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From Source Water to Drinking Water: Workshop Summary Abstracts THE INTERFACE OF SCIENCE AND POLICY: ARE THE CURRENT POLICIES ABLE TO MEET CURRENT AND FUTURE CHALLENGES? Fred Pontius To address the question of whether current policies are able to meet current and future challenges, we must first consider how we got to where we are and the forces that have shaped current drinking water regulation. Drinking water regulations are set by the U.S. Environmental Protection Agency (EPA) under the Safe Drinking Water Act (SDWA), enacted in 1974. Since that time, the SDWA has undergone several reauthorizations, resulting in major changes in the way contaminants are regulated. In addition, the number of contaminants regulated has increase to 92—some are regulated with a maximum contaminant level (MCL) and some with a treatment technique, but all have a nonenforceable health goal, the maximum contaminant level goal (MCLG). The scientific basis of and policy choices involved in regulating drinking water quality in the United States have changed as our experience has increased and as the SDWA has changed. In many respects, we are still adjusting as a society to recent policy shifts instituted by the SDWA amendments of 1996. The following key questions are discussed in this presentation, focusing on how science and policy choices have progressed over the years and whether current approaches can meet future challenges:
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From Source Water to Drinking Water: Workshop Summary How should contaminants be selected for regulation? How should MCLGs be established? How should MCLs be established? What constitutes the best science? What should be the role of source water protection? How can compliance be ensured? Since enactment of the SDWA in 1974, great progress has been made in drinking water quality and regulation in the United States. It seems now that only the most difficult issues remain—protecting sensitive populations, achieving sustainable water systems, providing affordable drinking water for small systems, avoiding risk-risk trade-offs, and controlling emerging waterborne pathogens, to name a few. The need for creative thinking and innovation in drinking water science, policy, regulation, and legislation has never been greater. ARE RECENT ADVANCES IN SCIENCE AND TECHNOLOGY ABLE TO MEET THE HEALTH CHALLENGES OF PROVIDING SAFE DRINKING WATER? Jeffrey K.Griffiths Narrowly, the provision of safe drinking water is dependent upon being able to (1) recognize the health risk of hazardous substances or microbes present in drinking water, (2) monitor drinking waters for the presence of these hazards, and (3) remove these hazards. Challenges to providing safe drinking water include a diminishing supply of usable water, often most acute in areas with rapidly growing populations; an increasing need to reuse wastewaters that include sewage and industrial contaminants; and the demographic constraint of an aging population with increased relative susceptibility to drinking water contaminants. Specific populations, such as people with HIV infection or AIDS, are especially sensitive to emerging pathogens that were essentially not recognized in the pre-AIDS era. Predictions regarding climate change strongly suggest that less water will be available over time in multiple regions of North America. Industrial food production, via concentrated animal feeding operations (CAFOs), is increasingly cited as a source of animal pathogens that place humans at risk of zoonotic infection. Industrial production of novel chemical contaminants through
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From Source Water to Drinking Water: Workshop Summary manufacturing also is increasing. These factors all conspire to increase the health risks that may be associated with drinking water consumption. The study of modern health hazards in drinking water is a field in crisis, with an acute need for novel ways to study the population. Traditional epidemiological study methods are confounded by the mobility of the population and by difficulties in exposure assessment. It is hard to know what a person’s integrated exposure is to drinking water contaminants that vary over time and space and how to assign a risk to a specific compound when a person is exposed to many of them. In addition, surveillance of the population is keyed to outbreaks of classical diseases, not to the detection of low-level or endemic emerging diseases. Fresh methods for monitoring the health of the community, such as those that look at population-wide outcomes and integrate exposures over time and space, are needed. Examples of such approaches are given here. At the laboratory level, drinking water hazards are usually studied via a reductionist model. In this approach, individual compounds are studied in the absence of their actual context (e.g., as part of the chemical soup, however weak or strong) in which they are found. It seems increasingly unlikely that resources will be available to test every new compound that can be found in drinking water, to say nothing of the combinations that exist. Reflecting this reductionist model, the regulatory structure that exists regulates chemicals on a compound-by-compound basis. Research into the health hazards of compounds is often driven by regulatory interest, yet our scientific infrastructure is unlikely to be able to test the thousands of new compounds that are produced each year. New scientific approaches and paradigms are needed that recognize these realities. Monitoring drinking water for chemical contaminants is difficult for a variety of reasons. For example, many compounds are present at such low concentrations that detection via standard methods is difficult. Furthermore, specific analytical techniques for the tens of thousands of chemical contaminants found in drinking water simply do not exist. Analytical techniques for the detection of pathogens in drinking water are primitive, relying almost solely on classical culture techniques. We now understand that conventional water treatment does not remove all risk of pathogen transmission. Chlorination-resistant organisms such as Cryptosporidium remain important risks for immunocompromised populations and for the general population when other measures such as filtration are weak or when they fail. Evolving technologies that involve water con-
