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.

Correlation of trace contaminants to wastewater management practices in small watersheds

“…2C). 44 The correlation between antimicrobial concentrations and detection frequencies and septic density observed in this study can be attributed to the low detection limits, 0.11 ng L À1 for triclosan and 0.32 ng L À1 for triclocarban, and the high usage rates. This site had the highest measured concentration, which was detected following initiation of excavation near the collection site.…”

Functional diversity changes of microbial communities along a soil aquifer for reclaimed water recharge

“…Humic acids, fluvic acids and certain trace pollutants (i.e. sulfamethoxazole and EDTA) are reported as refractory compounds, possibly producing these results (Drewes & Jekel, 1998;Conn et al, 2010;Maeng et al, Fig. 3.…”

“…sulfamethoxazole and EDTA) are reported as refractory compounds, possibly producing these results (Drewes & Jekel, 1998;Conn et al, 2010;Maeng et al, Fig. First, the continuous presence of certain carbon sources is required in the recharged water, meaning that such carbon sources are refractory.…”

Emerging Contaminants

“…The ecosystem and human-health risks associated with exposure to environmental concentrations of biologically active ECs are not known. Groundwater, especially in shallow unconfined aquifers, is vulnerable to contamination from many sources, including onsite wastewater disposal systems (Conn et al, 2006(Conn et al, , 2010Swartz et al, 2006;Stanford and Weinberg, 2010), which serve 420% of US households and 440% of residences in nine eastern US states (USEPA, 2002;U.S. In 2010, 42% of US community water supplies (serving 89 400 000 people) had groundwater sources (USEPA, 2013), and approximately 12% of US housholds depend on private wells for drinking water (US Census Bureau, 2011).…”