Which of the following is considered a physical means of disinfection?

Ultrasonic waves are considered a physical means of disinfection because they utilize high-frequency sound waves to disrupt and break down microorganisms in water. This method operates on the principle of cavitation, where the pressure changes create microscopic bubbles that collapse and produce shock waves, leading to the destruction of pathogens without the use of chemicals.

In contrast, chlorination, while effective for disinfection, relies on chemical reactions to kill or inactivate pathogens in the water. Similarly, coagulation is a chemical process that helps remove suspended particles from water by causing them to clump together, while filtration is primarily focused on the physical removal of sediments and particulates rather than direct disinfection of microbial life. Understanding these distinctions is essential in the field of water treatment and distribution, as they inform the choice of methods used to ensure safe drinking water.