Efficiency evaluation of PTA wastewater treatment with the ultrasound/H2O2 process

Abstract

In this study, we used the ultrasound/hydrogen peroxide (H2O2) process to treat the pure terephaltic acid (PTA) industrial wastewater. The BOD5 and TOC of raw PTA wastewater were 13,200 and 6,390 mg/L, respectively. Several semi-and non-volatile organics, such as benzoic acid, 4-methyl benzaldehyde, phenyl acetic acid, and 4-ethyl benzoic acid were detected in PTA wastewater by GCD (HP GCD 1800A). In the present paper, we discussed the effect of ultrasound/H2O2 process with various concentrations of H2O2 and pH values on mineralization and biodegradability of PTA wastewater. Mineralization of PTA wastewater was evaluated by the ratio of TOC removal and biodegradability by real residual BOD5 over theoretical residual BOD5. The results show that the lower the initial pH value and the higher the concentration of H2O2, the higher ratio of mineralization was found. During the reaction time, the ORP value at pH 3 was greater than at pH 7 and 11. The pH value affected ORP value more significantly than H2O2 dosage in this work. The biodegradability increased with the amount of TOC removal by ultrasound/H2O2 process but decreased with the amount of TOC removal by ultrasound only. The optimum condition to pretreat PTA wastewater with ultrasound/H2O2 process before biological treatment was pH 3 and H2O2 200 mg/L. However, when ultrasound/H2O2 process was used as a sole treatment without biological treatment, the optimum pH value was also controlled at 3, but the concentration of H2O2 must increase upto 500 mg/L. Under such conditions, the ratio of mineralization was 70%.