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From Source Water to Drinking Water: Workshop Summary centration, advanced chromatographic methods, and genomic recognition may prove extremely helpful. Advanced treatment modalities such as ultraviolet irradiation, activated charcoal absorption, and membrane filtration of water may provide a broad, blanket form of water treatment to inactivate or remove infectious organisms and chemicals, but their costs are perceived as primarily affordable only for systems that serve large populations. In sum, new scientific methods for the study of health risks in the population are needed, as are advanced monitoring and analytical methods. Water treatment technologies are not completely protective of the population and current advanced treatment methods are costly. OVERVIEW OF THE TEXAS SOURCE WATER ASSESSMENT PROJECT Greg Rogers In November 1999, Texas received U.S. Environmental Protection Agency approval of its Source Water Assessment and Protection (SWAP) Program. This approval represents a major milestone in an ongoing cooperative effort between the Texas Commission on Environmental Quality (TCEQ) and the U.S. Geological Survey (USGS) to develop and implement a scientifically defensible methodology for assessing the susceptibility of Texas’ public water supplies (PWS) to contamination. Background The 1996 amendments to the Safe Drinking Water Act require, for the first time, that each state prepare a source water assessment for all PWS. Previously, federal regulations focused on sampling and enforcement, with emphasis on the quality of delivered water. These amendments emphasize the importance of protecting the source water. States are required to determine the drinking water source, the origin of contaminants monitored or potential contaminants to be monitored, and the intrinsic susceptibility of the source water. Under the amendments to the SWDA, states must create SWAP programs. The programs must include an individual source water assessment for each public water
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From Source Water to Drinking Water: Workshop Summary system regulated by the state. These assessments will determine whether an individual drinking water source is susceptible to contamination. During 1997–1999, TCEQ and USGS staff met as subject matter working groups to develop an approach to conducting Source Water Susceptibility Assessments (SWSAs) and a draft work plan. The draft work plan was then presented to and reviewed by various stakeholder and technical advisory groups. Comments and suggestions from these groups were considered and a final work plan was produced and presented to the EPA. After EPA approval, work formally began on the Texas SWAP project. The project has an expected completion date of September 2002. At that time, initial SWSAs of all Texas public water supplies should be complete. Groundwater supplies can be considered susceptible if a possible source of contamination (PSOC) exists in the contributing area for the public supply well field or spring; the contaminant travel time to the well field or spring is short; and the soil zone, vadose zone, and aquifer/matrix materials are unlikely to adequately attenuate contaminants associated with the PSOC. In addition, particular types of land use or cover or within the contributing area may cause the supply to be deemed more susceptible to contamination. Finally, detection of various classes of constituents in water from wells in the vicinity of a public supply well may indicate susceptibility of the public supply well even though there may be no identifiable PSOC or land-use activity. Surface water supplies are by nature susceptible to contamination from both point and nonpoint sources. The degree of susceptibility of a PWS to contamination can vary and is a function of the environmental setting, water and wastewater management practices, and land-use or cover within a water supply’s contributing watershed area. For example, a PWS intake downstream from extensive urban development may be more susceptible to nonpoint source contamination than a PWS intake downstream from a forested, relatively undeveloped watershed. Surface water supplies also are susceptible to contamination from point sources, which may include permitted discharges, as well as accidental spills or other introduction of contaminants. The development of a scientifically defensible methodology for assessing the susceptibility of Texas PWS to contamination, based on the most accurate, readily available hydrologic, hydrogeologic, point source, nonpoint source, and other natural resource and environmental data, will better enable the TCEQ SWAP staff to do the following:
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From Source Water to Drinking Water: Workshop Summary Focus its source water protection efforts on PWS that are more susceptible to contamination. Potentially reduce monitoring costs associated with ensuring safe drinking water. Assist the public in developing an improved understanding of the source of its water. Support the implementation of best management practices as needed to protect source waters. Approach For the Texas SWAP project, the susceptibility of a PWS is defined as the potential for the PWS to withdraw water containing a listed contaminant(s), at a concentration that would pose concern, through any of the following pathways: (1) direct injection or discharge; (2) soil; (3) geologic strata including faults, fissures, or other types of secondary porosity; (4) overland flow; (5) up-gradient water or streamflow; and (6) cracks in a well casing or intake pipe. Susceptibility of a PWS to contamination is related to (1) the physical integrity of the well or intake and the pipe transmitting water from the well or intake, the treatment plant, and the distribution system; (2) the anthropogenic, physical, geologic, hydrologic, chemical, and biological characteristics of the source water area over which, or through which, water and contaminants will move to the supply point; (3) the type and number of PSOCs and land-use within the contributing area of a supply well, spring, or intake; and (4) the nature and quantity of contaminants that have been or potentially could be released within a contributing area, as well as measures in place to prevent such releases. The Texas SWAP project consists of work in three subject areas: (1) assessment software and database structures, (2) groundwater assessments, and (3) surface water assessments. The groundwater and surface water assessment areas are further defined as sets of components, where each component deals with a specific problem domain of the SWSA. Assessment Software and Database Structures The objectives of this subject area are to design and develop database structures, assessment software, and technical documentation specifically to support staff in performance of SWSAs on TCEQ computers.
