Wastewater Treatment Operator Certification Practice Test

Which of the following is not true about chlorine gas?

1. 2.5 times heavier than air

2. Extremely toxic

3. Common chlorine gas concentration at the treatment plants is 12.5%

4. Corrosive in moist atmosphere

The correct answer is: Common chlorine gas concentration at the treatment plants is 12.5%

In the context of chlorine gas, it is important to understand its properties as they relate to safety and its use in wastewater treatment. The statement about common chlorine gas concentration at treatment plants being 12.5% is not accurate. Typically, chlorine gas used in treatment processes is delivered as a compressed gas at much higher concentrations, often around 100%. In the wastewater treatment industry, chlorine is often used to disinfect water but is handled in controlled settings due to its hazardous nature. For comparison, sodium hypochlorite, a chlorine compound in liquid form, is used at concentrations around 10-12.5%, but that isn’t the same as chlorine gas itself. The other properties of chlorine gas, such as being 2.5 times heavier than air, extremely toxic, and corrosive in moist atmospheres, are well-documented. Chlorine’s density means it can accumulate in low-lying areas, increasing the risk to personnel. Its toxicity underscores the importance of proper ventilation and safety measures when handling it, and its corrosive nature demands careful considerations in equipment selection and maintenance in treatment facilities. Understanding these properties is crucial for operators to ensure safe practices and effective wastewater treatment.