Seasonal and diurnal surveillance of treated and untreated wastewater for human enteric viruses

Abstract

Understanding the abundance and fate of human viral pathogens in wastewater is essential when assessing the public health risks associated with wastewater discharge to the environment. Typically, however, the microbiological monitoring of wastewater is undertaken on an infrequent basis and peak discharge events may be missed leading to the misrepresentation of risk levels. To evaluate diurnal patterns in wastewater viral loading, we undertook 3-day sampling campaigns with bi-hourly sample collection over three seasons at three wastewater treatment plants. Untreated influent was collected at Ganol and secondary-treated effluent was sampled at Llanrwst and Betws-y-Coed (North Wales, UK). Our results confirmed the presence of human adenovirus (AdV), norovirus genotypes I and II (NoVGI and NoVGII) in both influent and effluent samples while sapovirus GI (SaVGI) was only detected in influent water. The AdV titre was high and relatively constant in all samples, whereas the NoVGI, NoVGII and SaVGI showed high concentrations during autumn and winter and low counts during the summer. Diurnal patterns were detected in pH and turbidity for some sampling periods; however, no such changes in viral titres were observed apart from slight fluctuations in the influent samples. Our findings suggest that viral particle number in wastewater is not affected by daily chemical fluctuations. Hence, a grab sample taken at any point during the day may be sufficient to enumerate the viral load of wastewater effluent within an order of magnitude while four samples a day are recommended for testing wastewater influent samples.

Occurrence of various viruses and recent evidence of SARS-CoV-2 in wastewater systems

“…Regarding seasonal changes, Farkas et al also found that AdV titres were high and relatively constant in different seasons. In contrast, high concentrations of NoV GI and GII and SaV GI titres were demonstrated in winter and fall, and low counts were observed in summer ( Farkas et al, 2018 ).…”

“…Although most studies have indicated that changes in the levels of viral pathogens in sewage over time are not governed by predictable rules ( Farkas et al, 2018 ), some studies have found that the levels of specific viral pathogens in sewage follow a pattern of imperceptible daily changes and obvious seasonal changes ( Abe et al, 2016 , Kitajima et al, 2018 ). Farkas et al detected diurnal patterns during sampling periods; however, obvious changes in viral titres were not found, apart from slight fluctuations in raw wastewater ( Farkas et al, 2018 ).…”

Surveillance of wastewater revealed peaks of SARS-CoV-2 preceding those of hospitalized patients with COVID-19

“…Wastewater based surveillance has been used to identify the spread of wild and vaccine derived polioviruses ( Asghar et al, 2014 ; Hovi et al, 2012 ; Shulman et al, 2014 ) . It may also provide early warnings on outbreaks of norovirus and hepatitis A in society ( Farkas et al, 2018 ; Hellmér et al, 2014 ). The excretion of SARS-CoV-2 in wastewater has so far, however, not been used to prospectively follow outbreaks by quantifying SARS-CoV-2 in consecutive wastewater samples for a longer period.…”

Passive Samplers, a Powerful Tool to Detect Viruses and Bacteria in Marine Coastal Areas

“…In these particular cases, passive sampling could improve the estimates made by point sampling or could substitute for composite samples. Composite samples have been suggested as an alternative to point sampling to improve the concentration estimates for enteric viruses as their concentration may vary during the same day, but this approach may be difficult to set up in the field ( Gerba et al, 2017 ; Farkas et al, 2018 ). Indeed, the main interest of our system is that it detected NoV during the whole autumn-winter season, whereas we did not detect the virus with point sampling although the sampling site was located downstream of the WWTP effluent outfall (data not shown).…”