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The Quality Of Drinking Water

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There are nearly 55,000 community water systems in this country, supplying water to meet the drinking needs of more than 90 percent of the U.S. population. The Environmental Protection Agency (EPA) defines a community water source as one that consistently provides water to at least twenty-five percent for at least sixty days during the course of a year. Living in Washington, D.C., this is a very personal issue at this point in time. Over the summer, we have dealt with serious testing on the quality of the city's water. When picking this topic, I believed that if I research more on it, I would become more knowledgeable of its impact on my immediate family and my community. So after finalizing my research, I formed my hypothesis stating that "if 20 residents of the Petworth subdivision of Northwest Washington, D.C. live in homes that tested positive for high levels of lead in their water, then less than half of them have replaced the pies since proper notification.

But in order to understand the problems of the city's water system, you must know the history in how the country's water systems and standards were formed. The United States has gravitated toward a modified minimal degradation policy that incorporates a best-available-treatment (BAT) criterion. Under this particular policy, their main objective is to minimize the effects of discharges on receiving waters, but it is recognized that the extent of wastewater treatment is technically and economically constrained. Best-available-treatment treatment is defined by the type of waste under consideration. For municipal wastewaters BAT standard is usually considered to be secondary treatment. However, the definition of BAT is situation-dependent. If phosphorus is a limiting nutrient in the receiving water, phosphorus removal is added to the BAT requirement. The current BAT standard for phosphorus is based on precipitation and granular-medium filtration.

It is important to note that the U.S. Environmental Protection Agency has included economic feasibility as a component in determining BAT. Distillation is always a technical possibility that would produce a noncontaminating or polluting discharge, but economic considerations eliminate it from consideration in most cases. Stream water quality standards are set, and wastewater discharges are not allowed to violate these standards. Requirements for wastewater discharges are set on a minimal degradation basis, and, in addition, all discharges are required to use BAT. Defining BAT is not always straightforward, and it must also be recognized that BAT changes with time. Application of the minimum-degradation approach must be flexible, and care must be taken to ensure that protecting water quality remains as the priority rather than simply forcing all discharges to have a particular level of treatment.

Contamination of drinking water originates in different ways depending on the source of the drinking water, the type of contamination, and the method of water supply delivery (i.e. type of plumbing). Groundwater, which may be used as a source of drinking water, often becomes contaminated from percolation of toxics through contaminated soil. Alternatively, contaminated runoff and direct discharges contaminate surface water, which may also be used as a drinking water source. Drinking water may become contaminated through the leaching of lead from plumbing systems. Finally, the intentional addition of substances to treat the water supply, such as chlorine, also represent a significant source of drinking water contamination in public water supply systems.

The potential dose of a toxic compound resulting from drinking water consumption is a function of consumption rate and contaminant consideration in the water. It is preferable that consumption rate be determined for the population of interest. If such population-specific data are unavailable, however, generic rates derived from relevant regional studies or national consumption surveys may be used. Consumption surveys often report averages and distributions for both "total fluid" and "total tap water" intake. Total fluid intake is defined as "consumption of all types of fluids including tap water, milk, soft drinks, alcoholic beverages, and water intrinsic to purchased foods." Total tap water is defined as "food and beverages that are prepared or reconstituted with tap water" in addition to straight tap water. As purchased foods and beverages are widely distributed and less likely to contain source-specific water, the use of total fluid intake rates may overestimate the potential exposure to toxic substances present only in local water supplies.

Until very recently, the U.S. EPA has recommended using default drinking water intake rates of 2 liters per day for adults. This value is a total tap water rate, as it includes drinking water consumed in the form of juices and other beverages containing tap water, such as tea and coffee. Numerous studies have generated data on drinking water intake rates that support using a significantly lower default value to represent average adult drinking water, while using 2 liters per day to represent the upper 80th to 90th percentile rate. Consequently, the USEPA recommends 1.4 liters per day as the default drinking water value for adult consumption.

Health effects of a toxicological nature are measured by blood lead levels. The effects are neurotoxic, which include irreversible brain damage. Such a toxic level I reached when the blood level exceeds 100-120 µg/dL. Severe gastrointestinal symptoms are associated with the encephalopathic symptoms. These symptoms start to be observed in adult lead workers at blood lead levels of 40-60 µg/dL. The subpopulation to be carefully studied is represented by children, where encephalopathy and death are registered at a starting level of 80-100 µg/dL (blood). In nonfatal cases, permanent, severe mental retardation with other neurologic symptoms is observed at levels as low as 40-60 µg/dL. Adverse health effects are noted in children with blood levels of 40µg/dL or higher with possible risks at levels as low as 15-30 µg/dL.

Legislated water quality standards are required to present misuse of the resource for individual gain. There is no actual benefit to a corporation or a city in maintaining downstream water quality. Despite this fact, many outstanding examples exist of sound water quality management based on ethical ideas, civic pride, and philanthropic generosity. Rivers and lakes are often symbols of a community or of a region, and residents, including corporations, often have an emotional stake in maintaining their beauty and quality. However, city councils are nearly always dealing with difficult budget constraints, and corporate leaders must face stockholder's demands for high return on investment. Thus, if maintaining



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