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From Source Water to Drinking Water: Workshop Summary Surface water susceptibility assessments are technically complex activities dependent on relational database programming and spatial analysis techniques. Spatial analysis techniques are mostly available in commercial geographical information systems (GIS) software as lower-level computer functions. These functions are available as macros or “system commands,” but require specialized expertise to combine them into usable software components capable of performing the higher-level analyses required for SWSAs. Decision rules governing the assessment of PWS susceptibility must be encoded and made available so that they may be applied to data derived from spatial analysis, local SWAP-specific databases, and data retrieved from TCEQ’s agency-wide databases. In some cases, these rules are simple yes or no tests; in other cases, a series of logic tests involving several relational database files must be applied. The software system developed will be easy to use by staff charged with assessing PWS and will be compatible with TCEQ’s existing databases. Specialized training in GIS technology will not be required. Because of the volume and variety of required data and the level of technical detail of SWSAs, the staff requires access to software documentation and help files, metadata, bibliographic, and other supplementary information. The system being developed will make these data files and references available to the analyst at all times. To complete the large number of assessments (more than 17,000) required, the software must be capable of supporting unattended (batch) processing of SWSAs. As larger-scale data sets are produced for Texas, SWSAs will be repeated—hence the ongoing requirement for unattended processing. In cases where a single assessment (a new PWS) or a small number of assessments are to be completed, an interactive version is desired. It is anticipated that as SWSAs become more technically complex and larger-scale data sets come online, assessments will require interactive rather than batch processing. Software development efforts include (1) requirements analysis, design, development, testing, and documentation of database structures and assessment software; (2) a data object model defining overall database structure, data tables, data fields within tables, and data-entity relations including a data dictionary; (3) user interface software for display of GIS coverage, database query, hard-copy output, or report generation; (4) spatial analysis software for delineation of contributing areas, and calculation or determination of weighted variables, characteristics, and threshold values; (5) software to assist the user in applying appropriate
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From Source Water to Drinking Water: Workshop Summary decision rules for determining susceptibility within SWSA components and determining overall susceptibility; and (6) a graphical user interface to provide access to databases, assessment software, online help, and documentation and support for interactive or batch processing. Groundwater Assessments The groundwater susceptibility assessment subject area consists of seven components, each addressing a specific problem domain. The primary focus of this subject area is the design and development of databases and software to enable SWSAs on PWS with groundwater as the primary source of water. Identification component It is necessary to identify which aquifer a well derives its water from, since all subsequent determinations in SWSAs are based on aquifer type and hydrologic characteristics. In Texas, 9 major and 20 minor aquifers have been mapped. These 29 aquifers have been subdivided and assigned some 450 aquifer codes, each having its own geologic, hydrologic, and water quality characteristics. These aquifer codes have been developed for several uses, including regulation of public drinking water; however, the 29 major and minor aquifers do not provide sufficient detail for the purposes of SWAP. Alternatively, data requirements for 450 aquifer codes are beyond the scope of this component. Thus, agreement was reached between various stakeholders, including representatives of TCEQ, the Texas Water Development Board (TWDB), and USGS, regarding a designation of about 45 aquifer codes that provide adequate detail. Texas aquifers, for the purposes of SWAP, are designated as one of five major aquifer categories. Four of the categories are unconfined isotropic aquifers, confined isotropic aquifers, alluvial aquifers along major rivers, and anisotropic karst aquifers. Additionally, there are some public groundwater supplies in Texas that do not obtain water from the mapped major and minor aquifer systems or that obtain water where an aquifer determination cannot be made. Thus, a fifth aquifer category of “unknown” is required for susceptibility assessment purposes. Separate approaches have been developed for the five aquifer categories, because of their hydrogeologic characteristics. Contributing area delineation component SWSAs require that the contributing area to each PWS well or spring be determined so that PSOCs
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From Source Water to Drinking Water: Workshop Summary occurring within may be identified and assessed as to their potential effect on water quality. Delineation of the contributing area for water to enter the groundwater system for a specific well field or spring is complicated by (1) complex geologic structure, (2) groundwater-surface water interaction, (3) heterogeneous aquifer matrix material resulting from the depositional environment of the aquifer, and (4) limited site-specific aquifer information. Although there are several methods for determination of contributing areas of a PWS well or spring, flow-net analysis was chosen because of the regional scale of the problem, as well as knowledge of and assumptions made about the hydrogeologic properties of Texas aquifers. Using specially developed GIS software, the portion of the flow net that defines the contributing area for the water supply well or spring will be identified and a determination of time of travel to the well for all aquifer categories will be made, with the exception of the Edwards aquifer, where data from the USGS flow path investigations will be used. Using this approach, the characterization of the aquifer is such that only the horizontal movement of water to the water table is approximated, not the vertical movement. The assumption is