at a reasonable cost can be secured for adding 

 chlorine to water in the proper dosage to destroy 

 harmful microorganisms. Such chlorinators are 

 essentially small liquid pumps that measure out 

 a certain dosage of chlorine and inject it into the 

 correct quantity of water. Chlorinators may be 

 operated by an electric motor, by a belt drive 

 from a water pump, or by a watermeter. 



An advantage of an automatic chlorinator is 

 that it can be used to add other chemicals to the 

 water to remove manganese and iron, destroy 

 iron bacteria, neutralize acid waters, control algae, 

 and correct certain tastes and odors. 



Ultraviolet sterilization is a practical alternative 

 method of water treatment. Certain psychrophilic 

 bacteria, known to be able to break down the fat 

 and protein in milk, resist very high concentrations 

 of chlorine (81). Concentrations of chlorine neces- 

 sary to destroy viruses and protozoa which have 

 formed cysts are not well understood. The latter, 

 which are particularly chlorine resistant (64) may 

 be present in ground water in areas where frac- 

 tured rock or limestone channels exist. Recent 

 developments in the design of components make 

 ultraviolet (UV) radiation an inexpensive and 

 generally successful method of treatment. Re- 

 cently, the USPHS accepted UV purification of 

 water if the installation includes safety devices 

 which shut off the flow of water if the intensity of 

 the light falls below acceptable levels. Meters have 

 been developed to keep a permanent record of UV 

 treatment. Ultraviolet treatment has the advantage 

 that it will destroy all types of microbial life known 

 to be a problem in farm water supplies (70). 



Limitations to the UV treatment of farm water 

 supplies include the fact that UV treated water 

 has no residual action, thus any contamination 

 beyond the point of treatment will pass to the 

 finished water supply. Periodic flushing and dis- 

 infection of the water distribution system must be 

 provided. Turbid waters will quickly coat the lamp, 

 reducing UV intensity. If automatic signalling 

 devices, instaUed to stop the flow of water, are not 

 properly treated, such coating could occur during 

 a period of abnormally heavy demand (as in fire- 

 fighting) . Insurance underwriters may cancel con- 

 tracts when UV systems are instaUed if an outlet 

 is not provided ahead of the treatment site for 

 fire protection. 



Heat treatment is satisfactory for destroying 

 normal water flora just as UV sterilization is 

 advantageous for treating chlorine-resistant bac- 

 teria. The system simply requires heating water 

 to a prescribed temperature for a sufficient length 



of time. An ordinary water heater can be used 

 if the temperature is high enough (756). Sediment 

 or temporary hardness will cause problems unless 

 removed prior to heating. When cool water is 

 needed, the heat must be removed, thus creating 

 a cost for cooling as well as heating. The water 

 pasteurizer has been accepted in some parts of the 

 country but is generally considered to be somewhat 

 expensive in comparison with chlorination and UV 

 treatment. 



Removal of Iron and Manganese: Insoluble 

 iron and iron bacteria will intensely foul the 

 mineral bed and the valves of a water softener. 

 Therefore, it's best to remove iron and manga- 

 nese before the water reaches the softener. 



Iron and manganese can be removed by a com- 

 bination of automatic chlorination and fine fil- 

 tration. The chlorine chemically oxidizes the iron 

 (forming a precipitate), kills iron bacteria, and 

 eliminates disease bacteria. The fine filter then 

 removes the iron precipitate. Some filters may 

 dechlorinate also. This chlorination-filtration 

 method corrects the iron problems and assures 

 disinfection as well. 



Iron can be removed effectively from water by 

 aeration and by some types of softening equip- 

 ment. 



Neutralization of Acid Water: Acidity of water 

 is usually caused by dissolved carbon dioxide. 

 The carbon dioxide, from decaying vegetation, 

 forms carbonic acid. Acid water can cause corro- 

 sion of the water system and release of objection- 

 able metallic ions. Acidity of water is easily cor- 

 rected by addition of a neutralizing solution. 



To correct acidity and disinfect with the same 

 equipment, a neutralizing solution may be fed 

 into the water supply by mixing with the chlorine 

 solution. Satisfactory equipment for adding soda 

 ash in powdered form is also available. 



Other methods for minimizing the effect of acid 

 water are: 



(a) Installation of plastic pipe for cold-water 

 lines when constructing new systems; 



(b) Reduction of the temperature of hot water; 

 and 



(c) Removal of oxygen or acid constituents 

 from the water. 



Control of Tastes and Odors: Depending upon 

 the cause, taste and odor can be removed or re- 

 duced by aeration or by treatment with activated 

 carbon, copper sulfate, or an oxidizing agent such 

 as chlorine. 



Aeration is an effective treatment for water 



128 



