Evaluating the fate of bacterial indicators, viral indicators, and viruses in water resource recovery facilities

Abstract

A year-long sampling campaign at nine water resource recovery facilities (WRRFs) was conducted to assess the treatability and fate of bacterial indicators, viral indicators, and viruses. Influent concentrations of viral indicators (male-specific and somatic coliphages) and bacterial indicators (Escherichia coli and enterococci) remained relatively constant, typically varying by one order of magnitude over the course of the year. Annual average bacterial indicator reduction ranged from 4.0 to 6.7 logs, and annual average viral indicator reduction ranged from 1.6 to 5.4 logs. Bacterial and viral indicator reduction depended on the WRRF's treatment processes, and bacterial indicator reduction was greater than viral indicator reduction for many processes. Viral reduction (adenovirus 41, norovirus GI, and norovirus GII) was more similar to viral indicator reduction than bacterial indicator reduction. Overall, this work suggests that viral indicator reduction in WRRFs is variable and depends on specific unit processes. Moreover, for the same unit treatment process, viral indicator reduction and bacterial indicator reduction can vary. PRACTITIONER POINTS: A year-long sampling campaign was conducted at nine water resource recovery facilities (WRRFs). The treatability and fate of bacterial indicators, viral indicators, and viruses were assessed. Viral indicator reduction in WRRFs is variable and depends on specific unit processes. For the same unit treatment process, viral indicator reduction and bacterial indicator reduction can vary.

Keywords: coliphage; indicator; recreational water quality criteria; virus; wastewater.

Figure 1

Raw influent concentration of bacterial indicators, viral indicators, and viruses for WRRFs A through I (WRRFs G through I are plotted on different axes).

Figure 2

Box‐and‐whisker plots of indicator organism concentrations at each sampling location for WRRFs A through I. Boxplot range is the 25th–75th percentile. Whisker range is 1.5 × the interquartile range (IQR). Means are depicted with squares.

Figure 3

(a) Scatterplots for primary process indicator reduction as a function of primary effluent ammonia (WRRFs G, H, and I); (b) scatterplots for secondary process indicator reduction as a function of the MLSS (All WRRFs except C); and (c) scatterplots for secondary process indicator reduction as a function of the SRT (all WRRFs except C).

Figure 4

Bacterial and viral indicator disinfection reduction as a function of residual CT for chlorine (WRRFs D, E, G, H, and I) and applied CT PAA (WRRF F).

Figure 5

Box‐and‐whisker plots of enteric virus concentration (gene copies) at each sampling location for Facilities G through I. Boxplot range is the 25th–75th percentile. Whisker range is 1.5 × the interquartile range (IQR). Means are depicted with squares.