Dear All

There is no doubt that leach pit causes ground water pollution, particularly in high ground water table areas. There are some literature available on the topic. However, I don't have much information on scientific data or published papers in journals on the topic. There is no standard paper/ review available on this topic from India, where leach pit toilet is most commonly used.
Elisabeth can help me with some published papers/ review, if available in library. Is there any paper / guidelines from WHO on safe distance from leach pit to drinking water sources or pollution of ground water from such toilets.

Best

Pawan


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Note by moderator:
This thread has a spin-off thread which is foccusing on nitrate as a pollutant: "Elevated nitrate concentrations in groundwater - causes and health implications":
forum.susana.org/forum/categories/193-gr...-health-implications

Hi Pawan,

This is a review of groundwater pollution from pit latrines in an open access journal: ehp.niehs.nih.gov/1206028/

Pit Latrines and Their Impacts on Groundwater Quality: A Systematic Review by Graham and Polizzotto

On Indian guidance/advice, I found this:

India
The Manual on Sewerage and Sewage Treatment (Second Edition), published by the Central Public Health and Environmental Engineering Organisation, Ministry of Urban Development, New Delhi in December 1993 states:
“If the distance between the bottom of the pit and ground water table is 2m or more throughout the year, the pit can be located at a minimum distance of 3.0m from the water source (tube well or dug well) for the effective size (E.S.) of the soil 0.2 mm or less.
If the effective size of soil is greater than 0.2 mm, same distance can be maintained by sealing the bottom of the pit by an impervious material such as puddle clay or plastic sheet and 500mm thick envelop of fine sand of 0.2mm E.S. around the pit.
If the distance between the bottom of the pit and ground water table is less than 2m during any part of the year, the above shall be increased to 10.0m.”
Informants: Aqbal Husain Khan, Principal Engineer, Water and Waste Water Group, Halcrow Consulting India; VR Baghirathan, Project Director, WSUP"

That is probably less than helpful, I will keep looking for something from WHO etc.

There is this from South Africa: www.sapork.biz/wp-content/uploads/2011/0...ting-groundwater.pdf

Guidelines on Protecting Groundwater from Contamination by the South African Department of Water Affairs and Forestry from 2004

Dear Pawan,
I remembered tht we had in the Forum some discussion, I used the seach function "groundwater pit latrines" because I did not remember when.
I found lots of topics. one is exactly what you looked for
http://forum.susana.org/forum/categories/64-wg-11-groundwater/4300-the-impact-of-pit-latrines-on-groundwater-quality

I hope that helps.
Christoph

I am so pleased to see from Christoph's reponse that the search function of the discussion forum worked well for him! (for those who don't know where the search function is: see at the top right, to the left of the manifying glass symbol)

I have also decided that it's high time that "groundwater pollution/protection" gets its own sub-category on the forum. So far it had been hidden under "working group topics" - see the blue round icon at the top right. But I don't think many people browse there. So it now has its very own sub-category (this one) which is also where I have moved the existing threads on this topic.
Let's give groundwater the recognition that it deserves!

Coming back to Pawan's question, I think Joe and Christoph have already given you good pointers.

From my side: if you are looking for a rule of thumb value for a safe setback distance, then the rule of thum is: "there is no such value, the further away the better, and ask your local geohydrologist for advice".

I also recommend the excellent new factsheet of the SuSanA Working Group 11 on this:
forum.susana.org/forum/categories/193-gr...f-sanitation-systems

And for anyone looking for a quick overview on the topic of groundwater pollution, I can also recommend the Wikipedia page (which I have edited together with others):
en.wikipedia.org/wiki/Groundwater_pollution

Pawan: if you find out more about groundwater pollution from leach pit toilets in India, or the local discussions around this topic, or specific examples of pollution incidences, please tell us more in this this thread. Thanks.

Regards,
Elisabeth

P.S. By the way, just wondering: was groundwater pollution not an aspect included in the handbook (Handbook on Technical Options for Solid and Liquid Waste Management in Rural Areas, released by the Ministry of Drinking Water and Sanitation, Government of India) which you posted about here
forum.susana.org/forum/categories/89-new...tation-govt-of-india ?

