During which process should powdered activated carbon be added for optimal results?

The addition of powdered activated carbon is most effective when done after the filtration process. This is primarily because powdered activated carbon serves to adsorb organic compounds, taste, odor, and certain contaminants in the water. By introducing it after filtration, the activated carbon can efficiently bind with these impurities that may not have been wholly removed during the filtration stage. As such, the quality of the treated water can improve significantly with this step.

Introducing powdered activated carbon at other times, such as during or before filtration, may interfere with the filtration media's ability to function effectively and could potentially not allow for sufficient contact time between the carbon and certain contaminants. Chlorination is generally performed to kill pathogens, and if carbon is added before this process, it might absorb some of the chlorine, reducing its effectiveness in disinfection. Therefore, the timing of adding powdered activated carbon is critical for ensuring optimal water quality.