326 WATER HYGIENE 
attention has to be given to the amount of bleach being added because 
one important function of storage, as Houston has pointed out, is 
equalization. 
For a time, there was some discussion with regard to whether the 
bleach should be added to the raw or filtered water. At present it 
seems to be the consensus of opinion that it should be added to the 
filtered water. The following facts bear on the consideration: 
1. When it is added to the raw water, a greater amount is required. 
2. The life in the ‘‘ schmutzdecke ” on the filter may be destroyed. 
3. Reactions between the organic matter and chlorine may yield 
compounds imparting a bad taste. 
4. The addition to the filtered water is easier since there would be 
no cumulative effect. 
The method of adding it to the filtered water has been standardized. 
It is usually mixed to a thick cream and later diluted with water. After 
settling, it is fed to the water supply through standard orifices by which 
the amount applied is regulated. This is an important part of the pro- 
cedure since overdosing must be avoided. 
Race (1918) has shown that by using a little ammonia along with the 
bleach, the amount of the bleach may be materially reduced. He 
regards the possibility of chloramine being formed as fairly conclusive. 
On Ottawa River water at flood period, when the water contained 
from. 500 to 1000 B. colt per cubic centimeter, satisfactory results were 
obtained with 0.60 p.p.m. of available chlorine, and 0.13 p.p.m. of 
ammonia. This method of treatment is recommended for those waters 
where the margin between the dose required for satisfactory treatment 
and successful purification is small. It is well known among certain 
practical waterworks men that such is often the case. The character of 
the raw water may demand an amount of bleach which is very close 
to the amount which may be tasted in the water. 
The question of tastes has caused much trouble to practical water- 
works men. Some of the essential oils excreted by microorganisms 
resemble very much the odor of chlorine. This has caused undue blame 
to be put on the bleach. Lederer and Bachmann (1912) found that 
under experimental conditions the average amount of available chlorine 
that could be detected was around 0.6 p.p.m. while 0.5 p.p.m. could 
often be detected. Van Brunt placed the amount that could be tasted 
at 0.6 p.p.m. While the chemical nature of these compounds which 
cause tastes in water treated with chlorine has not been carefully inves- 
tigated, it is generally admitted that they may be related to the chlora- 
mines. 
