Application of anaerobic–aerobic sequential treatment system to real textile wastewater for color and COD removal

A sequential anaerobic packed column reactor and an activated sludge unit was operated continuously for treatment of a textile industry wastewater, in Izmir, Turkey. Metal sponges were used as support material in anaerobic unit and pre-activated textile dyestuff biodegrading PDW facultative anaerobic bacterial culture was immobilized on the support particles. Effects of hydraulic retention times in anaerobic unit (θH anaerobic = 12–72 h) and initial COD concentration (COD0 = 3000 ± 200 mg/L and 800 ± 100 mg/L) at θH anaerobic = 24 h on color and COD removal performance of the system were investigated. The results indicated that over 85% decolorization and about 90% COD removal efficiency can be obtained up to θH anaerobic = 48 h but higher retention times causes decreasing in decolorization efficiency. Operating the system with real wastewater without adding any nutrients at θH anaerobic = 24 h resulted in over 60% improvement in color removal in studied wastewater compared to existing treatment plant.