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Aquaculture Chats: Preventing Outbreaks At Aquaculture Facilities

Aquionics Regional Sales Manager Brian Grochowski and Aquaculture Industry Expert Sunny Z. Akhter discuss how effective procedures at aquaculture facilities can help to prevent outbreaks among fish populations and how UV can be used to provide consistent water quality. To see the full discussion click on the video below.

Brian: I was just curious of this from your experience, you know when you look at even these couple outbreaks, it was kind of enlightening to me to some extent to see how many of the facilities, although they had a protocol in place it wasn’t what they considered to be validated, it wasn’t something they had a lot of confidence in, in many cases, it wasn’t something that they monitored regularly in many cases as well. So, when you’ve got those elements in play and then eventually let’s say you do have an outbreak at a facility like that, how easy really is it to trace back what happened or where that outbreak may have come from?

Sunny: …once this happens at least in Norway they have a proper system, that whatever happens you have to record it with the authorities and you go through the whole process, and normally these types of reasons that why it happened are already out, it’s quite public. Once it happens, for example if you have some infection, some viral disease, some bacterial kind of outbreak in the facility, so that’s quite open knowledge. You can’t hide it, by law… so it’s very open at least in Norway, I don’t know about the US, but here its quite open this information, which are the disease-causing agents.

Brian: I thought it was interesting to just again think about those organisms that were detected in these different facilities. Again, when you think about selecting a single disinfectant to try and kill all viruses and all bacteria, certain organisms are going to have higher susceptibility to chlorine for instance than others are going to have. Some are going to be slightly chlorine resistant, so I think it was kind of interesting that when you look at his survey it showed that chlorine was the top disinfectant that was used at these facilities, and I would say probably not surprisingly that’s a good reason why you don’t see a lot of viral outbreaks.

Generally speaking, viruses tend to be easily disinfected with chlorine, where certain bacteria have some level of chlorine resistance. What we’ve seen in other industries and we’re seeing a little bit more in aquaculture, I think it will be an increasing trend, is the tendency to do more of dual disinfection, just as an example with UV, some viruses, while there’s no organisms that are resistant to UV, some organisms do require much higher UV doses, or higher energy to inactivate them than others. When I think of about something like certain viruses like IPNV in salmon, its not resistant to UV but it requires very high UV doses to inactivate it. When you look at these three organisms that they had outbreaks of here, vibrio, Yersinia Ruckeri and Aeromona Salmonicida; all three are highly susceptible to UV disinfection, it doesn’t take a lot of UV energy, or much UV dose to inactivate those bugs. So, we could see in an application like that it would make sense to have some type of online disinfection to try and inactivate those organisms, again as long as you can get them to flow through the UV system.

One of the big challenges with using UV as compared to some of the other chemical oxidizers that were mentioned in his presentation is that there is no residual with UV so if you can’t get the water flowing through the UV system and there’s pockets or areas of low flow where those organisms are going to attach to as biofilm or whatever else, you could potentially have a problem there. But in a system, that’s well designed where you’re able to get flow through the UV system, some sort of combination in the case of something like chlorine as a primary disinfectant and UV as an online disinfection technology would really make a lot of sense for those organisms in particular.

Sunny: Ya that’s quite positive. If you don’t have the residues that’s also quite positive… there probably could be some hazards of using UV as other technologies as well because it might not be safe for the human being exposure, I don’t know how the fish react to it, or where do you put it? What is the process which goes with installation? …. Can you explain a little bit about what could be the downsides of this?

Brian: … for positive or negative, there is no residual post UV. The negative is of course if you don’t have great flow going through the RAS system and you have no residual going through this disinfection system, even if it is your primary disinfectant than there’s going to be pockets or areas that are going to promote microbial growth, especially if there’s biofilms in that operation…the positive of course is that because you don’t have those by-products that you would with chlorine or ozone in particular, than you don’t get that bioaccumulation that you might get from certain by-products in the fish, so that is a positive that you are less likely to get that.

I would say there is a negative, I think how the UV system is sized for the operation is pretty important to get right up front. I mean a UV system it’s not like chlorine, ozone, or other disinfectants where you just crank it up and add a little bit more. You know you add some more energy or add some more light, it doesn’t work like that. Most of the time you’d have to change out the vessel, you can’t just pack in more lamps or add bigger lamps, it doesn’t really work that way.

You always have to think about highest flow coming through the UV system, worst water quality coming through the UV system, and most difficult organisms you want to target; and if you get any of one of those elements wrong; I mean the flow rate is usually an easy one, the organisms for the most part you know what you want based on the fish species your growing, but the water quality is the tough variable. If your solids increase from 10 ppm to 20 ppm, that has an exponential effect on how well the UV system performs because those solids not only block or absorb the light, but organisms will shield themselves behind the solids and make their way through the system. So, you have to think about solids fluctuation, turbidity or UV transmittance changes, as turbidity increases, light can’t penetrate through the water quite as well and you’re going to have a reduced level of performance.

The same thing with color, so for operations that have issues with color coming through the water, that color is going to prevent the UV light from penetrating through. While the turbidity might still look ok, the UV transmittance which is what we really look at from a water quality standpoint we see that as a decline in transmittance, which again has a direct result in UV system performance. Talking about how it interacts with the fish, because it is in a closed system the light is not exposed to the fish so there would be no adverse effects there. There are some systems that are designed in what they call an open channel UV system, where essentially you think of a large trough where you drop in banks of UV systems and there can be light exposure in some cases for individuals walking past those channel systems. But what we’re see more and more and particularly in operation of course are more these closed vessel UV systems, which in very simplistic terms think of it as a light in a pipe…

Sunny: If I have understood you correctly, you are saying that one of the positive aspects that you can actually achieve with UV is that you can decide are you going to harm the good bacteria or bad bacteria, you can have some kind of parameters when you are treating water with the UV, and you can adjust the parameters, is that what you’re saying?

Brian: I won’t say that we can select between the good and bad so to speak. Every organism is going to have a different level of susceptibility to UV. Some are going to require very high doses, again something like IPNV in the salmon industry, which is a big one, that requires a very high UV dose, so a lot of energy to inactivate it. Whereas other things like these other three organisms that we mentioned previously… those don’t require a lot of energy. But its important to get it right up front, because if you were to select a UV system to target those other 3 bugs that don’t require high UV doses and then later find out “oh this other organism is something that we’re really concerned about” and it has a very high UV dose requirement, the UV light is not going to have really any effect on that organism.