Photoinactivation of virus on iron-oxide coated sand: enhancing inactivation in sunlit waters

Adsorption onto iron oxides can enhance the removal of waterborne viruses in constructed wetlands and soils. If reversible adsorption is not coupled with inactivation, however, infective viruses may be released when changes in solution conditions cause desorption. The goals of this study were to investigate the release of infective bacteriophages MS2 and Phi X174 (two human viral indicators) after adsorption onto an iron oxide coated sand (IOCS), and to promote viral inactivation by exploiting the photoreactive properties of the IOCS. The iron oxide coating greatly enhanced viral adsorption (adsorption densities up to similar to 10(9) infective viruses/g IOCS) onto the sand, but had no affect on infectivity. Viruses that were adsorbed onto IOCS under control conditions (pH 7.5, 10 mM Tris, 1250 mu S/cm) were released into solution in an infective state with increases in pH and humic acid concentrations. The exposure of IOCS-adsorbed MS2 to sunlight irradiation caused significant inactivation via a photocatalytic mechanism in both buffered solutions and in wastewater samples (4.9 log(10) and 3.3 log(10) inactivation after 24-h exposure, respectively). Unlike MS2, Phi X174 inactivation was not enhanced by photocatalysis. In summary, IOCS enhanced the separation of viruses from the water column, and additionally provided a photocatalytic mechanism to promote inactivation of one of the surrogates studied. These qualities make it an attractive option for improving viral control strategies in constructed wetlands. (C) 2012 Elsevier Ltd. All rights reserved

The utility of flow cytometry for potable reuse

Protecting public health from pathogens is critical when treating wastewater to drinking water standards (i.e., planned water reuse). Viruses are a principal concern, yet real-time monitoring strategies do not currently measure virus removal through reuse processes. Flow cytometry (FCM) has enabled rapid and sensitive bacteria monitoring in water treatment applications, but methods for virus and protozoa monitoring remain immature. We discuss recent advances in the FCM field and FCM applications for quantifying microorganisms in water. We focus on flow virometry (FVM) developments, as virus enumeration methods show promise for water reuse applications. Ultimately, we propose FVM for near real-time monitoring across treatment to more accurately validate virus particle removal and for pilot studies to characterize removal through understudied unit processes

Fate of the pathogen indicators phage phiX174 and Ascaris suum eggs during the production of struvite fertilizer from source-separated urine

Human urine has the potential to be a sustainable, locally and continuously available source of nutrients for agriculture. Phosphate can be efficiently recovered from human urine in the form of the mineral struvite (MgNH4PO4•6H2O). However, struvite formation may be coupled with the precipitation of other constituents present in urine including pathogens, pharmaceuticals, and heavy metals. To determine if struvite fertilizer presents a microbiological health risk to producers and end users, we characterized the fate of a human virus surrogate (phage ΦX174) and the eggs of the helminth Ascaris suum during a low-cost struvite recovery process. While the concentration of phages was similar in both the struvite and the urine, Ascaris eggs accumulated within the solid during the precipitation and filtration process. Subsequent air-drying of the struvite filter cake partially inactivated both microorganisms; however, viable Ascaris eggs and infective phages were still detected after several days of drying. The infectivity of both viruses and eggs was affected by the specific struvite drying conditions: higher inactivation generally occurred with increased air temperature and decreased relative humidity. On a log-log scale, phage inactivation increased linearly with decreasing moisture content of the struvite, while Ascaris inactivation occurred only after achieving a minimum moisture threshold. Sunlight exposure did not directly affect the infectivity of phages or Ascaris eggs in struvite cakes, though the resultant rise in temperature accelerated the drying of the struvite cake, which contributed to inactivation

Reproducibility and Sensitivity of Thirty-Six Methods to Quantify the SARS-CoV-2 Genetic Signal in Raw Wastewater: Findings from an Interlaboratory Methods Evaluation in the U.S.

In response to COVID-19, the international water community rapidly developed methods to quantify the SARS-CoV-2 genetic signal in untreated wastewater. Wastewater surveillance using such methods has the potential to complement clinical testing in assessing community health. This interlaboratory assessment evaluated the reproducibility and sensitivity of 36 standard operating procedures (SOPs), divided into eight method groups based on sample concentration approach and whether solids were removed. Two raw wastewater samples were collected in August 2020, amended with a matrix spike (betacoronavirus OC43), and distributed to 32 laboratories across the U.S. Replicate samples analyzed in accordance with the project\u27s quality assurance plan showed high reproducibility across the 36 SOPs: 80% of the recoverycorrected results fell within a band of ±1.15 log10 genome copies per L with higher reproducibility observed within a single SOP (standard deviation of 0.13 log10). The inclusion of a solids removal step and the selection of a concentration method did not show a clear, systematic impact on the recovery-corrected results. Other methodological variations (e.g., pasteurization, primer set selection, and use of RT-qPCR or RT-dPCR platforms) generally resulted in small differences compared to other sources of variability. These findings suggest that a variety of methods are capable of producing reproducible results, though the same SOP or laboratory should be selected to track SARS-CoV-2 trends at a given facility. The methods showed a 7 log10 range of recovery efficiency and limit of detection highlighting the importance of recovery correction and the need to consider method sensitivity when selecting methods for wastewater surveillance

A framework for using quantitative PCR as a non-culture based method to estimate virus infectivity

Measuring the efficiency of virus disinfection with quantitative PCR (qPCR) has been criticized as inadequate due to the production of false-positive signals. Such a claim, however, presupposes an understanding of the theoretical qPCR response. Many studies have assumed that the loss in qPCR signal upon disinfection should equal the loss in infectivity, without accounting for the fact that qPCR typically assays a fraction of the viral genome. This study aimed to develop a theoretical framework to relate viral infectivity with genome damage measured by qPCR. The framework quantified damage to the entire genome based on the qPCR amplification of smaller sections, assuming single-hit inactivation and a Poissonian distribution of damage. The framework was tested and modified using UV254 inactivation studies with bacteriophage MS2 (culturing and qPCR of approximately half the genome). Genome regions showed heterogeneous sensitivities to UV254 treatment, thus deviating from the assumption of Poissonian damage. We offered two modifications to account for these deviations, and confirmed that qPCR-based framework accurately estimated virus infectivity. This framework offers the potential to monitor the infectivity of viruses that remain non-culturable (norovirus). While developed for UV254-inactivated virus, the framework should apply to any disinfection technique that causes inactivation via single genomic lesions