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Water Treatment Systems, Chlorine, Ozone and Others
Tony Charles (firstname.lastname@example.org): Hi all, I run a hatchery in Australia, and I’m considering an upgrade to my disinfection system. As a result of the recent whitespot outbreak in Southern Queensland, Australia, I want to upgrade my current UV water disinfection system.
I’m considering ozone because it’s been used by shrimp farms for such a long time. Nonetheless, I was wondering if any of you had any experience using Cold Plasma Technologies (Scholarly Articles for Cold Plasma Technologies) or Singlet Oxygen Technologies (Scholarly Articles for Singlet Oxygen Technologies), like those offered by Silver Bullet Water Treatment. I have read that the Cold Plasma Technologies are becoming the standard for ballast water treatment.
Gianluigi Negroni (email@example.com): Tony, I’m working with a new, patented technology. The first machine will be produced this month. Contact me for details.
Tony Charles (firstname.lastname@example.org): Thanks, Gianluigi, but I’m only interested in technologies that have successfully treated the incoming water at a shrimp hatchery.
Daniel Gruenberg (email@example.com): Hi Tony, I recommend the Silver Bullet water treatment system. Silver Bullet has done validations at Don Lightner’s lab at the University of Arizona, at two commercial hatcheries in Panama and two hatcheries in Thailand. Using its equipment, we see consistent reductions in all pathogens, notably a persistent reduction in Vibrios in reservoir water. Its use has resulted in a marked decrease in mortalities as well as 10-20% increase in nauplii-to-postlarvae survival rates. The technology uses singlet oxygen which is much more effective on pathogens than ozone, and it’s also very gentle on your larvae and broodstock.
If you want more information, contact me, and I’ll put you in touch with Silver Bullet.
P.V.N. Rao (firstname.lastname@example.org): For the last two years, we have been using ozone to treat the water at our Penaeus vannamei hatchery. The quality of our water is very good after ozone treatment, better than it was when we were using chlorine to treat the water.
We use activated carbon filters at our terminal-water points to make sure all traces of ozone have been removed from the water.
We also use an ORP (Oxidation-Reduction Potential) meter to check our water.
Oxidation-reduction potential, or ORP, is a measurement that indicates the degree to which a substance is capable of oxidizing or reducing another substance. Because it involves the exchange of free electrons between two substances, it’s measured in positive and negative millivolts (mv) using an ORP meter.
A positive ORP reading indicates that a substance is an oxidizing agent. The higher the reading, the more oxidizing it is.
A negative ORP reading indicates that a substance is a reducing agent. The lower the reading, the more anti-oxidizing it is.
Most types of water, including tap water and bottled water, are oxidizing agents because their ORP values are positive.
ORP values can tell you if you need to change your water, if your aerators are doing their job and if your new probiotic is working properly. You can also check your influent and effluent with an ORP meter.
Shrimp like positive ORP values between 200-250 mv, which indicate low ammonia, healthy and hungry shrimp, adequate aeration, no feed or sludge problems and good water circulation. If you get ORP readings less than minus 100 mv, it means that something in your pond is not working properly and marks the point where mortalities begin. The sludge in shrimp ponds and tanks has an ORP value of around minus 350 mv. ORP meters don’t free you from checking all your water quality variables—like oxygen, salinity, pH and temperature—but they do help you interpret what’s going on with your water.
ORP checking should be like pH checking: twice a day in all your reservoirs, inlets, nurseries, growout ponds and outlets. Do your first check early in the morning to see what happened during the night. If something is out of whack, take corrective action. Do your second check in the evening, to see if your corrective action worked.
P.V.N. Rao (email@example.com): To disinfection our water, we’re increasing our OPR levels up to 600 mv. To disinfect your facilities and other infrastructure, the OPR levels should be above 800 mv. Before using any of that water for microalgae and larval rearing, the OPR levels should be below 300 mv.
