Why is sodium hypochlorite sometimes added to the head of a plant?

Sodium hypochlorite is commonly added to the head of a wastewater treatment plant primarily for its disinfection properties, which help control odors. When wastewater enters a treatment plant, it can contain organic matter and other substances that may produce unpleasant odors due to anaerobic decomposition. By introducing sodium hypochlorite, which releases chlorine upon dissolution, any odor-causing bacteria can be neutralized, thereby minimizing the release of odor into the environment.

In addition to combating odors, sodium hypochlorite also serves to disinfect the wastewater, reducing pathogens and improving overall water quality as it moves through treatment processes. This added benefit of disinfection further supports the control of odors, as it lessens the microbial activity that contributes to foul smells.

The other options involve processes that sodium hypochlorite does not directly influence. Adjusting pH levels is typically managed by the addition of acids or bases rather than disinfectants. Promoting algae growth would be counterproductive in a wastewater treatment context, as algae blooms can lead to further complications in water treatment. Enhancing sedimentation is typically achieved through coagulation and flocculation processes rather than the use of sodium hypochlorite, which is not intended to gather or settle solids but rather to disinfect.