that the contributing area to a well in an unconfined system is the area directly above the flow paths for a specified end time (2, 5, 10, 20, and 100 years). In a confined system, the contributing area is that area within specified end times or terminating in the outcrop of the aquifer for similarly specified end times. Tasks associated with this component are focused on developing data sets and software for delineation of contributing areas to PWS wells or springs that derive their water from the five categories of aquifers. GIS coverage produced under this component includes (1) time of travel and contributing area for wells or springs in confined or unconfined isotropic aquifers and alluvial aquifers, (2) contributing area for wells or springs in the Edwards aquifer, and (3) contributing area for wells or springs in unknown aquifers. Nonpoint source component This component will involve a statewide investigation to develop statistical relations between known occurrences of nonpoint source contaminants in groundwater and the natural and anthropogenic factors or activities (referred to as environmental variables) within the capture zone contributing the water. To supplement existing TCEQ and USGS contaminant occurrence databases, 160 PWS wells
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From Source Water to Drinking Water: Workshop Summary were sampled during 1999–2000. The PWS wells selected for sampling are located primarily in shallow, unconfined aquifers (those most susceptible to nonpoint source contamination) and have characteristics representative of a range of environmental variables that may influence source water susceptibility. Samples are collected using specialized, low-level detection sampling procedures developed by the USGS and analyzed for selected soluble pesticides, volatile organic compounds (VOCs) including methyl tert-butyl ether (MTBE), and nitrates. Environmental variable databases also are being compiled (to the extent that data are available) to support the development of statistical relations. These statewide databases of potential explanatory variables are wide ranging and include land-use (percentage urban, population density, animal densities or CAFOs, agricultural crop acreage, oil and gas production), selected natural factors (soil properties and hydrologic characteristics), and urban and agricultural pesticide and nutrient use. TCEQ will develop threshold values from the statistical relations. Point source component A primary step in assessing the susceptibility of a groundwater supply to contamination is locating PSOCs within the contributing area of a supply. Selected categories of PSOCs that may contribute contaminants to the PWS well or spring are underground storage tanks; operative and closed solid and hazardous waste management units, including landfills, surface impoundments, and waste piles; uncontrolled hazardous waste disposal and spill sites, including Superfund sites; waste injection wells, including the family of Class V wells; and septic systems. Texas state databases hold records for an estimated 65,000 known PSOCs. Although location information for the majority of these sites is available from the databases, this information is not accessible using the spatial analysis software in the various SWAP components. Approximately 10,000 PSOCs have no digital location information (latitude-longitude) as is required. The information for these sites may be available from a physical review of paper files maintained by TCEQ’s various PSOC programs. In some cases, PSOCs may have been located on USGS topographic maps; in other cases, only paper engineering reports, site drawings, or field sketches may exist. In still other cases, only street address information is available in the file. A large amount of work is going on to obtain accurate location data for PSOCs. Interviews with pertinent TCEQ staff who manage PSOC programs were conducted to determine data type, attributes, locations,
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From Source Water to Drinking Water: Workshop Summary quality, availability, and documentation. A comprehensive flowchart and list of interview questions to facilitate this process were developed and followed. For each PSOC for which location data are required, the paper file is physically pulled, reviewed, and pertinent information extracted, to allow the PSOC, if possible, to be located on a USGS topographic map or equivalent. Supplemental maps or commercial databases with address or location information will be required to locate some PSOCs. This information is then put into a GIS database that will provide a variety of information on PSOCs, including the TCEQ program that collects and manages the PSOC data, the source material for the data, descriptions of data quality, and minimal accuracy standards (or needs) for PSOC locations. The database will be linked to the list of regulated contaminants (and contaminant groups) and to Standard Industrial Codes. A relational database providing technical data on the environmental behavior and fate of contaminants will be developed to assist evaluation of a potential contaminant or group of contaminants associated with the PSOC. The output from spatial analyses and database software of this component is a list of PSOCs within the contributing area of the PWS. The software also will provide a list of contaminants and quantities (when available) associated with the PSOC that are analyzed as part of subsequent components. Contaminant occurrence component Some aquifers have naturally occurring contaminants that render the water less desirable for human consumption. Thus, an analysis, both spatial and temporal, of existing groundwater and PWS entry point monitoring data is needed to determine whether the measured occurrence of a contaminant in water from an aquifer is caused by natural or anthropogenic conditions. This analysis also may uncover sources of contamination caused by breaches of the confining unit for a confined aquifer. Several existing databases contain groundwater quality data useful for this analysis. Using spatial analysis techniques, water quality sampling sites will be identified within a 1-mile search radius around each PWS well and spring. If contaminants are detected within this area, the PWS would be assessed as being susceptible to either anthropogenic or naturally occurring contamination. These data will be used to identify sites with contaminant occurrences exceeding designated thresholds for specific constituents within a 1-mile search radius of the PWS well or spring.
