Can anyone tell me why in constructed wetland, there is continuous increase in TDS (BOD and COD are much reduced but not the TDS).I have used typha/ vetiveria zizanioides separately for treating sewage)
I assume then that this is an e!ectrical conductivity meter. You must thus remember that another name for your bioremediation process is mineralisation. This is very relevant since from the organic matter in the sewage which is not electrically conducting you are creating an increased number of ions such as ammonium, phosphate, nitrate etc. Remember that a large proportion of these ions are formed by the degradation of non- dissolved material. Even if your starting effluent were largely dissolved organic matter you would be creating electrically conducting ions from compounds which are,at best, poorly conducting.
Hope this helps.
Alan
Thank you Dr. Alan P Newman;Your explanation is scientifically correct; my doubt is these inorganic salts/ions must have got utilised up by plants during the treatment process.why it was not so.won't they create problem in receiving water body?
For you to get to the bottom of this problem you need to have a knowledge of what ions are contributing to this problem. Unless the TDS gets sufficiently high that it causes osmotic issues it is not, by itself such a problem but the nature of the pollutants which contribute to it.
If the problem is due to nitrogen compounds, as I suspect, you may be able to change the design to encourage denitrification but unless the macrophytes are regularly harvested you are unlikely to achieve sufficient net nitrogen removal by plant uptake. The plants will temporarily store the nitrogen but it will eventually be recycled back into the water and you are likely to see a more or less steady state.
You could benefit from looking at the work of Prof Jan Vymazal who has numerous publications on this issue on ResearchGate.
Dear professor,
Thank you so much ,points discussed were very much useful.
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