Back-washing Systems

In terms of water treatment, including water purification and sewage treatment, backwashing is the term for pumping water backwards with the filters media, sometimes including intermittent using compressed air during the process. Backwashing is really a form of preventive maintenance so the filter media could be reused. In water treatment plants, backwashing may be an automated procedure that is run by local programmable logic controllers (PLCs). The backwash cycle is triggered after having a set time interval, if the filter effluent turbidity is greater treatment guideline or in the event the differential pressure (head loss) along the filter exceeds a predetermined value.

Water treatment filters that could be backwashed include rapid sand filters, pressure filters and granular activated carbon (GAC) filters. Diatomaceous earth filters are backwashed in line with the proprietary arrangement of pumps, valves and filters linked to the filtration system. Slow sand filters and self-cleaning screen filters employ mechanisms in addition to backwashing to get rid of trapped particles. To keep water treatment filters functional, they should be cleaned periodically to clear out particulates. Ineffective backwashing is among the main reasons that water treatment filters fail.