Replacement of the mixing fresh water by wastewater olive oil extraction in the extrusion of ceramic bricks

This investigation deals with the possibility of incorporating effluents resulting from olive oil extraction activity, as wastewater from olive-washing stage (OW) or wastewater from olive-oil washing stage (OOW), in the brick-making process. The feasibility of replacing mixing fresh water (FW) by OW or OOW of the extraction process of olive oil, in the process for manufacturing clay bricks, has been studied. FW, OW or OWW (22 wt%) was added to the clay in order for it to acquire enough plasticity to the stage of molding by extrusion. Samples containing OW or OOW were found to be comparable in extrusion performance to a control product that used FW. Once extruded, test specimens were dried at 110 °C (24 h) and fired at 850 or 950 °C (3 °C/min) for 4 h. The influence of replacing fresh water by wastes on the technological behavior of fired bricks was assessed by linear shrinkage, bulk density, water suction, water absorption and apparent porosity. Their mechanical and microstructural properties were also investigated by compressive strength and scanning electron microscopy (SEM), and thermal behavior by thermal conductivity. Results indicated that replacement of FW by OW or OOW produced slight improvements in the physical, mechanical and thermal properties of bricks. This may have been due to porosity generated by these wastes mainly closed pore type. ore, the use of these residues can alleviate the environmental impact generated by the industry of extraction of olive oil and, at the same time, represent an economic and water saving for the ceramic industry.