LOL.
Frogs-n-logs is just a screen mesh filter used to make sure large, visible object often found in surface water is prevented from entering finer filter and clogging them up quickly. They are easy to clean and cheap top replace if need be.
Some cistern owners use an ozone treament placed in the cistern to very effectively treat the water before entering the home and more rfined treatment equipment.
http://www.tripleo.com/process.htm
Some just use hydrogen peroxide or bleach and occsionally shock the cistern.
ATS is a well-known company. They make versions EV, SL and DWS/SE series. Does it say which version? NSF, Standard-55, Class A systems have fail safe devices that prohibit water passing to the user if the UV system fails or has interferring occurances, water clarity is not within allowances, bulbs are not producing the correct wavelength, etc. These are more expensive but they are more effective at producing safe water. Some places require only Class A systems, especially in public water treatment.
The 5005 filter is actually a very good design. The outer section has a courser mesh than the interior section. This allows it to take out larger particles without clogging the filter and then filters finer particles.
Carbon filters are excellent at removing a wide range of contaminants. Some carbon filters are recommended for VOCs (volatile organic compounds) which may include farming chemicals, etc., that a normal carbon filter cannot remove. Carbon filters like pleated or GAC (granulated activated carbon) are meant for clarity, taste and odor, primarlily.
I would avoid putting carbon filter prior to a disinfection system. They can be an ideal place for bacterial colonization--making incoming water worse, not better.
When you say "within guidelines", that makes me wonder who conducted the tests. Public health will say your water is fine even theough you may have horrible iron stains and really stinky water caused by hydrogen sufide. Their interst is safety, and iron is not considered unsafe, so...it is within
their guidelines. Do you follow me on that? It is always best to have test results in numbers.
I would use an RO for drinking water purposes. As with most water treatment equipment, there are cheap units and excellent ones. This true with ROs as well.
Andy Christensen, CWS-II