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nasrin YaBB Newbies Offline I love Water and Wastewater.com Posts: 20 Gender: Company or Organization: Arya industry	COD determination Jun 09^th, 2012, 10:54pm Hi I know H2O2 is one of the most important interference in COD determination. we use H2O2 to decrease level of COD in our waste water. but when we want to measure amount of COD, we can not reach to correct amount. what should we do for elimination/removal of H2O2? thank you in advance
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Jeff Naumann God Member Offline I love Water and Wastewater.com Posts: 1133 Torrance, California Gender: Company or Organization: Jeff Naumann & Associates	Re: COD determination Reply #1 - Jun 10^th, 2012, 9:07pm Stop using it, maybe?
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nasrin YaBB Newbies Offline I love Water and Wastewater.com Posts: 20 Gender: Company or Organization: Arya industry	Re: COD determination Reply #2 - Jun 10^th, 2012, 10:42pm do you know any method that we can replace ?
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A4YB YaBB Newbies Offline I love Water and Wastewater.com Posts: 30 Company or Organization: awzi	Re: COD determination Reply #3 - Jun 11^th, 2012, 4:49am add a reductor like an inorganic salt? idk sodium bisulphite maybe, and add enough to fully strip the h2o2
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David S.

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Re: COD determination
Reply #4 - Jun 11^th, 2012, 8:06am

Peroxide is a relatively unstable molecule. You should be able to eliminate it by vigorous stirring of your sample or by letting the sample sit in the sun for an hour or so. To test for peroxide removal you can either get some test strips or stick a BOD probe in it. If the DO does not increase over a 15-20 minute span you have removed the peroxide. The decomposition products are just water and oxygen so you won't have any interference once the process is complete.

Just out of curiosity, what level of COD are you reading? How are you measuring it? When you say you aren't getting the right answer, do your results end up higher or lower than what you expect?

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« Last Edit: Jun 11^th, 2012, 10:17am by David S. »

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nasrin YaBB Newbies Offline I love Water and Wastewater.com Posts: 20 Gender: Company or Organization: Arya industry	Re: COD determination Reply #5 - Jun 11^th, 2012, 10:59pm thank s a lot about your answer we have lots of samples with different COD But the biggest problem is when we measure our high COD (1200-1300mg/L) we use HACH`s vial in HR(0-1500) hydrogen peroxide make positive error in determination(some times it is really higher than our COD range)
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David S. Senior Member Offline I have nothing clever to say here. Posts: 373 Gender: Company or Organization: Environmental Express	Re: COD determination Reply #6 - Jun 12^th, 2012, 7:45am Usually at that level the peroxide contributes a false high reading at least 4 times its concentration. So, 100 mg/L peroxide will give you a +400 mg/L COD value. I'm pretty sure the peroxide contributes to the oxidation/reduction going on from the dichromate.
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