The Design and Care of Rapid‐Sand Filters

At the risk of bringing down the wrath of some sanitarians, it will be stated that the real purpose of rapid-sand filtration is to remove turbidity, odor, taste and color from water. It is not to remove bacteria, although the process actually does remove a large proportion of those present. If the standards of removal of turbidity are as rigid as they should be, the removal of bacteria will be correspondingly high, so that the cost and difficulty of the later sterilization will be decreased. Under most conditions, however, if the filters remove practically all of the turbidity, odor, taste and color from the water, they have done all that should be expected of them and any further disinfection that may be necessary should be accomplished by other