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Effect of phase separation on anaerobic digestion of kitchen waste
Published in ICE Publishing
Volume: 7
Issue: 2
Pages: 91 - 103
The anaerobic digestion of kitchen waste was studied in both batch and continuous modes. The effect of increasing loading rates on pollutant removal and biogas production was investigated for single-phase digestion and twophase digestion systems. The anaerobic biodegradability of the kitchen waste obtained from the batch study was 83.5%. Single-stage digestion of kitchen waste was subjected to varying organic loading rates (OLR) ranging from 1.5 kg volatile solids (VS) m-3 d-1 to 5.5 kg VS m-3d _1, with a common, hydraulic retention time (HRT) of 15 d. The optimum performance of the system was observed at an OLR of 4.5 kg VS m -3 d-1 in terms of pollutant removal efficiency and biogas production. The removal rates for chemical oxygen demand (COD) and VS at this optimal OLR were 81% and 79%, respectively. Maximum, production of the methane was 0.288 m3/kg of VS added. Beyond the optimal OLR, the volatile fatty acids concentration increased and reached its maximum value (9.2 g/L) at the higher loading rate tested (5.5 kg VS m3 d-1). Anaerobic digestion of the kitchen waste was earned out in a two-stage reactor with different loading rates of 4, 6, and 8 kg VS m3 d-1. The retention time given to both hydrolysis and methanogenesis phases was 5 d, for a total HRT of 10 d. Best performances were observed in the third run with the OLR of 8 kg VS m-3 d-1. High removal efficiencies for COD and VS were found as 92% and 94%, respectively. A total of 0.22 m3 of methane was produced by 1 kg of VS added. Responses to the fluctuations in the loading rates were sudden and many times unfavourable in the singlestage system, while the fluctuations were suppressed or overcome at a faster rate in. the two-stage reactor, without creating too many problems. Comparison of the overall performance showed that phase-separated digesters or the two-stage digesters may offer the best choice for high efficiency, concerning pollutant removal. © 2008 NRC Canada.
About the journal
JournalJournal of Environmental Engineering and Science
PublisherICE Publishing
Open AccessNo
Concepts (8)
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    Anaerobic digestion
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    Chemical oxygen demand
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    Phase separation
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    Organic loading rate
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