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 biodegradation of 300mg/L naphthalene in the bioreactor with no glass beads proceeded slowly until depletion after seven days. In the presence of glass beads, the biodegradation rate was faster; it depleted after four days. The biodegradation rate of naphthalene was equal to 1.99 mgL-1 hr-1 for bioreactor with no beads, while it is equal to 5.42, and 5.54 mgL-1 hr-1 for bioreactor with 40%load, 6mm size and 50% load, 5mm size of glass beads, respectively. For 500mg/L naphthalene, nine days on the bioreactor with no glass beads and five days on glass beads bioreactors were required to complete depletion. The biodegradation rate is equal to 2.33, 7.29, and 7.85 mg/L-1hr-1 for bioreactors with no glass beads, 40% load with 6mm, and 50% load with 5mm glass beads, respectively. The specific growth rate was increased in the bioreactor with glass beads; it represents 0.031, 0.050, and 0.054 hr−1 for 300mg/L and 0.043, 0.061, and 0.065 hr−1 for 500mg/L respectively for the previously mentioned conditions. An artificial neural network was used to model naphthalene dissolution and biodegradation. A correlation coefficient 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 could efficiently predict the experimental results. Time represents the most influential parameter on the dissolution and biodegradation treatment.