Final answer:
Chlorine must be removed before water is released into the environment because it is toxic to aquatic life and can harm or kill marine organisms.
Step-by-step explanation:
Chlorine has to be removed before the water is returned to the watershed because it's toxic to aquatic life(C). During the disinfection process of wastewater treatment, chlorine is added to kill harmful bacteria and pathogens. Although chlorine is effective in treating water to make it safe for human use, it is quite harmful if added in excess, leading to a negative impact on aquatic organisms.
Marine life is sensitive to chlorine, which can cause them harm or potentially be lethal. Therefore, after the disinfection process, the chlorine in the water must be neutralized to protect the marine ecosystem.