Drinking water quality control requirements

Since important decisions affecting the health and welfare of humanity must be made on the basis of analytical results, considerable effort must be directed toward assuring greater confidence in the reliability of the output of analytical laboratories. The Commission of the European Communities, after performing a study to determine the comparability of chemical analyses for drinking water quality, concluded that analytical quality control must be required as a routine component of analytical work. They state ( ), "Only the combination of intralaboratory controls of precision and accuracy complemented by interlaboratory intercomparison tests can lead to a significant evaluation and improvement of analytical results."... 

The results described here demonstrate the importance of appropriate treatment and monitoring in actual drinking water processing plants, with attention to the specific requirements of the raw water matrix in use. In particular, the adverse effect of certain processes, namely pre-chlorination, which has been implicated in the inhibition of biodegradation in subsequent steps, and in the formation of alternative metabolites, is highlighted. Furthermore, the variable efficiency of GAC filtration in practice, emphasises the need for regular monitoring and quality control. The duration of specific process steps has also been shown to influence the efficacy of the technique, and should be addressed in application. 

Municipal water plants provide limited treatment, mostly intended to make the water safe to drink. A lot of contaminants, such as salts, dissolved gases, and organic materials contained in natural sources, remain in the municipal water supply. In addition, chlorine or other disinfectants are often added as part of the treatment process to control microbial contamination. For many critical applications required in pharmaceutical plants, such water quality is not sufficient, and further treatment is necessary. 

The cold-vapor technique for Hg allows detection limits of <1 ng to be obtained when using 50 mL of sample and they can be improved still further by trapping. With the hydride technique detection limits below the ng/mL level can be achieved for As, Se, Sb, Bi, Ge, Sn, etc. Accordingly, the levels required for analyses used to control the quality of drinking water can be reached. 

Analytieal methods used for the control procedures according to the European drinking water directive must be capable of measuring concentrations equal to the parametric value (Couneil Direetive 98/83/EC, 1998). This is a positive requirement and enables laboratories to ehoose a suitable method among alternatives. The European directive additionally specifies quality requirements eoneeming trueness, precision, and the limit of detection of the method (see Table 1.3). 

Water Treatmeat and Supply. Before water is consumed, it has to be collected first from either underground or above-ground sources. Therefore, source control is one of the most important tasks of water supply. Except for a few municipalities where the source water derived from deep aquifers, source water has to be treated to remove contaminants such as pathogenic bacteria, heavy metals, and pesticide residues. The process of treatment involves the removal of suspended solids and the use of chemicals or ultraviolet (UV) radiation to disinfect unwanted organisms so that the effluent water satisfies quality requirements dictated by the Federal Safe Drinking Water Act. For water used by industrial plants such as paper mills or nuclear power plants, special treatment is needed and its discharge is regulated. 

Water quality is modified to meet the requirements of specific uses. In most cases, we think of water quality modification in terms of treatment of surface or groundwaters for drinking or industrial purposes or of treatment of wastewaters to meet discharge requirements and discussion of these topics is the principal purpose of this section. However, water quahty can be selectively changed on a large scale through use of reservoirs and other constructed systems, as noted above. Temperature control is one of the most desirable potential benefits of large... 

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