Bio-nanoremediation of olive oil mill wastewater by Alternaria alternata fungi coupled with Ag-doped TiO2 nanoparticles and its use as biofertilizer for cereal crops

Despite its beneficial impact on plant growth, the olive oil mill wastewater (OMWW) generated during the olive oil extraction process represents one of the most harmful industrial effluents due to its pollutant and toxicity traits. Hence, in the present work, an eco-friendly method coupling a biological treatment with a photocatalytic treatment to detoxify OMWW was proposed. The biological treatment consists of using the extremophilic fungus Alternaria alternata , and the photocatalytic treatment consists of using Ag-doped TiO 2 nanoparticles. The results showed that the highest removal rates of chemical oxygen demand (COD) and phenolic compounds (PC) upon biological treatment were 65% and 50%, respectively. For the photocatalytic treatment, the highest removal rates of COD and PC were 64% and 91%, respectively. Upon using an integrated photocatalytic and biological process, the removal rates of COD and PC were 62% and 84%, respectively. The impact of the treated OMWW on barley seeds and seedlings was tested. The seed germination percentage (GP) and germination index (GI) were affected by OMWW treated by either the biologic or photocatalytic process. However, following the use of OMWW treated by the combined process, both the GP and the GI were 100%. The irrigation of barley seedlings with the treated OMWW led to an improvement in their growth (length, dry weight), hydric status, photosynthesis performance and chlorophyll content compared to those irrigated with raw OMWW. The best effect was noticed upon the use of the OMWW treated by the combined process, which suggests its potential use as a biofertilizer for cereal crops.