Nitrates removal technology for bore well water

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Nitrates removal technology for bore well water

In my project area, we use bore wells as a water source, but recently the water is contaminated by nitrates.

Could you please let me know which low-cost technology can be used to removes nitrates in borehole water in rural areas of a developing country? 

Conventional processes for nitrate removal - ion exchange, reverse osmosis and electro dialysis - are quite expensive and pose a question of subsequent disposal of generated nitrate waste brine. 

By the Zambian Drinking Water Standard (ZDWS), recommended nitrate levels are 10 mg/l NO3-N equaling 44.3 mg/l NO3. 
We would like to reach these levels so any advice is helpful.

A picture of one of our bore wells is attached. 

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37 Answers

  1. Nitrate is the indication of microbiological in the water, the best way is disinfection by using chlorine. Abstracting water from borehole to the reservoir/tank and disinfect water into the tank/reservoir with chlorine. This is the first option and the second option is iron exchange, reverse osmosis, and package plant. 

  2. Mr. Evan , 

     i think that you should try to treat the water by passing the water on a film of a Seaweed mounted on cement base then the water influent treat it by activated carbon to adsorpe any unwanted taste 

    in that way you are going to elimenat all Nitrogen and phosphate from water beside the COD and BOD are going to be decrease 

    Best regards 

    Hasan Akil 

     

  3. Hmmmm .... i wuld instal a natural garden with many diferent water cleaning and nitrat's infiltrating cultures ... what is with solar energy preheatig water systems ?

  4. Hmm. Reverse osmosis requires costly, energy intensive and requires skilled labour. Biology process requires carbon source for denitrification, not to mention that it also have to have a basin, technology elements, and a little bit more skilled staff. I would try to use some wetland-like technology, or deal with the source.

  5. I agree with Mr. Mann and Mr. Lauenstein. I would recommend a shallow, watertight pool which is populated by duckweed or water hyacint ( Lemnoidae and Eichhornia crassipes -take care, the second is considered to be highly invasive and dangerous, especially in Africa). If possible use local surface or underwater floating  water plant species, the ones growing the fastest. Let the water flow through slowly the pool. The size/volume of the pool, the flow and harvest intensity should be tested first with a pilot.  I would start with 15-20 cm depth, a few square meters, 2 day contact time (flow/volume) and a biweekly harvest of 25%. I would measure effluent NO2 daily, starting from the seventh day,  and I would set the parameters (flow, depth) based on the result. Temperature might influence plantal growth, if the water is cold, they grow slower. If this works: it is cheap but requires labour to harvest the yield intermittently. Also, the pool have to be cleaned regularly  to produce adequate water. Pumping needs at least a windmill wheel, so this one could be installed without electricity.

  6. We have same problem here in the uk.

    We have started to drill deeper and seal out the top water and have had great results.

    As always start with a good borehole that has been drilled correctly and has a good grout seal and this should reduce any contamination

  7. The easy method it will be blending, just pump water from different borehole and blend it. Make sure that the pumping took place at night in order for reaction to take place.

  8. The easy method it will be blending, just pump water from different borehole and blend it. Make sure that the pumping took place at night in order for reaction to take place.

  12. Denitrification by biological treatment is the most effective and cheapest way

  13. You can use aquaponics; the plants in an aquaponics system will see your nitrates as "fertilizer", and clean them out of the water. You'll then have to put the water through a secondary process to get any bacterial contamination out, but this will solve your first problem.

    For more, see http://www.friendlyaquaponics.com/ for tons of free information about what aquaponics is, what it does, and what it costs.

    Aloha, Tim............

    1 Comment

  17. Nitrate is a compound that is formed naturally when nitrogen combines with oxygen or ozone. Nitrogen is essential for all living things, but high levels of nitrate in drinking water can be dangerous to health, especially for infants and pregnant women. Nitrate contamination of ground water resources has increased in Asia, Europe, United States, and various other parts of the world. This trend has raised concern as nitrates cause methemoglobinemia and cancer. Several treatment processes can remove nitrates from water with varying degrees of efficiency, cost, and ease of operation.

