Organic Compounds in Running Gutter Brook Water Used for Public Supply near Hatfield, Massachusetts, 2003-05

Introduction

An investigation by the National Water-Quality Assessment (NAWQA) Program of the USGS characterizes the occurrence of 258 organic compounds in source water (defined as stream water collected at a surface-water intake prior to water treatment) and finished water (defined as water that has passed through treatment processes but prior to distribution) from the Hatfield Water Plant, a community water system that uses a flow-through reservoir on Running Gutter Brook as its primary source of water supply (fig. 1). Running Gutter Brook is a first-order tributary to the Connecticut River and drains a Connecticut, Housatonic, and Thames River Basins (CONN) mostly forested watershed that is adjacent to densely populated as well as sparsely populated watersheds (Rhodes and others, 2001). Running Gutter Brook is primarily fed by groundwater and by an ephemeral tributary stream, and about 1 square mile of the Running Gutter Brook watershed is upstream of the community water system intake. Discharge into the flow-through reservoir was measured as being about 1.3 million gallons per day or less during baseflow conditions. Samples were collected approximately monthly from the reservoir during 2003–05, and they included 31 source-water and 14 finished-water samples. The samples were analyzed for pesticides and selected pesticide degradates (breakdown products), solvents, gasoline hydrocarbons, disinfection by-products (DBPs), personal-care and domestic-use products, and other compounds. Community water systems are required to monitor finished water for compounds regulated under the Safe Drinking Water Act. Most of the compounds included in this study are not regulated under U.S. Environmental Protection Agency (USEPA) Federal drinking-water standards (U.S. Environmental Protection Agency, 2006). The Running Gutter Brook study is part of an ongoing NAWQA investigation of community water systems across the United States. More detailed information and references on the sampling design, methodology, specific compounds monitored, and the national study are described by Carter and others (2007). Additional USGS information on water quality in the Connecticut, Housatonic, and Thames River Basins (CONN) is available for the first cycle (1991 to 1995) of the NAWQA study (Garabedian and others, 1998).

Occurrence of Organic Compounds in Source Water

About one-tenth (26) of the 258 compounds studied were detected in at least one source-water sample. These compounds represent many different sources and uses and include pesticides, solvents, gasoline hydrocarbons, and personal-care and domestic-use products. Ten of the 26 compounds were commonly detected in source-water samples; chloroform was detected in all 31 source-water samples.

Recent advances in laboratory analytical methods have given scientists the tools to detect a wide variety of contaminants in the environment at low concentrations—typically 100 to 1,000 times lower than drinking-water standards (see inset, “What ‘Detections’ May Mean to Human Health”). Twenty-six of the compounds were detected in at least one source-water sample from Running Gutter Brook (Carter and others, 2007; Kingsbury and others, 2008).

Ten compounds were detected in at least 20 percent of the source-water samples (defined in this study as “commonly detected”; table 1). These included herbicides (atrazine and its degradates, and simazine), personal-care and domestic-use products (acetyl hexamethyl tetrahydro-naphthalene, or AHTN, caffeine, and hexahydrohexa-methylcyclopenta-benzopyran, or HHCB), a gasoline hydrocarbon (methyl tert butyl ether, or MTBE), and DBPs (chloroform and bromodichloromethane). The herbicides atrazine and simazine can be used for weed control in agricultural and residential areas in the Running Gutter Brook Watershed and across the Nation (Garabedian and others, 1998; Gilliom and others, 2006). Atrazine degradates including deethylatrazine (DEA) and deisopropyl-atrazine (DIA) also were commonly detected. The DBPs chloroform and bromodichloromethane were detected commonly in source-water samples; chloroform was detected in all of the source-water samples and may originate from the leakage of treated water from nearby supply lines. Several different personal-care and domestic-use products, including fragrances, detergent metabolites, and food or beverage ingredients, and other compounds, were detected in 47 percent of source-water intake samples. Their occurrence may be related to wastewater (Kolpin and others, 2002) from domestic septic-tank drainfields that leaches to groundwater and then discharges to Running Gutter Brook. Only about seven or eight houses are in the drainage basin and could contribute wastewater effluent to Running Gutter Brook, so the source of these compounds is unknown. Overall, the compounds detected most commonly in water from Running Gutter Brook are among those most commonly detected in ambient stream water across the Nation (Kingsbury and others, 2008).

Comparisons Between Source Water and Finished Water

Sixty percent of the compounds detected commonly in source water also were detected commonly in finished water, and generally at similar concentrations, typically less than 0.1 microgram per liter.

Comparisons between source water and finished water are not intended to characterize treatment efficacy, but to provide a preliminary indication of the potential importance of compounds found in source water to the quality of finished water prior to distribution (see inset, “Finished-Water Sampling, Water Treatment, and Significance of Comparisons to Source Water”).

Six of the 10 commonly detected compounds in source water also were detected commonly in finished water (fig. 2). Two groups of compounds in particular, DBPs and herbicides, were commonly detected in both source- and finished-water

Finished-Water Sampling, Water Treatment, and Significance of Comparisons to Source Water

samples. Chloroform was detected in all source- and finished-water samples, although concentrations in source-water samples were low, generally at less than 0.1 microgram per liter (tables 1 and 2; fig. 2).

Four of the 10 most commonly detected compounds in source water, which include MTBE and personal-care products, were not detected as commonly, or at all, in finished water. The decreased detection of these compounds in finished water may be due to reaction with the preservatives (termed “quenching reagents”) used to remove chlorine from samples (Valder and others, 2008), or possibly to sorption associated with sand filtration or degradation. An herbicide degradate, DIA, also was detected more commonly in source water than in finished water, and it too may be degraded or transformed during treatment.

