Chlorine and Ozone
Explanation
Water disinfection is a critical stage in the water treatment process designed to eliminate or deactivate pathogenic microorganisms (bacteria, viruses, and protozoa). This ensures the water is biologically safe for human consumption. Disinfection is typically achieved using chemical agents or physical methods.
Option Analysis
- Chlorine and Ozone: Correct.
- Chlorine: It is the most widely used disinfectant in public water supply systems. It is effective against a broad spectrum of pathogens and, crucially, leaves a residual concentration in the water. This residual protects the water from re-contamination as it travels through the distribution pipeline.
- Ozone: It is a powerful oxidizing agent and a very effective disinfectant, often stronger and faster-acting than chlorine. It is used to kill bacteria and viruses and to remove taste and odor. However, unlike chlorine, ozone does not leave a lasting residual, so it is often used in conjunction with a secondary disinfectant like chlorine or chloramine.
- Nitrogen and Phosphorus: Incorrect. Nitrogen and Phosphorus are nutrients. In water bodies, an excess of these elements typically results from agricultural runoff or sewage discharge, leading to eutrophication (excessive algal growth), which degrades water quality. They are pollutants, not disinfectants.
- Sulphur and Magnesium: Incorrect. Sulphur and Magnesium are not used for disinfection. Magnesium is a mineral contributing to water hardness, while sulphur compounds are often contaminants responsible for foul odors (e.g., hydrogen sulphide).
- Calcium and Iron: Incorrect. Calcium and Iron are common minerals found in water. Calcium contributes to hardness, and Iron can cause staining or metallic taste, but neither possesses disinfecting properties.
Key Takeaway
Chlorine and Ozone are the primary chemicals used for water disinfection. Chlorine is valued for its residual protection, while Ozone is utilized for its potent oxidizing capabilities.