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From Source Water to Drinking Water: Workshop Summary USDA Natural Resources Conservation Service’s (NRCS) (USDA, 2000) technical guidance. Although much work remains to be done to restore and protect the nation’s waters, the United States has made significant progress in cleaning up polluted waters, especially over the past few decades. Many farmers and ranchers, with assistance from NRCS, state conservation agencies, local conservation districts, and others, have been active stewards of soil, water, and other natural resources for decades. Based on 70 years of experience, lessons learned, and success stories to date, the USDA remains a proponent of the voluntary, locally led, incentive-based approach as the principal means to help agricultural producers reduce the environmental consequences of production. Environmental regulation has a proper role, as evidenced by EPA’s Concentrated Animal Feeding Operations Rule for the largest animal feeding operations, but it is largely a complementary role—providing the vehicle for regulatory authorities to address the actions of “bad actors” and/or set expectations for sensitive areas subject to the greatest environmental risk. Conservation technical assistance programs are the primary tools used by NRCS to improve water quality in agricultural settings. NRCS field personnel, in cooperation with other public and private technical service providers, supply technical assistance directly to farmers and ranchers to help them meet their goals for natural resource stewardship. USDA’s conservation programs, such as the Environmental Quality Incentives Program (EQIP), are used by many agricultural producers for the technical and financial assistance tools to help them comply with federal, state, and local regulations. Conservation practices, such as crop residue management, nutrient management, integrated pest management, grassed waterways, field borders, and buffer strips, combined into conservation systems, are proven to keep soil and nutrients in place and thereby minimize the risk of contaminated runoff leaving farm fields. NRCS does not work alone in its efforts to reduce the agricultural contributions to drinking water contamination. The agency’s relationship to its core conservation partners (including local conservation districts and state conservation agencies) ensures the efficient delivery of technical and financial assistance through locally led processes. Other USDA agencies, such as the Agricultural Research Service and the Cooperative States Research, Education, and Extension Service (CSREES), perform equally valuable complementary functions, including conservation research, education, and outreach. Additional federal partners include EPA
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From Source Water to Drinking Water: Workshop Summary and the U.S. Department of the Interior, where public and private land conservation and management issues interface. Located in the rural Potomac headwaters area in West Virginia, the North Fork Project is an example of a successful multiagency watershed partnership approach to solve a water quality problem on a scenic, high-quality stream. The Potomac River supplies drinking water to millions of people in the Washington, D.C., metropolitan region. The North Fork of the Potomac was plagued by elevated levels of fecal coliform bacteria, due primarily to polluted runoff from intensive animal agricultural operations along the waterway. As a result of the implementation of numerous BMPs funded under several federal and state water quality programs, the water quality of the North Fork of the South Branch of the Potomac River has improved to such an extent that the stream no longer exceeds criteria for the listing of impaired or polluted water bodies in West Virginia (Federal Clean Water Act, Section 303(d)). This success was made possible through funding from the USDA, the EPA, and the State of West Virginia, along with farmers’ individual contributions of time, knowledge, and resources. Numerous other partners at the state and local levels helped produce an 85 percent voluntary landowner participation rate in this exemplary watershed project. The North Fork Project and similar successes across the nation have elucidated the key ingredients for water quality improvement in impaired watersheds. Management of land and water resources on a watershed basis, enhanced partnerships and collaboration, and access to focused and accurate water quality information are critical components in mitigating nonpoint source pollution in agricultural watersheds. Increasing BMP adoption by landowners is a goal of NRCS and its partners. Achieving this goal will require the establishment of better links between best management practices and water quality improvements, better economic information on BMPs, and a greater awareness of social and cultural considerations to improve the effectiveness of outreach efforts to landowners. Additional research needs exist beyond the scope of BMPs. There is a need to characterize the nature, extent of occurrence, behavior, transport, and fate of emerging contaminants in the environment such as pharmaceuticals, hormones, endocrine disrupters, and environmentally robust and antibiotic-resistant pathogens. Development of economical, community-based solutions is necessary to address watershed-scale problems. Improved monitoring and modeling techniques and technologies
