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Treatment of a saline petrochemical wastewater containing recalcitrant organics using electro-Fenton process: persulfate and ultrasonic intensification

Integration of persulfate and ultrasonic (US) irradiation with electro-Fenton (EF) process was studied for treatment of a saline petrochemical wastewater, and the effect of operational parameters was investigated. First, effects of pH, applied voltages, electrode distance (ED), US irradiation and reaction time on COD removal were evaluated for combination of US and EF (US/EF). Afterwards, the enhancement of COD removal efficiency was studied through persulfate addition (PUEF). A COD removal of 94.1% was observed for US/EF process with initial COD concentration of 850 mg/L and the reaction time of 210 min. Persulfate addition decreased the reaction time significantly and yielded a COD removal of 91.7% in 120 min. Efficiency of PUEF process over US/EF was also confirmed with higher pseudo-first order reaction rate constant of 0.0169 1/min, compared with 0.0126 for US/EF. GC-MS analysis revealed the significant destruction of recalcitrant and aromatic compounds of raw wastewater to the simpler and aliphatic forms. This finding was confirmed with biodegradability enhancement of effluent with BOD 5 /COD ratio of 0.41. Current work indicated that PUEF is a reliable and efficient technology for treatment of saline industrial wastewaters containing recalcitrant aromatic organics.