Riverbank Filtration in the Platte River

Our study will assess bank filtration of selected endocrine disruptors at an established bank-filtration well field, including collector wells. The period of study of bank filtration at the well field will be placed in context with the natural variability in the hydrologic system through use of existing information. The study will examine riverbank-filtration efficiency at three sites in the well field in support of the development of regulatory approaches and guidelines about this natural treatment process. Variables to be considered include ground- water travel times, distances from river to well, tracer velocities (including effect of pumping rates), hydraulic conductivities, and physicochemical characteristics. In the evaluation of the data, consideration will be given to watershed characteristics such as point sources of anthropogenic contamination that may be located upstream of the well field.

The study will focus on the removal/attenuation of emerging contaminants such as endocrine disruptors and selected pesticides through bank filtration with emphasis on collector wells. Occurrences of endocrine disruptors including pharmaceuticals and selected pesticides on the USEPA Contaminant Candidate List in raw and bank-filtered water also will be evaluated. Study results will be compared to results of similar studies conducted at selected European sites. Natural variability in climate and hydrologic processes plays a role in the relation of surface and ground water. Changes in these hydrologic processes may have an effect on bank filtration. The study completed at the established bank- filtration will field will be placed in a longer-term hydrologic context. Examination of records of stream flow from existing U.S. Geological Survey stream-gaging stations and any existing data on ground-water levels in the vicinity of the well field will be used to determine where the period of study falls on a natural gradient between wetter and drier conditions.

Relevance and Impact

The study results can be used by USEPA to aid in the development of standardized protocols to evaluate bank-filtration efficiency as a drinking water treatment technique. The report also can be used as a general concept document of protocol to aid in the development of feasibility studies for municipalities interested in bank filtration as a treatment technique. Moreover, USEPA can use these data and interpretations to perform additional analyses, such as risk assessments.

The proposed project addresses five priority resources issues of the USGS-WRD strategic plan: surface-water and ground-water interactions as related to water-resource management (river-bank filtration to wells under the influence of surface-water); effects of climate on water-resource management (changes in flow and water-quality related to rainfall and stream flow); effects of urbanization and suburbization on water resources; drinking-water availability and water quality (effect of these releases on drinking-water quality and consequent effect on availability of a potable drinking-water supply); and waste isolation and remediation of contaminated environments (evaluation of the effectiveness of river-bank filtration as a pre-treatment method and more conventional treatment methods in a drinking-water treatment plant in an environment contaminated by waste). The findings of this study can be used by cities nationwide and worldwide to increase water-resources manager's knowledge about when, to what extent, and to which contaminants water supplies could be vulnerable given natural bank filtration and the treatment methods used. It also will provide information about bank-filtration efficiency under a variety of conditions.

Strategy and Approach

The City of Lincoln, Nebraska, well field has instrumentation (such as pressure transducers, hydrolabs), hydrologic background information, and good estimations of travel times and tracer velocities. Representative water samples will be collected from surface water, ground water, bank-filtered or pretreated water (or production wells of concern), untreated water, and treated water (5-9 subsites). Samples will be collected bi-weekly or monthly during base- or moderate-flow conditions of surface-water sites. Water samples also will be collected during differing flow conditions form all subsites, including a spring-runoff event, a summer-runoff event, and a fall-runoff event. In addition, integrated representative samples for all analytes will be collected biweekly, bimonthly, or quarterly form the Platte River to evaluate changes in concentrations and loading over time depending on the analyte. The pumping regime will reflect normal pumping scenarios during all collection times. Water samples from four point sources, two wastewater-treatment plants located upstream and two confined animal feeding operations (CAFO), also will be collected during a summer high-flow and a summer, fall, and spring base-flow event at each study site. During a summer base-flow event, five different pumping regimes will be used to evaluate the effect of pumping rates on removal of contaminants. Variables measured for the water samples will include pH, temperature, specific conductance, turbidity, total or dissolved organic carbon (TOC or DOC), microscopic particulate analyses (MPA), human tracers and endocrine disruptors [(cholesterol, caffeine, triclosan, estrogens, and 3B-coprostanol), EDTA, and 23 pharmaceuticals], major ions, selected herbicides and metabolites, as deuterium and oxygen isotopes. During one high- and one base-flow event the point sources (WWTP and CAFO) also will be sampled.

Published Reports

Data Series 117
Data Series 133
Data Series 141

Contact

Jason R. Vogel
U.S. Geological Survey
5231 South 19th Street
Lincoln , NE 68512-1271
(402) 328-4130

Keywords

riverbank filtration, Platte River, endocrine disrupting compounds, pharmaceuticals, stable isotopes, Giardia, Cryptosporidia, surrogate

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