Final answer:
Sustainable wastewater methods include using graywater to water yards and the use of artificial wetlands for treating wastewater. Chlorination and ozonation disinfection, while important for microbial control, are not inherently sustainable due to chemical byproducts.
Step-by-step explanation:
The question regarding sustainable wastewater methods asks which of the listed options are sustainable ways of handling wastewater. Sustainable wastewater methods include practices that lead to the effective treatment and reuse of wastewater without causing harm to the environment or society in the long term.
Option I, using graywater to water yards, is a form of wastewater reuse where water from sinks, showers, and washing machines is recycled for irrigation purposes rather than being discarded. This conserves potable water and reduces the burden on sewage treatment facilities.
Option III, the use of artificial wetlands, is also a sustainable wastewater method. These man-made ecosystems can treat wastewater naturally through the biological activity of plants and microorganisms. This process mimics natural wetlands, which are efficient in removing pollutants from water.
In contrast, option II, chlorination and ozonation disinfection, while effective in killing pathogens, is not inherently sustainable as it involves the use of chemicals which can produce harmful byproducts. These disinfection methods are crucial for microbial control but are not particularly designed with sustainability as the primary focus.
Therefore, the answer to the question is C: I and III only.