Immobilized ZnO nano film impelled bacterial disintegration of dairy sludge to enrich anaerobic digestion for profitable bioenergy production: Energetic and economic analysis

[Display omitted] •ZnO thin film deposited by DC Sputtering with annealing used for EPS removal.•COD solubilization was superior in Deflocculated sludge of about 23%.•ZnO thin film mediated bacterial disintegration enhances methane production.•Methane production of deflocculated sludge was 437.12 mL/g COD.•The net profit of the proposed work was 27 USD/ton of dry sludge. Proper treatment and disposal of sludge is a substantial task around the biosphere. To address this issue, sludge deflocculation using photocatalyst was opted to enhance bacterial disintegration which in turn accelerate sludge digestion anaerobically. During this investigation, Direct current (DC) sputtering together with annealing process was used to immobilize Zinc oxide (ZnO). This immobilized ZnO removes the extracellular components at 15 min. The deflocculation mediated bacterial pretreatment induced 22.9% of soluble organics solubilization which auguments the biodegradability to 0.195 g COD/g COD during anaerobic digestion. The quantity of methane generated by deflocculated sludge was 39.2% higher than sludge with bacterial disintegration only with maximum methane yield of 437.14 mL/g COD. Hence, the outcome of the proposed work confirmed that the method is scalable with a net profit of 27 USD with the maximum methane generation of 413.1 kWh. Additionally, this method reduced 57% of dry sludge (solid).