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What You Should Know about Bacteria Testing in Hot Weather

Written by Janice M on . Posted in Technical Tips

Hot weather will trigger an increased need for testing of bacteria in water. Bear in mind:

  • Low rainfall, coupled with warmer weather, can lead to a higher than usual bacterial count.
  • Higher evaporation levels will mean less water available to dilute the bacteria present in water.
  • It is vital to test the water for bacteria, to ensure the safety of plants, fish, humans and animals. Gastro-intestinal problems and diseases such as cholera and typhoid can result from a higher bacterial load in water
  • The most common bacterial tests in water that can be performed are for Coliforms and E.Coli
  • Test samples must be placed in cooler bag on ice immediately after collection
  • Surface water for irrigation also requires that certain precautions be taken
  • Drinking water should contain zero Faecal Coliforms and E.Coli
  • Bacterial counts are in CFU’s or Colony Forming Units
  • Bacterial counts of less than ten will cause some problems, counts between 10 and one hundred will cause infection to all users
  • Clean surface water commonly has a count of 1 to 10 per 100 ml – this can increase to as much as a million in sewage water
  • When it does start to rain after a long dry period, research has shown that pathogens are higher in stormwater and in sediments. After heavy rain, wait until the sediments have settled before testing / using the water

More detail about Coliforms and E.Coli

How to Test for Coliforms / E.coli:

See how to use a Lovibond® Coliform / E.Coli Test kit

If Test Results are Positive for Bacteria:

  • The water has likely been contaminated by sewage or manure
  • Try and find out how bacteria got into the water. Possible sources:
    • Groundwater may have been contaminated by surface runoff
    • Untreated sewage discharges
    • Domestic animals and wildlife
    • A layer of bacteria may have developed on the surface of the water
  • Don’t drink the water until it has been boiled for 10 minutes or treated with Chlorine (5ml : 20 litres water)
  • After investigation or treatment, test a new sample to make sure there is no bacteria present
  • Maintain a disinfection system by ensuring that Free Chlorine is constantly 0.2 – 0.5 mg/l


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