Treatment of Olive Oil Industry Wastewater

Since thousands of years, olive has been a worthwhile plant for human. Olive fruit and olive oil, which is produced from this fruit, are an important component of Mediterranean cuisine, because of its energy, its satisfying special taste and vitamins that are included. Although, olive oil production which is used little amount of energy and no any other raw material apart from olive oil, seems to be environmentally safe, using organic matter, suspended solids, oil and grease contents of vegetation water are too high. Therefore, it is thought that the olive mill effluent causes an important environmental problem. The aim of this study was to investigate the characterization and treatability of the olive mill wastewater from six olive oil processing industries. For the treatability examinations, several unit operations and processes performed using different samples. The efficiencies obtained from the same unit operation were quite different for different samples. These differences mainly due to the wide variability of olive oil mill wastewater characteristics. In the first part of experimental studies, different physical methods such as filtration, shaking, aeration, sedimentation, and distillation were applied to the wastewater. In filtration experiments, maximum COD removal efficiency (41 %) was achieved after filtration through filter paper Maximum COD removal efficiency in shaking experiment was 49% and it was obtained at the end of the eleventh day. In aeration experiment, COD removal efficiency achieved 43 % after 7 hours aeration. COD removal efficiency of 26 % was achieved after sedimentation experiment. Therefore plane sedimentation is not promising method as pretreatment step of olive mill wastewater. Distillation process after coagulation as a pretreatment step was the most effective method for the treatment of olive oil industry wastewater. 99% COD removal efficiency was achieved on the distillate. In the second part, chemical treatment studies were done. Coagulation-flocculation-precipitation and chemical oxidation methods were applied. After chemical coagulation and flocculation experiment with FeCl3.6H2O, 32% COD removal efficiency was achieved. Efficiency of chemical precipitation study with Ca(OH)2 didn't give sufficient result (13%). In acidic condition better results were obtained. After precipitation with HCl, 38 % COD removal efficiency was achieved. Maximum removal efficiency was obtained first acidic and then alkali condition with 55% COD removal efficiency. In chemical oxidation experiments, catalytic oxidation, oxidation using KMnO4, H2O2, NaOCl, and Fenton Reagent (H2O2+FeSO4) were applied. Chemical oxidation with Fenton Reagent was the most effective oxidation method on the removal of COD. Approximately 65 % and 70 % COD removal efficiencies were obtained for olive mill wastewaters. However, the COD concentration of treated effluent was still very high as about 32 000 mg/L. In biological treatment experiments, Oil Gator Bacteria were used in batch reactor and this reactor was aerated continuously. 60 000 mg/L COD concentration and 52% COD removal efficiency in treated water were achieved at the end of the 22nd day. As a result of all experimental studies, it was impossible to achieve the discharge standards with these methods, since the remaining COD concentration was approximately 1 000 mg/L. Therefore, further treatment is needed to reduce the COD concentration. When physicochemical, chemical or biological methods were applied alone, significant improvement in COD reduction was not observed. The removal efficiencies obtained from different treatment systems were variable. The reduction of pollution depends on flow diagram of the treatment. Generally, better treatment efficiencies obtained with methods using more steps. Physical treatment, chemical oxidation, and biological treatment alternatives should be applied sequentially for achieving wastewater discharge standards for olive mill wastewater.