Artificial Sweeteners Reveal Septic System Effluent in Rural Groundwater

Abstract

It has been widely documented that municipal wastewater treatment plant effluents are a major source of artificial sweeteners to surface waters. However, in rural areas, the extent to which septic systems contribute these same compounds to groundwater aquifers is largely unknown. We examined the occurrence of four commonly used artificial sweeteners in an unconfined sand aquifer that serves as a water supply for rural residents, as a receptor of domestic wastewater from septic systems, and as a source of baseflow to the Nottawasaga River, ON, Canada. Groundwater from the Lake Algonquin Sand Aquifer in the southern Nottawasaga River Watershed was collected from private domestic wells and as groundwater seeps discharging along the banks of the Nottawasaga River. Approximately 30% of samples had detectable levels of one or more artificial sweeteners, indicating the presence of water derived from septic system effluent. Using acesulfame concentrations to estimate the fraction of septic effluent in groundwater samples, ∼3.4 to 13.6% of the domestic wells had 1% or more of their well water being derived from septic system effluent. Similarly, 2.0 to 4.7% of the groundwater seeps had a septic effluent contribution of 1% or more. No relationship was found between the concentration of acesulfame and the concentration of nitrate, ammonium, or soluble reactive phosphorus in the groundwater, indicating that septic effluent is not the dominant source of nutrients in the aquifer. It is expected that the occurrence of artificial sweeteners in shallow groundwater is widespread throughout rural areas in Canada. Core Ideas Samples were collected from domestic wells and groundwater seeps in rural Ontario. Artificial sweeteners were found in >30% of rural groundwater samples. Acesulfame was used to estimate the fraction of septic effluent in groundwater. Septic effluent was not a significant source of nutrients in the aquifer.

Seasonal Variation of Water Quality in Unregulated Domestic Wells

“…While E. coli is not always correlated with pathogens or illness, its presence may indicate that there is contamination from animal and/or human feces and that there may also be enteric pathogens present in the water [64,65]. While both sucralose and E.coli likely arise from effluent discharged from septic tanks or NIWTP during the dry season, the greater concentration and presence of E.coli in the wet season is likely from additional input from animal feces in agricultural water runoff [66]. Additionally, sucralose was positively correlated with PFOS (wet season, ρ = 0.54, p -value < 0.0001), which may indicate similar sources, such as septic tank leakage or NIWTP.…”

Trace Organic Removal during River Bank Filtration for Two Types of Sediment

“…Due to high consumption rates, as well as largely unaffected passage through the human body and persistence during wastewater treatment [44,55], the artificial sweetener acesulfame is generally detected at elevated concentrations in treated wastewater [56,57] and therefore used as an indicator for wastewater influenced surface waters [58,59] and groundwater [60,61]. Presuming a low sorption affinity and recalcitrance to microbial degradation, acesulfame has formerly been proposed as an ideal anthropogenic marker [45,55,62].…”

Groundwater Seeps: Portholes to Evaluate Groundwater’s Influence on Stream Water Quality

“…A wide variety of studies have documented seeps acting as contaminant sources to rivers. Seeps and/or springs have been documented to transport nutrients (Williams et al ), pesticides (Van Stempvoort et al ), wastewater and pharmaceuticals (Humphrey et al ; Spoelstra et al ), coal combustion products (Harkness et al ), petroleum‐related compounds (Humphrey et al ), trichloroethylene (TCE) (Chapman et al ), road salts (Foos ), landfill leachate (Atekwana and Krishnamurthy ), bacteria (Fisher et al ; Baker et al ), Giardia (Rose et al ), and acid mine drainage (Brake et al ; Johnston et al ) to nearby streams and wetlands. Generally, these elevated seep contaminant inputs are related to land‐use and human activities within the seep catchment that are associated with fertilizer and manure, pesticide, coal, oil, and gas activities, waste management, wastewater, and livestock, pet, and wildlife waste.…”

“…Wastewater‐impacted groundwater and its transport to seeps can deliver pharmaceutical and personal care products to adjacent surface waters. In a recent study in the Nottawasaga River Basin, ON, Canada, Spoelstra et al () evaluated groundwater wells and seeps along the banks of the river to evaluate if wastewater from local septic systems was discharging at the seeps or present in well water. They utilized four common artificial sweeteners as tracers and found those tracers in approximately 30% of the samples.…”

“…For the seeps studied, 2 ‐ 4.7% of the seeps had a septic effluent contribution of at least 1%. This study showed that pharmaceutical and personal care products associated with onsite wastewater effluent can be transported to surface waters via groundwater seeps (Spoelstra et al ). In a similar effort in the Puget Sound watershed in WA, James et al () sampled approximately 20 seeps draining to the sound.…”