Is it possible to to detect coliform/fecal coliform if the same water shows presence of residual chlorine?

Taxonomy

• Treatment
• Chemical Treatment

12 Answers

1. Many correct indications were provided with the previous answers. I would just add that also biofilm contributes to protect coliforms and other pathogens from chemicals. This means that bacteria attached to surfaces (forming a layer usually known as "biofilm") are more protected from chemicals than free-floating bacteria, thus they can survive even very high concentrations of chlorine. Then, when parts of biofilm detach from pipe/tank surfaces and float away, you can find those survived pathogens also in the water.

2. 
   

   Yes it is ​possible. Some time ​Chlorine does ​not kill all ​coliforms, contact time is necessary , UV disinfection. Washing thoroughly with soap after contact with contaminated water can also help prevent infections. Gloves should always be worn when testing for  fecal coliform, coliform bacteria include a large group of many types of bacteria that occur throughout the environment. They are common in soil and surface water and may even occur on your skin. Large numbers of certain kinds of coliform bacteria can also be found in waste from humans and animals. Most types of coliform bacteria are harmless to humans, but some can cause mild illnesses and a few can lead to serious waterborne diseases.

   
   
   

    

3. Yes it is possible.

   
   
   

   The testing kit is not the problem but the the level of water pre-treatment before it is chlorinated  and the dosage of chlorine applied to allow a residual dose to be sustained

4. Hi Abdus,

   
   
   

   Yes it is possible. Chlorine does not kill all coliforms instantly. You might have to provide more contact time with the chlorine to kill any remaining coliforms. Alternatively you could try increasing your chlorine dosage.

   
   
   

   Regards,

   
   
   

   Daniel

5. All of the below answers are useful.  Organic material prevents chlorine from killing bacteria.  It is unusual to find E coli in chlorinated clean water providing there is sufficient contact time.  There are certain gram positive sporing rods Bacillus species, which grow on the specialist media providing a false positive.  They are normally in the spore form and not actively growing in the presence of chlorine.  As soon as they come across artificial media they germinate showing up as viable growth.

6. Plus, it depends on what method was used to test the water (some methods eventually trigger regardless of the presence of bacteria), how the water was tested, and how the sample was handled.  

7. Yes it is quite possible, low retention (contact)  time and quality of water will influence, as a sanity check you should always have more total coliform count than faecal coliform count

8. Yes it is quite possible, low retention (contact)  time and quality of water will influence, as a sanity check you should always have more total coliform count than faecal coligirmos count

9. Dear Abdus,
   
   Yes it could be possible.
   Even some others microrganisms as Giardia can be resistent to chlorine, but not to the ozone.
   
   Regards,
   
   Orlando D. Gutierrez Coronado

10. Could happen if high turbidity. The microbes tend to attach to particulates and could be shielded from the chlorine. 0.2 mg/L isn't a lot.

11. Yes, it is possible. 

12. Yes. The coliforms could be on bits of detritus that shielded them from the chlorine, but they still responded to the test