Elevated nitrate concentrations in groundwater - causes and health implications

  • jankn
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Elevated nitrate concentrations in groundwater - causes and health implications

Note by moderator:
This thread is focussing on nitrate and is a spin-off thread of this thread with the title "Ground water pollution from leach pit toilets (question from India)":

forum.susana.org/forum/categories/193-gr...-question-from-india
++++++++++++

This maybe touches only a certain part of the issue, but in the recent issue of the IWA Journal of Water, Sanitation and Hygiene for Development researchers from IISc Bangalore looked at the potential of permeable reactive barriers to mitigate groundwater nitrate contamination from on-site sanitation.

Abstract: "Nearly 50% of India's population depends on variants of pit-toilet systems for human waste disposal. Nitrate contamination of groundwater by pit-toilet leachate is a major environmental concern in the country as it sources a major proportion (50–80%) of potable water from aquifers. Therefore, minimizing nitrate contamination of groundwater due to leachate infiltration from pit-toilet systems is essential. Batch and column experiments demonstrated the capability of bentonite-enhanced sand (BES) specimens to reduce nitrate concentrations in synthetic solutions (initial NO3-N concentration = 22.7 mg/L, C/N = 3) by about 85–90% in 10 to 24 hour by a heterotrophic denitrification process. Based on the laboratory results, it is recommended that use of a BES-permeable reactive barrier layer at the base of pit-toilets will facilitate heterotrophic denitrification and mitigate nitrate contamination of the underlying aquifer."

The full article is behind a pay wall and can be found here .

Jan Knappe

Doctoral Researcher on environmental performance assessment and modeling of on-site wastewater treatment systems
Trinity College Dublin & University of Limerick
Email: jan.knappe(at)tcd.ie, Twitter: @JanKnappe

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  • Marijn Zandee
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Re: Ground water pollution from leach pit toilets (question from India)

Dear Jan,

Sounds like a very interesting article. Do they substantiate the claim that nitrogen pollution of aquifers is a big problem with any data / estimates in the full text? (I can't get the article, therefore I am asking you.

Regards

Marijn

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  • jankn
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Re: Ground water pollution from leach pit toilets (question from India)

Hi Marjin

Unfortunately, we only have the hardcopy subscription here which has not arrived yet (the latest issue has just been published); but I'll give it a read and let you know once I got a hold on the article.

But I know that the same group of researchers from IISc (Indian Institute of Science) has been looking at the relation of leaching pit latrines and groundwater quality for quite a while now. They have performed studies in Mulbagal, Karnataka, India. There is a paper "Impact of pit-toilet leachate on groundwater chemistry and role of vadose zone in removal of nitrate and E-coli pollutants in Kolar District, Karnataka, India" published in 2013. Again, the article is behind a pay wall and can be found here . I so hope, that more institutions and projects progress to open access publications!

Anyway, they were looking at groundwater samples from 69 drinking water wells in the area and compared different types of pollution within the city limits to the background concentration in rural areas and concluded that infiltration from pit toilets has contaminated drinking water wells. Looking at nitrate concentrations they found 148 mg/l (mean) within the city, and 30 mg/l outside the city, compared to a permissible limit of 45 mg/l. E. coli load was 189 MPN/100ml (mean, 55% of wells were contaminated) inside and nearly no E. coli contamination outside the city (9% of wells were contaminated with a mean of 1 MPN/100ml). They concluded that the unsaturated zone (soil above the groundwater) can remove 1 log E. coli every 4 m (Note: this really depends on the soil; Mulbagal has a rather sandy soil. In a more organic and clayey soil, the removal would be better.) and, thus, wells with a water table lower than 25 m below surface would be pathogen free, but not necessarily nitrate free (if properly constructed, of course).

And while we're at it, there is an aged, but nevertheless informative IRCWD review article about the risk of groundwater pollution by on-site sanitation in developing countries by Lewis et al. (1982) here for those who have not seen it yet.

