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Impact of coagulation on SARS-CoV-2 and PMMoV viral signal in wastewater solids

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Nada Hegazy at University of Ottawa
Nada Hegazy
Xin Tian at University of Ottawa
Xin Tian
Patrick Marcel D'Aoust at University of Ottawa
Patrick Marcel D'Aoust
Lakshmi Pisharody at Indian Institute of Technology Bombay
Lakshmi Pisharody
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Wastewater surveillance (WWS) of SARS-CoV-2 has become a crucial tool for monitoring COVID-19 cases and outbreaks. Previous studies have indicated that SARS-CoV-2 RNA measurement from testing solid-rich primary sludge yields better sensitivity compared to testing wastewater influent. Furthermore, measurement of pepper mild mottle virus (PMMoV) signal in wastewater allows for precise normalization of SARS-CoV-2 viral signal based on solid content, enhancing disease prevalence tracking. However, despite the widespread adoption of WWS, a knowledge gap remains regarding the impact of ferric sulfate coagulation, commonly used in enhanced primary clarification, the initial stage of wastewater treatment where solids are sedimented and removed, on SARS-CoV-2 and PMMoV quantification in wastewater-based epidemiology. This study examines the effects of ferric sulfate addition, along with the associated pH reduction, on the measurement of SARS-CoV-2 and PMMoV viral measurements in wastewater primary clarified sludge through jar testing. Results show that the addition of Fe3+ concentrations in the conventional 0 to 60 mg/L range caused no effect on SARS-CoV-2 N1 and N2 gene region measurements in wastewater solids. However, elevated Fe3+ concentrations were shown to be associated with a statistically significant increase in PMMoV viral measurements in wastewater solids, which consequently resulted in the underestimation of PMMoV-normalized SARS-CoV-2 viral signal measurements (N1 and N2 copies/copies of PMMoV). The observed pH reduction from coagulant addition did not contribute to the increased PMMoV measurements, suggesting that this phenomenon arises from the partitioning of PMMoV viral particles into wastewater solids.
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Vol:.(1234567890)
Environmental Science and Pollution Research (2024) 31:5242–5253
https://doi.org/10.1007/s11356-023-31444-1
1 3
RESEARCH ARTICLE
Impact ofcoagulation onSARS‑CoV‑2 andPMMoV viral signal
inwastewater solids
NadaHegazy1· XinTian1· PatrickM.D’Aoust1· LakshmiPisharody1· SyedaTasneemTowhid1· ÉlisabethMercier1·
ZhihaoZhang1· ShenWan1· OceanThakali1· MdPervezKabir1· WantingFang1· TramB.Nguyen1·
NathanT.Ramsay1· AlexE.MacKenzie2· TysonE.Graber2· StéphanieGuilherme1· RobertDelatolla1
Received: 16 June 2023 / Accepted: 5 December 2023 / Published online: 19 December 2023
© The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature 2023
Abstract
Wastewater surveillance (WWS) of SARS-CoV-2 has become a crucial tool for monitoring COVID-19 cases and outbreaks.
Previous studies have indicated that SARS-CoV-2 RNA measurement from testing solid-rich primary sludge yields better
sensitivity compared to testing wastewater influent. Furthermore, measurement of pepper mild mottle virus (PMMoV) sig-
nal in wastewater allows for precise normalization of SARS-CoV-2 viral signal based on solid content, enhancing disease
prevalence tracking. However, despite the widespread adoption of WWS, a knowledge gap remains regarding the impact
of ferric sulfate coagulation, commonly used in enhanced primary clarification, the initial stage of wastewater treatment
where solids are sedimented and removed, on SARS-CoV-2 and PMMoV quantification in wastewater-based epidemiology.
This study examines the effects of ferric sulfate addition, along with the associated pH reduction, on the measurement of
SARS-CoV-2 and PMMoV viral measurements in wastewater primary clarified sludge through jar testing. Results show that
the addition of Fe3+ concentrations in the conventional 0 to 60mg/L range caused no effect on SARS-CoV-2 N1 and N2
gene region measurements in wastewater solids. However, elevated Fe3+ concentrations were shown to be associated with
a statistically significant increase in PMMoV viral measurements in wastewater solids, which consequently resulted in the
underestimation of PMMoV-normalized SARS-CoV-2 viral signal measurements (N1 and N2 copies/copies of PMMoV).
The observed pH reduction from coagulant addition did not contribute to the increased PMMoV measurements, suggesting
that this phenomenon arises from the partitioning of PMMoV viral particles into wastewater solids.
Keywords Coagulation· COVID-19· Epidemiology· Normalization· Partitioning
Introduction
Wastewater surveillance (WWS) efforts for monitoring
active COVID-19-positive cases are ongoing worldwide
and are playing a major role in the early detection of com-
munity outbreaks (Randazzo etal. 2020a; Bivins etal.
2020; Medema etal. 2020; Ahmed etal. 2020a; D’Aoust
etal. 2021a; La Rosa etal. 2021; McClary-Gutierrez etal.
2021; Zhao etal. 2022; Jiang etal. 2023). The utilization
of solids-based viral extraction protocols for SARS-CoV-2
(ESM Table(1A) in List of Abbreviations) detection in
wastewater has proven to be highly effective particularly
in samples with a high solids content, such as primary
sludge, raw wastewater influent, and municipal waste-
waters within sewer systems (Balboa etal. 2021; Peccia
etal. 2020; D’Aoust etal. 2021b; Graham etal. 2021;
Petala etal. 2021; Westhaus etal. 2021; Espinosa etal.
Responsible Editor: Lotfi Aleya
Highlights
• Effects of primary coagulation on SARS-CoV-2 and PMMoV
measurements are unknown.
• Fe3+ addition to 60mg/L had no effect on SARS-CoV-2 N1 and
N2 measurements.
• Fe3+ addition to 60mg/L elevated PMMoV measurements due
to enhanced liquid-to-solid partitioning.
• Fe3+ addition to 60mg/L underrepresents PMMoV-normalized
N1 and N2 measurements.
• pH change associated with Fe3+ addition did not contribute to
the elevation of PMMoV measurements.
* Robert Delatolla
Robert.Delatolla@uOttawa.ca
1 Department ofCivil Engineering, University ofOttawa,
Ottawa, ON, Canada
2 Children’s Hospital ofEastern Ontario Research Institute,
Ottawa, ON, Canada
Content courtesy of Springer Nature, terms of use apply. Rights reserved.
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