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How do I work out which water quality analytes to test for in drinking water?

I'm working on a WASH program in rural Bangladesh, and we are reviewing the water quality analytes we test for. Can anyone suggest which additional contaminants should be tested? (Preferably with field test kits, as a laboratory is probably not available)...

Currently we test for:

• Turbidity

• pH

• EC

• Fe

• As

• Fecal Coliforms

Water sources include:

• Surface ponds

• Spring catchments in the hills, piped to lowland farms

• Shallow tube wells

• Deep tube wells

• Dug/Ring wells

Water sources are connected to hand pumps, or on the odd occasion submersible electric pump, and supply the surrounding households in a village setting.

The wells are dug/drilled into alluvial sediments (mostly clay, silt, some bands of sand). The consolidated rock beneath this is Miocene Bokabil shale – described as “silty shale with subordinate shale and minor sandstone bed and calcareous sandstone bands. The shales are laminated, grey to bluish grey)”. As wells are dug or drilled by hand, once hard rock is reached, drilling cannot continue. However, I think some of the wells are drilled into the weathered top of the shale.

The sediment samples from drilling that I’ve seen are silt and clay (light to dark grey, grains of muscovite, and dark grains (ilmenite/rutile?) are visible). Bands of sand (targeted for the water supply) are also found – the sand is silica rich and grey to yellowish-brown. Sometimes the team notes metallic or organic odours in the sediments and water samples.

The main industry in the area is small scale agriculture. Major crops include:

• Rice (Aman, Boro)

• Potatoes

• Betel leaf (pan)

• Kitchen gardens (many vegetables)

• Sunflowers

• Some cattle and goats

Some analytes I’m thinking about:

• Fertilisers/pesticides

• Nutrients -- N, P

• Metals from the sediments (Mn,… others?)

• Anything else?

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5 Answers

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This seems like an excellent list to start out with. I would suggest you consider changing your microbial testing from fecal coliform to E. coli, which is the most associated with diarrheal disease (see recent study by Gruber et al for the latest evidence on this). There are several low cost field methods now for this. We at mWater have a kit made up of off-the-shelf parts. Also see our resource guide on this for more options. Good luck! John

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For surface waters, chlorination is a must if no other treatment is given. Hence residual chlorine test should be included in routine test. If you could add nitrate (NO3-), that would be fine. If excessive fluoride (F-) is reported in the area, then it could also be included in the field tests as you are doing Arsenic testing. Hardness is another important test and easy to test also which could be considered if that is a problem parameter in that area. I do not wish to lengthen the list. I have used field test kit and all the test I have mentioned could be included in field kit. Please note that these additional tests are required for drinking water and not irrigation or other domestic uses. Let me know if you need additional info or help. Best. Jagdish Barot, Windsor/Canada

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BGS produced some groundwater quality summaries for WaterAid (some time ago now, but still useful). The one for Bangladesh is at www.bgs.ac.uk/downloads/start.cfm?id=...

What you need to look for does depend quite a bit on the source. If it's deep groundwater then it's much less likely to have problems from surface-related contaminants such as nitrate and pesticides. If it's pond water, on the other hand, these could be critical elements. Good luck getting pesticides analysed effectively, though! These are very expensive to do, and sample handling and lab techniques need to be very good - no adequate field kits that I'm aware of.

Usually community water supply programmes limit themselves to the kind of range of parameters that you are already looking at, for cost reasons as well as because of a lack of ability to transport samples to good lab facilities. Again, there may be good local reasons for assessing other chemicals e.g. in areas of fluoride prevalence or metal mining.

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Comments

Thanks for the info and the link Joe. Very helpful!

Yes I understand specific pesticides are difficult to analyse…Are there any indicator analytes for pesticides that could be tested for in the field?

Regarding fertilisers - would testing for nitrate be sufficient? Or should we test for other analytes also?

Do you think there could be any elements/compounds of concern originating in the sediments in which the wells are dug/drilled? - I’m not aware of Fluoride issues specifically. There is no mining, but I know the sediments have been investigated for mineral sands potential. Should we test for any other elements/compounds just to be sure, or do you think the risk is low and not worth the time/costs?

JS gravatar imageJS ( 2015-04-28 01:40:00 -0500 )edit

For pesticides, there is one test strip option that sounds promising. I cannot vouch for it as I haven't used this particular product, but I have been pleased with all the other test strip products from ITS / Sensafe. It is not cheap (2 tests for 30 USD) since it actually uses fairly sophisticated immunoassy technology, but it is certainly cheaper than setting up a lab with a mass spec or ion chromatography. For fertilizer runoff, nitrate is a good start and very cheap test strips are available. These Sensafe combined nitrate/nitrite strips work well.

johnf gravatar imagejohnf ( 2015-04-29 21:50:14 -0500 )edit

Check out the Plainest 7100 photometer system. This is simple and flexible to use, and low skilled staff can be trained to use it effectively in a few days. The initial capital cost is high ( approx. GBP 1500), but in my experience justified by the systems robustness, portability & accuracy, especially in long term monitoring programmes. The costs of individual tests is approximately 0.75 to1.50 GBP, and the tests coly with the relevant ISO Standards.

For Potable water supply I would focus on the parameters mentioned in your previous mail. The Chemical fact sheets in the WHO drinking water guidelines http://www.who.int/water_sanitation_h... give comprehensive assessments of the public health implications and relative risk of individual contaminants.

Sent from Windows Mail

From: support@knowledgepoint.org Sent: ‎Tuesday‎, ‎28‎ ‎April‎ ‎2015 ‎07‎:‎40 To: extcody@yahoo.co.uk

John Cody gravatar imageJohn Cody ( 2015-05-05 03:52:11 -0500 )edit
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Further to the comment by Jagdish Barot I would point out that there are quality guidelines for irrigation water too - http://www.fao.org/DOCReP/003/T0234e/... though generally lower water quality can be accepted than for drinking water. There is, of course, always the risk that irrigation water will also be drunk. The definitive guidelines of drinking water quality are published by the World Health Organisation. Both of these guidelines talk about a long list of potential contaminants and this is totally unrealistic in terms of field testing or small rural water supplies. Bangladesh probably has their own quality standards which may be based on the WHO guidelines but different in some details.

While the principal contaminants of concern have been discussed in the question and the other answers, one thing to consider before embarking on testing is the sustainability of the system and the ability (or otherwise) to rectify any problems that may be identified. While you may embark on a testing programme, this should be done with the local authorities (health/water) who may be required to carry it on in the future. Also consider how realistic it might be in the long term to either treat contaminated water or to stop people from using it.

Hope that this helps

Martin Ager

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Thanks all for your help!

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Asked:
2015-04-23 03:20:39 -0500
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Last updated:
Apr 28 '15