Coagulation of Surface Water

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There's a pipeline work upstream our plant and this has lead to an increase in total suspended solids of our raw water.

I am having trouble with coagulation.

I am using poly aluminum chloride as coagulant.

Raw water turbidity is 200-240 NTU.

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13 Answers

  1. Thanks to all the experts that contributed to this post.

    Currently have been able to get the coagulation right by varying the dosing rate and the purifier inlet flow.

    About jar test the company I work for have no provision for jar test. However, over the years have been able to master the characteristic of my raw water across the seasons.

    The current problem may be as a result of pipeline work upstream.

    Thanks.

  2. I would suggest carrying out jar tests looking at different coagulants, as it could be an alternative one could be better. But also use jar tests to establish the ideal pH and coagulant dosage. Jar tests could be carried out in combination with zeta potential measurements. 

    1 Comment

  3. Hi Brown,

    I suggest you test the physicochemical properties of the water to know the coagulants that will get the job done. You can perform jar tests, for each coagulant to determine the best one and quantity to be used.

    Regards

    1 Comment

  5. If the work upstream has caused upsets in your process then you have to find out exactly which water analysis parameters have changed i.e is it turbidity, pH, toc? Usually, if the PAC was working well before then it should still work, only now you have to compensate for the changes in the mentioned parameters by using a polyelectrolyte to deal with the high turbidity or adjusting the pH. If the organic content of the water has significantly increased, you might need to try Ferric Chloride as your primary coag. If these strategies do not work, then you have no other choice but to redo the process of finding a new coagulant altogether by doing new jar tests with many different reagents. Good luck.

  7. My experience with water treatment in water with high turbidity is very good. Normally I have problems with water with high colour. Of course you have to do several jar tests to find the best coagulation dosage. pH and alkalinity are also very important factors.

    I wish you good look in your trials. Best regards

  9. Whenever there is a  change in raw water inflow conditions or characteristics affecting flocculation, do a batch of jar tests with different poly types and different solution, also check if pH has changed?

    this should get you back on track

  11. You can check a higher doses of coagulant with corelation of the optimal pH range for the coagulant and you can try to use some of floculant. 

    Is the high turbidity is mainly organic or inorganic mater? 

    Do other paramiters of raw water increased? (excepting turbidity)

    2 Comments

    1. As early, I and the other have sugested, you should test a new optimal dose of the coagulant and optimal pH ​value for coagulation or you should try to use another  coagulant, for example aluminum sulfate, or mixture of different coagulants) and for the best flocculation you will try to use some polymer. For these necesery you should carry on laboratory tests. Good luck and good results!