I have a question about nitrate formation in groundwater due to septic tanks. The formation of nitrate from urine in anaerobic conditions is questionable. I think, if the conditions are anaerobic, urine can converted to Ammonium (this process namely Ammonification) not to nitrate. But in many related articles has reported that septic tanks caused nitrate pollution in groundwater.
This depends on the redox conditions in the ground below the septic tank and of the groundwater. In sandy soils the ground and groundwater can be aerobic and then bacteria will oxidize ammonia to nitrate (nitrification).
i agree with Henrik Andersen but this problem has occurred in the groundwater of Tehran and there are some assumption such as (a) air flushing through the sump or aqueduct and (b) Microbial activities of sulfate reducing bacteria
but these are hypothesis and this phenomenon is unknown.
Also, plant roots bring free oxygen to the soil environment, and in these soil microsites near plant roots nitrifying bacteria can convert the ammonium to nitrate. While ammonium tend to adhere to soil particles and are thus relatively immobile in soil, nitrate ions, being negatively charged, are repelled by soil clay particles and so are mobile in soil and quickly leach downward to the groundwater table.
Just to add to the above answers... the leaching beds which usually follow Septic Tanks are not that deep. They are placed less than a meter below ground. The perforated pipes - forming leaching beds- are placed on gravel beds. This section is fairly aerobic with sufficient oxygen to convert Ammonium ions to Nitrate via Nitrite, which mobile and can increase the nitrate concentration in groundwater.
Just to add to the above, there are whole books on this subject. See for example:
Cantor, L.W. and Knox, R.C., 1985, Septic Tank System Effects on Ground Water Quality. Lewis Publishers, Inc. Chelsea, 336 p.
or
Nitrate: Processes, Patterns and Management: Edited by Burt, T.P., Heathwaite, A.L., and Trudgill, S.T. 1993. John Wiley & Sons, Chichester, 444 p.
As well as numerous articles including the following that reference quite a few other articles:
Shipley, D.O. and Rosen, M.R., 2005, Identification of nitrate and dissolved-solids sources in ground water by GIS analyses. Environmental Practice, 7, 32-43.
or
Rosen, M.R., Kropf, C., and Thomas, K.A., 2006, Quantification of the Contribution of Nitrogen from Septic Tanks to Ground Water in Spanish Springs Valley, Nevada. US Geological Survey Scientific Investigations Report 2006-5206, 12 p.
a good paper intitled "Bacterial oxygen production in the dark" that can be helped about this question is found in following link:
http://journal.frontiersin.org/Journal/10.3389/fmicb.2012.00273/pdf
Dear Dr. Hossini,
Many thanks for your kindly helps to answer this question.
Warm regards,
B Ramavandi
Dear all,
Maybe you will like to continue this discussion at the IAH congress 2016 in France?
Would you like to contribute to the group in the following session? Indeed, I propose a session called « Groundwater demand and pollution: the links between water supply, on-site sanitation and agricultural practices » in the frame of the 43rd IAH international congress that will be held in Montpellier, France, next 25-29th September. (http://www.60iah2016.org/en/programme/main-topics).
Here attached, I provide the description of the session. To lead the session, we have recently formed a nucleus group of co-conveners. We are now searching for potential authors or participants to work with us in planning the session and forming a group in order to meet and collaborate during the congress.
To participate, please submit an abstract as soon as possible, since we are in a very tight schedule. The deadline for the abstract submission is March, 31.
In the case you could not participate to the congress, I call for your help to propagate the information in professional and academic networks.
We also ask for contributions in the reviewing process of manuscripts and posters for this session.
Beyond participation to the congress, this session aims at networking on the issues of environmental impacts on soils and aquifers due to infiltrated waters, either waste waters or rain waters, urban waters or rural waters. I coordinated a national project in France concerning on-site sanitation under the pressure of new state regulation. You will find publications of our team on ResearchGate.
I sincerely hope we will have a chance to benefit from your help.
Respectfully
Olivier Fouché
Research fellow
Leesu – Ecole des Ponts
------------------------------
Please see following paper:
https://www.nature.com/articles/s41598-017-07147-2
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