There are a few points that you want to make as you answer this question. First, to directly answer their question, let your interviewer know that you are comfortable with this aspect of the job. To do this, talk about any positions you've held in the past where you worked closely with hazardous materials. Discuss your role and any formal training you had. The other piece you want to reiterate is the importance of wearing PPE in handling chemicals and how you would always prioritize this on the job as a water treatment operator.

"Yes, I would be very comfortable with this aspect of being a water treatment operator. In my current job, our manufacturing process includes the use of zinc and cadmium and I've had extensive training in the handling of those. The use of personal protective equipment is vital in my job, and I wear protective eyewear and gloves at all times they are required and never let this slip. The safety of my colleagues and myself is always at the front of my mind and will continue to be if I join your team."