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Effects of solid retention time on anaerobic digestion of dewatered-sewage sludge in mesophilic and thermophilic conditions

Ivo Achu, Nges LU and Liu, Jing LU (2010) In Renewable Energy 35(10). p.2200-2206
Abstract
Anaerobic digestion of dewatered-sewage sludge using continuous stirred tank reactors (CSTRs) in duplicates was evaluated under thermophilic (50 degrees C) and mesophilic (37 degrees C) conditions over a range of nine solid retention times (SRTs). The 35- and 30-day SRTs were designed to simulate a full-scale plant operation while 25-, 20-, 15- and 12-day SRTs were planned to evaluate process performance at the various SRTs. The 9-, 5- and 3-day SRTs were performed to push the reactors to extend their degradation capacity and test the threshold for process imbalance. The corresponding organic loading rates (OLR) varied from 1.6 to 20.5 kg VS m(-3) Biogas production rate could be tripled when the SRT was shortened from 30 to 12 days and... (More)
Anaerobic digestion of dewatered-sewage sludge using continuous stirred tank reactors (CSTRs) in duplicates was evaluated under thermophilic (50 degrees C) and mesophilic (37 degrees C) conditions over a range of nine solid retention times (SRTs). The 35- and 30-day SRTs were designed to simulate a full-scale plant operation while 25-, 20-, 15- and 12-day SRTs were planned to evaluate process performance at the various SRTs. The 9-, 5- and 3-day SRTs were performed to push the reactors to extend their degradation capacity and test the threshold for process imbalance. The corresponding organic loading rates (OLR) varied from 1.6 to 20.5 kg VS m(-3) Biogas production rate could be tripled when the SRT was shortened from 30 to 12 days and more than doubled from 35- to 15-day SRT because of a concomitant increase in OLR. In general, higher biogas productivity was realized under thermophilic, but methane yields were comparable due to the higher methane content in the biogas under mesophilic digestion. The methane content in biogas fluctuated between 55 and 65% and the methane yield ranged from 0.314 to 0.348 Nm(3) CH4 kg VSadded-1 day(-1) for both thermophilic and mesophilic digestion. The VS-reduction at 12- and 15-day SRT ranged from 45 to 52% and there was no accumulation of VFAs. Increasing concentrations of VFAs, decreasing concentration of partial alkalinity and decrease in pH were noted as signs of reactor instability. Process imbalance started at 9-day SRT, souring of the reactors, cell wash-out and foaming was noted as the principal causes of process failure under both thermophilic and mesophilic conditions. This study projected the possibility of using CSTRs in treating dewatered-sewage sludge at a shorter SRT to achieve reasonable biogas production and VS-reduction without encountering adverse operation conditions as foaming and wash-out of cells. Crown Copyright (c) 2010 Published by Elsevier Ltd. All rights reserved. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
Volatile solids, Volatile fatty acids, Anaerobic digestion, Organic loading rate, Solid retention time
in
Renewable Energy
volume
35
issue
10
pages
2200 - 2206
publisher
Elsevier
external identifiers
  • wos:000278664500007
  • scopus:77954864682
ISSN
0960-1481
DOI
10.1016/j.renene.2010.02.022
language
English
LU publication?
yes
id
a9d7b12c-13a6-441f-abf3-876946c7ed69 (old id 1630838)
date added to LUP
2010-07-21 14:05:32
date last changed
2018-06-24 03:21:18
@article{a9d7b12c-13a6-441f-abf3-876946c7ed69,
  abstract     = {Anaerobic digestion of dewatered-sewage sludge using continuous stirred tank reactors (CSTRs) in duplicates was evaluated under thermophilic (50 degrees C) and mesophilic (37 degrees C) conditions over a range of nine solid retention times (SRTs). The 35- and 30-day SRTs were designed to simulate a full-scale plant operation while 25-, 20-, 15- and 12-day SRTs were planned to evaluate process performance at the various SRTs. The 9-, 5- and 3-day SRTs were performed to push the reactors to extend their degradation capacity and test the threshold for process imbalance. The corresponding organic loading rates (OLR) varied from 1.6 to 20.5 kg VS m(-3) Biogas production rate could be tripled when the SRT was shortened from 30 to 12 days and more than doubled from 35- to 15-day SRT because of a concomitant increase in OLR. In general, higher biogas productivity was realized under thermophilic, but methane yields were comparable due to the higher methane content in the biogas under mesophilic digestion. The methane content in biogas fluctuated between 55 and 65% and the methane yield ranged from 0.314 to 0.348 Nm(3) CH4 kg VSadded-1 day(-1) for both thermophilic and mesophilic digestion. The VS-reduction at 12- and 15-day SRT ranged from 45 to 52% and there was no accumulation of VFAs. Increasing concentrations of VFAs, decreasing concentration of partial alkalinity and decrease in pH were noted as signs of reactor instability. Process imbalance started at 9-day SRT, souring of the reactors, cell wash-out and foaming was noted as the principal causes of process failure under both thermophilic and mesophilic conditions. This study projected the possibility of using CSTRs in treating dewatered-sewage sludge at a shorter SRT to achieve reasonable biogas production and VS-reduction without encountering adverse operation conditions as foaming and wash-out of cells. Crown Copyright (c) 2010 Published by Elsevier Ltd. All rights reserved.},
  author       = {Ivo Achu, Nges and Liu, Jing},
  issn         = {0960-1481},
  keyword      = {Volatile solids,Volatile fatty acids,Anaerobic digestion,Organic loading rate,Solid retention time},
  language     = {eng},
  number       = {10},
  pages        = {2200--2206},
  publisher    = {Elsevier},
  series       = {Renewable Energy},
  title        = {Effects of solid retention time on anaerobic digestion of dewatered-sewage sludge in mesophilic and thermophilic conditions},
  url          = {http://dx.doi.org/10.1016/j.renene.2010.02.022},
  volume       = {35},
  year         = {2010},
}