Olive oil waste treatment: A comparative and critical presentation of methods, advantages & disadvantages

Since olive oil industries were considered responsible for a great amount of pollution there has been a strong need for optimization of olive oil waste treatment systems. The currently employed systems are numerous and fall in the following large categories; bioremediation (ex-situ, in-situ), thermal processes (incineration, pyrolysis, gasification), evaporation, membrane processes, electrolysis, ozonation, digestion, coagulation/flocculation/precipitation, and distillation. Both advantages and disadvantages in conjunction with respective methodology and explicit flow diagrams were presented per waste treatment method. Furthermore, most recent studies were reported and more than twenty-five figures showing mainly the effectiveness of the current waste treatment methods versus time or temperature were displayed. The comparative presentation of the various olive oil waste treatment methodologies showed that though bioremediation stands for the most enviromentally friendly technique, its required longer treatment time in conjuction with its weakness to deal with elemental contaminants makes imperative the employment of a second alternative technique which could either be a membrane process (low energy cost, reliability, reduced capital cost) or a coagulation/flocculation method because of its low cost and high effectiveness. Biogas production appears to be another promising and energy effective waste treatment method. On the other hand, methods like distillation and ozonation (high cost) and electrolysis (experimental level) are unlikely to dominate this field unless their high cost is substantially reduced in the nearfuture.