Biogas recirculation for simultaneous calcium removal and biogas purification within an expanded granular sludge bed system treating leachate

• Published in: Bioresource technology Vol. 173; pp. 317 - 323
• Main Authors: Luo, Jinghuan, Lu, Xueqin, Liu, Jianyong, Qian, Guangren, Lu, Yongsheng
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier 01.12.2014
• Subjects: Applied sciences; Biofuel production; Biofuels; Biogas; Biological and medical sciences; Biological Oxygen Demand Analysis; Bioreactors; Biotechnology; Calcium; Calcium - isolation & purification; Calcium carbonate; Carbonation; Energy; Exact sciences and technology; Fundamental and applied biological sciences. Psychology; Hydrogen-Ion Concentration; Industrial applications and implications. Economical aspects; Methane; Pollution; Purification; Sewage; Sludge; Solid Waste; Wastes; EGSB; Calcium removal; MSW leachate; Purification; Calcium; Biogas purification; Biogas recirculation; Biogas; Recirculation; Wastes; Leachate; Granular bed
• ISSN: 0960-8524; 1873-2976
• DOI: 10.1016/j.biortech.2014.09.128

Biogas, generated from an expanded granular sludge bed (EGSB) reactor treating municipal solid waste (MSW) leachate, was recirculated for calcium removal from the leachate via a carbonation process with simultaneous biogas purification. Batch trials were performed to optimize the solution pH and imported biogas (CO2) for CaCO3 precipitation. With applicable pH of 10-11 obtained, continuous trials achieved final calcium concentrations of 181-375 mg/L (removal efficiencies≈92.8-96.5%) in the leachate and methane contents of 87.1-91.4% (purification efficiencies≈65.4-82.2%) in the biogas. Calcium-balance study indicates that 23-986 mg Ca/d was released from the bio-system under the carbonized condition where CaCO3 precipitating was moved outside the bioreactor, whereas 7918-9517 mg Ca/d was trapped into the system for the controlled one. These findings demonstrate that carbonation removal of calcium by biogas recirculation could be a promising alternative to pretreat calcium-rich MSW leachate and synergistically to improve methane content.