i got to say that i have done some research and there is no concrete information out there. There are bits and pieces of information so i piece them together to give this answer, if the answer turns out to be wrong or inaccurate, please do come and correct me by posting the changes as a comment to this post. Thanks.
As the name implies, UV-transparent means that it allows UV light rays to pass through it. This is a scientific research that is still going on. UV ray is the third one from the left in the electromagnetic wave spectrum if gamma ray is the most left. Even though is quite near to gamma ray and X-ray, UV ray is actually does not have alot of penetration power, this means that UV rays that hit thick glass might not even pass through it (most deflected). Thus, there is the need to invent something that is UV-transparent.
the Internet does not say much about UV-transparent water tanks, but if there really is, than the possibility of UV-transparent water tanks is use for the sterilization of water is quite high.
we all know that UV-rays can be use to eliminate harmful germs and pathogens in water, thus, this UV-transparent water tanks could be fixed on roof tops to auto kill the germs, so it can act as a extra treatment to water so as to make sure that the water you are drinking it really devoid of any harmful microorganisms.
UV-transparency can be also use in industries, for example, alkanes in fossil fuels, usually petroleum has the structural formula of C(n) H (2n+2), where "n" is the number of carbon atoms, as such, every 1 carbon atom, it joint with 4 hydrogen atoms. Alkanes can undergo substitution reaction, which means that one of the hydrogen atom in the alkanes molecule is replaced by another element, for example, chlorine. This type of substitution reaction requires the presence of UV-light, thus, UV-transparent material could be use as containers for these types of chemicals when we want them to react.
I believe that the real technology break through should be how to invent a material that is NOT transparent to visible light but allows UV-rays to pass through.