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Thread: Filters Backwash - Water treatment

  1. #1
    Associate Engineer
    Join Date
    Oct 2013

    Filters Backwash - Water treatment


    I have two alternatives from which I need to choose:
    used backwash water shall be recirculated to the head of the water treatment
    without any further treatment.

    Designing a separate treatment for the used backwash water.

    The water treatment includes coagulation & flocculation, sedimentation and filtration.

    Can you please advise me why should I design a special side process for the used
    backwash water? In any case, most of the side treatments include the same
    processes as the main line.

    Source of water is a river and capacity is pretty low (about 700 m3/hr)


  2. #2
    Technical Fellow Kelly_Bramble's Avatar
    Join Date
    Feb 2011
    Bold Springs, GA
    Welcome to EE!

    This question is way out of my knowledge realm...

    I would first suggest that you research out any local od national regulations on how to design for water treatment. If no regulation are available I would suggest using the most likely to succeed design.

    It is way easier to over engineer than to engineering it "just right"...

    Good luck

  3. #3
    Associate Engineer
    Join Date
    Oct 2013


    Thank you

  4. #4
    New Member
    Join Date
    May 2023
    For a small plant like this, recirculating backwash water at the head of the plant is OK.
    Special separate treatment of the used water by a different, more efficient method (eg. lamellar sedimentation, membrane filtration, etc) may be necessary if raw water contains compounds that will not settle in the clarifiers. For example asbestos fibers or ******sporidium will be caught in the sand filters at low raw water concentrations, but if continually recirculated at the head of the plant with the backwash water, will over time raise the concentrations going into the filters and eventually escape in the filtered water.
    You are right to question a retreatment of the used water by the same process.
    Hope this is of help.

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