Hello Colleagues,
I'm working with wastewater for microbial fuel cell which operates completely anaerobically (No oxygen involved for chemical oxidation) for fermentation.
Is it enough if I use the difference between the initial and final TOC to determine the treatment efficiency ? Since the chances of chemical oxidation by oxygen are zero (Due to complete anaerobiosis) and thus COD may not be reliable!
Thank you.
Musa
Kanhaiya Lal: I don't quite understand what you mean. DOC is the dissolved organic carbon, which means you filter your sample before analysis. TOC is total organic carbon, which includes DOC and also non-dissolved=suspended organic particles, so you would not filter your sample before analysis. Do you agree? Furthermore: Don't you filter samples before COD-measurement?
Musa Bishir: what methods would you use to measure COD/TOC/DOC? Are you expecting living biomass to be washed out of your cell? If yes: do you want to capture this biomass as organic carbon or "COD" as well?
I am working more in the field of "traditional" wastewater treatment. I use cuvette test to measure DOC or COD before and after biological treatment as indicator for the efficiency of organics-removal. I also filter in both cases (0.45 µm), since I do not want to capture washed out sludge flocs / living biomass. Those can be eliminated via sedimentation afterwards and are therefore of no interest concerning the removal efficiency of my biological treatment step.
@Kanhaiya Lal : So, first, it depends on the methods of measurements (which Musa Bishir has not stated yet), since there is a whole variety of devices to measure particularly TOC/DOC, some of which are used to measure particulate organic carbon (POC) as well.
Second, there is the still open question, if intact microbes from the treatment are expected to be present in the samples, and if so: if this biomass should be regarded when it comes to removal efficiency. Of course biomass contains organic carbon (POC) as well, and also impairs COD measurement. If there is a significant amount of intact cells, but they should not be considered/measured, I would argue that the 11 µm which you mentioned are way to big to exclude intact cells, since the size of most bacteria is around 1 µm or less.
So in my opinion until now the questioner was not specific enough to answer the question adequately. Would you agree?
Regards
PS: ("TOC machine is recommended" I assume you meant to write "not recommended"?)
PPS: at least here in Germany there is a clear trend in environmental analytics to replace COD measurement with TOC/DOC measurement, not least because of the toxicity of the dichromate COD-method.
Musa Bishir : maybe the study below contains some valuable information for you:
"The study concludes that TOC can be reliably used for the generic replacement of both COD (...) and BOD5 (...) in influent wastewaters, but only for COD (...) in final effluents."
Article Replacement of chemical oxygen demand (COD) with total organ...
- Badges
- Science topic
- Similar topics
- Engineering
- Chemical Engineering