Treatment Of Simulated Dye Wastewater By Fenton-Aerobic Granular Sludge Process

Dye wastewater is featured by its high level of color, high concentration of salts and strong toxicity. The complicated components and non-biodegradability increase the difficulty of treatment. The aerobic granular sludge has advantage on the non-degradable wastewater treatment because of its special structure, kinds of microorganism and perfect biological activity.The first part of the experiment was the cultivation of aerobic granules in the sequencing batch reactor (SBR). Then a process combining physic-chemical method and biological method was applied to treat the wastewater containing Reactive Red X-3B. Fenton reagent was chosen as pre-treatment and SBR system with aerobic granules was used for biodegradation in the following step. In the pre-treatment research, the effect of Fenton reagent dosage on the treatment efficiency was analyzed and the optimum reaction condition is selected. In the biological process, the granular sludge was acclimated with simulated dye wastewater, and the influencing factors, such as auxiliary substrate concentration and salt concentration, were evaluated. Additionally, the characteristic of dye adsorption by the granular sludge was investigated experimentally and the dye removal mechanism was analyzed theoretically.The experiment results indicated: (1) Aerobic granules were cultivated with activated sludge seeds in 45 days. The mature granules had good physical structure and the average removal rate of COD, NH3-N and TN was 97.1%,97.6% and 92.6%, respectively. (2)When the pH at 3.0, the concentration of dye, Fe2+ and H2O2 was 200mg/L, 0.1mmol/L and 2.08mmol/L, respectively, after 60min the dye removal rate was 69.3% and the biodegradability of wastewater was remarkably improved. After the Fenton pretreatment, the wastewater with sodium acetate became the influent of aerobic granular SBR. When the COD concentration was 800 mg/L, operating cycle was 12h, the average removal rate of COD was about 95% and the effluent dye concentration could drop to 10 mg/L. (3) SBR with aerobic granules had stable performance in treating dye wastewater, and the influence of auxiliary substrate concentration and salt concentration were little. (4) When the dye concentration was 50mg/L, the operating cycle was 12h, the dye removal rate by aerobic granular sludge could reach 65%, but the dye removal rate by adsorption was only 13.8%. Therefore, the removal of reactive red X-3B by aerobic granules was mainly due to biodegradation rather than adsorption.