Ozone for primary sterilization

[pyrrhus]

Hello everyone,

I am in the process of designing a central filtration system for a new shop in my area. In the process of looking into sterilization I was fairly disturbed by the size of a UV unit necessary to effectively sterilize a system of the size I am planning (approx. 3500gallons livestock/5k with sumps, etc).

I will be running approximately 5k-6k GPH total flow through the system and my research indicated that a UV sterilizer of approximately 1200 watts would be needed for effective zero bypass UV sterilization. I am not a big fan of running 1200w of lamps 24/7 and the associated costs of replacement, cooling, etc.

Obviously my main concerns are control of bacteria, protozoans, and other pathogenic microorganisms for a retail fish system. I am planning to use a modified RK75PE (or similar body) for my skimmer/reaction chamber and will design the sumps to allow for 100% water processing through this skimmer with no bypass.

Is anyone out there using Ozone for their primary sterilization?
Approximately what size unit should I be looking for to treat around 5k gallons?
Do I need to reach a particular ORP within the reaction chamber for effective sterilization?
Am I crazy for considering this and should just go back to the UV Battery?

 

[ctenophore]

I'm in the process of designing and building an ozone reactor for a 4000g system. I think a specialized ozone reactor is far more efficient than running ozone through a skimmer. My design is 14" diameter PVC pipe, 60" tall, using an atomizing spray nozzle to inject system water. The plan is to use this with 1g/hr ozone, but I have found little info for determining ozone dosage & kill strength for a given flowrate and dwell time. I am basing my design on calculations from Escobal's book. I will report back with this unit's performance, but feel free to email me for more details. If anyone knows of an ozone concentration calculation I'd love to hear it.

Justin

 

[Clownfish75]

Hi pyrrhus

I have seen a few very large marine aquaculture farms and some do use Ozone, but mostly to steralise incomeing sea water.

I suspect it would work well in y our shop but you will need some excelent control gear to ensure no ozone gets away into the system proper, you can get ORP monitors.

I didnt check but i assum eyour in america, here in australia if you had such a toxic gas you would have ot have very good safety factors to do with your staff and customers getting high on the stuff. I expect it is just as bad there, so i would check out your liability in reguard to this as this could significantly add to the cost.

Having said that i think it will work well, but a UV on a bypass could be smart as an addition.

Christian

 

[spawner]

When your talking about sterilization with Ozone you must run ORPs of around 600mv in your reactor, followed by a large degree of degassing to remove the residual. If your running ORPs that high then you need to ensure you have a very large dedicated reaction column, I would suggest that being made of a fiberglass, epoxy resin would be best. ORPs of that level will react with PVC and most plastics. I have the experience of seeing Ozone eat through fiberglass, but the reactor was fairly old. You'll have to have a very large unit, plus good injectors, pure oxygen and multiple meters. This is standard practice at many public aquariums. Back up meters, controllers and gas monitors are required. It is a dangerous gas after all.

I'd suggest looking at running O3 just before a large UV unit. You don't need as large of a dose, UV will destruct your O3 and it's a very powerful way to sterilize water. Contact Emperor aquatics they can give you some good advice.

Your using artificial seawater?

 

[jhemdal1]

Its been my experience that in order to sterilize saltwater in regards to proto- and metazoans, you end up having to dose at a level where ozone-oxidants are formed, and these will persist and be pumped out into the aquarium (unless you use a bromine-free salt mix) . Here is a link to an abstract for a paper I wrote about this, and how to counter the oxidants using sodium thiosulfate:

http://afsjournals.org/doi/abs/10.1577/ ... 2.3.CO%3B2


Jay

 

[Anonymous]

Another use for sodium thiosulfate? Man, I love that stuff. This is getting better than pantyhose.

 

[Anonymous]

Its been my experience that in order to sterilize saltwater in regards to proto- and metazoans, you end up having to dose at a level where ozone-oxidants are formed, and these will persist and be pumped out into the aquarium (unless you use a bromine-free salt mix) . Here is a link to an abstract for a paper I wrote about this, and how to counter the oxidants using sodium thiosulfate:

http://afsjournals.org/doi/abs/10.1577/ ... 2.3.CO%3B2


Jay

This ^^^. Jay, what's the test for detection? Total Residual Oxidants?

If the RK2 75PE isn't already purchased, I would seriously reconsider one or two of ETSSs largest skimmers, I forget the model #. What modifications were you planning on doing to it?

 

[Anonymous]

You'll have to have a very large unit, plus good injectors, pure oxygen and multiple meters. This is standard practice at many public aquariums. Back up meters, controllers and gas monitors are required. It is a dangerous gas after all.

Yes, plus a maintained SCBA and, unless the life support is in a sealed room, an evacuation plan for your customers should an alarm go off...

All in all I think UV would be more foolproof in a public space like that.

 

[jhemdal1]

Matt,

IIRC, it is best to use DPD total chlorine tests. I never got the Hach ozone test to work properly for me, and I feel that ORP measurements are too difficult to quantify. Besides, although the DPD tests for all TRO's, there should only be ozone oxidants present, so it is pretty accurate. Pink color=things get sick. Red color=they die.

Jay

 

[ctenophore]

When your talking about sterilization with Ozone you must run ORPs of around 600mv in your reactor, followed by a large degree of degassing to remove the residual. If your running ORPs that high then you need to ensure you have a very large dedicated reaction column, I would suggest that being made of a fiberglass, epoxy resin would be best. ORPs of that level will react with PVC and most plastics. I have the experience of seeing Ozone eat through fiberglass, but the reactor was fairly old. You'll have to have a very large unit, plus good injectors, pure oxygen and multiple meters. This is standard practice at many public aquariums. Back up meters, controllers and gas monitors are required. It is a dangerous gas after all.

