If your question about plumbing - many people do use return pump with manifold, so they feed reactors and UV and other things, which means just UV is fine, but I would add true gate valve (round one) so you can set exact flow rate and forget it, keep existing ball valve too, so you can turn on/off flow to UV completely without adjusting speed (speed adjustment will be done by true gate valve).
Just to be clear - I personally against such approach since I like my water level consistent and dead silent overflow. If it starts to be noisy it means I have return pump issues, because return pump only delivering water to display. While with manifolds noisy drain, jumpy water level could be due to stuck reactor or other reasons with manifold itself, so much more difficult to validate.
For me its worth adding another pump into sump to feed all other things you need to.
