Diurnal changes in pathogenic and indicator virus concentrations in wastewater

Area of Science:

• Environmental microbiology
• Public health surveillance
• Virology

Background:

• Wastewater-based epidemiology (WBE) is crucial for monitoring infectious diseases like SARS-CoV-2.
• Understanding diurnal variations in viral load is essential for accurate WBE.
• Standard sampling methods (grab vs. composite) can influence WBE data.

Purpose of the Study:

• To investigate diurnal patterns of SARS-CoV-2 and crAssphage in wastewater.
• To evaluate the efficacy of passive sampling materials for WBE.
• To assess the impact of sampling location and time on WBE data accuracy.

Main Methods:

• Hourly collection of untreated wastewater samples over 4 days at two Welsh treatment plants.
• Deployment of three passive sampling materials (tampons, filter paper, gauze swabs).
• Quantification of SARS-CoV-2 and crAssphage using molecular methods; measurement of physico-chemical parameters.

Main Results:

• No significant diurnal variations were observed for SARS-CoV-2, crAssphage, ammonium, or orthophosphate.
• Grab samples from influent tanks showed less variability than influent stream samples.
• Tampons demonstrated higher viral recovery compared to other passive sampling materials.

Conclusions:

• Grab samples from wastewater influent tanks can be representative of 24-hour composite samples, reducing WBE costs.
• Passive sampling using tampons is a viable, cost-efficient method for WBE, though optimization is needed.
• WBE programs can benefit from simplified sampling strategies without compromising data representativeness.