Keywords: anaerobic digestion, biochemical methane potential, Escherichia coli, E coli, energy efficiency, microwave irradiation, nematodes eggs, pre–treatment, waste activated sludge, WAS, renewable energy, biogas production, sludge solubility
Impact of microwave treatment on properties of waste activated sludge
The impact of changing microwave (MW) operational parameters such as temperature, intensity, contact time, and sludge concentration on the physic–chemical and microbiological properties of waste activated sludge (WAS), as well as on biogas production have been investigated. Results obtained indicated that sludge solubility increases with the increase of MW contact time and temperature. At an ultimate MW temperature of 95°C, treatment of WAS with initial total suspended solids (TSS) concentrations of 0.1, 0.64 and 1.2% resulted in 2.37, 1.84 and 1.53 fold increase in CODs, respectively. Also, at high MW intensity (100%) maximum Escherichia coli destruction occurred. MW energy consumption computation indicated that it is more economical to use high MW intensity for a short period than low intensity for longer periods. WAS having 1.2% TSS (w/w), microwaved at 95°C and power intensity of 100% produced 116% increase in cumulative biogas production as compared to control samples after digestion for 43 days.