Settling difficulty

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Good day fam. 

I'm at a water treatment plant in Ghana. 

We were previously using aluminium sulphate salt for our coagulation process. 

Until recently we changed to electrolyte polymer. 

I have run flocculation test on a range of dosages. Dosage range of 15ppm - 25ppm work at the lab but when applying on the plant, the flocs don't settle. We even experience carry over at nights. 

Any suggestions? 

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11 Answers

  1. Several parameters, including mixing speeds, mixing intensity, and mixing time. The product of the mixing intensity and mixing time is used to describe flocculation processes.

    Check the following

    1. Check the equipment (bottom parts rack) rotating in settling unit
    2. Feed velocity and resistance time.
    3. Check reagent (aluminum ​sulphate salt )analysis.
    4. If not possible then add biological with settling.

  2. Hi,

    the problem is not with the coagulant, its the clarifier rake that broken, thus causing the floc to rise?

  3. Dear Abdulai,

    what is the retention time for the flocculation process? With alum salts, the floc formation is much faster than with polymer. With alum it might take 2 - 5 min, with polymer 30 - 45 min. Besides, you need to apply different mixer types and different mixer velocities when changing from a salt based coagulant to an organic flocculant.  

    Regards

    Carlos

  4. Aluminum is a suspect 

    Caused chemical 

    To prevent application 

    it strongly suggest 

    For the settling problem 

    I suggest to carry out jar test 

  5. From the info you gave, I'd say that the conditions at the plant might not have been faithfully duplicated in the lab. Also, be careful when you try to batch test a continuous operation.

    Answered on by

  6. We supply complete turnkey plant for bottling water.. and attached herewith 6000BPH complete bottling plant .. and you can use only water purifying plant without bottling plant and 
    also without hydrogen Hydrogen .

  7. Hi Abdulai, you have given us very limited information, but something else to consider is if the polymer is adequately diluted at the point of dosing, followed by adequate rapid mix and flocculation before settling. Without knowledge of the polymer I would say that the polymer should be less sensitive to rapid mix and flocculation energy than aluminium sulphate, while dilution could potentially be a bigger problem. Hope you get it sorted.

  8. You have to caliberate your Flow Rate dosing pump to insure that the dose you tested in lab. Is the in the field

  9. Hello,

    For the accelerated deposition of flocculants, clay particles and other polar compounds, we apply our in=house developed technique of electrosedimentation. In the case of positively charged particles, the anode is placed at the top of the tank and the cathode at the bottom of the settling tank. Otherwise, the position of the  electrodes are reversed. 

  11. Do you have NX filtration membranes?