Biodegradation of Naphthalene Using Glass Beads Roller Bioreactor: Application of Artificial Neural Network Modeling

Abstract

A roller bioreactor containing inert glass beads was employed to enhance naphthalene biodegradation in an aqueous solution. Mixed culture of microorganisms was isolated from sewage waste sludge and adopted for naphthalene biodegradation. The dissolution rate of naphthalene in the aqueous phase was studied at different conditions in the roller reactor. The results indicate that the best conditions for the biodegradation treatment in the roller bioreactor were 40% and 50% loads with 6 mm and 5 mm sized glass beads, respectively, at a rotation speed of 50 rpm. The biodegradation of 300 mg/L naphthalene in the bioreactor in the absence of glass beads proceeded slowly until depletion after seven days. In the presence of glass beads, the biodegradation rate was faster, depleting after only four days. At a concentration of 500 mg/L naphthalene, complete depletion was attained after nine days in the bioreactor with no glass beads and five days in the presence of glass beads. Both the biodegradation rate $({r}_{s}$) and the specific growth rate$\left(\mu \right)$ increased by utilizing the glass beads bioreactor compared with the bioreactor with no glass beads, thus confirming that the presence of glass beads enhances the mass transfer of naphthalene from the solid to the aqueous phase where it becomes available for utilization. An artificial neural network was used to model naphthalene dissolution and biodegradation. Correlation coefficients of 99.2% and 98.3% were obtained between the experimental and predicted output values for dissolution and biodegradation, respectively, indicating that the ANN model can efficiently predict the experimental data.

Highlights

• Mixed culture of microorganisms was used in a glass bead roller bioreactor.

• Increasing the load and size of glass beads enhanced the treatment.

• ANN was used to model the biodegradation process.