Arsenic contaminated tube wells (Bangladesh)

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  • Juergen
  • I am hydrogeologist and I am working for GIZ since 1992, always in ground water supply (rural and urban drinking water supply and groundwater exploration); about 8 years sector expert WASH with the European Commission's Humanitarian Office.
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Re: Arsenic contaminated tube wells (Bangladesh)

Hi Florian,

I couldn't write too much yesterday while just enjoying a coffee break in a meeting; let me first put in some links for in-depth information:

www.bgs.ac.uk/research/groundwater/healt...gladesh/reports.html
nora.nerc.ac.uk/12311/
www.bgs.ac.uk/research/groundwater/healt...Bangladesh/home.html
www.who.int/docstore/bulletin/pdf/2000/issue9/bu0751.pdf

While searching for scientifically water proof on the subject, mainly North American and British researches will come up and Dr. Paula Smedley certainly is one with the best reputation, having done research in Bangladesh (when the problem came up) and South and Southeast Asia. Try to get into contact with her using her link.

I myself have been involved in drinking water supply in Bangladesh (various areas) and the Terai myself for several years; being Hydrogeologist, I tried to gather as much information as possible on the issue - for the Terai, Smedley is still a very good source.

In brief, the study (1st Link) states the age of arsenic-free groundwater: it should be contained in sediments older than 10.000 years - just a split second for a geologist. Luckily, it happens that 'old' alluvial sediments are found along the Ganga and Brahmaputra rivers. In these sediments, Smedley states, arsenic (originating from natural minerals deposited in aquatic (alluvial) sediments in the Ganga trough along with the uplift of the Himalayas) has been washed out. Even luckier is the circumstance, that these 'old' sediments are easily detected even by untrained drillers: around Pleistocene, roughly 12.000 years ago, the environment in the Ganga valley was a dry land surface of dry hot climate, leaving behind red soils - just a layer a couple of meters thick. This change of colour is easily detected while drilling; once through it, you are down into the safe side. The rest is qualified, correct well construction, not more, and no rocket science neither. Depth of this layer increases eastwards and it disappears in the delta. To the west, you'll hit it between 20 and 30 meters below surface, to the east between 60 and 120 m. The water contained is as old as several hundred to a thousand years and of good quality; it is an unconfined aquifer.

It is safer and cheaper, to go for a safe source of water for a village, or a number of villages, than to install a bigger number of shallow wells and monitor them over the years. This policy failed in Bangladesh and continuous monitoring is done at best at random.

The use of marked 'bad wells' (painted red, but not destroyed) as source of water for irrigation for winter rice is commonplace; this way arsenic contamination through rice replaced contamination through groundwater in that country. Additionally, it became near-impossible to localize the areas of origin, since the rice is sold country-wide.

The study concerning filtration and using iron to eliminate arsenic is based on a field study done by under-graduate MIT students; in theory, it is correct and names the parameters explicitly. But, in real life, this will be a problem: arsenic reduction using iron is a surface reaction, so size and material quality of the nails are important; furthermore, they have to be replaced in time and safely deposited - the arsenic is in the rust, so it will stay at the surface once pumped out of the ground. Groundwater chemistry, filtration velocity, temperature, organic matters (algae) in the filters - they all play a role. If MIT students can do it, this does not mean, that the Nepali rural population can do it as well - over years and decades. If surface water (or shallow groundwater) is the source of water, it is certainly safer to use industrially built systems than improvised local solutions. Break down the price for potable water to the volume consumed and check what's more economic - a professionally designed system providing water to a few thousand consumers using piped systems and tapstands or hundreds, thousands of individual wells and filtration systems.

Best regards,

Jürgen
Facts are stubborn things, but statistics are more pliable. (Samuel Langhorne Clemens)

Truth is what stands the test of experience. (A. Einstein)
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  • Florian
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Re: Arsenic contaminated tube wells (Bangladesh)

Juergen wrote: it is in an immensely dangerous procedure to drill new wells near by and hoping they'be arsenic free.


I am not an expert myself in this field, I merely did some literature review on Bangladesh. From this I read that the government strategy currently focusses on providing safe water points and on screening and marking exisiting water points, but not on household water treatment for the above mentionned reasons.

You're certainly right, there are plenty of problems attached to this strategy. But if you come and say that one of the mainly employed mitigation strategies is "immensly dangerous", I'd also expect that you give your ideas on what should be done instead. What better strategies are theree that are safer and have the potential to be employed at large scale and immediately in these regions?

