A new integrated approach for NOx removal by absorption and anaerobic digestion of wasted activated sludge

Zihan Zhu, Tao Zhou, Haotian Qin, Youcai Zhao and Bin Xu

Applied Energy, 2024, vol. 362, issue C, No S0306261924004173

Abstract: Urban waste treatment and utilization are facing mounting demands, necessitating cities to evolve their infrastructure towards more efficient, affordable, and sustainable solutions. Achieving sustainable waste management in urban ecosystems is an intricate endeavor that spans multiple disciplines. Nitrogen oxides (NOx) from waste combustion and sludge from wastewater plant exemplify challenging urban secondary wastes with both environmental and energy implications. This study introduces a novel method for NOx removal, harnessing an integrated system of absorption and biological reduction through waste activated sludge (WAS) anaerobic digestion. Findings reveal that microbial adsorption amplified NO removal efficiency by an impressive 125.8%. A significant correlation emerged between pH, temperature, and NOx removal efficiency, with greatest removal (78.9%) occurring at pH 6.5 and 30 °C. On the other hand, concentrations of NOx and O2 exerted little influence on NOx removal. The presence of SO2 significantly enhanced the NOx removal efficiency, suggesting potential for concurrent SO2 and NOx extraction. The NOx removal mechanism was elucidated as a two-step reaction pathway comprising NOx absorption and subsequent conversion. This process integrates both the chemical absorption of NOx and microbial denitrification. Concurrently, nitrite accumulation was found to boost the hydrolysis rate and the methanogenic potential of anaerobic digestion. This innovative NOx removal strategy, which is devoid of chemicals, produces no secondary waste, and facilitates energy recovery, holds substantial promise for future applications in urban waste-to-energy initiatives.

Keywords: Urban waste to energy; Flue gas purification; Wastewater sludge utilization; Absorption; Anaerobic digestion (search for similar items in EconPapers)
Date: 2024
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DOI: 10.1016/j.apenergy.2024.123034

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