This is a knowledge-based question that interviewers might ask you. Like any knowledge-based question, do not make up a random answer - try to provide any relevant information and suggest that you will explore the topic further.

For xample: "Through my education and experience, I am most familiar with the use of chloramine and chlorine to disinfect water. That said, science and technology make swift advancements, so I would love to research this a bit further for any new developments in this area."