Removal of anthraquinone reactive dye from wastewater by batch hydrolytic–aerobic recycling process

Abstract

The degradation of anthraquinone dye Reactive Blue 19 (RB19) of 600 mg/L in the synthetic wastewater was studied using a biofilm hydrolytic–aerobic recycling process (recycling process). The COD (chemical oxygen demand) and RB19 removal efficiency could be up to 91% and 90% in 24 h, respectively, with the recycling rate being 10 mL/min. When the recycling rates were 8 mL/min and 10 mL/min, the average COD and RB19 removal rate reached the largest values of 109.9 mg/L h and 23.6 mg/L h, respectively. The results also showed that RB19 removal rate in both the hydrolytic and aerobic reactor declined whereas COD removal rate in the aerobic reactor increased with increasing of recycling rate. With the recycling rate of 10 mL/min, VFA (volatile fatty acid) in the wastewater was of the lowest value and pH value was apparently higher than those with other recycling rates. The ratios of VFA/alkalinity were all less than 0.6 when the recycling rate was more than 5 mL/min, which indicated that the activity of hydrolytic microorganisms had not been inhibited and the recycling process maintained a stable condition. Results in this work shown that hydrolytic–aerobic recycling process successfully dealt with the issues of over-acidification and inhibition in the hydrolysis process and effectively enhanced the removal efficiencies of RB19 and COD.