• Question: How would you check if water is pure and good to drink??

    Asked by free46pie to Ann, Amy Heather on 14 Nov 2019.
    • Photo: Amy Heather Fitzpatrick

      Amy Heather Fitzpatrick answered on 14 Nov 2019:

      Hi there. So there are lots of ways that we test if water is safe to drink. Sometimes instead of testing the water for specific bacteria and chemicals we use tests that indicate the water is safe, because those tests are quicker and cheaper to do. An important test is turbidity so here is a link to explain how you do this in an easy experiment, maybe in secondary school https://www.thirteen.org/edonline/studentstake/water/schoolwater/turbidity/turbidity.htm.
      The colour of the water and smell are also always to check as they indicate if the water has organic materials in there or pollutants, changing the colour and smell of water. We also look at pH of the water and amount of dissolved oxygen. If there is lots of dissolved oxygen that means that there is organic pollution and the water is not safe to drink. A high pH or a low pH might indicate too many chemicals were added to the water. We want the pH to be fairly neutral for drinking water. Then some samples are taken and tested for indicator bacteria.. that are not harmful but indicate that harmful bacteria might be there. So example faecal coliforms are tested using selective and differential media to grow bacteria and maybe MS2 coliphage are used in plaque forming assays to detect bacteriophage, indicating that there might be viruses. I hope that answers your question.

    • Photo: Ann Reen

      Ann Reen answered on 14 Nov 2019:

      Hi there

      I would test the water for chemical & micro parameters to see if it good to drink & compare the results to the limits for those parameters in the Drinking Water Regulations.

      So If some one handed me a bottle of water from a well they had at home I would ask them a few questiosn first to help me decide what to test the water for. So if the person told me the water was from a well on a farm I would probably be concerned that the well might be contaminated with slurry. Maybe the well was in field and that field gets slurry application frequently. Then I would test for nitrates because ammonia which is found in slurry breaks down to nitrates. High levels of nitrates can result in an illness called blue baby syndrome -this is when the oxygen in the blood is replaced by nitrogen, & this can be serious. Slurry contains bugs like E. Coli & Faecalis Enterococcus so I would suggest analysing the well for these bugs as they can make people very sick- diarrohea, vomiting etc.

      If the water looked a bit coloured (like red/brown colour) I would analyse it for Iron. High iron levels can stain clothes & utensils etc.

      If there was a lot of intensive farming in the area – where crops were grown then there might be a risk that some pesticied are in the water so I would test for pesticides.

      If the person told me that the pipes are eroded then I might check the pH, as water with a low pH can erode pipes & also result in the leeching of metals from the pipe. E.g if it was a copper pipe & the water running through this pipe has a low pH then it could result in the copper getting into the actual water supply.

      So it is very important to ralk to the customer to get an idea of what parameters to test for. Hope this makes sense!

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