This is a summary, written by members of the CITF Secretariat, of:

Hasing M, Yu J, Qiu Y, Maal-Bared R, Bhavanam S, Lee B, Hrudey S, Pang X. Comparison of detecting and quantitating SARS-CoV-2 in wastewater using moderate-speed centrifuged solids versus an ultrafiltration method. Water. 2021 Aug 6;13(16):2166. doi- https://doi.org/10.3390/w13162166

The results and/or conclusions contained in the research do not necessarily reflect the views of all CITF members.

A CITF-funded study, published in Water, reported the development and optimization of a method for SARS-CoV-2 detection in wastewater using moderate-speed centrifuged solids. This method was then compared to an ultrafiltration reference method for detection rate, cost, simplicity, and turnaround times. The study found that the moderate-speed centrifuge, solids-based method had similar sensitivity when compared to the ultrafiltration reference method and had the added advantages of lower costs, fewer processing steps, and a shorter turnaround time. The study was led by Dr. Xiaoli Pang (University of Alberta and Alberta Precision Laboratories)

SARS-CoV-2 was quantified in samples from 12 wastewater treatment plants in Alberta, using RT-qPCR targeting the N2 and E genes of the virus. The effects of using different amounts of solids, adjusting the sample pH to 9.6–10, and modifying the elutionElution is a process of extracting one material from another by washing it with a solvent volume at the final step of RNA extraction were evaluated.

Key findings:

  • Moderate speed centrifugation of 20 mL of wastewater to detect SARS-CoV-2 in solids revealed no statistically significant difference in detection rates compared to the ultrafiltration method.
  • The optimized wastewater solids-based method had a significantly lower rate of samples with PCR inhibitionProcess by which certain factors prevent the amplification of nucleic acids through the polymerase chain reaction (PCR) versus ultrafiltration (3% versus 9.5%). Lower PCR inhibition rates should translate to more accurate quantification of SARS-CoV-2 levels and higher virus detection rates.
  • The average cost per sample for the ultrafiltration method is $90 CAD. The solids-based method costs about half that amount, around $45 CAD.

Overall, the study identified that moderate-speed centrifuged solids are a reliable sample matrix for the detection of SARS-CoV-2 in wastewater. In terms of the detection rate, the optimized solids-based method performed comparably to the ultrafiltration reference method and had fewer processing steps, lower costs, and a shorter turnaround time. This work contributes to the development of improved detection methods for enveloped viruses in wastewater and provides an optimal alternative in settings with limited resources and equipment.