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/O3 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 (5-9), O3 dosages (1.5-4.5 g/h), and AcAc concentrations (0.01-0.03 M) were measured. For both processes, a reaction time of 120 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 (BOD5/COD = 0.12). In UV/O3 process, the optimal conditions were obtained at pH 8 and ozone injection at 4 g/h. The combined C&M-UV/O3 process removed 78.75% COD, 46.66% BOD5, 90.88% total phenol, 91.78% TSS, 99.14% oil and grease, and 98.38% turbidity, with promotion of BOD5/ COD from 0.12 to 0.33. In UV/AcAc process, the optimal conditions were achieved at pH 5 and AcAc concentration of 0.03 M. The combined C&M-UV/AcAc process removed 58.75% COD, 67.58% BOD5, 38.03% total phenol, 83.50% TSS, 93.65% oil and grease, and 95.00% turbidity, with promotion of BOD5/ COD from 0.12 to 0.22.
Conclusion: The results showed that the UV/O3 process is completely superior to the UV/AcAc process for removal of OMW contaminants, as well as promoting the biodegradability of OMW.