Ozone color removal from industrial wastewater and textiles is an effective approach as compared to other chemical solutions. In textile wastewater processing plants and in other industrial wastewater processes, ozone has been successfully used to remove color.
A biological treatment system such as activated sludge is often used in conjunction with ozone in wastewater treatment. The molecular size of organic dye molecules makes them refractory, and adsorption on activated sludge can only remove a small amount of them. The use of ozone has sometimes occurred prior to the biological process, but is rarely done before it. Activated sludge pretreatment is an option if the wastewater isn’t easily biodegradable or toxic.
Industrial wastewater treatment
Since it tends to break down organic molecules into smaller and more biodegradable species, it can be used prior to a biological process. The process can then be made more efficient. Furthermore, ozone treatment of wastewater elevates the oxygen content of the water (unconverted oxygen and ozone decomposing into oxygen, which is mixed with the water), which encourages aerobic processes to flourish.
The benefit of this is well known as it is well documented in the research, however, it has a difficult time being applied practically since it is difficult to predict how much the improvement will be, and it can be difficult to conduct pilot studies with ozone and biological processes. A biological system has been observed to improve textile wastewater treatment by 20-30%.
In terms of the effects of treated water on the receiving stream, ozone’s ability to improve biodegradability and reduce toxicity is worth considering. A water treatment process must be considered when testing for toxicity in treated water.
It has been observed that destroying one organic molecule in a treatment process can result in creating more toxic ones, for example, the chemical treatments of MTBE can create a more toxic wastewater. Surfactants and the need for their removal from water are other factors to consider. Concentrations of surfactant can be tightly regulated in some areas and must be less than 1 ppm. As a result, oxidant is required in greater amounts.
However, all dyes used in textile processing can be removed effectively with ozone. Color removal objectives for receiving water bodies determine the amount of ozone required for the ozone system. Oxygen consumption depends on several factors, including the amount of color removed during the biological process, the dye used, where the ozone is applied, etc. When exact previous experience is not available, pilot testing is often used in cases where it is difficult to predict the amount of ozone required.
Approximately 1 mg of ozone per mg of dye is necessary to remove 95% of the color, although the value depends on the dye type. About 1.5 mg of ozone per mg of dye is required to remove 100% of the color. It takes about 10 minutes for the dye to be removed. It is typical that the textile industry uses 15 milligrams per liter post biological treatment, but the level could easily exceed 25 milligrams per liter. It is important to note that the ozonation dose doesn’t have to mineralize the components of the dye compound to be effective.
How ozone generator works?
Corona (silent) discharge is a common method used by industrial ozone generators for converting oxygen to ozone. There are several methods to obtain oxygen: dry air, oxygen distilled from air, or oxygen dissolved in LOX.
An ozone generator is a better option for a given volume of production, less energy is consumed, and if venturi injectors are employed, ozone is mixed with less energy. These savings are offset by the cost of LOX, such as the equipment used to store and evaporate the LOX, or the compressed air necessary for the concentration process. Oxygen tends to be more favored as units grow in size. A high energy cost also favors oxygen, but LOX is disfavored.
Ozone solutions for textile wastewater applications typically include the following items: air compressors, air dryers, ozone generators, ozone water mixing systems, and ozone destroyers. The ozone generator is the most economically viable in general when compared to the other chemical solutions.
In order to operate an ozone generator effectively, dry air must be used. Today, most ozone systems employ pressure swing adsorption (PSA) using high pressure air driers. In this way, a refrigeration unit and heated desiccant dryer are not required, but the compressor must be able to provide around 100 PSI of pressure.
When ozone is mixed with water, it makes up a tiny fraction (2-3% when the gas is air, and 6-10% when it is oxygen). The gas can be mixed with the water using a venturi or fine bubble diffusers to dissolve the ozone. Once this is accomplished, the overflow gas must be dispersed. Injection systems using venturi type vacuum pumps require booster pumps. On the bottom of a contact vessel, fine bubble diffusers are normally deployed. As the booster pump would be eliminated, diffusers could replace the venturi and this would be cheaper.
A certain period of time must pass after the dissolved ozone is in contact with the water so that the reaction can complete. About 10-20 minutes are likely to be sufficient. An indirect contact vessel would be necessary in order to achieve the desired retention time. An indirect contact vessel can also be used to disengage gases and liquids. To cost this system, we opted to use an indirect contact vessel. In the tank, the liquid will disengage from the gas mixture and the gas will enter the tank.
All things considered, the ozone generator systems are effective in both air and water treatments in industries and can effectively remove color from textile and other industrial wastewaters. If you have any questions, you can reach us out. We would love to answer your queries.