Discussion Page on Coagulation and Flocculation in Water and Wastewater Treatment

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  • Pushpanathan Sellappan
    Pushpanathan Sellappan, 2010/04/15 10:36

    In water treatment alum is being used as one of the coagulant to reduce the turbidity/TSS of raw water. For a same turbidity of raw water the alum consumption to maintain the treated water turbidity as 0.95 NTU (for ex.) is varing. What could be the reason. or what are all the factors that increases the alum consumption.

    • frank sun
      frank sun, 2014/01/16 08:27

      The coagulation principle for any coagulant maybe the same,but different at that the floc settling flog size and velocity is different. Alum floc is called assembling body settling, but such as calcium floc is called crystallization settling. Difference at the molecule weight ,operation temperature,floc settling style cause different coagulation agent consumption.

  • Brian Hemphill
    Brian Hemphill, 2012/12/15 03:27

    I can think of two things, from my experience. Alum demand is sometimes affected by pH and/or alkalinity. If the pH and/or alkalinity are higher, then alum demand may go up. A second factor is dissolved organics, which sometimes shows up as color. That is likely the biggest factor in what you are seeing. This is typically a seasonal issue with surface waters, depending on what might find its way into the water, such as decaying leaves in the fall and winter.

  • Estíbaliz Huete
    Estíbaliz Huete, 2013/12/03 15:04

    There are a lot of factors that can affect the alum consumption. The ones that Brian Hemphill told before, and I would like to point out the importance of temperature: changes in temperature affect a lot the water nature (note that in this sense, it is very important the source of the water, for example, in lagoons and reservoirs the effect of temperature is critical)and also the effectiveness of the coagulants.

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