Effluent is a mix of tank wash water in a tank farm. The effluent may or may not contain oil depending on which tank is being washed. For oil bearing effluent there is a provision of DAF. I wish to know if anyone has experience in using ozonation prior to biological treatment for this type (or any other type) of effluent treatment
Ozonation do have considerable removal efficiecy for COD removal.However, ozone initially converts the suspended solids into dissolved solids and subsequent ozonation
destructs high suspended solids into very small molecules, which enhance COD level in the ozonated wastewater. Normally, ozonation has 75-85 % removal efficiency for COD levels 400-700 mg/L.
Thanks Areeb for your response. COD levels here are very high i.e. 10000 ppm. BOD is 5500 ppm (these are all maximum values). We wish to avoid UASB and hence thought of ozonation (oxidation of BOD and partial conversion of COD to BOD) before MBBR. We want to bring COD levels to 40% of feed. Is it possible?
should be possible, but I assume it is cheaper to let the MBBR do the work.
however you have so high COD that I wonder whether you can do a oil separation before ?
Thanks Kai for your response. Do you mean that high COD will obstruct oil separation?
I agree with Kai.
COD removal by ozone is quite expensive compared to biological oxidation. Therefore it is best to remove as much as the BOD in a first biological stage. Then ozonate the reciltrant COD with an intermediate COD dose that remove some COD but more importantly break up the organic matter so you make it more biodegradable. Finally you have a second biological treatment that removes the created BOD.
I have worked with two effluents with similar properties to that you describe that come from industries with mixed chemical and biological processes.
If you make 3 stage system as I suggest my prediction of the treatment is:
Stage 1: Activated slude/MBBR and particle separator - by experience you remove a bit more than the BOD measured according to the standard method so the effluent might have COD ~4000 ppm and BOD
Dear Yashwant I assume your COD is oil and I wonder whether it is really dissolved or it makse sense to separate it physically
DAF is properly doing the oil separation as good as it is possible!
https://en.wikipedia.org/wiki/Dissolved_air_flotation
Hello Kai and Henrik. We do have proposed DAF before ozonation and we expect 30% reduction in COD due to oil an TSS removal. Most of the oil reported is free oil. Thanks for your responses
ozonation has partial removal of the COD can reach up to 75 or 80% because of the degredation products arised from ozonation process can yield oragnic acid such as formic acid or phethalic acid which have an impact of COD.
but if you want full removal of COD I suggest to extend the time of ozonation process after you finish your treament if you want to achieve a full reomoval of COD but this may be not economic way and the 80% removal of COD may be good if you dont have any toxic compounds in your treated water.
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