Rejuvenation of Dormant Groundwater Wells

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I have recently reactivated a borehole which was used for drinking water 20+ years ago, to be utilized for household purposes and drinking water.

I would like to know what the recommended procedures are (besides thorough flushing of the well prior to use), to ensure the water is safe to drink.

I will be sampling the water to be analysed for chemical parameters, and am considering analyzing it for biological parameters as well. However, the well is located in a very remote area, and analysis of biological parameters is costly, which is why I am considering only analyzing its chemical parameters.

Any advice would be welcome. 

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15 Answers

  1. A quick question concerning the dosing of chlorine to 'shock' the well. Does anyone know how much should be used without running the risk of residual chlorine entering the aquifer? Is this even a risk?

  2. A lot of good answers here. An older well should be checked for physical condition of the casing.  Is the reason for abandonment known? The well should then be pumped and surged at a minimum and scrubbed if possible. You want to be certain that water from the aquifer is tested, rather than water that has been sitting in the borehole or is left over after brushing. Depending on the site geology, water could be coming through cracks / karst from a great distance at a rapid rate, vs. sedimentary material with much lower travel time.

    Check your pump literature to be sure the pump can be exposed to ~ 100 ppm chlorine. Whoever drilled the well may still have records. Disinfect using sodium hypochlorite solution or calcium hypochlorite dissolved in a bucket, surge, let stand 24+ hours, followed by flushing again to obtain zero chlorine residual before bacteriological testing. That is total coliform and e. coli. A heterotrophic plate count would provide additional info about general bact quality.

    Please do the cleaning, flushing, disinfection, flushing and analyses first, both bacteriological and chemical analyses, before evaluating the need of any treatment schemes - it is possible that no treatment beyond startup cleaning is necessary. Disinfection is the only treatment generally done as a precaution; other treatments are not done unless a specific contaminant needs to be addressed.

    Other notes, if near any flowing natural stream, even a dry arroyo, do not discharge chlorinated water onto the ground where it could possibly reach the stream.  If several days pass between cleaning etc. and drawing samples for analysis, pump to waste at least four times the volume of water standing in the bore column before sampling.

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  3. Testing is recommended for pH and total dissolved solids as well as tests related to land uses occurring or expected to occur within sight of the well. Additionally, if there are obvious stains, tastes, or odors in water, seek testing that will help identify the source of these symptoms.

    Also, you may wish to set  screen at the bottom of the well to filter out sediments and dissolves solids.

  4. Hallo Nicole

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  5. Hi Nicole

    First of all I would like to start my opinion by saying this "A stitch in time saves nine". 

    I recommend you to analyze the water sample for drinking water standards after flushing enoughly. Even though it is costly, however, I think this is a minimum investment for your future health and safety because there are many uncertainties to say water quality without sample analysis.

    And....

    Flushing the wellbore is an important process before use. A long-resting borehole is subject to have lots of chemical precipitation(scale) and biofouling in it, especially on the bottom of the borehole and dead zone in the borehole where is far from or between the major groundwater inlet and outlet. I've seen lots of those kind of wells using borehole camera. It is generally recommended  physical agitation such as air jetting, surging, swabbing and brushing or chemical agitation by injecting 15% HCl or 50-100 mg/L of Cl2 before flushing out. but budget problem.....At least I suggest flushing the borehole by moving the pump up and down.

    Remember the flushing is an process only to remove any existing contaminants within and closely sorrounding the borehole. Therefore, if you want to continue to use that well from now on, check the potential contamination source around the well, especially up-gradient area, such as agricultrual field, stock farm, private cesspool and so on. Groundwater velocity is very slow compared to surface water. So if there are any potential contaminant source around you, I recommend you to analyze the water sample periodically like every 2-3 year according to any regulations in your country.  If it is remote area as you say, the only thing you may concern about is contaminants from existing borehole materials which can remove by flushing like above and natural contaminants such as asenic, high concentration of iron which come from sedimentary medium. If the geological medium is granite, some radioactive component can be issue. Once water analysis report is safe with these natural contaminants, you don't worry about these any more from now on.

    In many cases, groundwater in remote area far from artifical contaminant source is safe to drink without any treatment. But health and safety cannot be emphasized enough. If you know any existing contaminant in water, you can choose a proper, cost-effective treatment method for drinking out of numerous commercial products.

    I hope the groundwater in your well would be clean enough to drink without any treatment.

     

    1 Comment

    1. Hi Yongcheol

      Thank you so much for your great feedback. I really appreciate it. I have pumped the well repeatedly now on and off over the past month to try flush it out, and I am sending a water quality specialist out to the site shortly to collect water samples. And yes, of course your are right, health is paramount, which is why I will be doing a full quality analysis as per your recommendation. Being in a remote location, and no evidence of historic agriculture beyond perhaps grazing, I am certain that we wont be drawing contaminants into the well. Additionally, the well is located very high up in the catchment. 

