Environ. Sci. Technol. 2008, 42, 2805–2811
Fate of Pharmaceutical and Trace Organic Compounds in Three Septic System Plumes, Ontario, Canada CHERILYN CARRARA,† C A R O L J . P T A C E K , * ,† WILLIAM D. ROBERTSON,† DAVID W. BLOWES,† M I C H A E L C . M O N C U R , †,‡ ED SVERKO,‡ AND SEAN BACKUS‡ Department of Earth Sciences, University of Waterloo, 200 University Ave W., Waterloo, ON, N2L 3G1, and Environment Canada, 867 Lakeshore Rd., P.O. Box 5050, Burlington, ON, L7R 4A6
Received February 10, 2007. Revised manuscript received January 4, 2008. Accepted January 10, 2008.
Three high volume septic systems in Ontario, Canada, were examined to assess the potential for onsite wastewater treatment systems to release pharmaceutical compounds to the environment and to evaluate the mobility of these compounds in receiving aquifers. Wastewater samples were collected from the septic tanks, and groundwater samples were collected below and down gradient of the infiltration beds and analyzed for a suite of commonly used pharmaceutical and trace organic compounds. The septic tank samples contained elevated concentrations of several pharmaceutical compounds. Ten of the 12 compounds analyzed were detected in groundwater at one or more sites at concentrations in the low ng L-1 to lowµgL-1 range.Largedifferencesamongthesiteswereobserved in both the number of detections and the concentrations of the pharmaceutical compounds. Of the compounds analyzed, ibuprofen, gemfibrozil, and naproxen were observed to be transported at the highest concentrations and greatest distances from the infiltration source areas, particularly in anoxic zones of the plumes.
Introduction Wastewater is a major source of pharmaceutical compounds and their metabolites to the environment because they often pass through the human body and are excreted into the environment at elevated concentrations (1, 2). Often, these compounds are not effectively removed by wastewater treatment processes and have been detected in sewage treatment plant effluents in many parts of the world (3–5). In suburban and rural areas, wastewater is often treated using on-site treatment systems such as septic systems. In North America, on-site wastewater disposal systems account for the largest volume of contaminated water discharged to the subsurface (6). In the United States, this volume equates to approximately 3.8 trillion L a- (7). Septic system plumes can extend tens to hundreds of meters downgradient of tile beds and are often tens of meters wide and several meters thick (8, 9). Frequently, areas that rely on septic systems also * Corresponding author e-mail:
[email protected]. † University of Waterloo. ‡ Environment Canada. 10.1021/es070344q CCC: $40.75
Published on Web 03/05/2008
2008 American Chemical Society
rely on local water wells as a drinking water source. In a recent study in Nebraska, 13 of 26 wells examined showed evidence of contamination of drinking water by septic waste (10). Few studies have been conducted to assess the potential for septic systems to release pharmaceutically active compounds (PhACs) into the environment. Godfrey et al. (11) detected 18 of 22 drugs studied in septic tank effluent in Montana, and Swartz et al. (12) observed transport of caffeine, estrogens, and other PhACs in groundwater up to 6 m down gradient of septic system leachate pits. Conn et al. (13) detected several PhACs at concentrations in the 10s of µg/L range in wastewater collected from residential and nonresidential on-site treatment systems. The current study involves a detailed sampling program carried out at three septic system sites in Ontario, Canada. Samples from septic tanks, groundwater directly below the tile beds, and groundwater downgradient from the tile beds, including groundwater from areas in different oxidation–reduction zones, were collected from each site to assess the fate and transport of 11 drugs and 1 antiseptic (Table 1), in the subsurface in relation to geochemical conditions. The occurrence of the selected compounds has been studied previously (Table 1), but not in a manner to allow direct comparison of within- and between-site transport potential. Chemical structures and CAS numbers are available in the Supporting