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.
Highlights
Responsible editor: Diane PurchaseThe combination of population growth and increased urbanisation has led to the progressive contamination of water environments with microbial pollutants (Jung et al 2014)
Understanding the microbial quality of treated and untreated wastewater is essential for Environ Sci Pollut Res (2018) 25:33391–33401 understanding and predicting the impact of wastewater discharge on the environment and public health and for the design of effective legislation aimed at mitigating these risks
While the treated wastewater from the Ganol wastewater treatment plants (WWTPs) is discharged to the open sea, its combined sewer overflows (CSOs) discharge to the Conwy estuary during heavy rainfall events (Fig. 1)
Summary
The combination of population growth and increased urbanisation has led to the progressive contamination of water environments with microbial pollutants (Jung et al 2014). This has increased the risk of human infection and illness associated with the consumption of contaminated drinking water, foodstuffs (e.g. shellfish, salad vegetables) and the pursuit of recreational activities (e.g. bathing). Understanding the microbial quality of treated and untreated wastewater is essential for Environ Sci Pollut Res (2018) 25:33391–33401 understanding and predicting the impact of wastewater discharge on the environment and public health and for the design of effective legislation aimed at mitigating these risks
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