Application of Ion exchange technology to olive mill wastewater treatment

Abstract

The present Doctoral Thesis is framed within the main research line of the Chemical and Biochemical Processes Technology Group (TEP025), from the Chemical Engineering Department of the University of Granada. In this research group, different treatments have been developed for industrial wastewaters purification through advanced oxidation processes, membrane technology as well as IE technique. Concretely, one of the research lines is focused on the depuration of olive mill effluents. During the two-phase olive oil extraction system, two wastewater streams are mainly produced: the first one comes from the washing of the fruit, and is therefore called olives washing wastewater (OWW), and the second one is generated in the extraction of the olive oil, thus referred to as olive oil washing wastewater, OOW, a mixture of the olive-fruit humidity along with process-added water. These effluents are commonly known as olive mill wastewater (OMW). Olives washing wastewater presents low organic load and constitutes the largest amount of the generated wastewater volume. On the other hand, olive oil washing wastewater has high organic load, highlighting the phenols content, which are phytotoxic and refractory, thus resistant to biological degradation. In moderate concentrations are often toxic to aquatic fauna and flora. Therefore, the wastewater from these industries great difficulty degrade by biological processes, both aerobic and anaerobic. Polyphenols gives a high antimicrobial activity inhibiting the development of flora responsible for self-purification processes, presenting phytotoxic activity. Improper disposal of OMW to the environment or to domestic wastewater treatment plants is prohibited due to its toxicity to microorganisms, and also because of the consequent surface and groundwater potential contamination. Moreover, there is a legislation requiring the reduction of the global indicators concentration - COD and suspended solids - so these effluents can be reused or discharged. On the other hand, this wastewater also presents a high inorganic compounds concentration, especially high levels of potassium salts (60-70%) and sulfates, phosphates and chlorides of iron and calcium.