I think it's best to put them in the sump with their own pump, unless you split the return with a ball valve and just have a low gph going through the uv. You may want to research the contact time thats required for the watt uv you have. If the water runs through them too fast they become useless.
Yeah i had read that but i didnt think to much about it. What is the recomended turnover through the refugium suppose to be i have read different things would about 4 times the tanks volume be ok and what about the sump side ?