Larry Drazba (firstname.lastname@example.org): For years, we used ORP meters to check our semi-intensive shrimp farm. We found that the best ORP levels for shrimp were 200-250 mv. It was our experience that an ORP change of 50 mv made a significant difference in controlling the ecology of large ponds. Inducing an ORP change by adding chlorine or some other strong oxidant to the water column will shift the microbiology of the water and help avoid pathogen issues. The amount of chlorine or other oxidants necessary to induce that change was not significant. We never tried to understand it, but it worked. We did this proactively when we saw the algae start to turn too green or when blue-green algae increased. We were working with estuarine water with variable salinities.
“Although measurement of the reduction potential in aqueous solutions is relatively straightforward, many factors limit its interpretation, such as effects of...temperature and pH, irreversible reactions, slow electrode kinetics, non-equilibrium, presence of multiple redox couples, electrode poisoning, small exchange currents and inert redox couples. Consequently, practical measurements seldom correlate with calculated values.”
Roger Kelso (email@example.com): By coupling ORP and pH readings, our predictions of future water quality conditions improved. We were able to stop developing problems, not just react to them after they happened. Having said that, while ORP holds some promise, it’s not a silver bullet and needs more work.
Larry Drazba (firstname.lastname@example.org): Back to ozone: We have been using ozone in our hatchery and nursery ponds for 20 years. It’s an excellent tool, and as far as I’m concerned, it replaces all other water prep and sterilizations tools.
I am not familiar with singlet oxygen technology, but here are a few suggestions for using ozone:
• First, filter your incoming water.
• Don’t use a one-pass system. It’s better to recirculate your water through your
• Use an activated carbon filter between the reservoir and culture tanks
• Ozonated water without activated carbon treatment can be used with PL-1s
• Reservoirs that have been ozonated to OPR 650 mv need to be used within
Jorge Cordova (email@example.com): After you disinfect a reservoir, how long does it take for the Vibrios to re-establish themselves? Does the new population of Vibrios spike and then crash? Please share any information you might have on this topic.
Larry Drazba (firstname.lastname@example.org): Jorge, if your reservoir were completely enclosed, it would last 7-8 hours without colonies forming. I’m talking about general contamination and not specifically pathogens.
When I first talked with Silver Bullet, I told them they were dreaming if they thought they could treat an entire reservoir. Then, as fate would have it, they came to Thailand, and I ended up installing one of their systems on a farm that had ten ponds. All the ponds were stocked at the same time, but only the treatment pond survived to harvest. All other ponds died from EMS within 45 days after stocking.
I was amazed at how Silver Bullet could control Vibrios in an open pond with very little gas.
Singlet oxygen has a very high affinity for Vibrio cell walls, so it reacts with Vibrios first before all other species, hence the name “Silver Bullet”.
Singlet oxygen reacts electrochemically with water so it isn’t simply a gas dissolution process like ozone. There is no toxic off-gassing.
Thirdly the singlet oxygen creates OH radicals and hydrogen peroxide (H2O2) at low concentrations. This is a very synergistic combination because Silver Bullet kills and oxidizes just like ozone, but then it also removes biofilms from pipe surfaces and reduces Vibrios in larval rearing tanks.
Nauplii-to-postlarvae survival always increased more than 10-20%, and deformities (a big problem in some areas when using chlorine) went to nearly zero.
The low residual H2O2 seems to be nontoxic for both broodstock and PLs, but sufficient to prevent Vibrio from blooming.
I am currently compiling data into a series of white papers: one specifically for hatcheries, one for ponds and one on whitespot control with Silver Bullet.
I own a hatchery, and I have never seen a better form of water treatment. I can give my full endorsement to the Silver Bullet system. It’s the best possible water treatment for any shrimp hatchery.