Information (Table SI-1). Site Descriptions. The Point Pelee study area is located within Point Pelee National Park near Leamington, Ontario (Table 2). This park receives approximately 500 000 day visitors per year, primarily between April and October. One of the highest volume tile beds in the park was selected for study. This tile bed has a dosing pump that feeds wastewater from a septic tank to a distribution bed which discharges directly into a 7 m thick medium-coarse-grained sand unit. The water table is approximately 2 m below the distribution lines. A dense clay unit underlies the sand unit. Samples were collected from a previously installed monitoring network of bundle piezometers (9, 14). The tile bed was in use for over 20 years, and because of heavy loading rates, wastewater has penetrated the entire thickness of the sand unit, and has spread in all directions from the infiltration bed above the clay unit (14). The Long Point study area is located in Long Point Provincial Park, on the north shore of Lake Erie near Port Rowan, Ontario (Table 2). The tile bed services approximately 200 campsites which operate in the summer only. The tile bed is installed directly into a fine-medium-grained sand unit. Groundwater flow is generally southward, but at times when loading rates are high, the water table mounds below the tile bed, resulting in flow in all directions from the infiltration pipes (15). Samples for this study were collected from a previously installed monitoring network (16). The Canadian National Institute for the Blind Lake Joseph Centre is located near MacTier, Ontario (Table 2). The seasonal campground services approximately 2000 guests annually. The tile bed, installed in a medium-grained sand unit, has been in use for over 10 years, and samples for this study were collected from a network of previously installed piezometers (17). The septic system plume is migrating southward, toward Lake Joseph.
Materials and Methods Field Methods. Sampling locations for each site were selected based on the results of previous studies, with samples taken from the most concentrated area of the plume, at varying depths and distances from the tank, and in different VOL. 42, NO. 8, 2008 / ENVIRONMENTAL SCIENCE & TECHNOLOGY
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TABLE 1. Summary of Previous Research on the 12 Pharmaceutical Compounds Evaluated in Septic Tank and Groundwater Systems in This Study presence in groundwater/septic systems
compound
pKa
Kow
clofibric acid
2.84
2.57
• detected in deep groundwater up to 290 ng/L (22) • nearly conservative transport in column experiment (24) • mobile in leaching experiments (25) • detected up to 7300 ng/L near contaminated surface waters (3)
ibuprofen
4.9
3.79
• attenuated in soils (25) • observed in groundwater up to 200 ng/L (26)
salicylic acid
2.98
2.24
• observed in groundwater up to 1225 ng/L at bank infiltration site (3)
gemfibrozil
n/a
4.77
• observed in groundwater up to 340 ng/L at bank filtration site (3)
fenoprofen
7.3
3.9
• analyzed for, but not detected in septic tanks (11)
naproxen
4.15
3.18
• no data available
triclosan
7.9
4.66
• detected in the most concentrated area of a landfill leachate plume at 210 ng/L (27)
ketoprofen
4.8
3.0
• observed in groundwater up to 30 ng/L at bank filtration site (3) • detected in 1 of 12 septic tanks in the ng/L range (11)
diclofenac
4
4.02
• detected in deep groundwater up to 50 ng/L (22) • retarded in column experiments (Rf ) 2) (24) • observed in groundwater near contaminated surface water up to 380 ng/L (3)
indomethacin
4.5
4.27
• no data available
bezafibrate
3.6
4.25
• no data available
fenofibrate
n/a
5.19
• observed in groundwater up to 45 ng/L (26)
geochemical zones of the plume. Water samples were collected from septic tanks and piezometers using dedicated tubing. 2806
