(3) The operation of filtration and washing is very important.
The municipality owns its waterworks and filtration plant.
The city added to its waterworks a filtration plant, with a total capacity of 150,000 gal.
There are pumping works and filtration beds for the water-supply of London.
Sand filtration, even when working in the best possible manner, falls short of the perfection necessary to prevent the passage of bacteria which may multiply after the filter is passed.