Jan Knappe

Doctoral Researcher on environmental performance assessment and modeling of on-site wastewater treatment systems
Trinity College Dublin & University of Limerick
Email: jan.knappe(at)tcd.ie, Twitter: @JanKnappe

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  • kevintayler
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Re: Ground water pollution from leach pit toilets (question from India)

The IISc work focuses on nitrate pollution. Excess nitrate in drinking water can cause methoglobinemia (blue baby disease. This has been reported in 'developed' countries but is rare. A couple of years ago, I helped run a course in Botswana and the question of nitrate in drinking water came up. I did a search on the internet and found a reference somewhere that said no case of blue baby disease had ever been reported in Africa - although that may relate to the lack of reporting mechanisms rather than the fact that the disease had never happened. Whatever the exact situation, it does seem that nitrate is likely to be a minor problem in comparison with that of pathogenic organisms. My impression, and I will explore this further from secondary sources, is that vertical pathogen movement below the water table is slow and that most will have died by the time the infiltrating water reaches depths of say 30 metres or 100 feet. The exception to this would be where polluted water moves down around the outside casing of a borewell/tubewell.

Nitrate does provide an indication that pollution from pits and soakaways is present (although the source might also be agricultural fertilizers). However, it will be more persistent than pathogens and the presence of nitrogen does not necessarily indicate that pathogens are present.

Others may wish to add their thoughts to this. For an introductory explanation of the effects of nitrate on drinking water see psep.cce.cornell.edu/facts-slides-self/f.../nit-heef-grw85.aspx

Kevin Tayler
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  • joeturner
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Re: Ground water pollution from leach pit toilets (question from India)

There have been a lot of studies looking at the movement of fluids and pollutants through soil - it is a difficult area.

In general, in an unsaturated soil, pollutants become more diluted and less concentrated with depth, depending on the soil texture (which related to the pores).

The problem is that real-world situations frequently do not match calculated conditions. One reason is because soil conditions can change in certain conditions - for example some clay soils will swell in certain conditions, leading to large channels through which fluids and pollutants can flow via something called bypass flow. This can mean that in certain circumstances pollutants move through the soil much more quickly than might be expected on paper. Vertical movement of pathogens is going to depend on the flow of water, which again will depend on conditions and soil type (including how big the pathogen cells are relative to the soil pores etc). So I don't think it is fair to suggest that there is a general rule.

Direct health effects of nitrates are highly disputed, however it is certainly true that there are environmental impacts of nitrate enrichment, which can indirectly lead to health impacts.

For me, the presence of pathogens is by far a bigger problem than the presence of nitrates - although the chemical measurement of nitrogen enrichment is an easier thing to measure than the presence of pathogens, so I think it is a reasonable suggestion that high concentrations of nitrate strongly suggest the possibility of pathogen movement as well.
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Re: Ground water pollution from leach pit toilets (question from India)

Very interesting thread. I just want to jump in on one particular aspect that was raised and that's the (alleged) Blue Baby Syndrome issue from nitrate pollution of groundwater. I am so glad that you raised this, Kevin, and that you also mentioned your doubts.

I actually had it on my to-do list for a while to ask people on this forum about this (it might warrant a separate thread?). In particular people who have worked in Bulgaria and Romania might be able to tell us more because that's where I saw this link stated from publications of Women in Europe for a Common Future (WECF) for example.

See e.g. this publication:
Buitenkamp, M., Richert Stintzing, A. (2008). Europe's sanitation problem - 20 million Europeans need access to safe and affordable sanitation. Women in Europe for a Common Future (WECF), The Netherlands
www.susana.org/en/resources/library/details/1317

See page 10:

When I visited villages in our project
regions in Romania and Bulgaria these last
months, I still hear from the Romanian
doctors that babies fall ill with blue baby
disease
from too high nitrates in the
drinking water. When we test nitrates,
far too often we find such excessive levels
in drinking water, 10 times more than the
maximum allowed. These nitrates are not
caused by excessive fertilizer usage, but
by infiltration of faeces into drinking water
wells, both animal dung as well as human
faeces from unsealed latrines, latrines
which are often close to wells.


