IOWA ACADEMY OF SCIENCES. 
81 
num saturated with the turbid matter and bacteria. The 
water collects in a large reservoir beneath, which supplies 
the city, 2,000,000 gallons being required daily. 
Nature’s plan of water purification consists of: 
Mixing waters. 
Filtration and sedimentation, 
Action of bacteria upon impurities. 
Sunshine and air. 
With the exception of sedimentation these processes are 
in vogue at the local plant as explained above. All correct 
methods of water purification are imitative of nature. 
Through the action of water bacteria upon impurities 
many forms of pollution are removed. 
During the first half of this month (April) the water 
has been in good condition, the gas forming bacteria exist- 
ing in very small numbers, frequently not at all. 
Bacteria coli communis were not found in the water 
during the time mentioned. In the latter part of Febru- 
ary and in March gas forming bacteria were very 
numerous, among them being found the coli communis. 
The water bacteria average about four hundred to the 
cubic centimeter. 
The following is the results of my analyses from Sep- 
tember to April, inclusive. The bacteriological work did 
not begin until March. The average of each month is 
given, and the chemical ingredients are calculated to parts 
per million. Nitrogen only in nitrogen compounds is 
given. 
Months. 
Bacteria, 
Free Ammo- 
nia. 
Alb. Ammo- 
nia. 
Nitrates. 
September. 
.04 
.13 
.50 
October 
.04 
.16 
.52 
November. 
.03 
.09 
.31 
December 
.07 
.09 
.62 
January 
.20 
.08 
.80 
February. 
.48 
.05 
.25 
March ...... 
500 
.50 
20 
.60 
April .... ........ 
410 
.26 
.20 
.32 
Nitrites. 
Chlorine. 
Total solids. 
Volatile mat - 
ter. 
Fixed resi- 
due. 
.00 
4.5 
268 
57 
211 
.00 
4.5 
349 
62 
287 
.00 
4.4 
3 
64 
250 
Trace. 
4.6 
313 
64 
249 
Strong. 
5.25 
346 
70 
276 
Strong. 
6.25 
313 
48 
275 
Strong. 
5.20 
270 
47 
223 
Trace. 
6.16 
322 
49 
273 
6 
