Which substance is non-toxic to aquatic organisms, a good virucide, and adds oxygen to treated wastewater?

The substance that is non-toxic to aquatic organisms, serves as a good virucide, and adds oxygen to treated wastewater is ozone. Ozone is a powerful oxidizing agent that can effectively disinfect wastewater by inactivating viruses and other pathogens, making it a reliable choice for virucidal applications.

One of the unique properties of ozone is its ability to decompose into oxygen, thus contributing to an increase in dissolved oxygen levels in the treated water. This is advantageous for aquatic life, as higher levels of dissolved oxygen can improve water quality and support the health of ecosystems.

In contrast, while chlorine is widely used for disinfection, it can be toxic to aquatic life and does not contribute positively to oxygen levels post-treatment. Hydrogen peroxide is an effective disinfectant and can introduce oxygen, but it is not as commonly utilized in large-scale wastewater treatment for this purpose. Ultraviolet light effectively disinfects without adding substances to the water, but it does not enhance oxygen levels in treated wastewater.

Overall, ozone's combination of effective virus inactivation, non-toxicity to aquatic species, and the ability to increase oxygen content makes it the best option in this context.