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Taking a hard look at chlorine

{Dr. Christina Bottaro}
Dr. Christina Bottaro

Recent debate over contaminated drinking water and the cry to reduce greenhouse gas emissions have helped make more people aware of the long-term effects of environmental damage. But being aware of the problem and doing something about it are two very different things, and it's a distinction that Dr. Christina Bottaro, Chemistry, knows all too well.

She has spent her entire research career working on the study of compounds that may produce negative environmental effects. Her research focuses specifically on the by-products that are produced from the chlorination of waste water and drinking water.

"About 62 per cent of all by-products that are formed when you chlorinate water with organic materials present have not been identified. Many of those that have been identified have been found to be carcinogenic or toxic," pointed out Dr. Bottaro.

The fact that most Canadian municipalities use chlorine as their primary disinfection method might cause a few people to question the reasoning. Is this the best way of eliminating bacteria in surface water, and thus the best way to ensure safe drinking water? And is it the most cost-effective method? It is a fact that useing chlorine in surface waters containing dissolved organic material results in the formation of chlorinated disinfection by-products.

"Chlorinated compounds are formed inadvertently in the extensive use of chlorine for disinfection of water and waste water before it is discharged into the environment," added Dr. Bottaro. "What people don't often realize is that sometimes they are forming compounds that are potentially more destructive in the long term than the bacteria they are trying to kill with the chlorine."

The amount of compounds produced is positively correlated with the levels of dissolved organic materials present in the water. These compounds may include trihalomethanes (THM) and chlorinated carboxylic acids, substances that have been proven to be mutagens. Prolonged exposure to these compounds has been linked to various forms of cancer, and other health problems. What is needed, according to Dr. Bottaro, is better analysis of these compounds in order to gain an informed assessment and remediation of risks associated with the use of chlorine as a disinfectant.

Other methods for eliminating bacteria during treatment include UV light and ozone. The problem, Dr. Bottaro explains, is that once the water leaves the plant and goes on down the line, ozone dissipates quickly and UV light only works when it is present, therefore chlorine has to be added at some point to prevent bacteria from flourishing. Chlorine disinfection will unlikely be gotten rid of completely, but there are steps that can be taken to minimize the environmental impact.

"Education is the most effective way of changing the way people look at environmental issues," said Dr. Bottaro. "There is little public awareness of the long-term effects of such contamination. We need greater understanding in order to achieve stronger regulations on water treatment.

"There are also a lot of things going down the toilet which are known to be bad and cause problems. Things like medications and estrogenic compounds like birth control pills. This is creating problems in river systems as a result. We need to paint a picture of what happens to the environment when people do this."

Dr. Bottaro hopes her work will shed some light on the significance of environmental monitoring and the importance of taking a long-term view of the issues. She has just submitted an application for a research grant that will allow her to recreate the conventional municipal disinfection process in her lab, and investigate the chlorinated compounds that are formed.

"Exploitation of the environment is a global issue and we each have to do our part to resolve it."

{Memorial University of Newfoundland}