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

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%.