All ozone reactors work roughly the same way. A gas stream containing ozone is brought into the ozone reactor. This gas stream is intensively mixed water to give it a chance to react with the pollution. A good ozone reactor will therefore intensively mix the ozone with water to reach a long contact time. A couple thing increase the effectiveness of an ozone reactor:<\/p>\n
- \n
- Small ozone bubbles (+\/- 2mm, too small isn\u2019t good either!)<\/li>\n
- Mixing under high pressure <\/li>\n
- Optimal water-ozone ratio<\/li>\n<\/ul>\n
<\/p>\n
How big should the ozone bubbles be?
\n<\/strong><\/p>\nA popular statement is that the ozone bubbles should be as small as possible, mostly between 0,1mm up to 3mm. But ozone gas (every gas actually) has a hard time exchanging from the bubble into the water. The rate of speed at which the bubbles move through the water plays a big role here. Bubbles of 0,1mm barely move through the water column and therefore hardly exchange gas. <\/p>\n
The optimal bubble size in normal reactors (skimmers, high pressure reactors) is around 2~2,5mm. This also depends on the flow through the reactor. If the bubbles are any smaller, they won\u2019t rise up through the water and will be taken along with the water into the outlet of the reactor. And on bigger bubbles, the contact time will be too small. <\/p>\n
If we take a look at venturis and static mixers, the bubbles can be smaller for optimal functioning because they will exit in the water anyways. Industrial systems can work with extremely small bubbles because the process parameters are way different (pressure and concentration). By changing the work pressure for example, it\u2019s possible to achieve a good exchange with very small bubbles.
\nIt\u2019s a little too complicated to fully explain, but in a nutshell; the ozone bubbles never consist of ozone for 100%, the other part is air or oxygen. When the bubbles are extremely small, just the ozone on the edge of the bubble will be able to exchange into the water. The ozone in the middle isn\u2019t able to move to the side, so only a small part of the ozone gets dissolved in the water.
\nWhen the bubbles are extremely small, the bubbles aren\u2019t moving in the water which causes the exchange to be relatively low. This can be solved by forcing the gas to dissolve in the water. <\/p>\nAs described above, mixing the ozone in is very important, but removing it is too. However, there are two \u2018kinds\u2019of ozone in water: free ozone and dissolved ozone. <\/p>\n
<\/p>\n
Free ozone <\/strong><\/p>\n
Free ozone is the ozone that\u2019s still in the gas bubbles in the water, these are visible. Free ozone should always be removed after the ozone reactor. If it\u2019s not removed, these bubbles will escape out of the water whenever they can, for example in a pool or basin of a zoo. This can be noticed because of the ozone smell around the outlet. This is also called surplus ozone. <\/p>\n
<\/p>\n
Dissolved ozone
\n<\/strong>What\u2019s in the name definitely applies here, ozone can dissolve in water just like oxygen can. In some situations (mostly disinfection) it\u2019s desired to have dissolved ozone in the water. That\u2019s because the disinfection of surfaces and product relies on the fact that the dissolved ozone in the water will react with the pollution present when it comes into contact with it. That\u2019s why we\u2019d like to have as much dissolved ozone possible in the water in this situation.
\nIn animal basins however, we would like to have little o no dissolved ozone because it will react with the things in the water. This can cause skin irritation for the animals in it. In pools, very small amounts, around 0,1 mg per litre are desired.
\nLet\u2019s get back to disinfection with ozone, where lots of dissolved ozone is desirable. This is only possible when the ozone was generated with oxygen as a supply gas and is mixed in under high pressure. The ozone concentration in the gaseous phase also has to be high or otherwise it won\u2019t be possible to get a high ozone concentration in the water.
\nMixing ozone under high pressure isn\u2019t without risk. The ozone treated water will be used as rinse water or something like that. When that happens, the pressure of the water will be atmospheric. Depending on the ozone concentration, the ozone will then degas from the water. This should definitely be taken into account in rooms where people or animals are also present because the ozone concentration can get dangerously high. <\/p>\nSkimmers
\nThere are many kinds of ozone reactors, they each have their own function and corresponding advantages and disadvantages. <\/p>\nProtein skimmers<\/strong>
\nThis type is often used in zoos and ponds. Skimmers originate from the \u2018salt\/seawater world\u2019, which is where they are most effective as well. There\u2019s little reason to use them in fresh water but they can still be spotted very frequently on ponds.
