Paragraph 1: Color 



A limit of 75 color units (platinum-cobalt 

 standard) has been recommended to permit the 

 defined plant to produce water meeting Drinking 

 Water Standards (10) with moderate dosages of 

 coagulant chemicals. At optimum pH the dosage 

 usually required is linearly related to the color of 

 the raw water, and higher color of the type com- 

 monly associated with swamp drainage and similar 

 nonindustrial sources can be removed by increas- 

 ing the coagulant dose. These criteria do not apply 

 to colors resulting from dyes and some other in- 

 dustrial and processing sources which cannot be 

 measured by the platinum-cobalt standard. Such 

 colors should not be present in concentrations 

 which cannot be removed by the defined method 

 of treatment. 



Paragraph 2: Odor 



The effectiveness of the defined method of treat- 

 ment in removing odorous materials from water is 

 highly variable depending on the nature of the 

 material causing the odor. For this reason, it has 

 not been feasible to specify any permissible cri- 

 terion in terms of threshold odor number. The raw 

 water should not have objectionable odor. Any 

 odors present should be removable by the defined 

 treatment. It is desirable that odor be virtually 

 absent. 



Paragraph 3: Temperature 



Surface water temperatures vary with geo- 

 graphical location and climatic conditions. Conse- 

 quently no fixed criteria are feasible. However, 

 any of the following conditions are considered to 

 detract (sometimes seriously) from raw water 

 quality for public water supply use: 



( 1 ) Water temperature higher than 85 F; 



(2) More than 5 F water temperature increase 

 in excess of that caused by ambient con- 

 ditions; 



(3) More than 1 F hourly temperature varia- 

 tion over that caused by ambient condi- 

 tions; 



(4) Any water temperature change which ad- 

 versely affects the biota, taste, and odor, or 

 the chemistry of the water; 



( 5 ) Any water temperature variation or change 

 which adversely affects water treatment 

 plant operation (for example, speed of 

 chemical reactions, sedimentation basin 

 hydraulics, filter wash water requirements, 

 etc.); 



(6) Any water temperature change that de- 

 creases the acceptance of the water for 

 cooling and drinking purposes. 



Paragraph 4: Turbidity 



Turbidity in water must be readily removable by 

 coagulation, sedimentation, and filtration; must 

 not be present in quantities (either by weight or 

 volume) that will overload the water treatment 

 plant facilities; and must not cause unreasonable 

 treatment costs. In addition, turbidity in water 

 must not be frequently changing and varying in 

 characteristics or in quantity to the extent that 

 such changes cause upset in water treatment plant 

 processing. 



Customary methods for measuring and report- 

 ing turbidity do not adequately measure those 

 characteristics harmful to public water supply and 

 water treatment processing. A water with 30 Jack- 

 son turbidity units may coagulate more rapidly 

 than one with 5 or 10 units. Similarly water with 

 30 Jackson turbidity units sometimes may be more 

 difficult to coagulate than water with 100 units. 

 Sometimes clay added to very low turbidity water 

 will improve coagulation. Therefore, it has not 

 been possible to establish a turbidity criterion in 

 terms of Jackson turbidity units. Neither can a 

 turbidity criterion be expressed in terms of mg/1 

 "undissolved solids" or "nonfilterable solids." The 

 type of plankton, clay, or earth particles, their size 

 and electrical charges, are far more determining 

 factors than the Jackson turbidity units. Neverthe- 

 less, it must be clearly recognized that too much 

 turbidity or frequently changing turbidity is 

 damaging to public water supply. 



The criterion for too much turbidity in water 

 must relate to the capacity of the water treatment 

 plant to remove turbidity adequately and continu- 

 ously at reasonable cost. Water treatment plants 

 are designed to remove the kind and quantity of 

 turbidity to be expected in each water supply 

 source. Therefore, any increase in turbidity and 

 any fluctuating turbidity load over that normal to 

 a water must be considered in excess of that per- 

 missible. 



Paragraph 5: Coliform and Fecal Coliform Or- 

 ganisms 



Bacteria have been used as indicators of sani- 

 tary quality of water since 1880 when B. coli and 

 similar organisms were shown to be normal in- 

 habitants of fecal discharges. The coliform group 

 as presently recognized by Drinking Water Stand- 

 ards (10) is defined in Standard Methods for the 

 Examination of Water and Wastewater (9). This 

 group includes organisms that vary in biochemical 

 and serologic characteristics and in their natural 

 sources and habitats; i.e., feces, soil, water, vege- 

 tation, etc. 



Because the sanitary significance of the various 



462-246 0-72-3 



21 



