Increasing density of population brings with it one penalty that cannot be escaped, an increase in the amount of waste from human bodies which must somehow be permanently removed. One of the simplest methods of sewage disposal is to turn the sewage into some body of water so large that oxidation processes may go on and a nuisance be avoided. This practice was long fraught with disastrous consequences to drinking water supplies, and in the generation before methods of water filtration and chlorination were worked out and applied, typhoid and kindred diseases ran riot. Although water-borne typhoid in this country is now largely a thing of the past, there are signs that the pollution of many streams is again approaching a danger point.
When the pollution of streams reaches a certain stage, it becomes more difficult and in some cases impossible to utilize the water for domestic use. There is