Conventional ozone treatment involves bulky, complex equipment with high costs and low efficiency
Conventional ozone treatment requires bulky, complex equipment that is both expensive and inefficient because it blows, into large concrete tanks, large volumes of gas with low concentrations of ozone. This ozone gas then reacts slowly with target substances in the wastewater.
While ceramic porous diffusers may be used for ozone bubbling, they produce bubbles of ozone gas that are millimeters or centimeters in diameter. These rise too quickly in the wastewater, resulting in large amounts of unreacted ozone escaping into the atmosphere. As unreacted (waste) ozone gas is hazardous to the environment, waste ozone decomposition equipment is an absolute necessity.
The OHR method: high efficiency, low cost
Breaks down both ozone gas and liquids into microparticles
Micro- and nano-bubbles
The OHR MIXER generates micro- and nano-bubbles that remain in liquids for a considerable length of time. In the case of ozone treatment, these fine bubbles of ozone contact and react highly efficiently with target substances in the wastewater. This is thanks to the much larger combined surface area of the OHR MIXER’s fine bubbles, as compared with conventional coarse bubbles.
A water treatment company independently evaluated the OHR gas–liquid reaction method and found that 70% of the gas injected was dissolved as nanobubbles, with the remaining 30% becoming microbubbles plus a small number of coarse bubbles. The pure-white clouds in the photo on the right are ozone microbubbles generated by the OHR MIXER. These bubbles, being 0.5–30 microns across, remain in the liquid much longer due to their low buoyancy. These invisibly small nanobubbles remain even longer and react even more efficiently with the target substances.
Direct reaction method
As they pass through the OHR MIXER, both ozone and wastewater are broken down into microparticles before centrifugal and centripetal forces cause them to collide and react.
In other words, the ozone gas and target substances make direct contact and react inside the OHR MIXER. Hence the name "direct reaction method".
By contrast, the conventional method is an indirect method. First, coarse ozone bubbles are dissolved into wastewater, then left to make contact and react with the target substances purely by chance.
Simple, compact equipment
The OHR ozone treatment method does not require waste ozone decomposition equipment. In addition, it uses small amounts of highly-concentrated ozone gas, so the ozonizer required is much smaller than the conventional method.
A certain paper mill, "T", has been using our treatment technology for decoloration of 5,000m3/day of colored wastewater for more than 10 years, over which the OHR treatment equipment has performed consistently. This set-up uses 1) no ozone gas bubbling tank, 2) no waste ozone decomposition equipment, and 3) a much smaller ozonizer than the conventional method. Because of this, the initial cost was $2 million, just one third of the $6 million required for the conventional method. The OHR method provides extremely effective ozone treatment at a fraction of the cost.
Further, conventional methods also require regular cleaning and replacement of clogged diffuser pipes and plates. With the OHR method, only the pump needs regular maintenance.
The OHR method can be used without waste ozone decomposition equipment
Waste ozone decomposition equipment is intended to promote the natural decomposition of harmful ozone gas into harmless oxygen by passing it through a tank filled with activated carbon or catalysts. Such equipment must be installed in any facility that uses the conventional ozone treatment method, which produces large volumes of waste ozone. The activated carbon and catalysts in the tank must also be periodically replaced as they are used up or deteriorate in quality.
With the OHR method, it is possible not to use waste ozone decomposition equipment, which greatly reduces costs. Please contact us for more information.
The OHR method can decompose dioxins with ozone alone
It is well-known that, with the conventional method, it is impossible to decompose dioxins solely using ozone. In this case, a process known as AOP is required*. Rigorous tests carried out by Company Y in Japan have demonstrated that the OHR method can decompose dioxins in wastewater with ozone alone. The results of their analysis are displayed to the right. Please contact us for more details.
*AOP (Advanced Oxidation Process) is a treatment method whereby ozone is combined with hydrogen peroxide or irradiated with ultraviolet light to create hydroxyl radicals, the strongest oxidant among all types of active oxygen.
WET: a new international standard for effluent wastewater
Unlike the BOD and COD methods, WET (Whole Effluent Toxicity) testing does not involve chemical analysis but instead directly measures the effect on the environment of aquatic organisms such as killifish, algae and water fleas.
BOD and COD indirectly measure the impurity of wastewater using the oxygen consumption of microorganisms or oxidizing agents. However, they are limited in that they can only measure a portion of the total organic matter. For example, potassium permanganate, an oxidizing agent commonly used for COD testing in Japan, can only detect 40–70% of the total organic matter contained in wastewater. Trace amounts of undecomposed organic matter that are not detected by these tests are discharged into the environment from wastewater emissions sources such as factories and sewage treatment plants. It is evident that this has a significant negative impact on life and the environment.
Accordingly, a new standard has been developed to measure the effect of treated water in these respects. This is not an indirect method like BOD and COD, but a direct measurement by bioassay; that is, by exposing living aquatic organisms to treated wastewater.
WET-based regulations have already been introduced in the US, Canada, UK, France, Denmark, South Korea and other countries, with slight variations in terminology and methodology. Similar regulations are shortly to be introduced in Japan.
The box below shows examples of treated water that may still contravene the WET regulations when it has an adverse effect on aquatic organisms.
- Examples of wastewater that may contravene WET regulations
- Treated water that passes the current effluent standard (BOD, COD, etc.)
- Treated water containing substances that are difficult to identify or currently unregulated
- Treated water containing trace chemicals
- Treated water that has an adverse effect on life caused by the aggregate toxicity of multiple chemicals
Ozone treatment is an accepted, effective and WET-compliant method that decomposes up to 90% of substances that remain undecomposed after conventional treatment.