Is Your Drinking Water Safe? The Dangers Of Excess Chlorine And The Push For Advanced Oxidation By Anna University
According to the National Water Quality Management Plan, excessive levels of coliform bacteria have been found in the drinking water consumed in most states.
Published : January 28, 2026 at 3:47 PM IST
By S. Ravichandran
Indore: Indore, one of the major cities in Madhya Pradesh and one that has received the award for the cleanest city in the country eight times, recently witnessed an incident that shook the nation. In the Bhagirathpura area of the city, eight people died after consuming contaminated drinking water. More than 100 other citizens were also affected. It is no exaggeration to say that this incident raised the question in our minds: Is the water we drink safe?
For a healthy life, not only clean air but also clean drinking water is essential. Consuming polluted water leads to diseases such as diarrhoea, cholera, dysentery, typhoid, intestinal worm infections and polio. Statistics reveal the shocking fact that 37.7 million people in India are affected annually due to consuming contaminated water, and nearly 780,000 deaths occur.
According to the National Water Quality Management Plan 2024, excessive levels of coliform bacteria have been found in the drinking water consumed by people in most states, including Rajasthan, Bihar, Gujarat, Tamil Nadu, Kerala, Andhra Pradesh and Odisha. Therefore, it is essential that the water we use is properly purified.
Water is currently purified and disinfected using the chlorination method. However, this method does not completely eliminate all germs. Therefore, Anna University in Chennai has invented a new technology that eliminates germs in drinking water at a low cost, as an alternative to the traditional chlorination purification method.
Regarding this, Dr. Kanmani, Associate Professor of the Civil Engineering Department at Anna University, in an exclusive interview to ETV Bharat Tamil Nadu explained the risks associated with the use of chlorine in water treatment plants, the harms caused by the chemicals used with it and also talked about alternative methods for safe water purification.
Chlorine Use and Risks in Water Treatment Plants
In India, chlorine is used in water treatment plants through pre-chlorination to remove germs and other impurities, and post-chlorination to eliminate residual disinfectants after filtration. According to the Central Pollution Control Board, 82.7 per cent of treatment plants in the country use chlorine gas for sedimentation, filtration and disinfection. The remaining 17.3 per cent of treatment plants use bleaching powder and liquid chlorine for disinfection.
However, the problem is that chlorine is being used in treatment plants in quantities exceeding the prescribed limit. That is, the chlorine concentration should be 0.2 milligrams per litre of water.
Disinfection By-products (DBPs) - A New Threat
Although chlorine is used as a disinfectant, the by-products (DBPs) used with it for purification create new contaminants in the water. To date, more than 700 disinfection by-products have been identified globally. The U.S. Environmental Protection Agency (USEPA) has categorised them as Trihalomethanes (THMs) and Haloacetic Acids (HAAs). Doctors warn that these by-products may cause colon, rectal, kidney, breast, lung, and pancreatic cancers, as well as birth defects.
Based on the World Health Organization's guidelines, the Bureau of Indian Standards (BIS) has provided guidelines for chlorine and its by-products.
Alternative Method: Advanced Oxidation Processes (AOPs)
In water treatment, organic and inorganic pollutants can be removed by using strong oxidants. It creates highly reactive molecules that break down pollutants into less harmful compounds. Ultraviolet radiation (UV), ozone (O3), hydrogen peroxide (H2O2), Fenton's reagent, and Nano bubbles are some of the oxidation methods used for water and wastewater treatment.
Oxidation methods demonstrate superior performance compared to conventional chlorination in disinfection, degradation of pollutants, and reducing the formation of disinfection by-products (DBPs).
A study on this topic was conducted at the Centre for Environmental Studies, Anna University. In this study, the disinfection efficiency and the potential for by-product formation were evaluated using oxidation methods, including ozonation and UV radiation.
It was found that chlorine-based disinfection produced a higher amount of by-products. In contrast, the radiation method resulted in significantly fewer by-products and ozonation produced even fewer. Therefore, Anna University has concluded that the oxidation method is more advantageous than the conventional chlorination disinfection method.
Professor Kanmani stated that the cost of implementing this technology is also lower than that of chlorine technology, and that using this method in overhead water tanks would enable the supply of completely purified drinking water to the public.
