Ontario Operator-in-Training (OIT) Practice Exam

Which parameter is crucial for public health and must be tested regularly by the operator?

1. pH levels

2. Chlorine residual (from secondary disinfection)

3. Temperature

4. Electrical conductivity

The correct answer is: Chlorine residual (from secondary disinfection)

Chlorine residual from secondary disinfection is essential for ensuring public health in water supply systems. This parameter is crucial because it indicates the effectiveness of the disinfection process in eliminating harmful microorganisms. Regular testing of chlorine residual helps operators ensure that there is an adequate level of disinfectant present in the water to prevent pathogen regrowth and maintain water quality throughout the distribution system. A proper chlorine residual provides a barrier against potential contaminants, enhancing the safety of the drinking water. Consistently monitoring this parameter is part of maintaining compliance with health regulations and standards, making it a fundamental aspect of water treatment operations. Other parameters, while important for overall water quality, do not directly correlate with the immediate safety and effectiveness of disinfection in the same way that chlorine residual does. For example, although pH levels are significant in affecting the efficacy of chlorine, they do not serve the same primary function in pathogen control. Temperature can influence chemical reactions and biological activity, but its direct impact on public health is not as critical as that of chlorine residual. Electrical conductivity can indicate the presence of dissolved solids, but it does not specifically indicate the safety of water from microbial threats.