Looking at your table in the EcoSmarte thread about the chlorine/ copper/ silver kill times, I'm wondering since chlorine only kills certain viruses (VSV, Herpes, Vacciniavirus) at greater than 1500 minutes, wouldn't a pool UV filter kill those in similar if not less time? That is pretty scary just to consider that it takes that long for apparently any method to kill Herpes.
You misread the table. It's "< 1500" which means "less than 1500 minutes" and it is likely significantly less than 1500 minutes since I used conservative assumptions translating the 10 minute kill time by 0.645% sodium hypochlorite (which is at rather high pH) to what would go on in pools (specifically, I didn't attribute ANY oxidation capability to hypochlorite ion and that's unrealistic). Since the adenovirus, poliovirus, coliphage, and influenza were all done at chlorine levels much, much closer to what is in pools, those much smaller numbers (1.8 to < 95) are likely to be closer to the truth for the other viruses.
Also note that the times in the table are for 3-log (99.9% kill) reductions. Roughly speaking, figure that half the viruses are inactivated every 10 minutes or so where some are killed faster and some somewhat slower, but these kill rates are still significantly faster than the hours it takes to turnover the water where a single turnover only has 63% of the water pass through a UV or ozone disinfection system. Even if the UV system killed instantly and completely, it would take 7 turnovers to have 99.9% of the water go through the system and achieve the same 3-log (99.9% kill) reduction. Even with a fast 3 hour turnover (and most residential pools have longer turnovers), we're talking 21 hours and that's assuming the pump is on all the time (usually it isn't). So you can see how ridiculous it is to rely on an in-line system such as UV or ozone to try and kill pathogens in the pool water quickly. Their only real use, mostly for commercial/public pools, is to kill the protozoan oocyst
Cryptosporidium parvum which is highly chlorine resistant and is introduced by bathers with the pathogen and associated diarrhea. They are also useful in controlling chloramines in higher bather load pools especially those not exposed to sunlight. They are also useful at oxidizing chemicals that chlorine doesn't or is slow to do so.
The following table shows how much pool water gets circulated with each turnover assuming perfect mixing:
Turnovers . % Pool Water
..... 1 ............ 63.2%
..... 1.2 ......... 69.9% ... about a 0.5-log reduction
..... 2 ............ 86.5%
..... 2.3 ......... 90.0% ... a 1-log reduction
..... 3 ............ 95.0%
..... 4 ............ 98.2%
..... 4.7 ......... 99.1% ... around a 2-log reduction
..... 5 ............ 99.3%
..... 6 ............ 99.75%
..... 7 ............ 99.91% ... around a 3-log reduction
..... 8 ............ 99.97%
..... 9 ............ 99.988%
..... 9.3 ......... 99.991% ... around a 4-log reduction
.... 10 ........... 99.995%
.... 11 ........... 99.9983%
.... 11.6 ........ 99.9991% ... around a 5-log reduction
.... 12 ........... 99.9993%
.... 13 ........... 99.99977%
.... 14 ........... 99.99991% ... around a 6-log reduction
So keep in mind that chlorine does 6-log reductions for fecal bacteria in under 2 minutes (and
Pseudomonas in around 3 minutes) while it would take a UV or ozone or other in-line systems 14 turnovers of the water to accomplish that same reduction so at a fast 3 hours per turnover that's 42 hours running the pump 24/7! Note that bacteria double in population every 15-60 minutes in their maximum growth phase so just to barely keep the bacteria at bay one must have a 0.5-log reduction (68.4% kill) that is at least that fast and that's roughly 1.2 turnovers. Pools don't have such fast turnovers (spas do, however).
Finally, many pathogens require surfaces to grow or can just get stuck there and such pathogens NEVER get circulated to the in-line disinfection system. This is why a bulk-water residual disinfectant is required.