Impacts of virus processing on human norovirus GI and GII persistence during disinfection of municipal secondary wastewater effluent

Abstract

Noroviruses cause significant global health burdens and waterborne transmission is a known exposure pathway. Chlorination is the most common method of disinfection for water and wastewater worldwide. The purpose of this study was to investigate the underlying causes for discrepancies in human norovirus (hNoV) resistance to free chlorine that have been previously published, and to assess hNoV GI and GII persistence during disinfection of municipal secondary wastewater (WW) effluent. Our results reveal that choice of hNoV purification methodology prior to seeding the viruses in an experimental water matrix influences disinfection outcomes in treatment studies. Common hNoV purification processes such as solvent extraction and 0.45-μm filtration were ineffective in removing high levels of organics introduced into water or wastewater samples when seeding norovirus positive stool. These methods resulted in experimental water matrices receiving an additional 190 mg/L as Cl of 15-s chlorine demand and approximately 440 mg/L as Cl of 30-min chlorine demand due to seeding norovirus positive stool at 1% w/v. These high organic loads impact experimental water chemistry and bias estimations of hNoV persistence. Advanced purification of norovirus positive stool using sucrose cushion ultracentrifugation and ultrafiltration reduced 15-s chlorine demands by 99% and TOC by 93% for loose (i.e. unformed diarrhea) stools. Using these methods, hNoV GI and GII persistence was investigated during free chlorination of municipal WW. A suite five of kinetic inactivation models was fit to viral reverse transcription-qPCR reduction data, and model predicted CT values for 1, 2, and 3 log reduction of hNoV GI in municipal WW by free chlorine were 0.3, 2.1, and 7.8 mg-min/L, respectively. Model predicted CT values for reduction of hNoV GII in WW were 0.4, 2.0, and 7.0 mg-min/L, respectively. These results indicate that current WW treatment plant disinfection practices employing free chlorine are likely protective for public health with regards to noroviruses, and will achieve at least 3-log reduction of hNoV GI and GII RNA despite previous reports of high hNoV resistance.

A review on detection of SARS-CoV-2 RNA in wastewater in light of the current knowledge of treatment process for removal of viral fragments

“…As a result of high volumes of dissolved NH 3 and organic matter (OM) in the wastewater, toxic residues called chloramines are produced, along with substitute derivatives for the disinfection treatment process; thus, causing ecotoxicological effects ( Luan et al, 2020 ; Verbyla and Mihelcic, 2015 ). The studies of Dunkin et al (2018) reported the reasons for the resistance of variable human noroviruses (hNoV) to free chlorine and examined the endurance of GI and GII fragments of hNoV at the time of disinfection of public wastewater effluent. As observed, prior to the cultivation of viruses in wastewater, the selection of the hNoV purification method assists in gaining significant disinfection outcomes.…”

“…As observed, prior to the cultivation of viruses in wastewater, the selection of the hNoV purification method assists in gaining significant disinfection outcomes. The tertiary wastewater treatment stage should employ free chlorine disinfection, which is beneficial for protecting public health from virus pollution ( Dunkin et al, 2018 ).…”

Regularized regression analysis for the prediction of virus inactivation efficiency by chloramine disinfection

“…At WWTPs, disinfection intensity, determined by some operational parameters in a disinfection reactor (e.g., contact time and initial concentration of the disinfectant), is suitable as a parameter at a CCP for monitoring because the log reduction value (LRV) of waterborne viruses is proportional to it. 12,13 Under the multiple barrier concepts, 14,15 CLs at a disinfection step must be determined in advance so that a target LRV is achieved. However, the fluctuation of wastewater quality affects the LRV in a disinfection process 13,16,17 because contaminants in wastewater consume disinfectants.…”

“…12,13 Under the multiple barrier concepts, 14,15 CLs at a disinfection step must be determined in advance so that a target LRV is achieved. However, the fluctuation of wastewater quality affects the LRV in a disinfection process 13,16,17 because contaminants in wastewater consume disinfectants. A method to determine the CL has not been developed, so a flexible prediction model of a virus LRV needs to be established to determine CLs based on water quality information as model variables, which enables WWTP operators to identify the disinfection intensity (e.g., disinfectant concentration and contact time) so as to achieve the target LRV.…”

Analysis of codon usage bias in the VP1 gene of the human norovirus GII.2 genotype

“…The challenge posed by these infections to global health is aggravated by factors such as immune-compromise and globalization of the food industry (4,5). The high diversity of genetic and antigenic noroviruses complicate the development of vaccines and therapies required to combat these challenges (6,7). Human norovirus belongs to the Caliciviridae family, and possesses a single-stranded positive-sense RNA genome (7.5 kb) with three open reading frames (ORFs) that encode different proteins (8).…”