Florida Drinking Water Operator "B" Practice Test

Which chemical must be filtered out after being added to a surface water source for odor reduction?

1. Chlorine

2. Hydrogen peroxide

3. Powdered activated carbon (PAC)

4. Ozone

The correct answer is: Powdered activated carbon (PAC)

When powdered activated carbon (PAC) is added to surface water, its primary purpose is to adsorb organic compounds and reduce odor and taste problems in the water. PAC effectively binds to various contaminants and impurities, allowing for their removal during the filtration process. The filtration process is critical because while PAC helps in reducing undesirable compounds, it must be removed afterward to avoid introducing additional particles into the treated water. If PAC remains in the system, it could lead to further water quality issues or interfere with subsequent treatment processes. In contrast, chlorine is commonly used for disinfection but does not typically require filtering out for odor reduction purposes. Hydrogen peroxide is sometimes used for oxidation and disinfection but has a different mechanism of action and does not focus on odor control in the same way as PAC. Ozone is another oxidizing agent that can be used for treating taste and odor issues but does not function in the same capacity as PAC in terms of adsorption. Thus, the requirement to filter out powdered activated carbon after its use for odor reduction is based on its role in the treatment process and the necessity to ensure that treated water remains free of residual treatment chemicals.