The Research On Sorbic Acid Wastewater Treatment By Combined Catalytic Ozonation And Biological Oxidation Process

Sorbic acid and its potassium is a kind of preservative which is efficient, safe, low toxicity and internationally recognized. But in its production process, a lot of wastewater was discharged. The COD concentration of this wastewater was very high, and there were some contaminants that inhibit microbial activity in this wastewater. Therefore, this wastewater have to be pretreated, so that which could be treated by biological process. An integrated process for the sorbic acid wastewater from a chemical plant in Nantong was developed in this research. First, the catalytic-ozonation was used for pretreatingthe sorbic acidwastewater to improve its biodegradability. Then, the conventional biological oxidation process was used to degrade COD. Finally, a coagulation process was applied for post-treatment of secondary effluent. In addition, the possibility of the sorbic acid wastewater treated by repeating catalyticozonationand biological processwas explored.The experimental results showed that the catalytic efficiency of nano-TiO2is the best in the catalysts of manganese sulfate, cobalt chloride, hydrogen peroxide,and nano-TiO2. As the nano-TiO2was applied to catalyze ozonation of the sorbic acid wastewater, the appropriate catalyst dose, pH value, ozone flowrate, and reaction time were2g/L,10.0,2L/min and25min, respectively. Under optimized conditions, the COD lvele was decreased from4579mg/L to3602mg/L, and the ratio of BOD5to COD was increased from0.19to0.45after the sorbic acid wastewater was treated by cataltic ozonation. The sorbic acid wastewater pretrated by cataltic ozonation was aeration in the sequencing batch reactior (SBR) for24h, its COD removal efficience was over85%. The effleuent of SBR was post-treated by coagulation and sedimentation, the supernatant COD level would be less than the local discharge limit as the poly ferric sulfate (PFS) dose was more than200mg/L. If the sorbic acid wastewater was treated by repeating catalytic ozonation and biological process, the final effluent COD also could fit with the discharged limit, but process units were more than normal.