Metagenomic Analysis of Infectious F-Specific RNA Bacteriophage Strains in Wastewater Treatment and Disinfection Processes.

F-specific RNA bacteriophages (FRNAPHs) can be used to indicate water contamination and the fate of viruses in wastewater treatment plants (WWTPs). However, the occurrence of FRNAPH strains in WWTPs is relatively unknown, whereas FRNAPH genotypes (GI-GIV) are well documented. This study investigated the diversity of infectious FRNAPH strains in wastewater treatment and disinfection processes using cell culture combined with next-generation sequencing (integrated culture-NGS (IC-NGS)). A total of 32 infectious strains belonging to FRNAPH GI (nine strains), GI-JS (two strains), GII (nine strains), GIII (seven strains), and GIV (five strains) were detected in wastewater samples. The strains of FRNAPH GI and GII exhibited greater resistance to wastewater treatment than those of GIII. The IC-NGS results in the disinfected samples successfully reflected the infectivity of FRNAPHs by evaluating the relationship between IC-NGS results and the integrated culture-reverse-transcription polymerase chain reaction combined with the most probable number assay, which can detect infectious FRNAPH genotypes. The diversity of infectious FRNAPH strains in the disinfected samples indicates that certain strains are more resistant to chlorine (DL52, GI-JS; T72, GII) and ultraviolet (T72, GII) disinfection. It is possible that investigating these disinfectant-resistant strains could reveal effective mechanisms of viral disinfection.

Occurrence and reduction of F-specific RNA bacteriophage genotypes as indicators of human norovirus at a wastewater treatment plant.

F-specific RNA bacteriophages (FRNAPHs) have been suggested as good indicators of the presence of human enteric viruses in water treatment facilities. The occurrence and reduction of norovirus (NoV) and FRNAPH genotypes in wastewater treatment plants (WWTPs) have been well studied; however, the relationship between these genotypes in WWTPs has not been fully elucidated. Thus, we aimed to investigate the occurrence and reduction of FRNAPH genotypes in an attempt to identify NoV indicators in a WWTP via a 1-year survey. All FRNAPH and NoV genotypes were detected in WWTP influents at high rates (71-100%), including the infectious FRNAPH genotype IV (GIV), which has been rarely detected in previous studies. The reductions of FRNAPH GII and NoV GII during wastewater treatment indicated a relationship between the two (r = 0.69, P < 0.01), and the mean values were not significantly different. These results suggested that FRNAPH GII could be used as an appropriate indicator of NoV GII during wastewater treatment. FRNAPH GI was also found to be an appropriate indicator of viral reduction because of its high resistance to wastewater treatment compared with the other FRNAPH and NoV genotypes; therefore, it can be considered as a worst-case scenario organism.

Removal characteristics and fluctuation of norovirus in a pilot-plant by an ultrafiltration membrane for the reclamation of treated sewage.

When ultrafiltration (UF) membrane processes that are able to effectively reduce viruses are installed in a waste water reclamation system, the security of sanitation safety for water-borne diseases is essential. It is important to understand the behaviour of enteric viruses such as Adenovirus, Rotavirus and Norovirus (NV), the detection rate of which is relatively high in sewage. This study focused on the UF membrane process for the reclaimed water treatment process, and investigated the removal performance in NV type GI and GII in the UF membrane process by performing coagulation and sedimentation as the pre-treatment process in a pilot-plant by considering the concentration fluctuation of the influent. The removal ratio of GI and GII by the UF membrane process alone was 3.3 ± 0.7 Log in GI and 3.6 ± 1.0 Log in GII, and no clear difference in the removal ratio by NV species type was observed. The removal ratio of NV GII was increased by about 0.6 Log on average (4.2 ± 1.1 Log) compared with the UF membrane process only when the coagulation and sedimentation process were conducted as pre-treatment. However, there was no significant difference in the removal of NV GI by conducting the coagulation and sedimentation process.