Comparing the performance of UV/Acetylacetone and UV/O۳ processes for treatment of olive mill wastewater

Background: Olive mill wastewater (OMW) is characterized by its high organic content and refractory compounds. The aim of this study was to evaluate and compare the efficiency of UV/O۳ and UV/ acetylacetone (UV/AcAc) processes for treatment of pretreated OMW by coagulation/microfiltration (C&M) process. Methods: In this study, a laboratory-scale UV plug flow reactor with ancillary equipment was fabricated. The experimental factors including initial pH (۵-۹), O۳ dosages (۱.۵-۴.۵ g/h), and AcAc concentrations (۰.۰۱-۰.۰۳ M) were measured. For both processes, a reaction time of ۱۲۰ min was considered. The effect of these variables on removal of wastewater contaminants including BOD, COD, TSS, turbidity, phenol, oil, and grease were investigated. Results: Results showed that raw OMW has a high load of pollutants and very low biodegradability (BOD۵/COD = ۰.۱۲). In UV/O۳ process, the optimal conditions were obtained at pH ۸ and ozone injection at ۴ g/h. The combined C&M-UV/O۳ process removed ۷۸.۷۵% COD, ۴۶.۶۶% BOD۵, ۹۰.۸۸% total phenol, ۹۱.۷۸% TSS, ۹۹.۱۴% oil and grease, and ۹۸.۳۸% turbidity, with promotion of BOD۵/ COD from ۰.۱۲ to ۰.۳۳. In UV/AcAc process, the optimal conditions were achieved at pH ۵ and AcAc concentration of ۰.۰۳ M. The combined C&M-UV/AcAc process removed ۵۸.۷۵% COD, ۶۷.۵۸% BOD۵, ۳۸.۰۳% total phenol, ۸۳.۵۰% TSS, ۹۳.۶۵% oil and grease, and ۹۵.۰۰% turbidity, with promotion of BOD۵/ COD from ۰.۱۲ to ۰.۲۲. Conclusion: The results showed that the UV/O۳ process is completely superior to the UV/AcAc process for removal of OMW contaminants, as well as promoting the biodegradability of OMW.

Keywords:

Olive mill wastewater (OMW) , Treatment , UV/O۳ , UV/AcAc , Biodegradability