      Thanks again. Regards, Nicole

       

  6. Hi. NB. Great feat. You need to worry when thiscneo water is used for potable needs. Have a good UV filter with trickle flow( maxm. contact time ) as a filtering process.. Others to incorporate would be candle fltr. carbon fltr.softning additive.pH improve to 7.5 minm. level.. well wishes.. from Prof Ajit Seshadri.Vels University.Chennai INDIA .. 

  9.  

    I use MgO (Magnesium Oxide) prill beads to purify drinking water. 
     

    The prill beads come from a deep mine in Nevada. They are processed at 700 degrees which turns them into ceramic beads that do not dissolve in water. 
     

    The beads place a positive charge in the water that shatters the magnetic bond that holds together any contaminants or pollutants (chlorine, fluoride, heavy metals: zinc, copper, lead, chromium-VI, pesticides, radiation, pharmaceuticals, mold, Ecoli, bacterias, etc) and gasses them out of the water. 
     

    It raises the water pH to 8.7, high alkalinity, high oxygen, and thins the water so that can penetrate the cell membranes and flush out your toxins. 
     

    As to hydration: 3 glasses of prill water is equal to drinking 1 gallon of reverse osmosis water. 
     

    Great for acid conditions: acid-reflux, heartburn and acne. 
     

    Regards, 
     

    Richard Fishman 
     

    Owner 
     

    PrillyPureWater.net
     

    Get a 3 gallon water container with spigot at Ace. Boil water, place both bags in boiling water for 3 minutes. Rinse in cold water, then place in the 3 gal already filled with tap water container. Wait 24 hrs, then enjoy perfect drinking water. 
     

    After this and every time thereafter, drink the water down leaving 1/3 remaining, then fill with tap water and it will be purified in only 2 hrs.
     

    Remember to refill at 1/3 level.

  10. If I was to be running on a budget, I would fill the bath with water. If there is a lot of precipitate or iron present the water will be discolored, if the water smells like hydrogen sulphide then there is possible anaerobic activity occurring, if you have copper in the system & the water has low pH you will start to see a blue color appearing on the white porcelain surfaces after a while. If you have a toilet cistern that holds water look inside & feel the surfaces. If they are greasy you will most likely have a severe bug problem. If there is a build up of solids in the toilet cistern then is possible corrosion products or muck coming from the well. If you are boiling water in a kettle check for scale build up on the elements if this is occurring you may have very high calcium & magnesium present. The most important parameters to test are pH, Ecoli & conductivity initially. If the pH is below 6.00 you will be dissolving metals in your water system & any metals present in the well surfaces will also be dissolving. Check with you local regional council to find out what is present in the local soils at the depth of your well. Hope this helps.

  11. Hi Nicole

    Being in the Public Health field I would recommend that you do biological testing. Better safe than sorry. I recommend testing at least for Total Coliform and E. coli. The E. coli will indicate if there may be any disease causing organisms in the water, including viruses. If the test is positive for any E. coli then the water is not safe to drink without treatment. High numbers of Total Coliform is also an indicator of possible disease causing organisms but low numbers (less than 5 per l00 ml of water) would be considered safe as long as E. coli level is 0 per 100 ml.

    Good luck and enjoy!

  12. Hi Nicole,

    You will probably have some duties from a legal point of view and depending on the location of the supply, you may need to comply to similar requirements as in the UK  and the Private Water Supply Regulations implementing European Drinking Water Directive (Council Directive 98/83/EC). You have some good advice on these here:

    http://dwqr.scot/private-supply/technical-information/pws-technical-manual/

    http://dwi.gov.uk/private-water-supply/regs-guidance/guidance-index.html

    Some geochemistry should be done to amke sure you're operating your pump correctly and subsequnet elements of the water distribution system are not subject to detrimental effects (e.g. metal precipitation).

    You may not be the only person in this remote area to use groundwater as a source of supply, check with your neighbours...

  13. Good day Nicole,

    Depending on the contaminations of water, it is possible to select mineral sorbents, including those having bactericidal properties. Filters can be make by yourself at home.

  14. Hi Nicole,

    According to the depth of the well, if it is shallow (under 100')  I would have a coliform test performed. If is deeper than that you will probably be ok with using a shock treatment of chlorine to clean the well.  If you do perform a coliform test make sure you shock and flush it before performing the test...

  15. Hello Nicole,

    It seems you have already made a good decision to flush it out and then do a couple of tests.  I would encourage you to at least do an e.coli test even though it is remote - there may be some contamination from an old toilet that was used there previously.  Also test for hardness (to see if the water may need softening for washing or perhaps cause scaling of rigid pipes), as well as total salts (may not be necessary if it tastes good), alkalinity and pH (to see how corrosive it could potentially be).  You may want to measure arsenic and fluoride if there is recorded problems in that area. If you do find too many e.coli (there may be a low number if the borehole has been standing a long time which are not of concern) try pouring some chlorine (sodium hypochlorite) into the borehole and allowing it to stand a few hours.  If you can, monitor the water for a few days after you start using it - taste, feel and pH (tests are affordable) - just to see if there are any changes.  Otherwise enjoy the remote lifestyle.

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