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:
• 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)
• Betel leaf (pan)
• Kitchen gardens (many vegetables)
• Some cattle and goats
Some analytes I’m thinking about:
• Nutrients -- N, P
• Metals from the sediments (Mn,… others?)
• Anything else?
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
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
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.
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
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