Effect of Ca(OH)2 dosing on thermophilic composting of anaerobic sludge to improve the NH3 recovery.

Autor: Koyama, Mitsuhiko1 (AUTHOR) koyama.m.ad@m.titech.ac.jp, Nagao, Norio1 (AUTHOR), Syukri, Fadhil1 (AUTHOR), Yusoff, Fatimah Md.1 (AUTHOR), Toda, Tatsuki1 (AUTHOR), Quyen, Tran Ngoc Minh1 (AUTHOR), Nakasaki, Kiyohiko1 (AUTHOR)
Zdroj: Science of the Total Environment. Jun2019, Vol. 670, p1133-1139. 7p.
Abstrakt: Abstract The primary biological treatment method for organic sludge is composting and/or anaerobic digestion, but their product (compost or biogas) is of little economic benefit; therefore, an improved process to produce a high-value product is required to make sludge management more sustainable. Maximizing NH 3 gas recovery during composting processes has the potential benefit of producing high-value microalgal biomass. However, the majority of produced ammonia does not evaporate as NH 3 gas but retains as NH 4 +-N in the compost after fermentation. The present study investigates the effects of the timing of Ca(OH) 2 dosing (on days 2, 5, and 9), and the Ca(OH) 2 dose (1.1–2.6 mmol/batch), on lab-scale thermophilic composting of anaerobic sludge. The effects on NH 3 recovery, organic matter degradability, and microbial activity are evaluated. Ca(OH) 2 dosing immediately improved the emission of NH 3 , with yields 50–69% higher than those under control conditions. The timing of the dosing did not influence NH 3 recovery or organic matter degradability. Higher Ca(OH) 2 doses resulted in higher NH 3 recovery, while microbial activity was temporarily and marginally inhibited. The pH of the compost reached 10–11.5 but quickly dropped to 8–8.5 within a day, probably because of neutralization of Ca(OH) 2 by the emitted CO 2 and release of NH 3 , which maintained the microbial activity. The present study indicated that Ca(OH) 2 dosing would be useful to apply during thermophilic composting for NH 3 recovery to cultivate high-value microalgal biomass, which enables this process to obtain a more economic benefit. Graphical abstract Unlabelled Image Highlights • Development of composting process for the NH 3 recovery to culture high-value algae • Ca(OH) 2 dosing for enhancing NH 3 volatilization during composting • Improvement of NH 3 recovery by high doses but the timing of dosing has no effect. • Alkaline pH by Ca(OH) 2 dose but quick pH drops within a day • Ca(OH) 2 consumption by reaction with CO 2 , and NH 3 released [ABSTRACT FROM AUTHOR]
Databáze: GreenFILE
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