I use prefilters before the membranes and a UV light after.
I make water where ever I am without problems. In the
winter in fresh water at my home
dock, in the ocean and bays or rivers. I have tested the water many times. It passes better than any city water. No heavy metals, no fluoride, etc.
I haven't drank city water or marina water in 14 years. My RO water also does my
cooking and
laundry. Clothes come cleaner in RO water than city water.
And we have been drinking, bathing and
cooking with water that once went thru dinosaurs.