Survey of sono-activated persulfate process for treatment of real dairy wastewater

The dairy industry is considered as one of the most polluting industries due to the presence of a very high percentage of organic matter in the effluent. Advanced oxidation processes, including ultrasonic/persulfate, are efficient processes for wastewater treatment. Therefore, the aim of this study, experimental laboratory research, was to evaluate the efficiency of US/persulfate process for the treatment of real dairy wastewater. In this study, the effects of pH (3, 5, 7, 9 and 11), persulfate concentrations (50, 100, 250, 500 and 750 mg/L), contact time (10, 30, 45, 60 and 90 min) and intensity of US waves (35, 37 and 130 kHz) on the efficiency of process were investigated using chemical oxygen demand (COD) as a dependent variable. According to the results, the efficiency was increased by decreasing the pH value, increasing the concentration of persulfate to an optimal level, and increasing the contact time and ultrasound intensity. The highest efficiency was obtained as 74.5% for real dairy wastewater. The high efficiency in the US/persulfate process was obtained at pH 3, persulfate concentration of 500 mg/L, US intensity of US 130 kHz and contact time of 60 min. The results showed that the sono-activated persulfate process for COD degradation of dairy wastewater follows the pseudo-first-order kinetic. According to the results, it can be concluded that US/persulfate process is an effective method for the removal of organic matter from real dairy wastewater.