A compact process for the treatment of olive mill wastewater by combining UF and UV/H2O2 techniques

Olive oil production results in important quantities of wastewater containing large amounts of total solids and organic carbon as well as low oil concentrations. This paper describes the treatment of olive mill wastewater (OMW) by combining an ultrafiltration (UF) technique and an advanced oxidation process (AOP) using UV/H2O2. It further demonstrates the technical feasibility of this compact and stable process to remove a large part of total solids and organic carbon. Indeed, UF reduces the pollutants contained in the OMW with an apparent rejection coefficient RCOD in the range of 94%. The UV/H2O2 oxidation process may be easily used, in combination with UF, to finish the treatment of the permeate. The results obtained in batch and continuous mode showed that this technique offered a treated solution which complies with legal requirements. A final concentration of 17 mgTOC dm!3 was obtained, which corresponds to a final COD of 52 mg dm!3, while the legal requirement is 125. Furthermore, the final effluent is fully decolorized.

On the basis of the above results, the following conclusions can be drawn: C Ultrafiltration, as a physical technique, can considerably reduce the pollutants contained in the OMW with RCOD in the range of 94%. However, because of the remaining substances present in the permeate, tertiary treatment is necessary. C The UV/H2O2 oxidation process may be easily used, in combination with UF, to finish treatment of the permeate. The results obtained in batch and continuous mode showed that this technique makes it possible to obtain a treated solution which complies with legal require- ments, as summarized in the Table 2. Moreover, the final effluent is completely decolorized. C The combined processes can treat OMW within short time (about 1.5 h for the whole process), with excellent efficiency in terms of COD, COT, TSS and decolorization. Despite the dilution that must be made before the AOP process, the proposed combination of UF and UV/H2O2 would be more efficient and profitable than other processes such as biotreatments that need more than 10 days [3] or hydrogen peroxide alone that yielded only 50% decolorization [23].