What is the primary purpose of backwashing a rapid sand filter?

Prepare for the American Water Works Water Treatment Plant Operator Test. Study with multiple choice questions, each with hints and explanations. Get ready to excel!

Backwashing a rapid sand filter serves to clean the bed by removing the solids that build up as water passes through it. Over time, fine particles accumulate, forming a mud layer that clogs the pore spaces and increases head loss, which reduces filtration efficiency. Reversing the flow fluidizes the bed and carries the trapped material to waste, reopening the voids so the bed can again pass water at the designed rate. After backwashing, the sand settles back into a porous, clean state ready to continue filtering. This is a mechanical cleaning process and it does not add chemicals, change temperature, or oxidize iron.