Evaluation of dead-end hollowfiber ultrafilter options for enumerating somatic and F+ coliphage in ambient waters and wastewater

Coliphage are viral indicators of fecal contamination in water while acting as possible proxies for enteric viral pathogens. Depending on contamination levels, coliphage could be present at concentrations necessitating the use of concentrating filters. Hollow-fiber ultrafilters (HFUF) such as Asahi Kasei Rexeed have successfully concentrated coliphage in a dead-end setup (D-HFUF) from environmental waters and are recommended within United States Environmental Protection Agency (USEPA) Method 1642. Asahi Kasei Rexeed are not available within the United States, so replacement filters need to be identified. Additionally, coliphage methods lack recommendations for sample holding times to prevent variability in coliphage concentrations between sample collection and analysis. We compared HFUFs, the Fresenius F160NRE and the Elisio-15H, to the Asahi Kasei Rexeed 15S to determine their efficacy in recovering somatic and F+ coliphage from river, lake, marine, and wastewater. A 2 L volume of each matrix (river, lake, marine, and final effluent [n = 10 each]), were concentrated using D-HFUF for each filter brand with coliphage enumerated using the single agar layer (SAL) assay. There was no significant difference in performance between the three filters regardless of sample matrix (p > 0.05). To establish sample holding times, each water matrix (stored at 4ºC) was analyzed on a weekly basis for endogenous coliphage. In wastewater, significant decay occurred within 48 h of collection (P value range: 0.0175–0.0006), while in other matrices, coliphages were stable ≥ 6 days. In this study, we identified replacement HFUFs and pertinent information regarding sample holding times for coliphage monitoring efforts moving forward.