Which statement about water treatment in aquatic systems is true?

Which statement about water treatment in aquatic systems is true?

• A. Activated carbon is a chemical filter
• B. Sodium thiosulfate dechlorinates water
• C. Ultraviolet light in the 200-280 nanometer range is germicidal
• D. All of the above

Answer: (D)

Water treatment in aquatic systems relies on a mix of methods to remove chemicals, neutralize residual chlorine, and inactivate microbes. Activated carbon removes dissolved chemicals, odors, and organics mainly through adsorption onto its porous surface, acting as a chemical filter in practice. Sodium thiosulfate dechlorinates water by chemically neutralizing residual chlorine (and chloramines), making the water safer to introduce into the system. Ultraviolet light in the 200–280 nm range is germicidal because UV-C wavelengths damage microbial DNA, preventing replication and inactivating pathogens. Because these approaches address different needs—chemical removal, dechlorination, and disinfection—the statement that all of the above is true reflects common water treatment in aquatic systems.

Water treatment in aquatic systems relies on a mix of methods to remove chemicals, neutralize residual chlorine, and inactivate microbes. Activated carbon removes dissolved chemicals, odors, and organics mainly through adsorption onto its porous surface, acting as a chemical filter in practice. Sodium thiosulfate dechlorinates water by chemically neutralizing residual chlorine (and chloramines), making the water safer to introduce into the system. Ultraviolet light in the 200–280 nm range is germicidal because UV-C wavelengths damage microbial DNA, preventing replication and inactivating pathogens. Because these approaches address different needs—chemical removal, dechlorination, and disinfection—the statement that all of the above is true reflects common water treatment in aquatic systems.