Pre-treatment processes optimization for the purification of olive mill wastewater through a pilot-scale membrane plant

The reported work deals with the evaluation of two different pre-treatment processes performances for the purification of a real olive mill wastewater. The wastewater was from an oil mill placed in the South of Italy and presents high Chemical Oxygen Demand (COD), Total Organic Carbon (TOC) and phenols concentrations, besides other organic pollutants, an acid pH and brown colour. Therefore, this complex wastewater resulted in low- biodegradable and difficult to be treated by a solely process. To this aim, the present work will evaluate optimal operating parameters of coagulation-flocculation and photocatalysis pre-treatments to achieve suitable physical-chemical properties of the effluent, before the membrane treatment in a pilot-scale plant. In detail, the wastewater was firstly treated with an organic coagulant (chitosan) and then a photocatalytic step follows before the more efficient integrated membrane process. After the photocatalytic process, the COD, TOC and Phenols concentrations decreased to up 42 %, 38 % and 36 %, respectively, in comparison with the initial values. Subsequently, a series of four separation processes (ultrafiltration, nanofiltration and reverse osmosis) was performed and almost the total initial COD, TOC and phenols concentrations were removed.