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Measurements of Eh, pH, alkalinity, and dissolved O2 and H2S were made in the field following standard procedures (18). Water samples were collected for laboratory analysis of CH4, Fe, Mn, Cl, SO4, nitrate (NO3sN), and ammonia (NH3sN). Samples for pharmaceutical analyses were collected in 1 L amber glass bottles, and acidified to pH < 2 with 18 N H2SO4. All groundwater samples were filtered with 0.45 µm cellulose-acetate filters, and septic tank samples from Long Point were also filtered. All samples were refrigerated until analysis. Analytical Methods. Samples were analyzed for trace metals using inductively coupled plasma optical emission spectrometry (ICP-OES) and for dissolved concentrations of Cl and SO4 using ion chromatography. Concentrations of NO2, NO3, NH3, PO4, and DOC were determined using automated colorimetric procedures. Pharmaceutical compounds and triclosan were extracted from the samples using a method accredited by the Canadian Association of Environmental Analytical Laboratories according to the International Standard Organization criteria 17025 (19). The procedure involved liquid/liquid extraction with dichloromethane as the solvent. The extract was evaporated, and the analytes derivitized by heating the residue with 5% (v/v) pentafluorobenzyl bromide (PFBBr), to form PFB esters. Silica gel columns were used for sample cleanup. The PFB esters were eluted and measured using gas capillary chromatography with negative ion chemical ionization-mass spectrometry detection (GC-NICIMS) (19). Recovery of the target compounds using this analytical procedure was assessed by spiking groundwater samples with the complete suite of the target compounds plus four isotope labeled surrogate compounds. The groundwater used for these analyses was collected from the plume core (bundle location 121, 1 m depth) and from two of the most contaminated downgradient locations (bundle locations 124 and 138, 1 m depth) from the Long Point site, the most contaminated of all sites investigated (Supporting Information Table SI-2, Figure 2). All groundwater samples were collected and analyzed in duplicate. Recoveries for all of the target compounds, with the exception of salicylic acid, were between 90 and 128%. For salicylic acid, recoveries were substantially lower, ranging from 44 to 62%, indicating greater errors associated with quantification of this compound. The four isotope labeled surrogates also showed good recoveries (Table SI-2). In addition to this recovery study, duplicate external standards and a laboratory blank were analyzed together with each set of 12 field samples using the same procedure (Table SI-3). The laboratory blank consisted of double deionized water, and the external standard consisted of double deionized water spiked with 50 ng/L of each target compound, both analyzed using the complete procedure. These analyses resulted in mean recoveries between 79 and 104%. For each field sample, an isotope labeled surrogate standard, d3-ibuprofen, was added prior to extraction. Sample recoveries of d3-ibuprofen were between 70 and 130% for 75% of the groundwater samples (Tables SI-4 to SI-6). For the remaining 25% of groundwater samples, the recoveries of d3-ibuprofen were more variable (Tables SI-4 to SI-6). Method detection limits reported are based on instrument signal-to-noise ratio only. For the septic tank samples, which were subjected to a prestep using Waters Oasis HLB cartridges according to Lee et al. (20), sample recoveries of d3-ibuprofen were poor (20%). Recoveries of the suite of unlabeled spike standards were also poor (ranging from 0 to 35%). The poor recoveries observed in the tank samples, in comparison to the good recoveries observed for the groundwater samples, may be due to the additional step in the analytical procedure or to the tank matrix. The reported concentrations for the target compounds were
TABLE 2. Properties of the Aquifer and Septic System at the Study Sitesa Point Pelee
Long Point
Lake Joseph
aquifer properties
unconfined poorly sorted med-coarse grained calcareous
unconfined homogeneous med. grained calcareous
unconfined homogeneous med. grained noncalcareous
% foc wt. % CaCO3 surface area (m2 g-1) septic effluent groundwater flow rate (m a-1) effluent discharge rate (L a-1) area of tile bed (m2) effluent loading rate (L m-2 a-) population served seasonal use depth to water table (m)
0.10 34.5 1.07 blackwater 10–60 3 600 000 800 4500 >100 000 visitors day–1 year-round 2
0.06 18.5 0.56 blackwater and graywater 40 2 300 000 260 8800 200 campgrounds seasonal 1.5
a
not available