\nThey perform okay as ozone reactors in fresh water, but don\u2019t expect the results as when used in seawater. Skimmers have definitely proven their worth in zoos. However, those are way different than the skimmers usen on ponds. There are two kinds of skimmers, the gravity skimmer and the power skimmer. <\/p>\nGravity skimmer<\/strong><\/em>
\nThis is the well-known version used on ponds. The water is brought into the skimmer on top. Below are air stones that bring the ozone into the water. The bubbles rise through the water column until they leave the skimmer through the foam compartment.
\n![\"afschuimer](\"https:\/\/tolwatertechniek.nl\/wp-content\/uploads\/2018\/10\/as_reactor.jpg\" "\\"afschuimer")
\nAdvantages:<\/em><\/p>\n- \n
- Low counter-pressure for the water pump (can even be fed by an air-lift) <\/li>\n
- Skims protein at the same time<\/li>\n
- Can be used to aerate the pond water at the same time<\/li>\n
- De-gasses surplus ozone <\/li>\n<\/ul>\n
<\/p>\n
Disadvantages:<\/em><\/p>\n
- \n
- Big<\/li>\n
- Expensive<\/li>\n
- Efficiency is relatively low <\/li>\n
- A lot of air is needed for a proper skimming function<\/li>\n
- Has to be partially placed above the water level <\/li>\n<\/ul>\n
<\/p>\n
Power skimmer<\/strong><\/em>
\nThis is the most used version in zoos. The water is pushed through venturis using powerful pumps. The ozone is added in these venturis, after that, the water enters the skimmer where the bubbles rise to the foam compartment. This type of skimmer is much more effective thanks to the use of venturis. However, the energy consumption is also much higher. <\/p>\nAdvantages:<\/em><\/p>\n
- \n
- Efficient<\/li>\n
- De-gasses surplus ozone <\/li>\n<\/ul>\n
<\/p>\n
Disadvantages:<\/em><\/p>\n
- \n
- Big<\/li>\n
- Expensive<\/li>\n
- High energy consumption <\/li>\n
- Has to be partially placed above the water level <\/li>\n<\/ul>\n
<\/p>\n
High pressure ozone reactors<\/strong>
\nThe high pressure reactor is an ozone reactor where air stones are used to bring the ozone into the water. The ozone bubbles will rise up through the water column and get mixed in again when they reach the top. This is why a high pressure reactor has a high efficiency and still a low counter-pressure(1,5~2m).
\nThis is the only ozone reactor that can de-gas and still be placed under the water level. It has the advantages of a power skimmer and a venturi, but not the disadvantages. This type is mostly used in ponds, pools and zoos and in the industry in smaller numbers.![\"hogedruk](\"https:\/\/tolwatertechniek.nl\/wp-content\/uploads\/2018\/10\/hd_reactor.jpg\" "\\"hogedruk")
However, the ozone reactors that are used here do work on roughly the same principle. <\/p>\nAdvantages:<\/em><\/p>\n
- \n
- High efficiency <\/li>\n
- Can be placed under the water level<\/li>\n
- Needs little air to function well <\/li>\n
- De-gasses surplus ozone<\/li>\n
- Can also skim in some situations <\/li>\n<\/ul>\n
<\/p>\n
Disadvantages:<\/em><\/p>\n
- \n
- Relatively big <\/li>\n<\/ul>\n
<\/p>\n
Static mixers<\/strong>
\nStatic mixers have been used to mix in ozone for a couple years now. This method for mixing gasses and fluids has been around in the industry for much longer though. The mixer on the picture is one of the few static mixers that do work and is therefore the only mixer we apply for industrial purposes.
\nA good static mixer makes the bubbles smaller. However, most mixers out there only spin them around and do nothing to decrease their size. These mixers have a very low efficiency. Please inform yourself on mixers before buying one. Besides that, you do need to think about a way to de-gas the ozone when using a static mixer because it doesn\u2019t do that for you.
\n<\/strong><\/p>\n
- Relatively big <\/li>\n<\/ul>\n
![\"statische](\"https:\/\/tolwatertechniek.nl\/wp-content\/uploads\/\/mixer-300x193.jpg\")
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