Backwashing (water treatment)

In water treatment plants, backwashing can be an automated process that is run by local programmable logic controllers (PLCs).

At the end of the backwash cycle, the upward flow of water is terminated and the filter bed settles by gravity into its initial configuration.

John R. Baylis developed a fixed grid system which consisted of pipes with nozzles that injected jets of water into the filter material during expansion.

A surface wash step in a backwash cycle usually takes place at the beginning of the filter bed cleaning process.

[3]: 199–200 [7]: 357–60 Spent backwash water is either discharged without treatment to a sanitary sewer system or is treated and recycled within the plant.

[10] The purpose of the regulation was to improve the control of microbial contaminants such as Cryptosporidium, by reducing the potential for recycled product streams to upset the removal efficiency of the main treatment processes.