Kazuhiko NAKAMURA

Anaerobic/Aerobic Treatment of Actual Dye Wastewater by Combination System of UASB and DHS Reactors

Akiyoshi OHASHICHideki HARADA

Recently, colored waters come under intense scrutiny due to rising concern over environmental issue, especially from textile factories. The amount of dye wastewater from those is huge, being 1 million m3Eday-1 in Japan. The present technologies in their treatment are costly and consume tremendous energy. On the other hand, there are a lot of reports about biological degradation of azo dye under reduced condition by anaerobic bacteria. Therefore, this research focuses on UASB reactor for decolorisation. And further more, we employed Down-flow hanging sponge (DHS) reactor as post-treatment to remove residual organics and to expect degradation of dye. In this study, a combination system of UASB and DHS reactors was investigated for biological degradation of actual dye wastewater. Both reactors were operated at a HRT of 8 hr.
In the result, the influent COD and BOD concentrations of the actual dye wastewater were reduced to 100 mgCOD/L and 5-20 mgBOD/L, respectively, under UASB circulation, which is a system to remove hydrogen sulfide from UASB effluent and send back it to UASB again, and UASB-DHS circulation system. Both systems operated effectively. Even wastewater containing high concentration of Sulfate comes into UASB, UASB circulation system made hydro-sulfuric inhibition reduce and UASB stably treated. About color removal, dye wastewater was treated cleanly by these systems. The transparency index of 2.5 cm at the influent improves to 30 cm.