Chlorine disinfection by-products sometimes become not under control because of high temperature or the necessity to add high doses of chlorine. So could advanced oxidation process (AOP) be used for removal of chlorine disinfection by-products, or generally in drinking water treatment process?
Hi Mr Ali
Advanced oxidation processes may be effective, but should be considered that this process are very expensive and complex and even can generate other adverse by-products. Thus, we must looking for better, cheaper and safer ways.
Advanced oxidation are both generally expensive treatment methods and known to have difficulties with degradation of chemicals containing many chlorine atoms such as the disinfection byproducts trihalomethanes and haloacetic acids.
It is usually better to treat the water before chlorination to remove the precursors (oxidation, sorption, coagulation).
Re: Dr Henrik
So Dr Henrik, is their limitation for use of AOP with surface water. In your opinion, what is the appropriate treatment technique with high ammonia level surface water.
Sorry Dr but if you please see this question also.
https://www.researchgate.net/post/What_makes_chloral_hydrate_at_high_concentration_although_concentrations_of_other_chlorination_by-products_are_below_MCL
thank you
I suggest to apply a treatment before chlorination to reduce the concentration of disinfection by-product precursors.
There are many methods in use in waterworks around the world: Ozone, permanganate, chlorine dioxide as pre-oxidation agents or sorption with powder activated carbon.
The optimal methods should be selected based on comparing cost of treatments with efficiency of the different treatment methods at different doses. The evaluation is done is batch experiments there the water treated with different doses of the treatment agents are chlorinated in standard conditions followed by analysis of disinfection by-products.
Hydroxyl radical produced in AOPs having higher oxidation potential (2.85V) than that of chlorine. Then what is the use of AOPs after chlorination? Anyway OH radical can attack organic compounds, even at complex form.
I do agree with Dr Andersen, the best way to decrease desinfection by-products is to reduce the level of dissolved organic carbon before chlorine desinfection. Once chlorine desinfection is applied it is not adapted to apply AOP because free chlorine will be destroyed and not available to ensure a remanent desinfection. I give just a precision, AOP do not have difficulties to degrade organic compounds containing chlorine atoms.
Drs. Nidheesh and Brosillon and López,
I did not write the AOP cannot degrade chlorinated by-products but that it is difficult.
Generally in AOP the rate constants for reaction of the hydroxyradical is about the same for most organic molecules, but for molecules that contain several chlorine atoms per carbon atom the rate constants are significantly lower (2-3 order of magnitude).
The implication of this in an AOP process applied to a real drinking water would be that you would need to essentially mineralize all the organic material in solution before you see significantly degradation of the chlorinated by-products. The cost of such a treatment is unrealistic high for full scale applications.
Our research demonstrated that chlorinated THMs and HAAs are poorly removed by UV/H2O2. Brominated DBPs are removed; primarily mechanism is direct UV and not reaction with hydoxy radicals. The citation is below.
Jo, C-H., A.M. Dietrich, J.M. Tanko. Simultaneous degradation of disinfection byproducts and earthy-musty odorants by the UV/H2O2 advanced oxidation process, Water Research, 45: 2507-2516, 2011.
We have similar results for direct photolysis of DBPs in pools with the UV lamps that are used in many municipal pools in Europe for combined chlorine control. Several of the more toxic brominated DBPs are removed significantly by this treatment.
Article Photolytic removal of DBPs by Medium pressure UV in swimming...
A colleague has written a review paper on DBP precursor removal that also covers AOPs. You may find this useful:
T. Bond , E.H. Goslan , S.A. Parsons & B. Jefferson (2011): Treatment of disinfection by‐product precursors, Environmental Technology, 32:1, 1-25
Dr Bolton, I am glad you agree as I have learned this from your book.
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