I meant to say chlorate.  Thanks 

Hydrogen peroxide in strong acid environment reduces chlorate, giving the following reaction with chlorate:

ClO3- + ½ H2O2 + H2SO4 give ClO2 + HSO4- + H2O + ½ O2

CLO2 then reacts with H2O2 giving chlorites

Both H2O2 and low pH from adding H2SO4 is likely harming the stream more than chlorate!

Chlorate are reduced by certain anaerobic bacteria so optimizing wetlands and other elements in the watersystem that usually promote denitrification can increase the removal of chlorate from streams.

Yes Dr Anderson, both peroxide and sulphuric acid are not acceptable in this stream. 

Bacterial action is too slow. Liking for sonething that can be introduced to the process

I am looking for something that can be introduced into the process to remove the chlorate. Did explore the use of activated carbon and also tried chemical regeneration. 

The use of activated carbon yielded some interesting results. Although it did not remove all of the chlorate, it was able to reduce it to a sufficient level. The regeneration of the chlorate by chemical methods showed loss in regenerated activity, giving rise to the possibility that some of the chlorate was chemisorbed onto the surface of the AC after reacting with some surface group thus rendering that surface no longer able to adsorb chlorate,

Granular activated carbon in cnntinuous mode can be used for this purpose

Also check this reference, it might be helpfull:

www.who.int/.../dwq/chemicals/chlorateandchlorite0505.pdf

Currently, there is no known completely effective treatment available to remove chlorate ion once it has been formed in potable water. There are three available treatment options for lowering chlorite water: activated carbon, sulfur reducing agents, iron reducing agents. I am not familiar with peroxide work mentioned by others but do know by itself peroxide reactions are notoriously slow-perhaps there is opportunity therein. Activated carbon can remove chlorite through adsorption and chemical reduction but the process is limited by early break-through (short bed life), operation costs, and is complicated with the oxidation of chlorite to chlorate if free chlorine is present in the feed water. If chlorite ion is present in water and is not removed, it will react with any applied free chlorine to produce chlorate and chloride ions. Ferrous iron will chemically reduce chlorite ion but chlorate ion will form only if the pH drops below 5. When the pH exceeds 7, the subsequent reaction of chlorite and ferrous iron forms insoluble ferric hydroxide. Sulfite when combined with metabisulfite will reduce chlorite to form chloride ion and the undesirable chlorate. There are few published peer-reviewed papers regarding chlorate removal. An emerging method that may have promise is using a membrane biofilm reactor – in bench scale work this method achieved 99% removal of chlorate but operational issues limit this usefulness at the large scale [See: Ziv-El, M., Rittmann, B.E. (2009). Systematic evaluation of nitrate and perchlorate biroreduction kinetics in groundwater using a hydrogen-based membrane biofilm reactor. Water Research, 43: 173-181.; Ziv-El, M.C., Rittmann, B.E. (2009). Water quality assessment of groundwater treated with a membrane biofilm reactor. Journal of American Water Works Association. 101 (12): 77-83]. We have been working with membrane bioreactors in our research and have limited data on chlorate removal but there appears to be some promise here.

Ion exchange resin should work for fast and effective chlorate removal from water (e.g., quartneary ammonium types similar to ones used for perchlorate). 

Yes Balaji, they do help remove chlorate. Not much work has been done in this field. 

Is a difficut task. It depends on water pH.

Try: to acidify pH 5 with HCl, add Fe2++ and then alkalinize with Ca(OH)2 to the admisible pH.

Unfortunately there is not a standardized treatment process for removal of chlorate once formed; hence, no treatment device is available to remove chlorate ion once it has been formed in drinking water. It is better to practice controlling its formation than that of its removal. I have attached an AWWA publication regarding the chlorate issue in drinking water for additional background information.

Dear Dr Duranceau,

That is exactly what the current research is trying to do.  One of the sources of release of chlorate to water streams is from Chlor Alkali plants.  There is currently uncontrolled release from these plants all over the world. 

We started research to remove chlorate and it is then we realised its toxicity.  We have had some measure of success in removing chlorate from brine streams using activated carbon.  The challenge now is to find a good method of regenerating the activated carbon and to convert the chlorate into some other (hopefully) useful form.

The extent of adsorption by activated carbon, is found to be higher than the rate that it is being generated.

But you are absolutely correct that the rate of adsorption from treated water is much lower.  Our research involves the removal of chlorate from brine, and the adsorption by AC is found to be 2-3 times better than when adsorbing from water solutions. 

I may addd that ij  it is not enoufh, heat with the HCL and try again.

It is more diffricult if youy talk about a big mas of water..

Your message is very encouraging. GAC can be a hit and miss with chlorate so I wish you well in your research, especially if it realizes a cost effective reliable method. Chlorate can be treated for in water as you know however at great cost. I look forward to future publications from your group in this regard!

Dr Duranceau, 

We experimented with three different types of GAC and all showed the same results.  Whilst the adsorption of chlorate in water was poor, all of them doubled their adsorption of chlorate from brine solutions.  In our case, the brine concentration is quite high.  Chlorate solubility drops as brine concentration increases, so this helps as well.

The point by Dr Bertello above is also good.  Using a strong HCl solution to regenerate the GAC results in reduction of the chlorate.  Hence this step not only allows the regeneration of the GAC but converts the chlorate to a more harmless form.