Why is Chlorine Used in Water Purification Plants?

Access to clean and safe water is essential for human survival and good health. Water purification plants play a vital role in providing safe drinking water to communities. However, before the water can be distributed, it needs to be treated to remove harmful bacteria, viruses, and other contaminants. One of the most commonly used disinfectants in water treatment is chlorine. But why is chlorine used in water purification plants?

Effectiveness and Cost-Efficiency

Chlorine is a highly effective disinfectant that can kill a wide range of harmful microorganisms, including bacteria, viruses, and protozoan cysts, such as Giardia and Cryptosporidium. It can also eliminate residual organic matter, such as algae and slime, and remove unpleasant odors and tastes from the water. Additionally, chlorine is relatively inexpensive and readily available, making it a cost-efficient option for large-scale water treatment plants.

Regulatory Requirements

Chlorine has been used as a disinfectant in water treatment for over a century, and it is still a popular choice due to regulatory requirements. The World Health Organization (WHO) and other governmental agencies require water suppliers to maintain a residual amount of disinfectants, such as chlorine, in the water distribution system to prevent the growth of harmful microorganisms. The required level of residual chlorine varies depending on factors such as the type of water source, the treatment process, and the distribution system's design and maintenance.

Chlorine Safety Considerations

While chlorine is highly effective in killing harmful microorganisms in water treatment, it should be used with caution due to safety concerns. Chlorine gas is highly toxic and poses a risk to human health, especially in high concentrations. Therefore, water treatment plants must adopt safety measures, such as proper storage, handling, and transportation of chlorine, and use equipment that can minimize the risk of accidental release of chlorine gas. Additionally, the use of chlorine in water treatment produces disinfection by-products (DBPs), such as trihalomethanes (THMs) and haloacetic acids (HAAs), which have been linked to increased risk of cancer and other health effects. As a result, water treatment plants must monitor and control the level of DBPs to ensure that they comply with regulatory requirements.

Alternatives to Chlorine

Despite the effectiveness and cost-efficiency of chlorine, concerns around safety and DBPs have led to the development of alternative disinfection methods. These methods include ultraviolet (UV) radiation, ozone, and hydrogen peroxide. UV radiation can effectively kill microorganisms but does not produce DBPs. Ozone is highly effective in removing organic matter and microorganisms and does not produce significant amounts of DBPs. Hydrogen peroxide can be used as an alternative disinfectant but requires high doses and long contact times to be effective.

Conclusion

In conclusion, chlorine is widely used in water purification plants due to its effectiveness in killing harmful microorganisms, cost-efficiency, and regulatory requirements. However, safety concerns and the production of DBPs have led to the development of alternative disinfection methods. Choosing the right disinfection method depends on various factors, such as the type of water source, the desired level of disinfection, and the regulatory requirements. Regardless of the disinfection method used, water treatment plants play a critical role in ensuring access to clean and safe water.