Olive mill wastewater treatment by combined chemical-physical and membrane-SBR processes

The aim of the present research was the study of a combined treatment scheme of the Olive Mill Wastewaters (OMWs) made by chemical-physical and membrane-Sequencing Batch Reactor (M-SBR) processes for their proper disposal and possible reuse. As pre-treatments, the chemical precipitation with different reagents (lime, alum and iron chloride salts), the acid cracking (AC) with salt addition and the granular activated carbon (GAC) adsorption were selected. The best removal efficiencies in terms of COD, total polyphenols (TP), lipids and total suspended solids (TSS) were determined. A further pre-treatment was tested to be used as alternative to or in combination with chemical precipitation consisting of the physical separation trough an ultrafiltration (UF) membrane. Permeate quality indicated that membrane separation was able to achieve about 30% COD and 60% polyphenols removal efficiencies. Based on these results, lime precipitation was chosen as the feed of the following biological process that consisted of a lab-scale SBR later converted into a membrane-SBR, inserting the UF membrane inside the reactor. A comparison between the performances of the reactor fed with either diluted OMWs or with the chemically pre-treated OMW was carried out through periodical analysis on inlet and outlet samples and kinetic studies within typical operating cycles.