Viral Surrogates in Potable Reuse Applications: Evaluation of a Membrane Bioreactor and Full Advanced Treatment

This study employed quantitative polymerase chain reaction (qPCR) to evaluate the occurrence and removal of five microbial surrogates at two water reuse facilities. The surrogates were (1) the 16S rRNA gene; (2) the AllBac assay for Bacteroides; (3) the Bacteroides bacteriophage phi B124-14; (4) the Bacteroides bacteriophage phi crAssphage; and (5) the pepper mild mottle virus (PMMoV). Log removal values (LRVs) were quantified for a membrane bioreactor (MBR) and across a full advanced treatment (FAT) train. PMMoV, phi B124-14, and phi crAssphage were detected in the MBR feed at concentrations of approximately 10(3) gene x copies(gc)/mL, 10(5) gc/mL, and 10(6) gc/mL, respectively. Only PMMoV was above the limit of quantification (LoQ) in the MBR filtrate (25 +/- 8 gc/mL), resulting in a wide range of viral LRVs: 1.4 +/- 0.5 for PMMoV, >3.9 +/- 0.3 for phi B124-14, and >6.2 +/- 0.3 for phi crAssphage. All molecular targets were above the LoQ in the biologically treated FAT feed, but only the bacterial 16S rRNA gene was >LoQ after ozonation and biological activated carbon (BAC) and in the reverse osmosis (RO) concentrate. The gene was