
Flow to filter is stopped |

Backwash is started and bed fluidizes |

Backwash continues as long as required to flush
particles blocking flow from filter |

Particles blocking flow from filter are now in
water above media |

Backwash stops. Particles coated with biofilm settle into original pre-backwash position - on the
surface of the media |

Water containing suspended particles is discharged
|

State of filter after backwash
and discharge complete. Note that the particles with
biofilm are at the surface |

Filtration
resumes |