Texas Commission on Environmental Quality (TCEQ). Class C Water License Exam

What process involves adding chlorine to complete reactions and leave free chlorine in water supply?

1. Initial chlorine treatment

2. Continuous chlorination

3. Break point chlorination

4. Standard dosage method

The correct answer is: Break point chlorination

Break point chlorination is the process where chlorine is added to water to ensure that all organic compounds, ammonium, and chloramines present in the water are fully reacted before leaving a residual of free chlorine in the water supply. This process is essential in ensuring effective disinfection, as it guarantees that all contaminants are addressed, allowing for a sufficient level of free chlorine to remain in the water. During break point chlorination, chlorine is added to the water in increasing amounts until a point is reached where there is a marked increase in free chlorine residual. This occurs after all the other compounds have been oxidized, at which point the chlorine becomes effective in providing a disinfecting residual. The knowledge of this critical point aids operators in determining how much chlorine is necessary to achieve desired water quality standards. Other processes, like initial chlorine treatment and continuous chlorination, may not ensure the complete reaction of all residual contaminants before reaching an optimal level of free chlorine. Standard dosage methods also do not specifically reference the necessary step of achieving break point to ensure effective water treatment.