Design and Operation of High‐Rate Filters‐Part 1

coagulation and filtrationso much so, in fact, that under certain conditions, adequate treatment might be carried out in the filters alone, thus eliminating the need for coagulation, flocculation, and sedimentation tanks. This procedure often can produce a better quality of water at a considerably higher flow rate than can conventional sand filters where filtration is simply the last step in a four-step process. Even so, it is acknowledged that not all types of water and wastewater-treatment problems can be solved by the filtration process alone and that the conventional approach will probably always be required in certain applications. The primary objective in filter design is to provide a facility for steady production of high-quality water with minimum operational and maintenance costs. Therefore, engineers should be responsible for the design of an efficient, reliable, simple, and economical filter from both operational and construction aspects. Generally, most engineers rely on either their experience or available design criteria in filter design. Filters constructed on this basis usually provide satisfactory results. Engineers, however, should consider certain design variables such as size and thickness of media, filtration rate, and maximum head loss, depending upon the condition of raw water and the required degree of pretreatment. The filter designer should also choose a proper type of filter bottom, filter wash system, and size of filter. -