Wiktionary
n. A form of water treatment in which water is pumped backwards through the filter media, sometimes with intermittent use of compressed air.
Wikipedia
In terms of water treatment, including water purification and sewage treatment, backwashing refers to pumping water backwards through the filters media, sometimes including intermittent use of compressed air during the process. Backwashing is a form of preventive maintenance so that the filter media can be reused. In water treatment plants, backwashing can be an automated process that is run by local programmable logic controllers (PLCs). The backwash cycle is triggered after a set time interval, when the filter effluent turbidity is greater than a treatment guideline or when the differential pressure ( head loss) across the filter exceeds a set value.
Water treatment filters that can be backwashed include rapid sand filters, pressure filters and granular activated carbon (GAC) filters. Diatomaceous earth filters are backwashed according to the proprietary arrangement of pumps, valves and filters associated with the filtration system. Slow sand filters and self-cleaning screen filters employ mechanisms other than backwashing to remove trapped particles. To keep water treatment filters functional, they have to be cleaned periodically to remove particulates. Ineffective backwashing is one of the main reasons that water treatment filters fail.
Usage examples of "backwashing".
His presence seemed to swirl and eddy around me, backwashing against the partitions of my cubicle and rising until it seemed he was behind me, too.
My nostrils flared as force surged into me, backwashing at my theoretical extremities until the power equalized.
This was the phenomenal effect of a sailship's amazing gravitonic sails, backwashing the torrent of gravitons back up and out of the black hole, pulling in a depression in the first event horizon as the backwashing gravitonic flow reduced the black hole's universe ripping effect.
His whisper of breath followed his thoughts through my being, backwashing into a warm wave that soaked into me like water through sand.
My own blood began to dribble down my chin and I turned my face back, backwashing my own blood into the torn flesh of Chalice's abdomen.