Nano-layered TiO₂ for effective bacterial disintegration of waste activated sludge and biogas production

BACKGROUND: Proper management of the huge amount of waste activated sludge generated during the conventional treatment of wastewater is nowadays a major environmental issue. Proper treatment of sludge needs huge investment and proper handling. To address this issue, the immobilized photocatalyst (TiO₂) mediated exocellular fractionation of bacterial pretreatment for anaerobic digestion was utilized as a sludge treatment technique. RESULT: Ti was deposited on glass substrate by a DC spluttering technique, and a TiO₂ layer was formed by annealing in oxygen atmosphere. This immobilized TiO₂ efficiently extricated the extracellular components after 45 min by removing 99% of the total extractable extracellular polymeric substances. The exocellular fractionated bacterial pretreatment induced 20% of COD solubilization with methane generation of about 0.0217 g COD g^-1 COD d^-1, which was higher than the sludge without any treatment and sludge with bacterial pretreatment only. CONCLUSION: An 8% increase in COD solubilization was achieved, which generated high quantities of methane. With the advantage of methane generation, the maximum profitable sludge reduction was obtained. Thin film deposition of TiO₂ enables easy recovery of TiO₂. The cost, energy, and solid balance analysis confirmed that this treatment method is field applicable.