Quality considerations 



Taste and Odor 



The water supply should be substantially free 

 of substances offensive to sight, taste, or smell. 

 Taste and odor in water may result from the pres- 

 ence of a wide variety of substances including or- 

 ganic compounds, inorganic compounds, and al- 

 gae. Knowledge concerning the source of taste and 

 odor components is useful in determining what 

 treatment, if any, is necessary to make the water 

 acceptable. 



The odor of water is usually due to the presence 

 of dissolved gases such as hydrogen sulfide and 

 volatile organic compounds. Threshold odor values 

 in excess of three units (159) are generally con- 

 sidered objectionable. Dissolved inorganic salts 

 of iron, zinc, manganese, copper, sodium, potas- 

 sium, and others may be detected by taste. Limits 

 for many of these ions are listed later in this 

 report. 



Color 



The water supply should be substantially free of 

 color. Dissolved organic material from decaying 

 vegetation and certain inorganic matter cause color 

 in water. Occasionally, excessive blooms of algae 

 or the growth of aquatic microorganisms may also 

 impart color. While color itself is not usually ob- 

 jectionable from the standpoint of health, its 

 presence in excess of 15 color units (159) is aes- 

 thetically objectionable and suggests that the water 

 needs appropriate treatment. 



Temperature 



The temperature of the water supply is not an 

 important quality consideration for most farm- 

 stead uses. Where large volumes of water are to be 

 used for hydrocooling farm products, however, the 

 natural temperature can be a factor influencing its 

 acceptability for such use. 



Ph 



The pH of waters can range from 5.5 to 9.0 

 (177) but most surface waters fafl between pH 

 7.0 and 8.5 (179) usually due to the presence of 

 bicarbonate and carbonate ions. Waters with a 

 pH below 6.0 can cause excessive corrosion in 

 plumbing systems while waters with a pH above 

 8.5 suggest excessive sodium. Knowledge of the 

 water pH is useful in determining necessary meas- 

 ures for corrosion control, sanitation, and ade- 

 quate disinfection. It is recommended that the pH 



of farmstead water for milkhouse use fall between 

 6.8 and 8.5. 



Total Dissolved Inorganic Compounds 



Firm standards for total dissolved inorganic 

 solids are not realistic in view of the naturally 

 occurring difference in waters from various sources 

 and geographical locations. The importance of 

 total dissolved inorganic solids in farmstead waters 

 for domestic use relates largely to taste, hardness, 

 and laxative properties. It is desirable that the total 

 dissolved inorganic solids not exceed 500 mg/1. 

 Chlorides and sulfates should not exceed 250 

 mg/1. No general recommendations are appropri- 

 ate for sodium, magnesium, potassium, phos- 

 phorus, sulfur, or calcium. 



Although in excess of the above recommenda- 

 tions, waters containing up to 5,000 mg/1 total 

 dissolved inorganic solids can be used if alternate 

 sources are not available. Under these conditions, 

 however, the acceptability of the water depends 

 upon the ionic composition of the dissolved solids 

 and the feasibility of treatment to remove ob- 

 jectionable ions. 



Dissolved Organic Compounds 



Determination of total dissolved organic com- 

 pounds in water by measurement of carbon 

 chloroform extractable substances (CCE) is too 

 involved and expensive to be considered for ap- 

 plication to farmstead water supplies. If surface 

 waters are being used, an estimate of the CCE may 

 be obtained from nearby municipalities using the 

 same or similar sources. If deep ground waters are 

 being used on the farmstead, the problem of total 

 dissolved organic compounds may be ignored 

 unless there is reason to expect contamination. 



The organic compounds of possible concern in 

 connection with farmstead supplies are persistent 

 chlorinated organic pesticides. Although the data 

 currently available (55, 120, 171) indicate that 

 contamination of both ground and surface water 

 with any of these materials rarely exceeds 0.1 

 fxg/l and, accordingly, is negligible in terms of 

 human health, it is highly desirable that water 

 supplies remain in such a condition. Some criteria, 

 such as those suggested by Ettinger and Mount 

 (52) are too low to be broadly applied at the 

 present time in water quality evaluation. It is 

 considered appropriate, therefore, that the permis- 

 sible levels of specific pesticides in a farmstead 

 water supply should not exceed the limits sug- 

 gested by the PHS advisory committee, on use of 

 the PHS drinking water standards. The work of 



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