Ontario Operator-in-Training (OIT) Practice Exam

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Which of the following factors is critical for effective disinfection in water treatment?

  1. pH Level

  2. Temperature Variation

  3. Concentration and Contact Time

  4. Flow Rate

The correct answer is: Concentration and Contact Time

The concentration of the disinfectant and the contact time are vital factors for effective disinfection in water treatment. The concentration refers to the amount of disinfectant present in the water, while contact time is the duration for which the water is in contact with the disinfectant before it is used. Both of these factors play crucial roles in ensuring that the microorganisms present in the water are adequately inactivated or killed. When the concentration of the disinfectant is too low or the contact time is insufficient, there may not be enough disinfectant available to effectively eliminate harmful pathogens. Conversely, a higher concentration or longer contact time can enhance the effectiveness of disinfection. Therefore, ensuring the right balance between these two factors is essential for achieving safe, potable water. Other factors, while relevant to the disinfection process, such as pH level, temperature variation, and flow rate, do influence the overall effectiveness of disinfection but do not carry the same weight as concentration and contact time in determining the efficiency of the disinfection process. For instance, pH can impact the efficacy of certain disinfectants, and higher temperatures can enhance disinfection, but without the correct concentration and sufficient contact time, disinfection may still fail to eliminate pathogens adequately.