Abstract
In this work, the performance of an ultrafiltration (UF) membrane in the treatment of the effluents by-produced by olive mills is addressed by applying different pretreatments on the raw effluents. By conducting a photo-catalytic process (UV/TiO 2 PC) after pH-temperature flocculation (pH-T F) higher threshold flux values were observed for all feed stocks than by applying solely the pH-T F process, with an 18.8–34.2% increment. In addition, the performance of the UF membrane was also improved in terms of rejection efficiency, such that higher rejection values were yielded by the membrane for the organic pollutants (R COD ) by 48.5 vs. 39.9% and 53.4 vs. 42.0%. The UF membrane performance was also improved in terms of the volume feed recovery factor (VFR), achieving up to 88.2 vs. 87.2% and 90.7 vs. 89.3%. Results in the same line were also observed when the highly polluted olives oil washing wastewater raw stream was previously mixed with the effluent stream coming from the washing of the olives. This permits the UF to permeate, achieving the standard limits to reuse the purified effluent for irrigation purposes (COD values below 1000 mg·L −1 ), which makes the treatment process cost-effective and results in making the olive oil production process environmentally friendly.
Highlights
The seasonal production of olive oil using continuous centrifugation-based technology has replaced the ancient batch press method to cope with the increasing worldwide demand for olive oil in the last decades
Very significant enhancement was confirmed, from 75% for total suspended solids (TSS), 75.2% for Chemical oxygen demand (COD) and 52.1% for total phenols (TPh) for the OOWW stream pretreated by pH-temperature flocculation (pH-T F) alone, up to 75% for TSS, 86.5% for COD and 56.9% for TPh for OOWW further pretreated by UV/TiO2 PC
The performance of the UF membrane was improved in terms of rejection efficiency, such that major rejection values were yielded by the membrane for the organic pollutants (RCOD), at 48.5 vs. 39.9% and 53.4 vs. 42.0%
Summary
The seasonal production of olive oil using continuous centrifugation-based technology has replaced the ancient batch press method to cope with the increasing worldwide demand for olive oil in the last decades. As a side-effect, this growing demand has led to a substantial increase in the effluents generated by olive oil industries, commonly called olive mill wastewater (OMW). Two main effluents are generated in twophase olive oil mills, which result from the washing procedure of the olives (olives washing wastewater, OWW) and from the washing of the olive oil during vertical centrifugation (olive oil washing wastewater, OOW). In Spain alone, the main olive oil producer worldwide, this signifies a total amount of more than 9 million m3 of OMW per year, which represents a huge volume of these highly contaminant effluents. Olive oil production is an emergent agro-food industry in China and several other countries such as the USA, Australia and the Middle East, the treatment of OMW is becoming a task of global concern
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