I am treating the industrial effluent by AOP using H2O2+ O3. I am getting higher COD values than raw wastewater itself. I quenched the H2O2 by adding MnO2. Samples were filtered 0.2-micrometer filter to avoid any residual MnO2. Please suggest the reason and solution.
Thanks in advance.
Hi.
From what you describe, I'm assuming you know that H2O2 will contribute for the net value value of COD. MnO2 is just a catalyst that increases the velocity at which H2O2 will decompose into water and O2. Thus, maybe you just need to give it some more time before measuring COD? Maybe there was still some H2O2 in your samples.
Elements such as N or S are also known to be partially oxidized in the presence of H2O2 and O3 generating species that will contribute for COD (for example, nitrogen can end up as NO or NO2), however these are typically part of carbonated molecules that are destroyed by the treatment and should not cause increase in COD values.
Cheers!
Cheers!
Do you have ammonia (NH4) in the influent? may it be converted to nitrite (NO2) but not nitrate (NO3)? If yes you have to take in account 1.14 mg/L COD for each mg/L of nitrite, according to APHA standard methods.
Thank you Giaime Tocco . Yes I have NH3 content in samples. I will check the Nitrate concentration.
Thank Mário Silva . I left the samples overnight with MnO2 still getting the higher COD. After Ozonation, I tried the adsorption of ozonated sample on activated char but no further removal of COD observed.
What other ionic "species" do you have in that water?
Industrial effluents are different from municipal wastewater and suppose some reactions that occur by components.
When you use H2O2 and/or O3 it is possible to obtain COD "influencers".
In terms of toxicity, we have obtained that O3 cause reactions that result in much more toxic compounds.
It depends on the type of wastewater (COD) and the time you applied AOP. It's very logical for COD to increase initially, for example when you treat textile wastewater, because very complex compounds like dyes degrade to simpler molecules that can be more easily oxidized. That's the reason COD increases initially. However, if you apply AOP for more time you will observe COD to decrease...
Dimitri Georgiou Thank You. I will try my samples with higher reaction time.
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