First, run your water through a pressured sand filter, then chlorination it at 10-20 ppm while simultaneously running it through a powerful oversized foam fractionator. This will remove suspended micro-particulate solids, including protozoa, bacteria and viruses that passed through the preliminary sand filter. It takes between 8-24 hours, depending on the amount of water, or until the foam fractionator stops foaming.
The main problem in shrimp hatchery production is not in the method of seawater disinfection. It’s the contamination after the disinfection process.
Dallas Weaver (email@example.com): Nelson, the main problems with your approach are high costs and chlorination byproduct formation. A lot of chlorination byproducts are toxic and soluble. That’s why water providers go to great lengths to minimize or eliminate chlorination byproducts.
I have seen hatcheries that use fine micron filtration and ozone get erratic production.
Also, every hatchery, before using the cleaned-up water from its storage tanks and reservoirs, passes its water through activated carbon filters then through 2-5 micron canister filters.
Dallas Weaver (firstname.lastname@example.org): Nelson, chlorine treated water creates toxic compounds that can create lots of problems, unless you use a ton of carbon to adsorb them. Check Google Scholar.com on “chlorination byproducts”, especially those formed from chlorinating humic and fulvic acids found in waters that have passed through sand filters. The water treatment literature on this subject is massive.
Your bureaucratic-type solution of a single system and design for all situations is a less-than-perfect and overly expensive idea that could lead to system failures in some cases. I know of saltwater-well cases where your solution would kill every larva that went into the water and ocean water cases where just a slow sand filter with mechanical filters and UV made excellent input water.
Tony Charles (email@example.com): Hi Daniel, you mention that the low residual H202 seems to be nontoxic for both broodstock and PLs, but sufficient to prevent Vibrio from blooming. What about eggs, nauplii and the larval stages? Are they sensitive to the residual H202?
Giovanni Chasin (firstname.lastname@example.org): HI all, as an alternative to the process recommended by Nelson, you can disinfect and reduce organics from previously and properly mechanical filtrated seawater as follows:
1. Chlorinate at 10-20 ppm in a reservoir, mix well for a few minutes with
2. Pass the water through charcoal filters in a loop with the reservoir for 24 hours.
3. Check for chlorine residual and apply sodium thiosulphate if required.
4. Your water is now ready to use.
This simple method lowers Vibrio concentrations in larval rearing tanks and algae cultures.
If your incoming water is high in particulate matter, before you treat it with ozone or chlorine, always run it through a sediment or mechanical filter first.
I successfully used the above protocols at some huge hatcheries.
Nelson Gerundo (email@example.com): Giovanni, regarding organic matter (micro-particulate suspended matter) including dissolved organic nutrients not seen at the naked-eye level, I totally agree with you. The best way to extract them from your water is to spike it with chlorine and then suck it through a powerful multi-Venturi foam fractionator. The result? Crystal clear, clean, disinfected seawater.
After simultaneous disinfection (chlorine) and organic matter extraction via foam fractionation (with or without ozonation) just run your water through activated carbon and you have the perfect medium for larviculture and diatom culture.
Otherwise, just use Giovanni’s practical disinfection technique: 10-ppm chlorine through activated carbon. No thiosulphate.
Nelson Gerundo (firstname.lastname@example.org): Yes, Gary, I designed it myself and built it with my bare hands with just one assistant to help me hold things in place. I did all the cutting of the pipes, sealing the joints, installing the pumps, and all the drilling and bending. The materials were sourced locally, and some parts even came from surplus materials and junk. You could fabricate your own foam fractionator. Anyone could! It’s not expensive!
Whitespot is very quickly deactivated by Silver Bullet gas because it is a protein encapsulated DNA virus that is highly susceptible to singlet oxygen oxidation!
Daniel Gruenberg (email@example.com): I want to point out that using ozone in a foam fractionator is a very effective way to clean seawater, but you must watch your ORP levels in the fractionator. Don’t let them exceed 450 mv, or you risk the formation of toxic bromates.
Carbon filtration after ozonation is mandatory.
