Treatment of Photographic Wastewater with Combined Process of Electrochemical and Biological Methods

摘要

Photographic wastewater bears high levels of pollutants being composed of various organic and inorganic chemicals which are difficult to be reduced to the levels permitted for discharge with a single biological or chemical method. The authors have proposed a three-stage treatment system of the 1st biological, chemical and 2nd biological process. The purpose of the chemical stage is to reform the refractory chemicals into biodegradable ones. In this study electrochemical oxidation with a ferrite anode is applied to the chemical stage to improve their biodegradabilities. Electrolysis of the photographic wastewater, which had been biologically treated at the 1st stage, en- hanced BOD of the wastewater. Mechanism has been discussed on the upgrade in biodegradabilities of chemicals, used in photographic processing, by electrochemical oxidation. The 1st biological-electrochemi- cal-2nd biological process removed 95 in COD, the contributions to COD removal were 42, 11 and 42 by 1st biol., electro. and 2nd biol. stages, respectively 48 of TN was removed and 94 among the remain- ing N-compounds was NO_3~-. The principal process for COD removal from photographic wastewater have been established, but the additional N removal process is necessary to discharge the processed wastewater into the N regulated water bodies.