I got onto this topic via a discussion with Joe and other editors of the Wikipedia article on Blue Baby Syndrome. Please see our conversation here on the talk page of this article:
en.wikipedia.org/wiki/Talk:Blue_baby_syn...me_has_been_disputed

I used to think it was a well established clear link but after reading that I realised it's not so clear cut.

Joe had written on the talk page:

I am in no sense an expert, but I'd just note that the link between nutrient enrichment and human health has been disputed to my knowledge for at least 20 years, so I support what User:Jermakka has said above. It seems to me that there is very little evidence of a direct link between blue baby syndrome and nitrates, most of the talk about it is spurious. It is one of those internet memes which are repeated without any real scientific basis, as far as I can see. JMWt (talk) 07:25, 13 May 2015 (UTC)


One thing that had always puzzled me is that the safe nitrate level in drinking water is actually quite high - 50 mg/L NO3 (this is for the molecule NO3, not for N like wastewater engineers prefer as a measurement unit). See e.g. here for England and Wales:
https://en.wikipedia.org/wiki/Water_Supply_(Water_Quality)_Regulations_1989_(England_and_Wales)

So I am also thinking that nitrate in groundwater is not really a primary health concern, at least not compared to pathogens. But I would be keen to hear what other people know or have read about the issue of nitrate in drinking water.

Regards,
Elisabeth

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  • pkjha
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Re: Ground water pollution from leach pit toilets (question from India)

Dear Jan and Marjin

I have that paper from the Indian Institute of Science Bangaluru. The copy is not from the Journal, it is from the author available at the web site. It is based on the results of ground water pollution in Kolar District, Karnataka State. Same is attached.

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pawan

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  • jankn
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Re: Ground water pollution from leach pit toilets (question from India)

Hi Pawan

Yeah, this is the one I tried to summarize in my last post which looked at nitrate and E. coli among others. Since it is not the published "journal version", I think it can be shared here; although this might be a bit of a grey area that is, however, widely utilized.

Is the 2015 paper also available as softcopy on the author's website?

Jan Knappe

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Trinity College Dublin & University of Limerick
Email: jan.knappe(at)tcd.ie, Twitter: @JanKnappe

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Re: Ground water pollution from leach pit toilets (question from India)

Thanks Pawan for posting the paper. It is a useful addition to the literature I think- with good results relating to E.Coli as well as nitrate. It does suggest that more pathogens may leach through the unsaturated zone than suggested by some other papers - perhaps because of the fractured nature of the ground. I will look at it in more detail but my first quick read through suggests that it is exactly the sort of study that can be used to inform debate on groundwater pollution.

Kevin Tayler
Independent water and sanitation consultant
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Re: Ground water pollution from leach pit toilets (question from India)

Dear all,

does anybody know the relationship of nitrate and nitrite in groundwater? While nitrate is not particularly toxic, nitrite is highly toxic, and nitrite is derived from nitrate by reduction (removal of oxigen in an oxigen depleted environment). So, nitrate can be a source of nitrite, isn't that the main danger of nitrate?

Thanks,

H-A

Hanns-Andre Pitot
M.Eng. Environmental Pollution Control
presently in Seesen, Germany
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  • joeturner
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Re: Ground water pollution from leach pit toilets (question from India)

Nitrite is more chemically reactive than nitrate, so will do more damage to the body if it gets into the blood. But it also does not stay long in the environment so exposure is much lower.

