The wastewaters from dyeing, printing, photocopy, dry cleaners, and hairdressing salons contain various chemo- and bio-reluctant pollutants such as the dyes, aniline, and phenolic compounds which to date, are still difficult to degrade by the biochemical and their related Advanced Oxidation Processes (AOPs) at a large scale. Conversely, it would be ideal if a single treatment eliminated all dyes and other organic pollutants, regardless of their structures. In this patent, 6 UV light-emitting diodes (LEDs), 6 UV lamps, and a small amount of H2O2 are employed to increase color removal from the identified wastewater within short reaction times at once. Also, this novel AOP would effectively degrade the organic pollutants, and the effluent would be ready for re-use or discharged into any sanitary sewer, septic systems, storm sewer, municipal or boiler waters. On illumination at the appropriate UV frequencies, the hydroxyl radicals would be generated within the reactor for the photolysis oxidation of organic compounds. The ultraviolet radiation, represented as hv, causes the dissociation of the H2O2 into two OH•. Usually, when the water or wastewater containing H2O2 is irradiated with UV light, OH• are formed. However, it is believed that the photolytic decomposition of H2O2 occurs in parallel with the formation of extra H2O2. Likewise, many experimental results for the UV photolysis of H2O2 in the literature suggested for the photolysis of H2O2 in an aqueous solution.
Design challenges of UV light-based treatment processes include the following: Ultra-low UV transmittance (UVT) results in low penetration depth at 254 nm, Various organic pollutants are strong UV light absorbers, Matching different UV treatment sources with absorption spectrums of different wastewaters is problematic, Designing of separate reservoirs for the colored wastewaters to be treated by multiple UV sources and the delivery of the treated waters to other reservoirs for recycling or other functions.
In the presence of UV lamps and UV LEDs, more of OH• would be formed to become stronger oxidants that can readily oxidize and mineralize all the organic compounds faster. These OH• have been proven to be selective in oxidizing the organic pollutants by separating protons to yield organic radical compounds, which led to either an abstraction of hydrogen atoms or addition to double bonds (read my 3 publications in the Resources below). Indeed, this patent is a state-of-the-art approach by using multiple UV lamps mixed with UV LEDs in the treatment of wastewater containing myriad dyes. Importantly, this kind of multiple UV light doses of different foundations can cause mineralization of unwanted pollutants in the wastewater faster.Dr. Ing. Nditange Shigwedha, BSc, MSc, PhD, Post-PhD, Pamba