can anyone recommend the best cheapest filters and UV sterilizer?

I am setting up a potable rainwater catchment system for a client. i have a plan for transferring water around and i want to achieve 1 micron filtration and flow through a UV sterilizer before it enters the in house holding tank. what I'm looking for in the UV unit is :
# 1: 4gallons per minute or higher,
#2 : pex or poly compatible (dont want to deal with copper)(i think they're mostly npt anyway...)
#3: it actually works
#4 lowest price


any recommendations?
and how about filtration down to 1 micron?
i'm looking for the right balance of cost and longevity

Joe Blankenship says magnetite [but not black sand] does an amazing job.
A cheap option you can use yourself by ordering some magnetite.