I'd suggest looking at running O3 just before a large UV unit. You don't need as large of a dose, UV will destruct your O3 and it's a very powerful way to sterilize water. Contact Emperor aquatics they can give you some good advice.

Your using artificial seawater?

I was under the impression that RK2 switched to HDPE over fiberglass since the plastic was ozone resistant for longer. My experience with PVC and acrylic has been pretty good. It won't last forever, but then again it doesn't cost much to build either.

You shouldn't need pure oxygen if using a UV-based O3 generator. Would 1g/hr pose a serious health hazard if it leaked? I'd think you'd smell it pretty fast and could just turn the thing off. I don't think you'd need any more than that given the system size and an efficient reactor.

I'd like to see an equation that provides ozone input given flowrate, dwell time, and ORP. Obviously the injectors and reaction surface area (i.e., misting nozzles vs. bubbles in a skimmer) are factors too, but they are pretty hard to quantify.

Interesting tidbit on using UV to destruct O3. It forms it in air, but destroys it in water. huh.

 

[spawner]

You don't want to UV based ozone unit. They are not very efficient and not that reliable, unless they have really upgraded them in the very recent past. Industry standard is corona discharge with pure O2 or air dryers for large units. Smaller units can get by with being in a dry A/C room.

By the time you smell ozone it is above safe limits. If your in your own hatchery or its in your house it's up to you. If your in a commerical setting and you have a leak, someone complains or gets injured your in a very large pill of stink. It's a very dangerous gas. Most facilities us a UV destruction to remove O3 in the vent air; that is normally sucked out of the system's vent (using a air blower in reverse), sent through a UV unit, and vented to the outside air. UV O3 generators and UV lights for O3 destruction work very differently.

If you think about it, O3 is a highly reactive molecule. UV light is produces a very reactive energy state. When you combine them you increase your kill rate.

Using O3 in a protein skimmer is counter intuitive if your using a large dose. Your breaking down your organic molecules in to small chunks, the more 03, the smaller your molecules become. So if you over does O3 into a skimmer its harder for the skimmer to pull out the small organics. If you add a small dose you can shorten large organic molecules you might make skimming more effective.

I think the fiber reactor column I saw start leaking was 10 years old, maybe older.

 

[ctenophore]

You don't want to UV based ozone unit. They are not very efficient and not that reliable, unless they have really upgraded them in the very recent past. Industry standard is corona discharge with pure O2 or air dryers for large units. Smaller units can get by with being in a dry A/C room.

Can you elaborate on this? I've had pretty good luck with the hobby sized UV generators (up to 350 mg/hr). I was looking at Clearwater units on recommendation from somebody else. They are a lot cheaper to run vs. del ozone or ozotech + oxygen concentrator. The UV units need bulb changes just like water sterilizers, but they are as reliable as a ballast and housing, which IME are pretty good. Corona units need air prep and cleaning and just seem overly complex for anything 1g/hr and less. For much larger amounts, yes, I think corona is better. Again, this gets back to how much O3 is needed for a given flowrate and ORP target. I think this number is a lot less when using an atomizer-injected reactor vs. a skimmer.

 

[skearse]

EPA and the AWWA publish "CT" [concentration x time] dosages for oxidation processes, including ozone. These are primarily for drinking water and wastewater treatment, so they may only be of limited use, but several of them are included in this presentation:
http://www.icwt.net/conference/WaterSup ... erbeck.pdf

Slide 19 shows a number of them for things like E. coli, Streptococcus, etc. Slide 32 has some more detailed info on other microbial strains. And, an O3 folloewd by UV system is shown on slide 40.

On page 21 of the following publications catalog is a collection of papers focusing on O3 in aquatic systems (for $65):
http://www.io3a.org/OzonePublicationCat.pdf. No idea what's in it, but may be of worth to some.

HTH!

 

[Shawn Wilson]

Ozone is a great oxidizer for overall water quality, but UV irradiation is a more efficient disinfectant and easier to dose in a commercial system where a 100% kill ratio is desired. Ozone is better suited for a public aquarium facility where livestock have already been quarantined. The degradation of plastics, air drier maintenance, ORP monitoring/controlling and loss of bubble stability in protein skimmers make ozone a less attractive methodology of disinfection.

Many commercial ozonizers operate on timers or controllers, so you won't have the 24/7 protection offered by UV irradiation. The cost of UV sterilizers won't be that much more, and modern T5 bulbs last longer than traditional ones, so operational costs are reasonable especially when you consider the cost of not having them (higher mortality rates).

You might want to consider running a smaller ozone unit in conjunction with UV sterilizers and run them only at night when fish have a slower respiration and customers aren't in the store. Commercial systems are pretty rich in organics, so ozone isn't as easy to overdose as it is in a pristine display tank at a public aquarium. Commercial locations also have good air exchangers to vent Co2 from customers/visitors and to minimize humidity.

Another consideration is to break up the large system into a series of smaller ones to isolate pathogens. This will also help segregate fish from different shipments and places of origin. Scaleless fish like wrasse and gobies etc. can be housed in a copper free system and problematic fish like angels and tangs can get the extra meds they need. There's nothing worse than having to tell customers that nothing is for sale because you put all of your eggs in one basket. Smaller systems also make it easier to acclimate new orders by matching temperatures with ice or hot water, salinity adjustments, and PH lowering with acid.

If the budget is tight, you can concentrate UV irradiation to certain systems or certain rows of tanks within a system. This way the disease prone fish get the extra protection they need and you save a few bucks. More units can always be plumbed in later.