Two compounds were detected commonly in finished water but not as commonly, or at all, in source water. These include a DBP, dibromochloromethane, and a solvent, 1,2-dichloroethane (table 2; fig. 2). The presence of DBPs in finished water is well documented, understood, and regulated, and is an expected outcome of disinfecting drinking water. The source of the detection of 1,2-dichloroethane is not known, but its occurrence in finished water may be a by-product of water treatment.

Figure 2. Six of the 10 compounds detected commonly in source water also were detected commonly in finished water for paired samples. Some compounds detected commonly in source water were not detected in finished water (x-axis). Other compounds were detected only in finished water (y-axis).

Although Running Gutter Brook had no major wastewater input upstream from the sampling point, DBPs and personal-care products were detected commonly in source-water samples. Possible sources include chlorinated drinking water (for example, from lawn or tree-farm irrigation or leaking supply lines), septic systems (Ivahnenko and Zogorski, 2006), and also from natural sources such as from the formation of chloroform in soils by microbial processes (Laturnus and others, 2002). Caffeine and fragrance compounds AHTN and HHCB were commonly detected; in the absence of major wastewater discharges to Running Gutter Brook, septic-tank drainfields could be a possible source. An understanding of local hydrology and sources of contaminants is needed to fully characterize the quality of source water.

Commonly used herbicides and their degradates present in Running Gutter Brook could be from applying herbicides to agricultural lands, which include an ornamental tree farm and a small residential area within the watershed. Concentrations of atrazine and other herbicides and their degradates in Running Gutter Brook were one or more orders of magnitude less than concentrations at the other community water systems sampled by the USGS that included more agricultural land use in the contributing watersheds (Kingsbury and others, 2008). Transformation can result in the conversion of a parent compound to a compound that is commonly less toxic, but some degradates have toxicities that are similar to, or greater than, that of their parent pesticide (Gilliom and others, 2006). Herbicide degradate compounds are not regulated under the Safe Drinking Water Act.

Concentrations for all detected compounds in source and finished water generally were less than 0.1 microgram per liter and were always less than human-health benchmarks, which are available for about one-half of all compounds detected. On the basis of this screening-level assessment, adverse effects to human health are expected to be negligible (subject to limitations of available benchmarks, see inset “Human-Health Benchmarks Used in This Assessment”).

Concentrations of eight compounds that were detected in source and (or) finished water (table 1) were greater than 0.1 microgram per liter (table 2). In general, compounds with concentrations greater than 0.1 microgram per liter, such as those used in personal-care products (methyl salicylate, nonylphenol diethoxylate total (NP2EO), and octylphenol monoethoxylate total (OP1EO)), reflect their abundant use in a relatively small area of urban land and their physical properties that allow them to persist in the environment (Gilliom and others, 2006; Zogorski and others, 2006). Concentrations did not exceed USEPA drinking-water standards (MCLs) for regulated compounds (table 2) in any sample. Concentrations also were less than USGS Health-Based Screening Levels (HBSLs) established for selected unregulated compounds (see inset, “Human-Health Benchmarks Used in This Assessment”).

An important consideration in assessing potential effects for human health is the common occurrence of mixtures of organic compounds in source- and in finished-water samples. For example, the median number of compounds in source-water samples at Running Gutter Brook was 5. This is comparable to findings at community water systems on streams sampled by the USGS that drain relatively undeveloped watersheds (Kingsbury and others, 2008). Continued research is needed because human-health benchmarks are based on toxicity data for individual compounds, and the effects of mixtures of compounds at low concentrations are not well understood (Gilliom and others, 2006).

Human-Health Benchmarks Used in This Assessment Running Gutter Brook Findings in a National Context and Possible Implications

Many of the compounds detected most commonly in water from Running Gutter Brook (tables 1 and 2) are among those most commonly detected in ambient stream water and groundwater across the Nation (Gilliom and others, 2006; Zogorski and others, 2006). In addition, the occurrence and concentrations of compounds in source and finished water sampled from Running Gutter Brook were similar to those detected at other community water systems sampled for the USGS national investigation of rivers that do not receive any major upstream wastewater discharge and that drain relatively small areas of agricultural and urban land (Kingsbury and others, 2008). Findings in a national context, however, are considered preliminary because some compounds included in this study have only recently been monitored systematically in source and in finished water, including, for example, plant- or animal-derived biochemicals (such as cholesterol) and those used for personal-care, including AHTN, HHCB, caffeine, camphor, indole, methyl salicylate, menthol, NP2EO, OP2EO, and OP1EO. Continued research is needed to better understand sources, transport mechanisms, trends, fate in the environment, and possible linkages of these compounds to human health.

USGS will continue to collaborate with, and complement the work of, other Federal, State, and local organizations, and continue to communicate findings and possible implications and future needs, including, for example:

• Increased emphasis on watershed management and source-water protection strategies to help minimize the sources and transport of compounds to source water and ultimately to finished water.
• Continued research to enhance toxicity information for commonly occurring unregulated compounds and mixtures that are detected commonly in source water and finished water.
• Current and future monitoring and assessment to identify compounds not typically monitored in source water, but commonly present in finished water, which may ultimately identify or lead to the development of treatment technologies for their removal.

References Cited

By Craig J. Brown and Thomas J. Trombley

USGS Promotes Public Access to Water-Quality Information

For additional information contact

Craig Brown, U.S. Geological Survey, (860) 291-6766, cjbrown@usgs.gov

Greg Delzer, U.S. Geological Survey, SWQA Coordinator, (605) 394-3230, gcdelzer@usgs.gov

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