"lenses that modulates the sun’s rays to UVC frequency to directly hit every water molecule passing by in order to get the water purified"

The designer has no idea how UVC works, and demonstrates complete ignorance of optics. Lenses can't "modulate" frequencies in sunlight; they can only focus light, and perhaps separate the light in a prism-like fashion. The designer also has demonstrated ignorance about how much exposure to UVC water needs before it is sterilized, and how much UVC is in sunlight.

If the sunlight had enough UVC to sterilize the water and break up harmful molecules, the user would get toasted. Instant deadly sunburn. Heck, if the sun light coming through our atmosphere had that much UVC, the water would be sterilized sitting in the pond or stream; no lenses necessary.