Q The Philippine Journal of Science i9i6 



CHLORINATION 



In spite of the purification effected by storage, the city water 

 as it leaves the reservoir has a rather high bacteria count, and 

 as it is a surface water, there is always a chance of contamina- 

 tion. Therefore chlorination has been resorted to further to 

 purify the water. The method of application is simple. Chloride 

 of lime is mixed with water to form an emulsion, strained to 

 exclude large particles, and poured into the water just as it 

 leaves the reservoir and enters the main service pipe. The 

 addition of disinfectant is regulated according to the flow of 

 water, the latter being determined by means of a Venturi meter. 

 The water has a fairly high velocity and is sufficiently agitated 

 by its own motion to insure thorough mixing within a few 

 minutes. 



There are a number of factors militating against the efficiency 

 of the chlorination. The turbidity and high content of organic 

 matter greatly reduce the sterilizing action of the chlorine. Only 

 limited amounts of chloride of lime can be used on account of 

 the disagreeable odor imparted to the water by relatively small 

 additions, probably because of the high temperature (27-29°) 

 of the water and because of the lack of a period of storage 

 between the time the water is chlorinated and the time it enters 

 the service pipes. There is no provision made for destroying 

 any excess chlorine. 



Owing to sedimentation in the distribution pipes and to other 

 factors, comparison of the unchlorinated water in the reservoir 

 and the water from the city taps has given confusing results. 

 In the series of observations here enumerated, therefore, it has 

 been found advisable to study the water at two places, the first 

 at the reservoir, the second at a point in the supply pipe where 

 the main distribution system has not been reached and where 

 the velocity of the water has not appreciably diminished. At 

 this second place, located at San Juan bridge, there is a much- 

 used public hydrant in almost direct connection with the main 

 supply pipe at which the water, it is calculated, arrives about 

 forty-five minutes after it leaves the reservoir. As nearly as 

 could be ascertained, by bacteriological tests of the water in 

 different parts of the distribution system, the chloride of lime 

 reached its maximum effect at about this point. 



As might be expected, the chemical change in the water caused 

 by chlorination is slight. There is an insignificant increase in 

 turbidity, while alkalinity, hardness, and total solids show no 

 appreciable change. The variation in chlorine and oxygen-con- 



