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Influence of ammonia in the anaerobic digestion of food waste

Influence of ammonia in the anaerobic digestion of food waste
Influence of ammonia in the anaerobic digestion of food waste
Ammonia toxicity was investigated in mesophilic (37 °C) and thermophilic (55 °C) digesters using high and lownitrogen food wastes (FW). Mesophilic inoculum was successfully acclimated to thermophilic conditions by a step change in temperature followed by incremental increases in organic loading rate (OLR). Digestion performance and stability were monitored via volatile fatty acid (VFA) profiles, alkalinity, specific methane production (SMP) and volatile solids (VS) destruction. High-nitrogen mesophilic digesters stabilised by day 70 and responded well to increases in OLR, with a SMP of 0.45 L CH4 g−1 VS, stable pH, and VFA<0.2 g L−1. Thermophilic digesters fed on high and low-nitrogen FWs showed almost identical responses to acclimatisation. Behaviour then deviated, with high-nitrogen digesters accumulating VFA. Stable pH could be maintained for up to 310 days before eventual failure at total ammonia nitrogen (TAN) concentration>5.0 g N L−1, although accumulation of propionic and other longer-chain VFA began at TAN ∼3.5 g N L−1. The low-nitrogen digesters showed no VFA accumulation, and had a SMP of ∼0.39 L CH4 g VS L−1 day−1 with 91% VS destruction. After 384 days the TAN concentration was increased from ∼0.7 g N L−1 by urea addition. This resulted in progressive VFA accumulation in one digester when TAN reached ∼3.5 g N L−1, while stable operation at very low VFA was possible at up to ∼2.5 g N L−1 in the second digester. The results confirmed acclimatisation to thermophilic conditions was possible on a far shorter timescale than to high TAN concentrations.
Ammonia inhibition, Thermophilic digestion, Methane production, Total ammonia nitrogen, Acclimatisation
2213-3437
5131-5142
Yirong, Chaowana
8eba88bc-1a30-4900-91bd-4509593a90c5
Zhang, Wei
2ddf6d07-244b-4a0b-8a96-2867deb060d5
Heaven, Sonia
f25f74b6-97bd-4a18-b33b-a63084718571
Banks, Charles
5c6c8c4b-5b25-4e37-9058-50fa8d2e926f
Yirong, Chaowana
8eba88bc-1a30-4900-91bd-4509593a90c5
Zhang, Wei
2ddf6d07-244b-4a0b-8a96-2867deb060d5
Heaven, Sonia
f25f74b6-97bd-4a18-b33b-a63084718571
Banks, Charles
5c6c8c4b-5b25-4e37-9058-50fa8d2e926f

Yirong, Chaowana, Zhang, Wei, Heaven, Sonia and Banks, Charles (2017) Influence of ammonia in the anaerobic digestion of food waste. Journal of Environmental Chemical Engineering, 5 (5), 5131-5142. (doi:10.1016/j.jece.2017.09.043).

Record type: Article

Abstract

Ammonia toxicity was investigated in mesophilic (37 °C) and thermophilic (55 °C) digesters using high and lownitrogen food wastes (FW). Mesophilic inoculum was successfully acclimated to thermophilic conditions by a step change in temperature followed by incremental increases in organic loading rate (OLR). Digestion performance and stability were monitored via volatile fatty acid (VFA) profiles, alkalinity, specific methane production (SMP) and volatile solids (VS) destruction. High-nitrogen mesophilic digesters stabilised by day 70 and responded well to increases in OLR, with a SMP of 0.45 L CH4 g−1 VS, stable pH, and VFA<0.2 g L−1. Thermophilic digesters fed on high and low-nitrogen FWs showed almost identical responses to acclimatisation. Behaviour then deviated, with high-nitrogen digesters accumulating VFA. Stable pH could be maintained for up to 310 days before eventual failure at total ammonia nitrogen (TAN) concentration>5.0 g N L−1, although accumulation of propionic and other longer-chain VFA began at TAN ∼3.5 g N L−1. The low-nitrogen digesters showed no VFA accumulation, and had a SMP of ∼0.39 L CH4 g VS L−1 day−1 with 91% VS destruction. After 384 days the TAN concentration was increased from ∼0.7 g N L−1 by urea addition. This resulted in progressive VFA accumulation in one digester when TAN reached ∼3.5 g N L−1, while stable operation at very low VFA was possible at up to ∼2.5 g N L−1 in the second digester. The results confirmed acclimatisation to thermophilic conditions was possible on a far shorter timescale than to high TAN concentrations.

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Yirong et al Thermo FW - scholar text - Accepted Manuscript
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More information

Accepted/In Press date: 22 September 2017
e-pub ahead of print date: 23 September 2017
Published date: October 2017
Keywords: Ammonia inhibition, Thermophilic digestion, Methane production, Total ammonia nitrogen, Acclimatisation

Identifiers

Local EPrints ID: 416335
URI: http://eprints.soton.ac.uk/id/eprint/416335
ISSN: 2213-3437
PURE UUID: 7e467c55-cfd4-45ae-8145-73a88116c094
ORCID for Sonia Heaven: ORCID iD orcid.org/0000-0001-7798-4683

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Date deposited: 13 Dec 2017 17:30
Last modified: 07 Oct 2020 05:39

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