In this posting we would like to discuss the use of ozone in recycling industrial process water. Recycling water is becoming more important as the availability of high quality water is decreasing, the cost of purchased water increases, costs associated with discharging water increases and compliance and liability issues continue to be more serious. Water reclaim is becoming especially important in industries where water use is high. A key example is the semiconductor industry.
Ozone can offer the following benefits to industrial user: First, in some industrial processes the build-up of organics in the water allows for the build-up of micro organisms. Since ozone is an excellent biocide, it can prevent this build-up and allow for the recycling of water that otherwise might have to be discarded. Second, ozone, either alone or in combination with UV or peroxide, can reduce organic chemical loading (BOD/COD/TOC) in water which may prevent its reuse as these levels rise with use.
Ozone is most likely to be a good solution when the organic loading are relatively low, most likely less than 100 ppm as measure as TOC. Higher TOC levels may be economically treated if the total flow is low.
In determining the usefulness of an ozone based solution, it is important to characterize the nature of the organic and the treatment objective. The treatment objective is directly related to the nature of the water reuse. For example, water in the semiconductor industry can be recycled back to the ultra pure water treatment area or sent to a less demanding application such as cooling water make-up. If the water is sent to ultra pure water make up system, the treatment objective is going to be similar to the requirements for drinking water.
In terms of the nature of the organic to be treated, certain molecules are not readily oxidized by ozone such as small chain aldehydes, ketones and carboxylic acids. These compounds will need to be treated with an advanced oxidation process (AOP) that employs ozone in combination with UV, peroxide or some combination of both compounds. Ozone alone is unlikely to breakdown most organics to CO2, so called mineralization. If this is part of the treatment objective, an AOP would be required.
Certain geographic areas are becoming increasingly concerned about water use and the governments are limiting water supplies to industries located in their area of authority. In some cases there are mandated recycling requirements. It is expected that these requirements will continue to increase with time.
Spartan Environmental Technologies can supply ozone based solutions for water recycling applications. We invite you to contact us with your water treatment challenges.