Which of the following is a method for disinfecting water in distribution systems?

Chlorination and UV disinfection are widely recognized as effective methods for disinfecting water in distribution systems. Chlorination involves adding chlorine or chlorine compounds to water, which effectively kills or inactivates pathogens, ensuring that the water remains safe for consumption as it travels through the distribution system. This method is preferred because it not only disinfects the water but also provides residual protection against possible recontamination in the distribution pipes.

UV disinfection employs ultraviolet light to disrupt the DNA of microorganisms, rendering them unable to reproduce and thus eliminating their ability to cause illness. This method is advantageous because it does not introduce any chemicals into the water, thus avoiding the formation of potentially harmful byproducts associated with chemical disinfectants.

While the other methods listed, such as filtration and sedimentation, are important for removing physical particles and improving water quality, they do not specifically target pathogens in the same way as chlorination and UV disinfection, which are directly aimed at ensuring microbiological safety. Boiling and freezing can effectively kill pathogens but are not practical methods for large-scale water distribution systems. Distillation and reverse osmosis primarily focus on removing contaminants and impurities rather than disinfection.