INSTRUMENTATION FOR INVESTIGATING AND OPTIMIZING FILTER BACKWASHING

Backwashing of rapid gravity filters is an important part of the water treatment process, particularly in drinking water treatment. Understa nding the mechanisms in the backwash process is fundamental for the de sign of an effective and efficient backwash system, The development of instrumentation to increase our knowledge of backwashing has shown th at combined air and water wash is the most effective method of cleanin g the bed, although this may cause operational difficulties requiring a different design of filter, Techniques that have been developed to s tudy backwashing include the use of video cameras and endoscopes with subsequent image analysis, More recently, work has focused on the deve lopment of pressure transducers for detecting whether the bed is being subjected to sufficient agitation, e.g. that collapse-pulsing is occu rring within the bed, The paper-describes the development of these tec hniques and the results of laboratory and full-scale research that has employed them.