Which method is satisfactory for disinfecting water that is not grossly polluted?

Chlorination is recognized as a highly effective method for disinfecting water that is not grossly polluted. This process involves adding chlorine or chlorine compounds to water, which effectively kills bacteria, viruses, and other pathogens that may be present, thereby ensuring the water is safe for human consumption. Chlorination is widely used because it is relatively inexpensive, easy to apply, and leaves a residual effect, which helps protect the water supply from re-contamination as it moves through the distribution system.

On the other hand, fluorination primarily involves adding fluoride to prevent dental caries and is not utilized for disinfection purposes. Oxygenation is a process aimed at increasing the oxygen content in water, typically to improve conditions for aquatic life and doesn't serve as a disinfectant. CO treatment, or carbon monoxide treatment, is not a standard method for disinfecting water and could introduce further contamination risks, making it unsuitable in this context.

Therefore, chlorination stands out as the appropriate choice for ensuring the microbiological safety of water that is not heavily contaminated.