title: Fate of trace organic compounds during vadose zone soil treatment in an onsite wastewater system.
abstract: During onsite wastewater treatment, trace organic compounds are often present in the effluents applied to subsurface soils for advanced treatment during vadose zone percolation and groundwater recharge. The fate of the endocrine-disrupting surfactant metabolites 4-nonylphenol (NP), 4-nonylphenolmonoethoxylate (NP1EO), and 4-nonylphenolmonoethoxycarboxylate (NP1EC), metal-chelating agents ethylenediaminetetraacetic acid (EDTA) and nitrilotriacetic acid (NTA), antimicrobial agent triclosan, stimulant caffeine, and antibiotic sulfamethoxazole during transport through an unsaturated sandy loam soil was studied at a field-scale test site. To assess the effects of effluent quality and hydraulic loading rate (HLR) on compound fate in the soil profile, two effluents (septic tank or textile biofilter) were applied at two design HLRs (2 or 8 cm/d). Chemical concentrations were determined in the two effluents and soil pore water at 60, 120, and 240 cm below the soil infiltrative surface. Concentrations of trace organic compounds in septic tank effluent were reduced by more than 90% during transport through 240 cm (often within 60 cm) of soil, likely due to sorption and biotransformation. However, the concentration of NP increased with depth in the shallow soil profile. Additional treatment of anaerobic septic tank effluent with an aerobic textile biofilter reduced effluent concentrations of many compounds, but generally did not affect any changes in pore water concentrations. The soil profile receiving septic tank effluent (vs. textile biofilter effluent) generally had greater percent removal efficiencies. EDTA, NP, NP1EC, and sulfamethoxazole were measured in soil pore water, indicating the ability of some trace organic compounds to reach shallow groundwater. Risk is highly dependent on the degree of further treatment in the saturated zone and the types and proximity of uses for the receiving groundwater environment.
authors.affiliation: Environmental Science and Engineering Division, Colorado School of Mines, 206 Coolbaugh Hall, Golden, Colorado 80401.
authors.forename: Kathleen E
authors.initials: KE
authors.lastname: Conn
authors.affiliation: Environmental Science and Engineering Division, Colorado School of Mines, 206 Coolbaugh Hall, Golden, Colorado 80401.
authors.forename: Robert L
authors.initials: RL
authors.lastname: Siegrist
authors.affiliation: U.S. Geological Survey, 3215 Marine Street, Boulder, Colorado 80303.
authors.forename: Larry B
authors.initials: LB
authors.lastname: Barber
authors.affiliation: U.S. Geological Survey, 4821 Quail Crest Place, Lawrence, Kansas 66049.
authors.forename: Michael T
authors.initials: MT
authors.lastname: Meyer
mesh_terms: D005618:Fresh Water / Q000032:analysis*; D009930:Organic Chemicals / Q000032:analysis*; D012989:Soil Pollutants / Q000032:analysis*; D014865:Waste Disposal, Fluid; D014874:Water Pollutants, Chemical / Q000032:analysis*; D018508:Water Purification
chemical_list: D009930:Organic Chemicals; D012989:Soil Pollutants; D014874:Water Pollutants, Chemical
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