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Evaluating the potential of bank filtration to enhance groundwater resources in the Thames basin

Congress: 2008
Author(s):

Keyword(s): River bank filtration, isoproturon, biodegradation, adsorption, pesticides
AbstractThis research aims to explore the behaviour of riverbank filtration schemes towards pesticides. One of the favourable sites in the UK for researching riverbank filtration is the Thames basin (Gatehampton) where there are already existing Chalk abstraction boreholes next to the Thames. To evaluate the potential of riverbank filtration to attenuate pesticides, six glass column models have been set up in the laboratory. Two processes, biodegradation and adsorption, are being investigated as the primary factors to remove or retard contaminants. The glass columns (9 cm length x 4 cm diameter) are packed with riverbed sediment or inner material (pumice stone). River water sampled from the River Thames is circulated through the columns. The typical pesticide, isoproturon (ipu), is spiked in the river water and circulated with a flow rate 2.0 mL/min. An HPLC and SPE techniques are used to monitor the concentrations of the pesticide. The initial concentration (C0) of ipu is around 100 μg/L. With the degradation examinations, assumed that the kinetic is a first-order type. The degradation rate of ipu (kipu) is 0.0206 (h-1), and the half-life value (t1/2) is 33.6 (h). With the adsorption tests, the retardation coefficient of ipu (Rd) is 1.6 and the adsorption coefficient of ipu (K) is 0.198 (cm3/g). In general, ipu is well degradable in riverbed-sediment and river water. Using strongly simplifying assumptions, Rd and K can be used to estimate approximately the transport velocity of the retarded substances such as ipu in comparison with water flow. The results could be extended to the amine group pesticides like ipu. Overall, this project should assess the vulnerability of bankside wells to river water contaminated with pesticides and therefore enhance groundwater resources in the south of England where groundwater is a precious but limited resource.
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