Effluent polishing by means of advanced oxidation

Three different Advanced Oxidation Processes (ozonation at pH 7.5, electron beam irradiation and a combination ozonation/electron beam irradiation) have been applied to study decomposition of aqueous naphthalene-1,5-disulfonic acid (1,5-NDSA) with regard to mineralization and formation of biodegradable intermediates. Formation of biodegradable intermediates could not be indicated for any of the processes used, single electron beam irradiation treatment was the most efficient process for mineralization of organic carbon contained in aqueous 1,5-NDSA. Applied to a real wastewater effluent from a mixed municipal/industrial wastewater electron beam irradiation with a radiation dose of 2 kGy was sufficient to reduce the concentrations of all naphthalene sulfonic acids and some of the alkylphenol ethoxylates by about 2 orders of magnitude. Moreover, high energy electrons effectively inactivate indicator bacteria in effluents from municipal wastewater treatment plants and eliminate simultaneously any estrogenic activity originating from natural and synthetic hormones also contained in the wastewater effluents. Inactivation of bacteria and bacterial spores by electron beam irradiation was found to be practically unaffected by the water matrix and suspended solids. There is a strong indication from literature data that these findings are also relevant to viruses of concern in water hygiene like poliovirus. Cost analysis of the irradiation process based on actual numbers from the first full scale wastewater treatment plant in the Republic of Korea indicated a total cost of about 0.2 US$/m3 treated water for 2 kGy irradiation dose. (author)