Dear Joe, Christoph and Elisabeth

Thanks for your quick response. I compiled report from 7 nos. of research papers/ review article. There is one good paper from India. Review article from Graham and Polizzotto is very informative. Manual of CPHEEO,( 2013) Ministry of Urban Development, GOI is also important.
Yesterday there was an important discussion on this aspect in a meeting where I raised this issue. There is a planning of the Government to make Villages ODF, located near the bank of Ganga River by implementing twin pit household toilets. I had to submit documentary evidence of ground water pollution from leach pit toilet particularly for areas having high ground water table.
Elisabeth, I am putting reply of your queries on respective topic.

best regards
Pawan

I will try and get my colleague Paramasivan to write something. There are several villages in Tamil Nadu that he knows of that implemented pit toilets and it destroyed the ground water source from which they used to collect their drinking water. He's been promising me he will do it for a long time and I will now give him an extra nudge when I see him on Tuesday!!

I have just caught up with this discussion after a few weeks when other concerns have kept me from looking at recent topics on SuSanA. One thing that interests me is how contamination from leach pits and septic tank soakaways penetrates down into groundwater. Clearly, there is a high risk of contamination where the water table is high and a pit latrine or leach pit is located close to a shallow well. But what is the situation when the water supply is drawn from a greater depth via a tubewell. In some parts of the World, household tubewells with a depth of 30 metres or more are not uncommon.

The relevant facts on this seem to be:

Groundwater movement below the water table is predominantly horizontal so the only vertical movement under 'natural' conditions is likely to be by diffusion.

However, vertical movement is presumably induced when water is drawn from tubewells, so that water must be drawn towards the tubewell to replace that which has been extracted.

There is likely to be vertical movement down the sides of poorly constructed tubewells - I would guess that this is an important cause of contamination.

Chemicals will be more persistent than bacterial pollution but I assume that the latter is more important.

I have been able to find very little discussion of the topic of likely water flows below the water table and the consequences for leach pit and groundwater source planning. Does anyone have any information on this?

From the Sphere Handbook on disaster relief, the specify as minimum standard for latrine distance from water source as 30 m horizontal distance, and 1.5 m vertical distance to water table.

( www.spherehandbook.org/en/excreta-dispos...e-from-human-faeces/ )

One problem is that this is highly dependent on the nature of the latrine; type of soil and nature of the water source (as I'm sure you are well aware). But these numbers would seem to agree with a fairly conservatively sized soakage field for a septic tank system.

Nigel Langdon
BE (Natural Resources)

Here are some papers on movement on pathogens through soil, in case anyone is interested:

On movement in unsaturated soil:

www.americanalpineclub.org/uploads/mce_u...ough_soil%5B1%5D.pdf

Movement of the protozoan pathogen Cryptosporidium parvum through three contrasting soil types by Jane Mawdsley, Alison Brooks and Roger Merry

General conclusions: most of the spiked pathogens were found in the top 2cm of soil

On bypass flow:

www.researchgate.net/profile/Malcolm_Mcl...b2811697be000000.pdf

Regionalizing Potential for Microbial Bypass Flow through New Zealand Soils
by Malcolm McLeod, Jackie Aislabie, Janine Ryburn, and Alexandra McGill

Conclusion: Gley, Ultic, and Granular Soils have high potential for bypass flow of microbes.

As with all these things, the solution is to ask a soil scientist about specific conditions

Dear Pawan,

With respect to your first post, I'm attaching 2 publications. One is by USEPA (Drinking Water from Households - see pp. 14), and the other one is titled: Guidelines for separation distances based on virus transport between on-site domestic wastewater systems and wells.

I trust, you will find them useful.

Regards,

F H Mughal

Very interesting thread and discussion.
This topic needs to be brought into attention more not least when we are in a era of CLTS and pour flush latrines are constructed indifferently to the geohydrological conditions.

We did a global survey to try to better understand the trends in sanitation and the pit latrine is one of the fastest growing technologies in Africa (see attached document). The health risk complexities in densely poplulated areas in African cities with life-threatening diseases like malaria, severe diarrhoea, typhoid etc.

In this context to avoid this kind of contamination I believe that WHO Safe Sanitation Planning manual is really an excellent tool:
www.who.int/water_sanitation_health/publications/ssp-manual/en/

Keep the conversation going,

Madeleine