Nitrate Ion Removal from Water Wells

Published on by in Technology

The city of Natal, Brazil, is supplied by water from water wells contaminated by the nitrate ion.

Concentrations are in the range of 15 to 80 mg / l of nitrate as nitrogen, well above the limit allowed by the World Health Organization (10 mg / l).

Intake of water contaminated by nitrate causes various diseases and diseases.

Which inexpensive water treatment technologies can solve the problem of high nitrate concentrations in public water supply?

Taxonomy

21 Answers

  1. A best suggested practice on nitrates in residential wells is available from the National Ground Water Association, USA.  Some principles may be applicable to larger systems.  Additionally, search our Web site's archives for additional literature on nitrates in groundwater.  Many of the citations have papers attached and can be downloaded.

  5. Hello Carlos

    In the UK ion exchange has been used effectively to reduce nitrate levels once blending with low nitrate sources is not possible.  Assuming Natal has a population of 1 million plus and all the water is supplied from the same wells you are looking at a massive treatment system.  Biological denitrification systems are usually used for wastewater and the plant footprint and operating costs are significant.  Ion exchange and RO are effective but can be expensive in capital and operating costs and there are associated waste brine disposal issues. More recent trends are to chemical denitrification but there are few full scale examples of this.

    Technical Report No.6 - Drinking Water Treatment for Nitrate published by the Center for Watershed Resources, University of California, Davis (http://groundwaternitrate.ucdavis.edu/files/139107.pdf) provides and excellent guide to nitrate treatment alternatives with decision trees and costed examples.

    Best Regards

    Richard

  6. The economic and easy way to remove nitrate from potable water supply would benanofiltration. It can remove all divalent ion at a lower energy consumption than RO. It is reliable operation.

     

    To remove nitrate from wastewater, it would be better to be treated biologically: denitrification. Ion exchange will generate a lot of regeneration waste and cost of chemicals.

  7. Hi Carlos, Clinoptilolite (natural zeolite) cation exchange filter media is an inexpensive and efficient way of removing nitrates from the water. Quality thermally activated natural zeolite may have CEC (by NH4) in the range of 0.7-1.8 mg.eq/g, which is easily regeneratable by backflushing with light solution of NaCl and may be regenerated 50 times or more. 

  10. Dear Carlos, 

    I hope you are well, please see below the in-put from my business partner, if it helps and you wish more informaton please let me know:

    Best solution would be to use Ion Exchange units to remove nitrates and nitrites from drinking water. These could be point of use systems. 

    Alternately,  if the technology is sought for point of source like reservoirs,  we can help them with Nitrate absorbing media which is dissolved in water and spread across the water body.  The slurry will absorb the nitrates and pushes them to the bottom of the Water body and the layer firmed will continue to bind the nitrates from the natural springs as the empty themselves into the water body. 

    Best wishes

     

    Jenny

     

     

     

  11. Hi Carlos, as others have suggested, biological denitrification is a relatively inexpensive process. Rather than using organic matter as the energy source for the bacteria involved, I would suggest using sulphur. That way, potential pathogens and e.g.toxin-producing fungi will be unable to thrive. Essentially, at low or zero dissolved oxygen concentrations, many bacteria can use nitrate for respiration in place of oxygen. If sulphur is used to supply the energy, a sub-set of autotrophic bacteria will oxidise it to sulphate and reduce the nitrate to nitrogen gas. Thus, you end up with sulphate in the water rather than nitrate. The WHO guideline limit for sulphate is 500 mg/L but that is for taste rather than toxicity reasons, and many mineral waters contain a high concentration of sulphate. Furthermore, autotrophic metabolism produces less biomass than heterotrophic metabolism (organic matter as energy source), so there will be less biological sludge to dispose of. Rather than treating the entire flow, a proportion can be treated and blended with the untreated portion, to supply water with nitrate less than the WHO guideline concentration (50 mg/L, as the nitrate ion = 11.3 mg/L as N, which is maybe where your value of 10 mg/L came from). Best wishes, Mike

    2 Comments

    2. Very good information Mike. We used alcohol as the energy supply for treating underground mine water to remove the nitrates from blasting activities. The nitrate levels were quite high. Do you have any information on what flow through capabilities are attainable by this sort of system? What is the maximum GPM? Thank you.

  14. Compared to ion exchange,biological denitrification[using shredded newspapers,for instance]found to be effective. Other suggestions can also be given.

  15. Use of liquorice and reed is reportedly useful as natural organic carbon sources for biological denitrification.

    Also iron sludge removal is important,being a linked issue in well waters.

    I have found the following chemicals very effective in addressing the issue.

    Use of quick lime,baking soda,alum plus less than 10mgs.,of pot.permagnate is found very useful in addressing iron related issue,initially.

    Use of coriander leaves or dried seeds of drumstick found useful from my experience.

    I suggest a combinatorial approach,repeating these alternatively,at 2 or 3 months interval for sometime,for well water

  16. From past experienced if the iron sludge is controlled from build up within water systems it tends to resolve most issues - have you looked at using https://envirofluid.com/worksafe-environmental-chemistries/water-wastewater-treatment/triple7-envirobore ?

    1 Comment

  17. Dear Carlos Henrique,

    You can find a very interesting summary of the technologies applicable to this situation in the document found at  http://groundwaternitrate.ucdavis.edu/files/139107.pdf.
    This document is based on a real case in California.

    I hope it can help you.

    Best regards.

     

  20. Dear Carlos,

    The WHO Guideline Value is 50mg/l nitrate - the following document should be useful; http://www.who.int/water_sanitation_health/dwq/chemicals/nitratenitrite2ndadd.pdf

    In terms of consumers, it is formula (bottle) fed infants that are at greatest risk - high nitrates can in rare cases cause blue-baby syndrome - the above document will have further information on this.  For other age groups elevated nitrate is generally not an issue.

    There are various ways of reducing nitrate;

    1).  Nitrate exchange - this uses a resin-based media that exchanges the nitrate ion for chloride.  It is a very common process and should be easily available.  The issue is that depending on the volume needing to be treated it could be quite costly.  Excess chloride may also be problem, particularly if the ground water is saline influenced.

    2).  Blend-treating with a low nitrate source.  This is also very common but requires a low-nitrate source to be available.  Careful control/blending/monitoring would be needed to ensure the nitrate remains under the GV.  As a note, I've known nitrate levels to vary significantly in groundwater sources that are relatively close.

    3).  Identifying (and removing) the source of the nitrate.  This is a longer term solution and probably not practical but worth being aware of.  Nitrate in groundwater will typically come from sources such as sewage disposal to ground and agricultural practices; if changes can be made to reduce such harmful practices close to water abstractions eventually the nitrate should reduce (although can be a very large area).

    Kind regards, Andy

  21. Carlos, Nitrate(NO3) and Nitrite(NO2) are both Anions and are removable by Anion Exchange Resin Specific for Nitrate/Nitrite removal. The media is regenerable with Softener Salt using the Negative Chlorine Ion's of the NaCl. Reverse Osmosis will also Remove approximately 76% of Nitrate/Nitrite, but is also more expensive initially and in operation costs. Also, once equipment is in operation, the water quality should be tested at regular intervals.