The concentrated organic pollutants discharged from fine chemical industries are usually nonbiodegradable or even toxic to microorganisms disturbing the biological treatment systems. The wastewater including naphthalene sulfonic acid(NSA), phenol, benzene, and pyridine are quite resistant to biological treatment. In this respect, it was attempted to improve the biodegradability of the pollutants by ozone oxidation. In order to determine the optimal conditions for ozonation, various operation factors such as initial pollutant concentrations, pH, and ozone dose were evaluated.
Generally, ozone utilization rate was improved with the increase of initial concentration of pollutants and also, removed COD was increased in proportion to the absorbed ozone dose. In case of NSA, 19-84% COD and 6-50% TOC changed to biodegradable(BOD5/COD=0.27-0.48). The ratio varied depending upon initial concentration of NSA(500-5,000ppm). But ozonation of phenol had an adverse effect on the biodegradability, judging from the decrease of BOD5/COD from 0.78 to 0.51. Also, efficiency of pyridine and phenol improved with the pH increase. Biodegradability of the mixture of phenol and NSA with equal amount of 1,500 ppm increased remarkably to BOD5/COD=0.52 by ozonation for 150min.
The treatment efficiency of an industrial wastewater containing NSA in the activated sludge system was investigated after acclimating microorganisms for 45 days. COD removal efficiency of ozonated wastewater gradually increased up to 81% in 20 days however, that of unozonated wastewater was only 32%.