    Safe & Economical Process

    1. Biological denitrification exploits the ability of certain naturally-occurring bacteria to use nitrate for respiration under anoxic conditions (absence of oxygen). The overall process is the reduction of nitrate to nitrogen gas and proceeds as follows:

    NO3 - → NO2 - → NO → N2O → N2

    Denitrification can be achieved using both heterotrophic and autotrophic bacteria. In heterotrophic denitrification an organic carbon substrate, such as methanol, ethanol or acetic acid, is required as a food source for the bacteria. In autotrophic denitrification an inorganic energy source such as sulphur, reduced sulphur species (e.g. thiosulphate) or hydrogen is required; the carbon needed for bacterial growth is obtained from bicarbonate in the water.

    1. Trickling filter followed by flash aeration may do the trick.
    2. Algal turf scrubber.
    3. Electrolytic reduction method

    1 Comment

  18. Nitrate is a compound that is formed naturally when nitrogen combines with oxygen or ozone. Nitrogen is essential for all living things, but high levels of nitrate in drinking water can be dangerous to health, especially for infants and pregnant women. Nitrate contamination of ground water resources has increased in Asia, Europe, United States, and various other parts of the world. This trend has raised concern as nitrates cause methemoglobinemia and cancer. Several treatment processes can remove nitrates from water with varying degrees of efficiency, cost, and ease of operation.

    Safe & Economical Process

    1. Biological denitrification exploits the ability of certain naturally-occurring bacteria to use nitrate for respiration under anoxic conditions (absence of oxygen). The overall process is the reduction of nitrate to nitrogen gas and proceeds as follows:

    NO3 - → NO2 - → NO → N2O → N2

    Denitrification can be achieved using both heterotrophic and autotrophic bacteria. In heterotrophic denitrification an organic carbon substrate, such as methanol, ethanol or acetic acid, is required as a food source for the bacteria. In autotrophic denitrification an inorganic energy source such as sulphur, reduced sulphur species (e.g. thiosulphate) or hydrogen is required; the carbon needed for bacterial growth is obtained from bicarbonate in the water.

    1. Trickling filter followed by flash aeration may do the trick.
    2. Algal turf scrubber.
    3. Electrolytic reduction method

  19. You have covered all of the typical ways to reduce nitrate in drinking water.  Another way requires some chemistry and biology.  I have seen some biological processes that reduces nitrate to nitrate and eventually de-nitrification.  I think there is some research published on the microbiological reduction of nitrate.  I hope this leads your research to find a low cost and SIMPLE solution.    

  20. You have covered all of the typical ways to reduce nitrate in drinking water.  Another way requires some chemistry and biology.  I have seen some biological processes that reduces nitrate to nitrate and eventually de-nitrification.  I think there is some research published on the microbiological reduction of nitrate.  I hope this leads your research to find a low cost and SIMPLE solution.    

  21. I agree that minimum cost segregates the end users. Make a small bottled water plant for mothers of young infants and find a way to fund this minimum cost approach. Minimum cost technology for this minimum flow can be designed if you define the flowrate and water quality parameters fully / completely.  Purpose driven funding might be available for the identified target group.

    1 Comment

    1. @ David,, that can be a great idea,, but communities may receive that message with mixed feelings where others (pregnant mothers) who will be asked not to drink from the same water (high nitrate)..also setting-up a bottled water treatment may be a big challenge more especially that the Government is still struggling to provide 100% conventional water treatment to its people..!

  22. I agree that minimum cost segregates the end users. Make a small bottled water plant for mothers of young infants and find a way to fund this minimum cost approach. Minimum cost technology for this minimum flow can be designed if you define the flowrate and water quality parameters fully / completely.  Purpose driven funding might be available for the identified target group.