Robert Bauman (firstname.lastname@example.org): My guess, if you had low survivals and deformities from using chlorine, you overdosed with thiosulfate or metabisulfite. This would cause stressed larvae, which would be followed by over feeding and Vibrio counts going up. I’ve managed 16 different hatcheries, worked with three species of shrimp and used chlorine almost exclusively. At the hatchery level, I expect 75% survivals.
Daniel Gruenberg (email@example.com): So far we have tested Silver Bullet in four hatcheries, two in Panama and two in Thailand and the massive reduction in Vibrios in the larva tanks was consistent across all applications. Survivals also increased.
In many parts of the world, EHP is becoming endemic. If you throw 2,000-ppm chlorine at EHP spores, they will not die. Silver Bullet is the only practical solution I know of that is capable of controlling EHP spores without harming the shrimp.
Daniel Gruenberg (firstname.lastname@example.org): Nelson, I do not work for Silver Bullet. I was hired to do some testing for them, so I have first-hand knowledge of their equipment, and I wanted to share my results with The List—and only because the question came up.
Michael Mogollon (email@example.com): Daniel, other postings recommend a target of ORP 650 mv for hatchery reservoirs, yet you recommend not going over 450 mv in the skimmer to avoid toxic bromates. What should the target ORP reading be in hatchery reservoirs when using ozone? 450 or 650?
Larry Drazba (firstname.lastname@example.org): There is no problem with bromates at 650 ORP mv and you can forget about the need for a foam fractionating if you recirculate the water and get the whole reservoir to 650 ORP mv before you use it. You can also forget about chlorine by-products and effective chlorine concentrations due to the presence of organics in the incoming water.
I did not say that bromates could or would not be created. I said that they did not present a problem in the system that I described.
Dan Fegan (email@example.com): Larry, that’s my experience. Regardless of the chemistry involved, shrimp hatcheries using chlorination have been pretty successful for the past 30 years. Of course, I have seen the occasional tank go down at the zoea stage with cloudy water and a pretty high monoculture of some nasty Vibrio, but I have had many more tanks go through without any issues. By far the biggest variables affecting success have nothing to do with water treatment and more to do with people!
Daniel Gruenberg (firstname.lastname@example.org): EHP spores are known to be resistant to even extremely high levels of chlorination. Just because chlorine has been the mainstay for hatchery water treatment for 30 years, doesn’t mean that it’s the best possible option.
EHP wasn’t an issue before. Now it is. Isn’t it time to adapt?
In southern Thailand, shrimp are dying in such large numbers that emergency harvesters are working 24/7 and still can’t harvest all the shrimp, resulting in a huge drop in shrimp prices due to oversupply from emergency harvest.
Is everything just fine in the shrimp industry? From what I see at farms in Thailand and from what my staff sees in Vietnam, Malaysia, China and India, I would say our problems are only worsening and in my view will continue to get worse in the foreseeable future.
Anyway, each situation is different. I would say greater than 90% of the hatcheries are using chlorine without problems. All the power to them, but for those that are facing new difficulties and challenges, there are new and improved water treatment technologies that can help them.
I understand that some of you will interpret this as scare mongering for commercial reasons. I am just trying to stick to the science and keep the list abreast of advancements. Each situation is unique, but I feel I am doing a service to the industry by keeping people informed.
Sources: 1. The Shrimp List (a mailing list for shrimp farmers). Subject: Is Ozone Still the Best Water Treatment and Seawater Disinfection in Indoor Aquaculture Production System. 2. The Shrimp List (a mailing list for shrimp farmers). Subject: Article on ORD. February 24 to 25, 2017. 3. Wikipedia. Reduction Potential. April 8, 2017. 4. Aqua Health Products’ Webpage. Understanding pH and ORP. Website Visit on April 8, 2017. 5. Bob Rosenberry, Shrimp News International, April 12, 2017.
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