Integration between bacterial consortium and magnetite (Fe3O4) nanoparticles for the treatment of oily industrial wastewater.

The study aimed to investigate the efficiency of exogenous bacterial consortium (Enterobacter cloacae and Pseudomonas otitidis) decorated (immobilized) with Fe3O4 Nanoparticles for the treatment of petroleum hydrocarbon-contaminated wastewater. Glycine coated magnetite Nanoparticles (Fe3O4 NPs) were prepared using reverse co-precipitation method and were characterized using X-ray diffraction, transmission and scanning electron microscopy and vibrating sample magnetometer. They were used to decorate exogenous bacterial consortium (Enterobacter cloacae and Pseudomonas otitidis) at 3 different Fe3O4/bacteria ratios (1:1, 1:3 and 3:1 w/w). Bioremediation of oil contaminated wastewater collected from one of the petroleum distribution companies, Alexandria was conducted for 168 h using Fe3O4/bacterial association at the best ratio (3:1) and compared with non-decorated consortium and the indigenous bacteria in the control. Analysis indicated crystalline structure of Fe3O4 NPs with spherical particles (size: 15-20 nm) and superparamagnetic properties. Glycine modified-Fe3O4 exhibited high ability to immobilize bacteria which acquired its magnetic properties. The highest coating efficiency (92%) was achieved at 3:1 Fe3O4/bacteria ratio after 1 h. This ratio positively affected bacterial growth reaching the highest growth rate (5.07 fold higher than the control) after 4 h. The highest removal efficiencies of the total suspended solids (TSS), chemical oxygen demands (COD), oil and grease (O&G) and total petroleum hydrocarbons (TPH) recording 96, 65.4, 83.9 and 85% reaching residual concentrations of 9.5, 598, 99 and 60 mg/l respectively were achieved after 4 h by the Fe3O4-bacteria assembly. Compared with the maximum permissible limits of the tested parameters, TSS residue was highly compiled with its limit (50 mg/l), while COD, O&G and TPH were 7.5, 9.9, and 120-folds higher than their limits (100, 15 and 0.5 mg/l respectively). To the best of our knowledge it is first time to use integrated Enterobacter cloacae and Pseudomonas otitidis consortium decorated with Fe3O4 NPs for the treatment of petroleum hydrocarbon-contaminated wastewater. The proposed system proved to be a very efficient, economical and applicable for the removal of the included contaminants in very short running time which increases its biotechnological added value.