See this fact sheet from the WHO:
www.who.int/water_sanitation_health/dwq/...atenitrite2ndadd.pdf
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  • F H Mughal
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Re: Ground water pollution from leach pit toilets (question from India)

I’m afraid, my views are at variance, regarding no link between nitrates and blue-baby syndrome. I don’t think a spurious thing will receive an 8-page discussion in the authoritative WHO publication – 2008 Guidelines for Drinking Water Quality (pp.417). I have never come across a publication, during the last 40 years, that dispute link between nitrate and blue-baby syndrome. Countless publications talk of blue-baby syndrome. In fact, my very first contact with water engineering, at post-graduate level, at AIT, in 1973, showed nitrate impact on babies.

Elisabeth is puzzled by the high value of nitrate in WHO guidelines (50 mg/L). There are other parameters in WHO guidelines that have, seemingly, high values: in 1971 edition, total solids level is 500 mg/L (1,500 mg/L, max); TDS is 1,000 mg/L; sodium is 200 mg/L; sulfate is 400 mg/L (1984 ed.); total hardness is 500 mg/L (1984 ed.), and so on.

The guideline value for nitrate in WHO guidelines (2008 ed.), reads as follows:

50 mg/litre to protect against methaemoglobinaemia in bottle-fed infants (short-term exposure)


As stated, it is a short-term exposure. In addition, the guideline value is targeted at babies. This implies that nitrate is relatively safe for adults at levels 50 to 100 mg/L.

A Western Australian Government flyer (attached) says:

The 2004 Australian Drinking Water Guidelines, available from the National Health and Medical
Research Council or from the website mentioned on the next page, recommend acceptable
nitrate and nitrite concentrations based on health related criteria, as summarised below.

Less than 50mg/L: Safe to drink

50mg/L – 100mg/L: Safe to drink for adults, including pregnant women. Seek alternative water supplies for infants up to 3 months of age.

More than 100mg/L: Drinking not recommended for any age. Treat water or seek alternative water supplies. If necessary seek Health Department advice.


The 2008 ed. of WHO guidelines says (pp. 418):

Absorption of nitrate ingested from vegetables, meat or water is rapid and in excess of 90%, and final excretion is in the urine. In humans, about 25% of ingested nitrate is recirculated in saliva, of which about 20% is converted to nitrite by the action of bacteria in the mouth. There is also the potential for endogenous formation of nitrate from nitric oxide and protein breakdown. In normal healthy adults, this endogenous synthesis leads to the excretion of about 62 mg of nitrate ion per day in the urine. Endogenous formation of nitrate can be significantly increased in the presence of infections, particularly gastrointestinal infections. When nitrate intake is low, endogenous formation may be the major source of nitrate in the body. Nitrate metabolism is different in humans and rats, since rats actively secrete virtually no nitrate in their saliva.

And on pp. 418a, it says:

The guideline value for nitrate of 50 mg/litre as nitrate is based on epidemiological evidence for methaemoglobinaemia in infants, which results from short-term exposure and is protective for bottle-fed infants and, consequently, other parts of the population. This outcome is complicated by the presence of microbial contamination and subsequent gastrointestinal infection, which can increase the risk for this group significantly. Authorities should therefore be all the more vigilant that water to be used for bottle-fed infants is microbiologically safe when nitrate is present at concentrations near the guideline value However, the water must also be known to be microbiologically safe. The latter is a minor modification of previous guidance to give greater emphasis to the role of microbiological quality.

While, the WHO gives a guideline value for nitrate as 50 mg/L, the USEPA gives a value of 10 mg/L (nitrate, measured as nitrogen). The Philippine standard for nitrate is 50 mg/L. Thailand standard for nitrate is 45 milligrams per cubic decimeter.

Treatment processes such as ion exchange, distillation, and reverse osmosis can remove nitrate. Boiling water will not remove nitrate. On the other hand, boiling will increase the nitrate concentration, because of water evaporation. Mechanical filters or chemical disinfection, such as chlorination, will not remove nitrate from water.

F H Mughal

F H Mughal (Mr.)
Karachi, Pakistan

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