I treat about 20 000 L of effluent before discharge aiming to correct the pH, Conductivity, reduce sulphates and chlorides to below 1500 mg/l. Reducing the COD as well to levels below 5000 mg/l. I have been achieving good results with ferric chloride as coagulant and reducing the sulphates, suspended & dissolved solids using lime.
I'm just interested in knowing the advantages of using organic coagulants, I do all my preliminary tests in the lab (jar tests) and in my pilot plant on site (treating 1000 L of influent).
It is obvious that in your case the advantage of using an Organic Coagulant will be that no salts will be added avoiding to increase Chlorides. You will on the other hand not achieve the pH reduction that you have by using FeCl3.
Thanks Kim,
I was not getting significant changes in pH any way seeing the amount of the influent I treat. May you please comment on the effectiveness of the coagulants themselves may be?
In terms of the result I will get looking at sludge settlability rate of the sludge, clarity of the resulting liquid? I know I will have to carry out experiments for this but I just want to have a rough estimate if you do have some experience on it.
Well I have some experincve with PolyDADMAC from Kemira and these results were very close to those of using FeCl3, but price wise the operation cost for the Coagulant as almost 50% higher, but sometimes you do not have the choice.
Ok thank you very much, yea FeCL3 works very well for me currently. However I will try a number of the organic coagulants and look at using both FeCl3 and others.
But I must say it's working quiet well with the lime treatment, I have managed to reduce sulphates (obtaining more than 75% reduction), reducing the COD by 72%, TSS from above 1100 FAU down to 28 FAU.
The main advantage of using an organic coagulant is reducing sludge volume and bulk and thus reducing the amount of material to manage (i.e. de-water) or dispose of. These coagulants are very effective; however, as Kim points out, they are pretty pricey. If sludge management and disposal costs are reasonable where you are relative to the price of FeCl, then that's less of a concern. In the USA most facilities have moved away from ferric.
Thanks Karl.
One of our divisions deals with synthetic organic and inorganic coagulants so I will try a few and compare the costs.
In my opinion, the benefit included low cost and little dosage of some organic coagulant application. If use ferric chloride and aluminum sulfate, some pollutant could not be efficiently removed from water and some metal remain residual. Instead of using some natural organic coagulant (e.g., xanthan, chitosan, etc.) they could be use little with high removal efficiency and decomposed by bacteria in short time, most important, they have no persistent second byproduct pollution.