Enhanced biodegradation of GTL process wastewater using immobilized bacteria in PVA/TiO₂ nanoparticles hydrogel matrix

A spouted bed bioreactor (SBBR) was utilized to treat GTL process wastewater in batch mode incorporating a special biocatalyst using an immobilized bacterial consortium in PVA/TiO₂ (1.0 w% nanoparticles) composite hydrogel. Batch experiments were carried out in the SBBR at different operating parameters that influence the GTL process wastewater treatment. Parameters optimization was carried out using Response surface methodology (RSM), where the effect of temperature, pH, and initial COD (Chemical Oxygen Demand) on the removal of the organic compounds was investigated. The experimental design results were used to determine the influence of the operation parameters on the biodegradation rate of the contaminants. The optimization results indicated that the optimum pH, temperature, and initial COD were 6.0, 30˚C, and 2100 mg/L, respectively. Under these conditions, the maximum biodegradation rate was 255 mg/L.h. The airflow rate influences the COD reduction by maintaining the dissolved oxygen (DO) level and providing mixing in the bioreactor. The optimum DO value was obtained at an airflow rate of 3 L_a/L_r.min. At the optimum conditions, the system can reduce the COD content by 85 % at 12 h HRT; this residence time can be applied in the continuous biological treatment of GTL process water.