Performance evaluation of upflow anaerobic sludge blanket reactor using immobilized ZnO nanoparticle enhanced continuous biogas production

Abstract

In this study, zinc oxide nanoparticles immobilized by methylenebisacrylamide were used for anaerobic consortium application and were examined for biomass retention capacity characterized in terms of volatile solids and specific methanogenic activity. The upflow anaerobic sludge blanket reactor was operated at various hydraulic retention times and was fed with palm oil mill effluent as a carbon source. The highest methane production rate of 510 mL CH₄·L⁻¹·h⁻¹ with a methane yield of 68.3 L CH₄ g⁻¹·COD_added was obtained at palm oil mill effluent concentration of 20 g COD·L^-1 and 24 h of hydraulic retention time. The average biogas (4.5 L) showed methane content and chemical oxygen demand reduction of 84.5 and 95.7%, respectively. R_max was 570 mL L⁻¹·POME·h⁻¹ at 15% of zinc oxide nanoparticles, with butyrate and acetic acid in an effluent contained when operated at a hydraulic retention time of 24 h and a palm oil mill effluent concentration of 20 g COD L⁻¹. A CO₂ reduction of 93.6% was obtained at 15% w/v loading of zinc oxide nanoparticle. Experiments demonstrated that with the granule bead size of immobilized zinc oxide nanoparticle of 3.99 mm, production of CH₄ and sequester of CO₂ were 650 m³·d⁻¹ and 456 m³·d⁻¹, respectively. At 15% zinc oxide nanoparticle, granule leakage was found to be 0.065 mg·L⁻¹. It is significant that this is the first report on immobilized zinc oxide nanoparticle granule biomass for biogas production from wastewater.