Effect of ozone pretreatment on characteristics of dissolved organic matter formed in aerobic and anaerobic digestion of
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RESEARCH ARTICLE
Effect of ozone pretreatment on characteristics of dissolved organic matter formed in aerobic and anaerobic digestion of waste-activated sludge Haixia Du 1 & Yanxia Wu 1 & Huifang Wu 1 & Fusheng Li 2 Received: 28 May 2020 / Accepted: 23 August 2020 # Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract The characteristics of dissolved organic matter (DOM) formed in aerobic and anaerobic digestion of waste-activated sludge (WAS) after ozone pretreatment were investigated with three ozone dosages (4.72, 10.96, and 13.8 mg O3/min) and four ozonation times (0, 10, 20, and 30 min) using six aerobic and six anaerobic digestion reactors. High decreasing rate of volatile suspended solid/total suspended solid indicated enhanced destruction of volatile solids and efficient sludge reduction. The results of TOC and UV absorbance indicated that increasing ozone dosage and time significantly enhanced hydrolysis and degradation of DOM. Data analysis with a first-order sequential reaction model revealed that, for aerobic digestion, kh increased in the range of 0.00049–0.00154 day−1; and for anaerobic digestion of WAS, kh increased in the range of 0.00302–0.00796 day−1 and kd increased in the range of 0.24910–0.54548 day−1. Detailed analysis of the composition of DOM showed that ozone pretreatment increased irreversible membrane resistance (IMR) and enhanced the breakdown of large DOM molecules, the formation of aromatic proteins, and tryptophan- and tyrosine-aromatic amino acids, as well as the accumulation of humic acid– and fulvic acid–like substances. Keywords Aerobic/anaerobic digestion . Dissolved organic matter . Humic substances . Irreversible membrane resistance . Ozonation . Waste-activated sludge
Introduction Huge amount of waste-activated sludge (WAS) is generated in municipal wastewater treatment plants (WWTPs), and its quantity is increasing because of population growth and rapid urbanization (Li and Yu 2011). The treatment and disposal of WAS are challenging tasks in WWTPs and represent up to 60% of their operating cost (Ramdani et al. 2010). Reducing WAS production in WWTPs thus presents an obvious economic interest. WAS is also undesirable for the following reasons: (1) its high content of biodegradable constituents Responsible editor: Vítor Pais Vilar * Haixia Du [email protected] 1
College of Urban Construction, Nanjing Tech University, Nanjing 211800, China
2
River Basin Research Center, Gifu University, 1-1 Yanagido, Gifu 501-1193, Japan
causes viruses, bacteria, and other pathogenic microorganisms; and (2) its high water content (containing more than 99% of water) requires dewatering prior to disposal (Ramdani et al. 2012). Aerobic and anaerobic digestions have been regarded as efficient methods for reduction and stabilization of WAS and energy recovery (Zhang et al. 2017; Chiavola et al. 2013). But, in the liquid digestate of the WAS, some intermediates and final products are still remaining as dissolved organic matter (DOM) that includes some non-biodegradable organic cons
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