Dear Evans, you may have ...
Published by Barry Jackson
Dear Evans, you may have realised from the replies that treatment of nitrates is difficult and neither practical nor affordable in rural Zambia.
I have done a little research and recommend the following websites to substantiate my suggestions. They are: http://www.who.int/water_sanitation_health/diseases/methaemoglob/en/ and https://en.wikipedia.org/wiki/Methemoglobinemia and http://pediatrics.aappublications.org/content/116/3/784 .
A key concept is as follows: "The current EPA standard of 10 ppm nitrate-nitrogen for drinking water is specifically set to protect infants" i.e. to protect bottle-fed infants under 6 months. So in rural Zambia, if mothers habitually breast feed their infants beyond 6 months then it is fairly safe to allow other humans to consume the non-standard water. Where bottle-feeding is unavoidable you should advise mothers to seek other sources that have lower nitrate content, e.g. rainwater harvesting for babies' bottles. (Admittedly it is not easy in rural Zambia to harvest, store and keep clean.)
The other issue is the source of the nitrates. In Europe and USA it comes mostly from widespread use of fertilizers. In Rural Africa it is more likely from nearby pit latrines, cattle kraals etc. So, in general do not allow householders to site their pit latrines close to the borehole, or site boreholes near to latrines and kraals. Alternatively, if there are many such latrines and the borehole is surrounded by them, you may need to propose a borehole further away from habitation. Not ideal but may be a solution. Also users can learn to differentiate between sources and the specific source for a particular activity. Hope this helps. Barry M. Jackson
2 Comments
@ Barry,, well said and thank you for the in-depth search and advise,,,the problem is that Nitrate concentrations in drinking water are not only increasing in rural but also in peri-urban areas where we have working mothers who may not breast feed their babies for the full 6 months,,, hence now the search for a low cost treatment technology..!!
Published by Evans Tembo, Senior TVET Advisor - WASH & Solar Energy - GIZ
Barry's comments are correct. There is is increasing risk to infants as the concentrations exceed the WHO Guideline values for nitrate and nitrite. Nitrite is the greatest concern because it is the proximate toxic agent. The greatest risks are for infants who have a GI infection, and that is often a matter of microbial contamination of the source water, because the bacteria may be pathogens, and the water will also be under reducing conditions converting nitrate to nitrite. So the first thing to do is to assure that the source is safe and disinfected with chlorine. There is some leeway in the exceedance of the WHO guideline--be sure to read the short discussion in the 4th edition. If you are exceeding nitrate and the water is disinfected, you should both notify consumers (mothers) to be alert for the symptoms, and probably temporally use alternate low nitrate water. Methaemoglobinaemia is detectable and reversible.
Published by Joseph Cotruvo, President at Joseph Cotruvo & Associates, Water , Environment and Public Health