Chittaranjan Ray

Clogging-Induced Flow and Chemical Transport Simulation in Riverbank Filtration Systems

Riverbank filtration is a low cost treatment technology which is effective in removing various chemical, and biological contaminants from the surface water. In the United States, utilities that employ horizontal collector wells, have reported clogging of the riverbed in vicinity of the wells, particularly around the laterals that go toward the river. In this paper, we show the impact of clogging and associated reduction in leakage on flow and transport simulations.

Polymer effect on soil erosion reduction and water quality improvement for selected tropical soils.

Screening tests were performed using two negatively charged and one positively charged polymers on fourHawaiian soils (an Oxisol, a Vertisol, and two Aridisols, collected from the Islands of Oahu, Molokai, andHawaii) to examine erosion reduction and water-quality improvement. These soils present a degree of contrastin terms of their physical and chemical properties. A laboratory-scale rainfall simulator was used to producerainfall at intensities between 5.5 and 7 cm h -1. The polymers were applied in various forms and amounts to drysoil and the effects of consecutive rainfall events were evaluated. The impact of polymer on particle settling wasalso evaluated for many of these soils. Overall, there was substantial reduction in soil loss for soils treated withthe polymer, as well as enhanced settling of dispersed soil solutions.

Transport of selected contaminants in recycled water through a Hawaii soil

Leaching behavior of seven organic contaminants, including lindane, atrazine, Nnitrosodimethylamine (NDMA), estrone, 17�-estradiol, octylphenol, and nonylphenol, found in the wastewater of a treatment plant in Honolulu were evaluated for leaching in an Oxisoil (a red soil with high iron oxide content) of Oahu using both batch sorption and packed soil column experiments. Soils from two depths (0.6 m and 3.9 m) were used for the study. Two column leaching experiments were conducted using a solution of the contaminants in an artificially created ground water (deionized water with small concentrations of calcium chloride) and treated wastewater. The breakthrough curves obtained from the column experiments were used in inverse numerical modeling (HYDRUS 1D) to obtain the transport parameters for the column experiments. Sorption characteristics of each compound were obtained through batch sorption studies with different controlling parameters such as pH, ionic strength, and organic carbon content. The results of the experiments indicated that NDMA possessed the maximum potential to leach through the tested soil. Both atrazine and lindane showed moderate leaching properties. The estrogenic and the phenolic compounds were strongly adsorbed to the soil and were retained in the columns. Transport parameters obtained from the column study will be applied to the field setting to determine the arrival time and extent of contamination of ground water where widespread irrigation with wastewater over potable water aquifers to be practiced. Increases in leaching under different controlling parameters (pH, ionic strength, etc.) will also provide additional information about leaching potential.