Current status and future challenges of table olive processing wastewater valorization

• Table olive processing generates large volumes of polluting wastewaters (TOPWs).
• Lye, washing waters and fermentation/storage brine are the main TOPW streams.
• Anaerobic digestion of TOPWs offers great potential for biogas generation.
• Lactic acid and hydroxytyrosol can be efficiently produced from TOPWs.
• Bioprocessing and green chemical treatment of TOPWs may be combined.

Table olive production is expanding worldwide. This production is associated with the generation of enormous amounts of polluting and difficult to handle wastewater streams. Thus, research on different technologies to decompose their organic load is currently needed. The economic benefit of the potential detoxification routes is expected to increase if processes for upgrading Table olive processing wastewaters are designed. This makes biological treatment of particular interest. The current review analyzes a relevant number of scientific studies dealing with promising technologies for biological treatment of table olive processing wastewaters from laboratory to pilot-scale systems. Concise details of the various technologies involved such as anaerobic digestion, lactic acid fermentation and fungal fermentation are determined. The most significant advances in the manufacturing of value-added products (e.g. biogas, platform chemicals, natural antioxidants) from table olive processing wastewaters through different microorganisms, bioreactor design modifications, and operational conditions are critically discussed. Future prospects of valorizing table olive wastewaters are presented.