EXPERIENCE WITH POWDERED ACTIVATED CARBON [with DISCUSSION]

The availability of a cheap powdered activated carbon opens wide the field for experimentation with its use in combating tastes and odors in water supplies from existing water purification plants. Several plants have adopted the application of powdered activated carbon to remove tastes and odors, some shifting the point of application in a search for the most effective treatment with existing facilities. None, however, has yet made structural changes in facilities designed to secure the greatest efficiency of the carbon. Through the cooperation of those responsible for introducing powdered activated carbon in the treatment of water at fifteen purification plants, it has been possible to summarize the methods used and results obtained. In this early experimental stage, with a substance that acts differently on different impurities in water, it is not surprising to find differences in adopted methods and in results obtained from its use in the treatment of water from fifteen different sources of supply. The popular method of applying the powder is to run it through a dr> feed machine into a hopper where water is added and a water eductor picks up the mixture and forces it through a pipe or hose to the point of application. Efficient distribution through the water appears highly desirable. At one small plant a pound of powder is thrown into the filter wash water trough when influent water is admitted following the washing operation. The efficacy of this method is naturally limited. Another way is to maintain a water suspension of the powder by agitation and pump the mixture through a pipe fitted with nozzles located below the water surface at the point of application. Apparently the dry feed and water eductor means of introducing proportional amounts of the powder are best adapted for feeding considerable volumes and present no difficulties. The black dust makes it desirable to handle the powder in a room or building separated from other operating rooms of the plant and it is