Ichimlik suviga qo'yilgan gigiyenik talablar, suvni sifatini tozalash va zararsizlantirish usullari

Ichimlik suviga qo'yilgan gigiyenik talablar suvni sifatini tozalash va zararsizlantirish usullari Reja: Ichimlik suviga qo'yilgan gigiyenik talablar. Ichimlik suviga gigiyenik baho berish Suvni tozalash va zararsizlantirish usullari. Sources of drinking water The primary sources of drinking water are groundwater and surface water. In addition, precipitation (rain and snow) can be collected and used. Water within the upper water table can be accessed through dug wells. Such wells generally extend 1.5-6 meters (5-20 feet) beneath the ground surface. Groundwater located in deeper reservoirs or aquifers can be accessed through wells that are driven or drilled. These may penetrate to depths of 450-600 meters (1,500-2,00 feet) (Figure 7.3). Springs, which are outcrops where the underground aquifer intersects the surface of the earth, represent another source of groundwater (Symons, 1992). Sources of surface water include lakes, reservoirs, and rivers. Surface water may also come from protected watersheds. Each of these sources has its advantages and disadvantages. Groundwater The widespread use of groundwater stems not only from its general availability but also from economic and public health considerations. Groundwater is commonly available at the point of need at relatively little cost, and reservoirs and long pipelines are not necessary. It is also normally free of suspended solids, bacteria, and other disease-causing organisms unless it contains contaminants introduced by human activities. Unfortunately, as of 1992 it was estimated that more than 10 percent of the community water-supply wells and almost 5 percent of the rural domestic wells in the United States contained detectable concentrations of one or more contaminants, primarily agricultural pesticides. About 1 percent contain one or more contaminants in excess of health-based limits. Protected runoff Many homeowners have systems for collecting the rainfall from their roofs, storing it in a cistern, and using it as a source of drinking water. Such sources, however, are almost certain to have some degree of pollution. One step that can be taken to reduce contamination is to delay collecting the water until enough rain has fallen to cleanse the roof. Several types of diversion valves have been developed to accomplish this task. Some systems also incorporate units for filtering the water prior to use. Cisterns in which the water is collected should be watertight, and manholes or other ports of entry should be leakproof. Rainfall and accompanying runoff can also be collected on a wider scale to provide drinking water to large municipalities. Cities that employ this ...