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From Source Water to Drinking Water: Workshop Summary are needed to provide decision makers with targeted, accurate water quality information. The USDA and EPA are working together to address these research needs. The enhanced federal partnership between USDA and EPA in recent years has led to more effective interactions on significant water quality activities. Collaboration on the Concentrated Animal Feeding Operation Rule, the Chesapeake Bay and Mississippi River basin nutrient over enrichment challenges, and source water protection activities provide an impetus for additional successes in the future. An important ongoing collaboration between the two agencies is an effort to promote the adoption of water quality trading projects in impaired watersheds. The USDA supports EPA’s voluntary Water Quality Trading Policy (USEPA, 2003) and is currently developing its own environmental credit trading policy that will describe key principles and policies, as well as identify agency roles and responsibilities. In 2002, Congress provided the USDA with powerful tools to address water quality concerns through new authorities and increased funding in the Farm Bill. An example of the significant increase in funding authorized by Congress is for EQIP, which in federal fiscal year 2004 is authorized at $1 billion. NRCS is proceeding rapidly with program implementation in order to deliver this increased funding to more producers to facilitate more widespread on-the-ground conservation. The USDA is committed to improving water quality and reducing the effects of agricultural nonpoint source pollution on drinking water and human health. Providing incentives for good stewardship, supporting research and innovative science-based technologies, expanding and enhancing partnerships, and informing and supporting locally led decision making are the cornerstones of this commitment. NUTRIENT LOADING: CRITICAL LINK IN THE CHAIN Kenneth H.Reckhow The nutrients in natural waters of greatest concern for human and ecological health are nitrogen and phosphorus. In the United States nitrate nitrogen is regulated in drinking water standards for human health concerns and nitrogen and phosphorus criteria have been proposed for the control of eutrophication in surface waters. Nitrate has a direct human health effect in infants; excessive nitrogen and phosphorus loading
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From Source Water to Drinking Water: Workshop Summary to surface waters has an indirect effect through algal growths that may produce toxins or serve as trihalomethane precursors. These effects are discussed briefly. The primary focus of this presentation is on nutrient loading; that is, the particularly concerned about the input of nitrogen and phosphorus to surface and groundwaters, with emphasis on the sources, assessment, and management. Current scientific knowledge is strongest concerning the recognition of important sources of nitrogen and phosphorus. In the absence of human activity (or “background”), there are typically low-level contributions of nutrients to surface and groundwater from the atmosphere, decaying plant material, and erosion and bedrock weathering. This contribution is natural, and while it can be modified by human activities, it occurs with or without human intervention. Anthropogenic inputs of nitrogen and phosphorus to surface and groundwaters may be far greater in magnitude than natural inputs; the most significant anthropogenic sources are wastewater treatment plants, urban runoff, agricultural activity, and fossil fuel burning. Fortunately, we know the cycles of nitrogen and phosphorus; thus, from a conceptual standpoint, we understand the set of possible outcomes once nitrogen and phosphorus are introduced into the environment. In other words, we know the transformations that nitrogen and phosphorus undergo and we can characterize the reaction rates for these transformations of nutrients under controlled (i.e., laboratory) conditions. The picture becomes considerably less certain, however, when applying this general “laboratory” knowledge of nutrient sources and transformations to assess the effect of nitrogen or phosphorus loading in a specific aquatic environment. The natural environment is complex and highly variable; thus, our ability to predict the response of an aquatic system to nutrient loading will always be restricted by our ability to understand and characterize this complexity and variability. As a consequence, predictions of the effect of nitrogen and phosphorus loading to surface and groundwater are not very accurate in many situations. A case study addressing the effect of nitrogen loading to the Neuse River in North Carolina provides an example of the difficulties in (1) estimating nutrient loading, (2) assessing the effect of that loading, and (3) determining appropriate management strategies.
