Ozone vs UV Sterilizer

[KEITHHAYS_2000]

I have two 135 Gallon tanks that I am plumbing together(one reef, one fowlr). They drop into a 75 gallon sump. A secondary sump is set off to the side for an Aquac ev400 skimmer (ozone ready) that is about 40 gallons which drops back to the main sump. So accounting for actual water volume in the sumps there is about 340 Gallons with about 1200 GPH (600gph/each tank) running through the main sump.

On the UV side, I would be looking at a size that could produce a 280,000 µWs/cm² zap. In order to get the twice-a-day zap at that rate the system would need to move only 170 Gallons over 12 hours period or in my case of running it for 2-10hour periods would be 17GPH. This would seem to be easily achieved by a 25 Watt (8 UV-c watts) SMART UV Sterilizer emitting 180,000 µWs/cm² at 79gph which would double to 360,000 µWs/cm² at about 39gph and double again at 17gph.

First: For anyone who knows, does that above calculation work or have I skipped something?
Second: What would the equivalent system look like on the Ozone side. The skimmer vendor recommends dosing no more than 50-100 mg/hr on the ev-400.
Third: what are the pro/cons of each type of system.

Note: I am not concerned with whatever beneficial life that might happen to flow through either the UV or Ozone. I am looking for near sterilization not clarification of water passing through the system.

Thanks ahead of time to anyone responding.

[Fishbulb2]

Hi,

I would think that if you want to go for sterilization and not clarity, I would continue to research UV over ozone. It takes A LOT of ozone to sterilize water and UV is probably better suited for the job. If your ORP gets too high dosing lots of ozone, then the system will shut off and you technically won't be sterilizing while this happens. If you can afford both however, they will work synergistically. The clearer water produced by the ozone will make the UV sterilizer much more efficient.

I looked into the Emperor Aquatics charts for your roughly 340g system and they seem to recommend the 65W model with a maximum flow of 285 gph through the sterilizer. They give sizing for both algae/bacteria and protozoa and if you really want sterilization, I would go with their more conservative protozoa rating.

It seems to me that the discrepancy between your calculations (which argue for the 25W unit) and their recommendations (of the 65W unit) is the tank turnover rate. You said you want a twice-a-day turnover but they are recommending 285gph for a 480g tank (for protozoa) so one full turn over about every two hours. That seems to be a big big difference. Out of curiosity, where did you get the twice-a-day value from? It seems very low to me. The goal is to both kill whatever passes through the unit and to pass the tanks volume through the unit often enough so that organisms aren't reproducing in the tank faster than we are killing them. I doubt a turnover of twice a day would do that.

I would opt for the more conservative value that Emperor Aquatics is recommending if you really want it to sterilize properly.

Just my thoughts,
FB

[KEITHHAYS_2000]

I like the idea of using them together. I agree; the 65W model would be better, but to get 280,000 uv dose or Cryptocaryon Irritans levels, I would have to cut the flow to about 180gph. Largely, the discrepancy in the calculation is due the conversion to 280k from 180k on the flow rate and only looking at the life cycle of Cryptocaryon Irritans which would likely allow almost everything else to grow faster than I would be able to kill them. That slow a flow rate (17gph) would likely heat up the water also. Unfortunately, in order to fully do what I would like, I would have to have something in the neighborhood of 340 watts to hit 280,000 uv@1200 gallons an hour.
The twice-a-day thing is less about UV in particular and more about how long it takes to reach 99.99% “purity” in a given volume of water. If the water coming out of a filter has filtered out 100% of what it is supposed to filter out, that water would be “pure”. The pure water would then be dumped backing into unfiltered water. At some point, mathematically, the water will reach 99.99% pure. My goal for this particular equation was to have that happen twice per day. The actually link to where I found this equation and the author is: http://www.livingreefs.com/introduction-uv-sterilizers-t431.html. I am now researching the life cycle of the remaining marine microorganisms' life cycles that I will be destroying.

[Fishbulb2]

I briefly checked the link you posted and saw they referenced Pedro Escobal's book. I really like that book as a reference and think it's a great place to start. I didn't check the exact numbers on your equation though because the last time I did math on these forums, I got myself into a lot of trouble!

If you are trying to kill ich, I think you will most likely want to go with at LEAST Emporer Aquatic's recommendation of the 65W unit. I believe ich is rather difficult to kill (compared to their lower ratings for algae and bacteria).

I'm still not sure I entirely follow the twice a day argument. When sizing a filter of any sort, one needs to consider not only the volumes, purification rate of the filter, but also the rate at which whatever you want to filter out is accumulating or multiplying in the tank. So if you have a microorganisms that can double every hour (like some bacteria), the turnover rate will need to be much higher than a different organism that has a life cycle of 24 hours (even if the lethal dose of UV is the same for each). The faster reproducing organisms whould just need a more powerful unit to reach the same dose. The twice a day shouldn't apply to all cases. Are you saying you only calculated it for ich or are you saying it's a general turnover for all cases?

FB

[Randy Holmes-Farley]

If you want ozone for sterilization, you'll need much more ozone and for a longer contact time than folks normally use ozone on reef tanks. Using it in a skimmer, for example, won't sterilize it. You'll need a specialized reactor followed by GAC treatment.

I discuss ozone and sterilization here, especially the first one and equipment for it in the second:

Ozone and the Reef Aquarium, Part 1: Chemistry and Biochemistry
http://reefkeeping.com/issues/2006-03/rhf/index.php

Ozone and the Reef Aquarium, Part 2: Equipment and Safety
http://reefkeeping.com/issues/2006-04/rhf/index.php

Ozone and the Reef Aquarium, Part 3: Changes in a Reef Aquarium upon Initiating Ozone
http://reefkeeping.com/issues/2006-05/rhf/index.php

[KEITHHAYS_2000]

My primary goal with multiple aquariums connected would be to kill as many bad guys as possible after filtration and before moving the water back to the tanks. This is more of a prevention issue since I am having no specific issues.

Ozone appears to be, in reef aquariums doses anyway, better suited to water clarity which I will likely do. UV looks like the right way to go, but would cost at least $4000 dollars to achieve and larger electric bill. While the $4000 is achievable, I am not sure the cost is worth the benefit vs separate sumps. What I have figured out is that it isn't so much that UV isn't useful in the reef as many people think, but the cost to achieve a meaningful change to the more relevant microorganisms in a reef tank is cost prohibitive at least with the devices I have come across so far.

[Randy Holmes-Farley]

One reason they are not always effective is that many organsims will not pass through it during their life cycle, regardless of the intensity. Completely sterilizing all of the water passing through it may not rid a tank of ich, for example.