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Chlorination To Maintain Water Quality Levels : Pro's & Con's - Alternative Technologies? Kerala

Our well water in Central Kerala was contaminated with Choliform, E-coli, Pseudomonas and Sulphate reducing anerobes. It was for the first time the contamination was noticed which could have been due to various reasons like contamination of sewage water running about 50 feet away or due to the presence of our well in a industrial area. It is only with the onset of monsoons that the intensity has increased. After searching through the net and speaking to various consultants i treated the source well water directly with Shock Chlorination.

I maintained a 100 ppm of chlorine in the well which subsided to 10 ppm after 24 hours and 2 ppm 48 hours. It was noticed later that most of contaminants disappeared and only with further inflows of water due to good monsoon showers the contaminants did appear but with less intensity. I have been treating the well further with 2-3 ppm chlorine and having been maintaining the same. The results are they are controlled but they do remain with very low intensity. Since i am involved in the water processing business it is of paramount importance to me to ensure clean and pathogen free water. All the chemical parameters have been observed are either below detectable limits or well below the BIS prescribed limits.

The questions that I have are: 

1. Is chlorine the right method to use for disinfection in water.

2. What is the desired level of chlorine for treatment.

3. What is the minimum period of contact with chlorine that necessarily need to be maintained for pretreatment.

4. Is there an alternative for chlorine , if so how effective is it and how does one apply it.

5. i have tried hydrogen peroxide with silver but the result is very disappointing as the disinfection seems to be effected only on the surface and the bacteria still remained even at levels of 15 and 17 ppm. And I have also realised that hydrogen peroxide with silver is not advisable as they are harmful to the human body.

6. is Adding chlorine by dosing the best method or is there a better method. Kindly advise on what is the right steps to be taken to get pathogen free water at the pretreatment stage itself.

 Korah Paul



1. Some related resources from


Dear Mr. Paul

The answers to your questions are as below.

1. Yes chlorine the right method to use for disinfection in water. The residual chlorine ensure the protection from post contamination.

2. 1 to mg/l as chlorine for treatment.

3. 30 minutes as contact time

4. Yes Ozonization & UV treatment

5. Hydrogen peroxide is not good for well water. Water treated with Hydrogen
peroxide is not harm full to the human body.

6. For your problem Adding chlorine by dosing is the best method

It is not recommended to add disinfectant in well water. You may doze Chlorine in the delivery line of pump.

Prof. R. V. Saraf
Viraj Envirozing India Pvt. Ltd.

21 Radhakrishna, Near SBI
Paud Road, Pune 411 038
Tele/Fax: (020) 25433445
E Mail:


Dear Paul,

World over gaseous chlorine is used for killing micro-organisms in water. It is simple and very effective process. Micro-organisms load in untreated water varies season to season and also dependent on water temperature. 30-40 deg Celsius temp is good to grow bacteria exponentially. free residual chlorine in treated water should be 0.5 ppm.

If bacteria load is more you may require to dose 10 ppm chlorine in untreated water. Chlorine kills bacteria effectively if water PH is 7.5. Minimum 5 minutes contact time should be there before coagulation and flocculation.

If there is not any coagulation/flocculation requirement contact time should be atleast 30 minutes.

there are some chlorine dioxide generators in the market claiming it will half the consumption of chlorine. I have not tried any one so far.

with best regards
AK Singla




After treating the well with bleaching powder the intensity of most bacteria is low but the level of [i]Pseudomonas[/i] is still high and keeps occurring in my treated water time and again and is causing sleepless nights on account of it. a white biofilm occurs a few days later after filtration and even after treating with uv and ozone.

My question is can:

1.Chlorine at 10ppm effectively eradicate completely the [i]Pseudomonas[/i] bacteria.Is chlorination the best bet or are there alternate technologies to treat the same at the pretreatment stage.
2. Being engaged in the water industry one has to ensure pathogen free water
so , the chlorination is given using a doser pump . will any additions like floculator and aeration help or ensure a better product. Kindly advise.

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