Biodegradation of Olive Mill Wastewater by a newly isolated novel bacterial consortium under RSM optimized culture conditions

Olive Mill Wastewater (OMW) is the main olive processing residual product and its disposal represent a relevant environmental issue in Mediterranean countries, specialy in Tunisia where olive oil production is largely received in a revised form and concentrated in a short-lasting period. OMW is characterised not only by its high pollutant load, salinity and phytotoxic levels of polyphenols, but also by a high amount of organic compounds and plant mineral. Therefore, the optimization process was analyzed using custom response surface methodology (RSM) and central composite design (CCD). In the present study, the effect of different combinations of nine strains S1 (Aeromonas salmonicidae), S2 (Cryptococcus humicolus), S3 (Penicillium sp.), F1 (Aeromonas hydrophyla), F2 (Candida boidinii), F3 (Bacillus sp.), T1 (Sphingomonas paucimobilis), T2 (Staphylococcus xylosus) and T3 (Lactobacillus sp.) was studied using the equilateral triangle diagram and a mixture experimental design to assess color and COD removal during the species growth., Under optimal conditions, the developed bacterial consortium (59% (S, S2 and S3), 28.28% (F1, F2 and F3) and 12.62% (T1, T2 and T3)) was able to decolorize completely (> 84%) the OMW within 4 days at static condition. The color and COD removal were 90% and 86%, respectively. A very high regression coefficient between the variables and the responses: color and COD removal were R-2 = 84.78% and R-2 = 80.44%, respectively indicating an excellent evaluation of experimental data by polynomial regression model. UV-vis spectroscopy analysis confirmed the biodegradability of OMW by the developed bacterial consortium.