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From Source Water to Drinking Water: Workshop Summary STATUS AND TRENDS IN ATMOSPHERIC DEPOSITION OF NITROGEN AND MERCURY IN THE UNITED STATES Mark A.Nilles Approximately 23 million tons of nitrogen oxides, 5 million tons of ammonia, and 158 tons of mercury from anthropogenic sources are estimated to be emitted annually to the atmosphere in the United States (USEPA, 1998, 2003). Current assessments identify fossil fuel combustion as the primary source of nitrogen oxide and anthropogenic mercury emissions, while livestock agriculture and fertilizer application are the primary sources of ammonia emissions. Since 1978 a cooperative national monitoring effort has tracked the status and changes in wet deposition in the United States. The National Atmospheric Deposition Program (NADP) is cooperatively supported by more than 100 organizations, including 8 federal agencies, state and local agencies, universities, and private industries who pool resources to support centralized program management, site operation and maintenance, chemical analysis, data management, and quality assurance programs. NADP currently supports 250 sites nationwide to monitor acidity, nutrients, and base locations. In 1996, NADP initiated the Mercury Deposition Network (MDN), which now comprises 100 sites to monitor total mercury and methyl in precipitation. Deposition of atmospheric nitrogen compounds to aquatic and terrestrial ecosystems can range from a negligible contribution to the predominant source of overall nitrogen inputs. NADP data indicate that the concentration and deposition of nitrate in precipitation are greatest in and downwind of the industrialized Midwest and Northeast regions of the United States, while for ammonium, the greatest flux occurs in and downwind of the primary plant and animal agricultural regions of the Midwest. The spatial distribution of mercury wet deposition in the United States exhibits greater complexity, possibly due to the integration of large-scale regional and global atmospheric processes with local emission and deposition processes (NADP, 2002) (see Figure A.1).
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From Source Water to Drinking Water: Workshop Summary FIGURE A.1 Wet deposition of nitrogen compounds and mercury in the United States. SOURCE: National Atmospheric Deposition Program, National Trends Network (2002). Trends in wet deposition of oxidized and reduced forms of nitrogen have not followed the well-documented declines in sulfate deposition in the United States. Monthly data from 149 sites in the NADP National Trends Network were evaluated for trends over the period 1985–2001 using a parametric model to remove the influence of interannual variations in precipitation amount, followed by a nonparametric test for detection of monotonic trends (Nilles and Conley, 2001). Characteristics of wet deposition that must be considered in trend analysis include the influence of seasonality on data variability, typically nonnormal data distribution, missing data resulting from data screening steps, and considerable variation in the apparent form of trends exhibited at NADP sites (step-function, linear, or nonlinear). To address these constraints, the trends were analyzed for statistical significance using the Seasonal Mann-Kendall Test (SKT). The SKT is a robust nonparametric test for detection of monotonic trends that implicitly removes the influence of seasonality, while accommodating nonnormal data distributions and missing data. Wet deposition data typically vary strongly with season for many constituents, and the SKT compares only like months in a stepwise, time-ordered fashion to implicitly remove the influence of seasonality. For ammonium deposition, statistically significant increases were detected at 58 of 149 sites examined, while only 2 sites exhibited declining trends. On a network-wide basis, ammonium deposition increased by
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From Source Water to Drinking Water: Workshop Summary 19 percent over the 17-year period of analysis. A number of the sites with increasing trends were located in areas of the country coincident with intensive animal agricultural production—states such as Arkansas, Oklahoma, Kansas, Illinois, and North Carolina. The Northeast region exhibited the fewest positive trends for ammonium concentrations compared to the Southeast and Western United States. While the majority of sites did not exhibit any trend in nitrate deposition, 23 sites exhibited a significant increasing trend versus 12 sites with a declining trend. Sites with increasing trends in nitrate were predominantly located in the Western and Southeastern United States, while sites with declining trends were located mostly in the Northeast. The median trend of all 149 sites examined was less than +3.0 percent over the 17-year period. Measures to control nitrogen oxide (NOx) emissions such as those in Title IV of the Clean Air Act Amendments and in mobile source NOx controls implemented to date have mitigated increases in NOx, despite substantial increases in power production and vehicle-miles traveled over the past two decades. Hence, the finding here of few observed reductions or increases in NO3- concentrations in precipitation is consistent with the emission control policy promulgated in the United States over the period examined. The median concentration of mercury in precipitation at NADP/ MDN sites was approximately 10 ng/L in 2001 (NADP, 2002). The highest concentrations of mercury in precipitation occurred in Florida, Minnesota, and Wisconsin. Deposition, which integrates chemical concentration with the amount of precipitation, was highest in the Southeastern United States. Mercury deposition exhibits strong seasonality, with greater concentration and deposition in the warmer months. A preliminary trend analysis of NADP/MDN mercury deposition data at 51 sites for the period 1996–2002 indicated no trend at 42 sites, a downward trend at 8 sites, and an upward trend at 1 site. Irrespective of statistical significance, most of the 51 trend slopes were negative. The NADP demonstrates the value of a long-term, high-quality national network to gauge the spatial and temporal distribution of wet atmospheric deposition. The network provides an accountability mechanism to gauge the effectiveness of ongoing and future regulations intended to reduce atmospheric chemical emissions and subsequent effects on land and water resources. All NADP data are available at http://nadp.sws.uiuc.edu/.
