MICHIGAN ACADEMY OF SCIENCE. 
77 
system depends on several treatments with ozonized air of a low con- 
centration. 
While there is no longer any doubt of the ability of ozone to purify 
water if conditions are right there is one factor that stands in the way 
of its very wide adoption at the present time. That is the considera- 
tion of the cost of operation. While an ozone plant could probably be 
installed as cheap if not somewhat cheaper than slow sand filters the 
cost of operation is many times higher and needless to say depreciation 
much greater. 
The following table shows approximate maximum and minimum costs 
of installation and operation of the four leading types of water puri- 
fication devices. The unit of quantity being one million gallons per 
day in each case. 
Slow sand filters. 
Mechanical filters. 
Ozone. 
Hypochlorite. 
Min. 
Max. 
Min. 
Max. 
Min. 
Max. 
Min. 
Max. 
Capital 
$35,000 
$50,000 
$10,000 
$25,000 
$15,000 
$25,000 
$2,000 
$4,000 
Operation (not includ- 
ing interest) 
$1 40 
$3 00 
$2 00 
$4 00 
$7 00 
$15 00 
$0 20 
$0 70 
Supposing Detroit which until recently at least had no system of 
water purification should adopt one of these methods what would be 
the effect on the meter rate. The meter rate as given a few months ago 
being .$30.80 per million gallons — $1.75 for the first thirty thousand gal- 
lons and then three cents per thousand. 
Without allowing for interest the rates would be something like this: 
Slow Sand. — Minimum .... ($32.20) Maximum ($33.80) Per million. 
Mechanical. — Minimum .... ( 32.80) Maximum ( 34.80) Per million. 
Ozone. — Minimum ( 37.80) Maximum ( 45.80) Per million. 
Hypochlorite.— Minimum . . ( 31.00) Maximum ( 31.20) Pier million. 
I do not doubt but that if some cheaper way, either chemical or 
electrical, for the production of ozone should be discovered that the 
process would find extensive application as a means of water purifica- 
tion. However, at the present time we have other methods that are 
very efficient and which are much more economical. 