  23. I agree that minimum cost segregates the end users. Make a small bottled water plant for mothers of young infants and find a way to fund this minimum cost approach. Minimum cost technology for this minimum flow can be designed if you define the flowrate and water quality parameters fully / completely.  Purpose driven funding might be available for the identified target group.

  25. Depending on the volume of water to treat, you could possibly use biofiltration. Under anoxic conditions, bacteria can remove, "digest" the nitrates.
    You would need enough residence time to do the appropriate removal.

    Usually another vessel is added after the sediment filter and used as the biofilter. The biocidal treatment is done after the biofiltration.
    To determine how much removal can be done, you would need to do preliminary bench work.This is, by far, the least expensive way to treat water.
     

    If you need more info, feel free to ask.

    1 Comment

  26. There arenot quiteexpensivewater treatmenttechnology-if interested-please sendthe amount andcomposition of the water-will send thecost of the equipment.

     

     

    1 Comment

  27. There arenot quiteexpensivewater treatmenttechnology-if interested-please sendthe amount andcomposition of the water-will send thecost of the equipment.

  28. Dear Evans,

    If no low nitrate well water sources would be available to replace or blend the nitrate rich well water, then nitrate shall best be reduced to inert nitrogen gas as applied at full scale over at least 30 years. This nitrate reduction can be achieved in various ways but - as always - the most sustainable and cost-effective solution for a specific case depends on the design flow rate (m³/h) and on the nitrate concentration (mg/l). Also the raw well water composition, pH and temperature would be important. Please specify as to advise more specifically for your case.

    Bruno

    1 Comment

  29. Dear Evans,

    The cheapest option is by blending but this relies on an alternative source of low nitrate water and a vessel where blending can occur. Dependent on the nitrate levels, the amount of low nitrate source may be minimal. Targeting the water for consumption against any used for washing may also reduce the volume of quantity of water you need to treat. 

    Good Luck with finding your solution

    Helen

  30. 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

    1. @ 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..!! 

    2. 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.

  31. Dear Evans,

    A trickling filter followed by flash aeration may do the trick. Though this may require some electrical energy and tanks to be constructed, the water post this treatment will definitely have acceptable levels of nitrates. Just need to initiate a nitrification denitrification cycle. Also, if the water requirement is 20 - 40000 liters, the RO units cost quite less. In India, we provide an RO of that capacity for approximately 5 - 6 lakh rupees. It comes to around $10000 USD. And its worthwhile if you want to use the water for drinking.

  32. Mr Evans Tumbo    

    Is it possible for you to build a tank / pond to store the water from the borewell for a few days before use. If so treating the water in the tank / pond would be possible.  We have a solution to grow Diatom Algae in such tanks / ponds. Diatoms would consume the Nitrate and some of it would escape into air as N2 gas.   

  33. Depending on the aquifer, bore water may also cause scaling issues.  Take a look at our website for a maintenance free, chemical and salt free water conditioner that does not require electricity. www.softerwatercondioners.com 

    1 Comment

    1. Is the web page written wrong? Maybe this one: http://softerwaterconditioners.com/

  37. It is tricky to remove nitrates as they are so stable, and I expect that management of water quality in a borehole will bring with it many other challenges!  Depending on the amount of water needed daily, you could consider looking into an algal turf scrubber where water is abstracted and passed through conditions optimised for algal growth (i.e. lots of sunlight) to remove nutrients and various pollutants.  Algal productivity essentially strips nitrates from the water, and you simply have to harvest the algae at times to maintain healthy continuous growth.  There is quite a lot of literature on this method, but I have only used this approach for my marine fish tank at home.  It is scalable though.  However, the best (and most direct strategy) perhaps would be to identify the direction of groundwater flow to the borehole, and trace this back to the source of the nitrates (overuse of artificial fertilisers?  septic tanks? agricultural practices?).  You will then need to work with the various stakeholders to put in place some measures to reduce input of nitrates to the groundwater.  Good luck!

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