Which of the following is NOT one of the six barriers in a multiple barrier plan for water treatment?

The correct choice is the option that reflects a method rather than a barrier. In a multiple barrier plan for water treatment, the barriers typically consist of strategies and systems that collectively ensure safe drinking water. These barriers include processes that manage water quality at various stages—such as securing water sources, implementing treatment processes, and monitoring systems that safeguard water distribution.

Desalination is a specific treatment method used to remove salt from seawater or brackish water, rather than a barrier to ensure water quality. While it may play a role in certain water supply systems, it does not fit into the framework of barriers that protect against contamination or other risks associated with drinking water.

In contrast, education, security, and standard treatment processes are integral components of a comprehensive water supply protection strategy. Education raises public awareness and fosters safe water practices, security involves protecting water sources and infrastructure from intentional and unintentional threats, and established water treatment plant processes are designed to eliminate pathogens and contaminants before the water is distributed.