In some instances, water sources near bodies 

 of salt water may be contaminated with salt due 

 to lowering of the water table. Once contamina- 

 tion occurs in this manner, restoration of the 

 underground aquifers is not considered economi- 

 cally feasible. 



In dairy sanitation, cleaning chemicals can be 

 selected to correct many problems of common, un- 

 desirable chemicals in the farmstead water supply. 

 Removal requiring expensive treatment systems 

 is unusual. 



Water Treatment Possibilities, Including 

 Economics 



The quality requirements for water to be used 

 on a farm are not difficult to meet in most cases. 

 Treatments which render a supply potable, com- 

 bined as necessary with treatments to remove un- 

 desirable chemicals, are sufficient for most ground 

 water sources. 



The use of surface water should not be con- 

 sidered unless ground sources are undependable 

 or unavailable. Surface water should always be 

 considered contaminated and individually tailored 

 treatment processes must be used to make it safe 

 as well as satisfactory for farm uses encompassed 

 by this report. Farm ponds, if properly maintained, 

 can provide raw water of high bacteriological 

 quality requiring a minimum of treatment to be 

 made suitable for domestic and livestock uses 



UOO). 



Microbial Contaminants and Their Control: The 



common method for controlling pathogenic bac- 

 teria has been chlorination in any one of several 

 ways. Certain problem areas must be considered 

 if the system is to be successful. The following 

 are important: 



(1) The chlorine demand in the raw water 

 supply may vary greatly. This is particu- 

 larly true of surface water or when it is 

 obtained from several sources. When chlo- 

 rine demand is low, the water may be 

 objectionable to taste because of excess 

 chlorine in the system. The operator may 

 reduce the rate at which chlorine is fed 

 into the system which then becomes inade- 

 quate when chlorine demand again in- 

 creases. 



(2) Chlorine-feeding equipment differs greatly 

 in cost and design. Venturi systems which 

 become inoperative may disrupt the entire 

 water system. Sediment may be a prob- 

 lem in some systems and equipment should 

 be recommended by competent authority. 



(3) Chlorine mixing must be complete and an 

 adequate residual maintained. The system 



must allow sufficient contact time for maxi- 

 mum killing efficiency. This is not possible 

 in some types of equipment nor is it pos- 

 sible in systems which do not include a 

 mixing tank as a basic component. Com- 

 plete mixing is unlikely in the piping sys- 

 tem alone (755). 



(4) An adequate supply of chlorine must be 

 available at all times. Chlorine residuals 

 must be checked and equipment inspected 

 on a regular basis. Human error and ne- 

 glect are common problems in the opera- 

 tion of individual, small water systems. 



(5) Certain water supplies may give a false 

 picture of the efficiency of a chlorination 

 system. Nitrites, manganic manganese, or 

 ferric iron in water will produce a false 

 color when a free-chlorine residue test 

 is made. Water which is highly alkaline or 

 very cold is more difficult to disinfect. In 

 some hard waters, precipitates may par- 

 tially clog the check valves of the feeder 

 pump, reducing its effectiveness. 



Shaw {155) has commented on some of the 

 problems commonly encountered in treating indi- 

 vidual farm water systems to remove pathogenic 

 bacteria. He states that: 



The big problem today is not whether or not something 

 should be done about individual water systems, but rather 

 what and how. It is a problem that is at the same time 

 both extremely simple and frustratingly difficult. 



The simple part is that the bacteriologists can tell us 

 what kills most pathogenic organisms and the sanitary 

 engineers can tell us what methods and equipment have 

 been in successful use for years in municipal waterplants. 



The difficult part is the adaptation of proven methods 

 and techniques, or the development of new ones, which 

 will, at a low cost, automatically and surely perform an 

 operation that in a municipal water treatment plant re- 

 quires expensive equipment, constant maintenance, super- 

 vision, adjustment, and testing by trained personnel. 



It is also reported by Shaw that about half 

 of the individual water supplies tested in Penn- 

 sylvania were found to be polluted. Many of the 

 water treatment devices in use are not doing an 

 effective job even though they satisfy regulatory re- 

 quirements. He points out that monthly sampling 

 of individual water systems "seems unreasonably 

 troublesome and expensive," yet the usual require- 

 ment of annual sampling is inadequate. 



There are three common methods and many 

 pieces of commercial equipment which may be 

 used in the treatment of water in individual sys- 

 tems. The methods are chlorination, ultraviolet 

 sterilization, and heat treatment. 



Chlorination is best accomplished by the method 

 known as superchlorination. Efficient equipment 



127 



