Jaeho Lee, Jeongmin Lee, Sanghoon Lee, Hyanggi Kim, Youngwoo Kim, Taejoo Park and Imgyu Byun
Department of Civil and Environmental Engineering, Pusan National University, South Korea
Microwave (MW) is a promising method for the solubilization of waste activated sludge (WAS) due to the accelerated reaction rates, environmental friendliness and low overall cost compared to conventional heating. In this study, several chemical agents, including H2SO4, NaCl and food wastewater, were applied to enhance the MW effect on the solubilization of WAS. NaCl had a positive effect on WAS solubilization compared to that of the MW only-assisted pretreatment by 30.1%. Therefore, food wastewater was used to enhance the MW efficiency in WAS solubilization owing to its high NaCl content. Food wastewater also improved the WAS solubilization efficiency by 60.3%. In the experiment of H2SO4-assisted MW pretreatment, the WAS solubilization efficiency was improved by 50.6% compared to that by MW-only assisted pretreatment. After the WAS pretreatment by microwaves with the chemicals, a biochemical methane production (BMP) test was conducted. In these experiments, the amount of biogas produced from WAS pretreated with NaCl, food wastewater and H2SO4 assisted microwaves was 11.3, 31.6 and 29.7% higher, respectively, than that of the nonpretreated WAS. Therefore, the most appropriate chemical is food wastewater because of solubilization efficiency as well as waste reuse, cost and environmental friendliness.
Keywords: Anaerobic digestion, Solubilization, Microwave, Pretreatment, Waste activated sludge