TY - JOUR
T1 - Acidic aerobic digestion of anaerobically-digested sludge enabled by a novel ammonia-oxidizing bacterium
AU - Wang, Zhiyao
AU - Zheng, Min
AU - Duan, Haoran
AU - Ni, Gaofeng
AU - Yu, Wenbo
AU - Liu, Yanchen
AU - Yuan, Zhiguo
AU - Hu, Shihu
N1 - Funding Information:
This work was financially supported by UQ Vice-chancellor's and Deputy Vice-Chancellor Research Strategic Initiatives Fund and District of Columbia Water and Sewerage Authority (DC Water). Zhiguo Yuan is a recipient of the Australian Research Council (ARC) Laureate Fellowship FL170100086. Dr. Min Zheng thanks the support of Early Career Researcher Award at The University of Queensland. Dr. Gaofeng Ni acknowledges the Advance Queensland Industry Research Fellowships (AQIRF050–2019RD2). The authors thanks Urban Utilities for providing the full-scale sludge sources and Mr. Shane Watts for collecting the sludge. The particle size distribution was performed in part at the Queensland node of the Australian National Fabrication Facility, a company established under the National Collaborative Research Infrastructure Strategy to provide nano- and micro-fabrication facilities for Australia's researchers.
Funding Information:
This work was financially supported by UQ Vice-chancellor's and Deputy Vice-Chancellor Research Strategic Initiatives Fund and District of Columbia Water and Sewerage Authority (DC Water). Zhiguo Yuan is a recipient of the Australian Research Council (ARC) Laureate Fellowship FL170100086. Dr. Min Zheng thanks the support of Early Career Researcher Award at The University of Queensland. Dr. Gaofeng Ni acknowledges the Advance Queensland Industry Research Fellowships (AQIRF050?2019RD2). The authors thanks Urban Utilities for providing the full-scale sludge sources and Mr. Shane Watts for collecting the sludge. The particle size distribution was performed in part at the Queensland node of the Australian National Fabrication Facility, a company established under the National Collaborative Research Infrastructure Strategy to provide nano- and micro-fabrication facilities for Australia's researchers.
Publisher Copyright:
© 2021 Elsevier Ltd
PY - 2021/4/15
Y1 - 2021/4/15
N2 - Anaerobic digestion is a commonly used process for the reduction and stabilization of wasted activated sludge generated in wastewater treatment plants. However, anaerobically-digested (AD) sludge is still a problematic waste stream due to its large volume and often poor quality. In this study, two aerobic digesters were set up to treat anaerobically-digested sludge, with one digester operated in self-generated acidic condition as the experimental reactor, and one at neutral pH as the control reactor. The acidic condition in the experimental reactor was driven by an inoculated special ammonia-oxidizing bacterium, ‘Candidatus Nitrosoglobus’, which can tolerate low pH. As a result of ammonium oxidation by Ca. Nitrosoglobus, the pH decreased to 4.8 ± 0.2 and nitrite accumulated to and stayed at 200.0 ± 17.2 mg N L−1, from which free nitrous acid (FNA) at 8.5 ± 1.8 mg HNO2[sbnd]N L−1 formed in-situ. As a combined effect of low pH and high concentration of FNA, the experimental reactor reduced the total solids (TS), volatile solids (VS) and non-volatile solids (NVS) in the AD sludge by 25.2 ± 7.0%, 29.8 ± 4.3%, and 22.6 ± 5.5%, respectively. In contrast, the control reactor without Ca. Nitrosoglobus inoculation (operated at a near-neutral pH of 6.8 ± 0.3 and no FNA formation) only reduced VS in the AD sludge by 10.4 ± 4.3%, along with negligible NVS reduction. Additionally, the acidic aerobic digestion in the experimental reactor significantly stabilized AD sludge, decreasing the specific oxygen uptake rate (SOUR) to 0.5 ± 0.1 mg O2 g−1VS h−1 and the most probable number (MPN) of Faecal Coliforms to 2.4 ± 0.1 log(MPN g−1TS), both of which meet USEPA standards for Class A biosolids. In comparison, the control reactor produced biosolids at Class B level only, with an SOUR of 1.8 ± 0.2 mg O2 g−1VS h−1 and a Faecal Coliforms MPN of 3.6 ± 0.1 log(MPN g−1TS). By reducing the volume and improving the quality of the AD sludge, the acidic aerobic digestion of AD sludge enabled by Ca. Nitrosoglobus has the potential to significantly save the sludge disposal costs in wastewater treatment.
AB - Anaerobic digestion is a commonly used process for the reduction and stabilization of wasted activated sludge generated in wastewater treatment plants. However, anaerobically-digested (AD) sludge is still a problematic waste stream due to its large volume and often poor quality. In this study, two aerobic digesters were set up to treat anaerobically-digested sludge, with one digester operated in self-generated acidic condition as the experimental reactor, and one at neutral pH as the control reactor. The acidic condition in the experimental reactor was driven by an inoculated special ammonia-oxidizing bacterium, ‘Candidatus Nitrosoglobus’, which can tolerate low pH. As a result of ammonium oxidation by Ca. Nitrosoglobus, the pH decreased to 4.8 ± 0.2 and nitrite accumulated to and stayed at 200.0 ± 17.2 mg N L−1, from which free nitrous acid (FNA) at 8.5 ± 1.8 mg HNO2[sbnd]N L−1 formed in-situ. As a combined effect of low pH and high concentration of FNA, the experimental reactor reduced the total solids (TS), volatile solids (VS) and non-volatile solids (NVS) in the AD sludge by 25.2 ± 7.0%, 29.8 ± 4.3%, and 22.6 ± 5.5%, respectively. In contrast, the control reactor without Ca. Nitrosoglobus inoculation (operated at a near-neutral pH of 6.8 ± 0.3 and no FNA formation) only reduced VS in the AD sludge by 10.4 ± 4.3%, along with negligible NVS reduction. Additionally, the acidic aerobic digestion in the experimental reactor significantly stabilized AD sludge, decreasing the specific oxygen uptake rate (SOUR) to 0.5 ± 0.1 mg O2 g−1VS h−1 and the most probable number (MPN) of Faecal Coliforms to 2.4 ± 0.1 log(MPN g−1TS), both of which meet USEPA standards for Class A biosolids. In comparison, the control reactor produced biosolids at Class B level only, with an SOUR of 1.8 ± 0.2 mg O2 g−1VS h−1 and a Faecal Coliforms MPN of 3.6 ± 0.1 log(MPN g−1TS). By reducing the volume and improving the quality of the AD sludge, the acidic aerobic digestion of AD sludge enabled by Ca. Nitrosoglobus has the potential to significantly save the sludge disposal costs in wastewater treatment.
KW - Acidic aerobic digestion
KW - Anaerobic digestion
KW - Candidatus Nitrosoglobus
KW - Sludge reduction
KW - Stabilization
UR - http://www.scopus.com/inward/record.url?scp=85101636624&partnerID=8YFLogxK
U2 - 10.1016/j.watres.2021.116962
DO - 10.1016/j.watres.2021.116962
M3 - Article
C2 - 33657493
AN - SCOPUS:85101636624
SN - 0043-1354
VL - 194
JO - Water Research
JF - Water Research
M1 - 116962
ER -