members of the coliform group derives from their 

 natural sources, differentiation of fecal from non- 

 fecal organisms is important to evaluate raw water 

 quality (5). Fecal coliforms are characteristically 

 inhabitants of warmblooded animal intestines. 

 Members of other coliform subgroups may be 

 found in soil, on plants and insects, in old sewage, 

 and in waters polluted some time in the past. 



The objective of using the coliform group as an 

 indicator of the sanitary quality of water is to eval- 

 uate the disease-producing potential of the water. 

 To estimate the probability of pathogens being 

 contributed from feces, the coliform and fecal 

 coliform content must be quantified. 



In relation to raw water sources, the following 

 suggestions are offered to help resolve some of the 

 difficulties of data interpretation. 



Fecal coliform organisms may be considered 

 indicators of recent fecal pollution. It is necessary 

 to consider all fecal coliform organisms as indica- 

 tive of dangerous contamination. Moreover, no 

 satisfactory method is currently available for dif- 

 ferentiating between fecal organisms of human and 

 animal origin. 



In the absence of fecal coliform organisms, the 

 presence of other coliform group organisms may 

 be the result of less recent fecal pollution, soil run- 

 off water, or, infrequently, fecal poUution contain- 

 ing only those organisms. 



In general, the presence of fecal coliform or- 

 ganisms indicates recent and possibly dangerous 

 pollution. The presence of other coliform orga- 

 nisms suggests less recent pollution or contribu- 

 tions from other sources of non-fecal origin. 



In the past the coliform test has been the prin- 

 cipal criterion of suitability of raw water sources 

 for public water supply. The increase in chlorina- 

 tion of sewage treatment plant effluents distorts 

 this criterion by reducing coliform concentrations 

 without removing many other substances which the 

 defined water treatment plant is not well equipped 

 to remove. It is essential that raw water sources be 

 judged as to suitability by other measures and cri- 

 teria than coliform organism concentrations. 



The defined water treatment plant is considered 

 capable of producing water meeting Drinking 

 Water Standards (70) bacteriological criteria from 

 these limits. The difference between the suggested 

 concentration of 10,000 coliforms per 100 ml and 

 the erstwhile figure of 5,000 per 100 ml is justified 

 by the difference between the Phelps Index and 

 the MPN. The Subcommittee suggests these num- 

 bers and the additional consideration of fecal coli- 

 forms in order to provide more realistic parame- 

 ters in full recognition of modern knowledge and 

 not as a means of sanctioning increased bacterial 

 pollution of waters destined for public water sup- 

 ply use. 



Paragraph 6: Alkalinity 



Alkalinity in water should be sufficient to 

 enable floe formation during coagulation, must not 

 be high enough to cause physiological distress in 

 humans, and must be proper for a chemically bal- 

 anced water (neither corrosive nor incrusting). A 

 criterion for minimum and maximum alkalinity in 

 public water supply is related to the relative 

 amoimts of bicarbonates, carbonates, and hydrox- 

 ide ions causing the alkalinity; and also to the pH, 

 filterable (dissolved) solids, and calcium content. 

 Because the permissible criterion for filterable 

 solids is 500 mg/1 and the pH range is 6.0 to 8.5, 

 alkalinity should not be less than about 30 mg/1. 



The criterion for maximum alkalinity cannot be 

 expressed in calcium carbonate equivalents as 

 determined from 0.02n H2SO4 titration because of 

 the interrelationships stated above. However, al- 

 kalinity values higher than about 400 mg/1 to 

 500 mg/1 would be too high for public water sup- 

 ply use. Within the range of 30 mg/1 to 500 mg/1, 

 the alkalinity criterion should be that value which 

 is normal to the natural water and which from 

 experience is satisfactory for public water supply 

 use. Frequent variations from normal values are 

 detrimental to public water supply processing 

 control. 



Paragraph 7: Ammonia 



Ammonia is a significant pollutant in raw water 

 for public water supplies because its reactions with 

 chlorine result in compounds with markedly less 

 disinfecting efficiency than free chlorine. In addi- 

 tion, it is frequentiy an indicator of recent sewage 

 pollution. 



In the early days of waste treatment, the oxida- 

 tion of ammonia to nitrates was one of the major 

 objectives of waste treatment, but with the de- 

 velopment of the BOD test, this objective became 

 neglected. Greater attention to the design and 

 operation of waste treatment plants for the oxida- 

 tion of ammonia and organic nitrogen is needed to 

 minimize the concentration of pollution forms in 

 these receiving waters. 



Paragraph 8: Arsenic, Barium, Cadmium, 

 Chromium (Hexavalent), Copper, Chloride, Cya- 

 nide, Iron, Lead, Manganese, Phenols, Selenium, 

 Silver, Sulfate, Zinc, and Radioactive Substances 



The significance of these substances as con- 

 taminants of drinking water is discussed in Drink- 

 ing Water Standards (10). The permissible cri- 

 teria in this report are those included in Drinking 

 Water Standards. With the possible exception of 

 iron and in some instances copper and zinc, the 

 defined treatment plant does little or nothing to 

 remove these substances. 



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