Filter Problems and Water Softening

The problems connected with filtering water which has been softened with lime and soda, or with lime alone, are not necessarily more troublesome than those of filtering other treated waters. In some cases they are fewer and simpler than they would be without softening. When treated and settled water is brought to the filters in chemical balance, and with turbidity reduced to only one or two parts per million, it may well be expected that filter runs will be long and filter problems reduced to a minimum. Such is the case. Runs of 100 to 200 hours are not uncommon at some plants. Algae interference with filter runs is but little known. It is true that crustacea such as Cyclops and Daphnia sometimes collect in drifts on filter beds in softening plants and at times insect larvae may reach the filters in great numbers, but the smaller microscopic plankton which shorten filter runs are so thoroughly removed in the settling basins that they are not noticed in the applied water at all. «ludging by the results obtained at times, one would seem to be justified in proclaiming the gospel of perfection in treatment as the cure or preventive of all filter troubles in a water softening plant, and this should indeed be kept in mind. It is along this line that water softening practice has been moving. But this gospel is only another way of saying that filters will work well if they have nothing to do.