Reduction of total polyphenols in olive mill wastewater by physico-chemical purification

The presence of phenolic compounds in wastewater from olive oil manufacturers (i.e. olive mill wastewater, OMW) makes them highly toxic and ecologically noxious to the waterways into which they are dumped unprocessed, as is usually the case in Andalusia (Spain). In addition, direct unloading onto the ground may result in phytotoxic effects on account of the marked herbicidal character of this type of waste. Because it contains the aforementioned toxic compounds and of the peculiar production habits of olive oil manufacturers, olive mill wastewater calls for rather specific purification procedures in order to avoid agroindustrial pollution. In this paper we analyse the influence of the two abovementioned factors and discuss the results obtained in the reduction of total polyphenols by a purification process that was implemented both on the laboratory scale and at two OMW purifying plants dealing with various wastes of this kind.