Transport of Selected Contaminants in Recycled Water through a Hawaii Soil

Leaching behavior of seven organic contaminants, including lindane, atrazine, N-nitrosodimethylamine (NDMA), estrone, 17Beta-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.