Best regards,
Florian

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Re: Arsenic contaminated tube wells (Bangladesh)

Yes I totally agree and I was merely reporting what their "alternative solution" was. Obviously that "solution" comes with its own set of problems.

I don't think there is a really good small scale solution to the problem of arsenic contamination... either you have to have a more sophisticated treatment plant, or you are probably better off treating the available non-arsenic-contaminated surface/rain water I guess.

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Re: Arsenic contaminated tube wells (Bangladesh)

Hi dear Makowka, Florian,

it is in an immensely dangerous procedure to drill new wells near by and hoping they'be arsenic free. first, people tend to use the water from the old wells for irrigation in rice paddies and vegetable garden, where arsenic accumulates in the crops; secondly, measuring arsenic in wells makes only sense, when it is done regularly over time, starting earliest 6 weeks after installation of the well (arsenic needs some time in contact with air to show up in testing) and thereafter every 3 months for 2 years at least, carefully monitoring arsenic contents. In both, Bangladesh and the Terai, wells are known to increase arsenic contents suddenly after having shown low or no arsenic contents over years.

Regards,

Jürgen
Facts are stubborn things, but statistics are more pliable. (Samuel Langhorne Clemens)

Truth is what stands the test of experience. (A. Einstein)
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Re: Arsenic contaminated tube wells (Bangladesh)

JKMakowka wrote: Back in 2010 when I was working in Nepal, an expert on those iron filters from UNICEF told me that they more or less phased out the promotion and construction of these, as they caused a lot of maintenance issues and became a source of bacterial contamination (I only have his word for that though, would be interesting to see actual data).

Their alternative approach was/is to test and mark the wells that had elevated arsenic levels and since the shallow wells in the Terai region are cheap to build, they could usually find a place nearby where a new well had less arsenic problems.


This matches what I read about Bangladesh, see my post above.

As for in-situ treatment, I also stumbled over this recently and agree, that looks promising. The technique is already used for iron removal in Germany as well. However, as you say, that's something for medium to large communal water supply system, and not really for household water treatment.

Regards, Florian

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Re: Arsenic contaminated tube wells (Bangladesh)

Back in 2010 when I was working in Nepal, an expert on those iron filters from UNICEF told me that they more or less phased out the promotion and construction of these, as they caused a lot of maintenance issues and became a source of bacterial contamination (I only have his word for that though, would be interesting to see actual data).

Their alternative approach was/is to test and mark the wells that had elevated arsenic levels and since the shallow wells in the Terai region are cheap to build, they could usually find a place nearby where a new well had less arsenic problems.

However, I think this: www.insituarsenic.org/ kind of in-situ removal is quite promising for medium sized systems.
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Re: Arsenic contaminated tube wells (Bangladesh)

Dear mr. Wahed,

I Nepal there is a similar problem. One solution tried here is a sand-filter with a bed of rusty nails above it. As Sjoerd Nienhuys pointed out the iron rust should bind the arsenic. I know the technology received an award at one time. Not sure if it also was a success in practice, if needed I could try to put you in touch with people who would know more.

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Marijn Zandee
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  • mdwahed
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Re: Arsenic contaminated tube wells (Bangladesh)

Dear Sir/Madam

I am so please to your kind cooperation.All of the documents and information will helpful to me for our further processing.


Thanks again

Md. Abdul Wahed
Secretary General
Eakok Attomanobik Unnayan Sangstha
Bangladesh

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Re: Arsenic contaminated tube wells (Bangladesh)

Dear Mughal,

I eliminated 3 of your documents as they had copyright disclaimers.

Best regards,

The SuSanA Secretariat



[Posted by Hector]
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Re: Arsenic contaminated tube wells (Bangladesh)

Two more publications are attached

F H Mughal


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Re: Arsenic contaminated tube wells (Bangladesh)

Dear Mr. Abdul Wahed,

I'm attaching some publications.
Sectt: Please check for copyright issues, before uploading them - Thanks

Regards,

F H Mughal


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Re: Arsenic contaminated tube wells (Bangladesh)

I was researching the same issue some time ago in Pakistan Himalaya. What I remember is to pass the water through a deep filter with rusty scrap iron. This seems to bind the arsenic. Maybe some chemical specialists can help.
Sjoerd from The Netherlands.
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