltrates and reaches the RBF
wells depends on local geology, streambed characteristics, well type and pumping stresses, and
the distance of the wells from the riverbank. During the pumping process, dissolved and
suspended contaminants from the surface water are removed by the porous media due to
biogeochemical reactions, microbial degradation, straining, and colloidal filtration. Further, if the
respective contaminants have lower concentrations in the alluvial aquifer, dilution is possible.
While a number of small-capacity RBF systems (with vertical wells some distance away from
the river) do not further treat the filtrate except for disinfection, most large-capacity systems use
RBF as a pre-treatment. At present, the USEPA is allowing 0.5 to 1.0 log-removal credit for
Cryptosporidium to treatment systems that employ RBF as pre-treatment depending on the
distance of the intake point of the well with respect to the streambed or high water level in the
river. This has prompted renewed interest in RBF for drinking water production in the United
States. Many other countries in Asia, including China, India, India, Vietnam, and Thailand have
tremendous potential to use RBF for water supply. In India, it is gaining increasing popularity as
the rivers are becoming increasingly polluted.
In this presentation, we will discuss the site suitability for RBF, potential production capacity,
and market growth in the United States. We will also review the operational efficiency of RBF
systems to remove pathogens, microscopic particulates, and other dissolved chemicals from a
variety of studies. Then, we will discuss site hydrogeology and well construction/placement
factors for optimal operation of RBF systems. We will pose the research issues that need to be
addressed. Finally, we will present summaries of modeling studies dealing with biogeochemical
processes involved in riverbank filtration and pathogen filtration.
Brief resume of Prof. C. Ray
Dr. Chittaranjan Ray is a Professor in Department of Civil and Environmental Engineering at the
University of Hawaii, and Interim Director of the University’s Water Resources Research
Center. He is also the Chief Environmental Engineer of the Applied Research Laboratory (of the
US Navy) at the University of Hawaii. He is a fellow of the American Society of Civil
Engineers. Dr. Ray holds a doctoral degree in Civil Engineering from the University of Illinois at
Urbana Champaign. Dr. Ray worked as a staff engineer in the firm of Arcadis Geraghty& Miller
prior to pursuing his doctoral degree where he gained significant experience in remedial
investigation of contaminated sites. He was also employed as a scientist at the Illinois State
Water Survey prior to taking an academic job with the University of Hawaii in 1997. Dr. Ray’s
research focuses on the impacts chemicals and pathogens on ground water surface water, water
quality assessment, and surface and ground water interaction in the context of water supply. Dr.
Ray advises the Hawaii Department of Agriculture on the leachability of new chemicals for their
registration of the state of Hawaii. He has worked extensively in the Pacific Rim countries on
topics such as riverbank filtration for water supply and development of low-cost water treatment
systems for emergency use during disasters. He has received competitive funding from the
Department of Defense, USDA, EPA, NSF, NATO, USAID and other agencies for various water
and environmental related projects. Currently, he is in the editorial board of the journal Clean
Technology and Environmental Policy and he serves as an Associate Editor of the journal
Irrigation and Drainage Engineering.