Effect of Microbial Inoculation on Lipid and Phenols Removal During the Co-composting of Olive Mill Solid Sludge with Green Waste in Bioreactor
2021
Bouhia, Youness | Lyamlouli, Karim | Fels, Loubna El | Youssef, Zeroual | Ouhdouch, Yedir | Hafidi, Mohamed
In Mediterranean countries, the olive oil industry generates the most important agro-industrial wastewater, which results in the production of a highly toxic sludge following effluent decantation, thus endangering the environment. In this investigation, an optimized composting process via microbial inoculation is suggested as to alleviate the toxicity of olive mill solid sludge (OMS-Sludge) through addressing its high polyphenol and lipid content. The composting assay was carried out in a bioreactor using mixtures of sludge and green wastes, with or without microbial inoculation, namely: E1 (49% sludge + 49% green waste + 2% thermophilic Inoculum), and E2 (50% sludge + 50% green waste). After 4 months of composting the inoculation had affected at significantly (p < 0.05)pH, EC and total organic carbon degradation compared to control. Furthermore, HPLC analysis revealed that OMS-Sludge composting significantly diminished the polyphenol content (95% and 85% for E1 and E2, respectively), and the lipid content (90% and 81% for E1 and E2, respectively). More importantly, microbial inoculation resulted in a significant composting efficiency, which was corroborated by a decomposition rate 65% for E1 compared to 62% for E2. In-planta assays showed that both the lipid and polyphenol contents werestrongly correlated with the sludge phytotoxicity with respect to seed germination, which was demonstrated by a substantial improvement of the germination index of Cabbage (64.44%), Turnip (86.58%) and Cress seeds (120.85%). Overall, enhancing the composting process through microbial inoculation resulted in a significant alleviation of the initial mixture phytotoxicity, and proved to be an efficient strategy for OMS-Sludge valorization.
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