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From Source Water to Drinking Water: Workshop Summary PATHOGENS IN WATER: ADDRESSING A PUBLIC HEALTH THREAT VIA THE POTENTIAL SYNERGISM OF THE CLEAN WATER ACT AND THE SAFE DRINKING WATER ACT Joan B.Rose Waterborne disease statistics and potential risks are divided into recreational outbreaks and drinking water outbreaks. In terms of the current status of waterborne disease in the United States, during the last few years of reporting there has been an increase in disease associated with both drinking water and recreational fresh waters. Enteric bacteria, parasites, and viruses are the key microorganisms associated with these public health risks and are very similar despite the different exposure routes. The largest source of microbial fecal loading and contamination is sewage in the form of untreated and treated wastewaters, combined sewer overflows (CSOs), sanitary sewer overflows (SSOs), and septic tanks and—in the case of bacteria and protozoa—animal excreta. Exposure to untreated sewage has long been known to cause disease. The probability that any waterborne pathogen may cause illness will depend on the type of contact made; exposure; concentration of the organisms in the contaminated water; temperature of the receiving water, which influences survival; transport of the pathogen from source to contact point; and level of individual or population susceptibility to pathogen-borne illnesses. Only a small percentage of outbreaks are documented, as little as 10 percent (Harter et al., 1985). Gastrointestinal illnesses are largely unreported due to the lesser severity of illness in healthy individuals. When etiologic agents have been identified, most often the source of the fecal contamination has not. Thus, the burden of disease is not readily recognized. While the Clean Water Act (CWA) has focused on protection of recreational waters, the Safe Drinking Water Act has focused on drinking water. In most cases, the different targets, approaches, and regulatory framework have resulted in a disconnection in regard to the protection of public health. Table A.1 shows the comparison in a number of areas. The CWA has the tools for watershed protection to address sources, survival, transport, and risk, yet none of the rules have addressed pathogens or used a science-based risk assessment approach for examining appropriate public health microbial targets. The SDWA on the other hand has allowed for the use of quantitative microbial risk assessment
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From Source Water to Drinking Water: Workshop Summary TABLE A.1 Comparison of the Clean Water Act and the Safe Drinking Water Act Area CWA SDWA Goal Recreational waters, no illnesses while swimming No national standards Drinking water: health and safety goal, MCLG of zero for pathogen Focused efforts On source waters, at the beach area relies on indicators On treated water, water entering a distribution system, includes pathogen target Reliance Minimal monitoring of different targets in different states, in some cases wastewater disinfection and dilution Daily monitoring, some pathogen monitoring in source waters. Relies on filtration and disinfection Risk assessment Used for ecological end points but not for public health Used for examining pathogen targets, sensitive populations Pathway forward Epidemiological studies Contaminant candidate list Tools for watershed protection CAFOs, SSOs, CSOs, NPDES, septic tank permitting, TMDL Limited under “water quality protection plans” Pathogen monitoring No Yes NOTE: NPDES=National Pollutant Discharge Elimination System; TMDL=total maximum daily load. with public health goals but has focused on treatment technology and has little authority for implementing watershed protection approaches except in a few cases. The complementary nature of the two laws is obvious, particularly for freshwater systems; however, changes that focus on pathogen targets in sources would have to be made.
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From Source Water to Drinking Water: Workshop Summary In the future, new challenges will face the water industry and communities struggling with protection of both recreational waters and drinking waters. These may include changes in disinfection: ultraviolet disinfection with new microbial targets of resistance such as adenoviruses; changes in discharges: blending untreated and treated effluents, greater volumes, animal waste discharges; discovery of new microbial contaminants (cancer-causing viruses; zoonotic pathogens); and uses and interpretation of molecular data (source tracking, pathogen detection, and virulence factors). The harmonization of a risk assessment framework to serve the goals of both the Clean Water Act and the Safe Drinking Water Act will ensure that efforts in the future to protect waterways from pathogens will be synergistic. CHANGE: IMPLICATIONS AT THE WATER-HUMAN HEALTH INTERFACE Peter H.Gleick The failure to meet basic human and environmental needs for water is the greatest development failure of the twentieth century—one that carries with it adverse health effects of vast proportions. By the best estimates of the World Health Organization, two million to five million people die annually from preventable water-related diseases that result from lack of safe drinking water and adequate sanitation. In partial recognition of these effects, the United Nations adopted the Millennium Development Goals (MDGs), two of which specifically address water poverty; these call on the world community to work to reduce by half the proportion of people without access to safe drinking water and sanitation services by 2015. Even if we meet the Millennium Development Goals for water, 34 million to 76 million people will die of preventable water-related diseases by 2020, and we are not going to meet the MDGs given current commitments. Further complications include the broad issue of global change, including geophysical aspects such as global warming and po-
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From Source Water to Drinking Water: Workshop Summary litical and economic aspects associated with rapidly changing population dynamics, political alliances, and economic power. If we are to solve the water problems remaining, new approaches, solutions, and ways of thinking must be applied.
Representative terms from entire chapter: