Effects of Two-Stage Operation on Stability and Efficiency in Co-Digestion of Food Waste and Waste Activated Sludge

Xinyuan Liu, Ruying Li and Min Ji
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Xinyuan Liu: School of Environmental Science and Engineering, Tianjin University, Tianjin 300350, China
Ruying Li: School of Environmental Science and Engineering, Tianjin University, Tianjin 300350, China
Min Ji: School of Environmental Science and Engineering, Tianjin University, Tianjin 300350, China

Energies, 2019, vol. 12, issue 14, 1-21

Abstract: The two-stage anaerobic digestion (AD) technology attracts increasing attention due to its ability to collect both hydrogen and methane. A two-stage AD system feeding with food waste and waste activated sludge was investigated in order to achieve higher energy yield and organics removal. The two-stage process consists of a thermophilic H 2 -reactor and a mesophilic CH 4 -reactor, achieved the highest hydrogen and methane yields of 76.8 mL/g-VS and 147.6 mL/g-VS at hydraulic retention times (HRTs) of 0.8 d and 6 d, respectively. The co-digestion process in this study required much less external alkalinity to maintain the pH values than sole food waste digestion in the literature. Compared with the single-stage mesophilic methane AD process, the two-stage AD system had better performance on operation stability, biogas and energy yields, organics removal and chemical oxygen demand (COD) conversion at high organic loading rates (OLRs). According to the TA-cloning analysis, the dominant bacteria in H 2 -reactor was closely related to Clostridium sp. strain Z6 and species Thermoanaerobacterium thermosaccharolyticum . The dominant methanogens in two-stage and single-stage CH 4 -reactor were recognized as acetotrophic methanogens and hydrogenotrophic methanogens, respectively. The presence of the genus Nitrososphaera in the two CH 4 -reactors might contribute to the low NH 4 + -N concentration in digestate and low CO 2 content in biogas.

Keywords: two-stage anaerobic digestion; hydrogen production; methane production; food waste; waste activated sludge (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2019
References: View references in EconPapers View complete reference list from CitEc
Citations: View citations in EconPapers (1)

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