Comparative study of four microporous filters for concentrating viruses from drinking water

Our plain-English summary of Comparative study of four microporous filters for concentrating viruses from drinking water, by W. Jakubowski, W.F. Hill, N.A. Clarke (Applied Microbiology, 1975).

The study

• Authors: W. Jakubowski, W.F. Hill, N.A. Clarke
• Journal: Applied Microbiology
• Published: 1975;30(1):58-65
• Cited by: 37 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Four microporous virus-absorbent filter media for recovering low levels of virus from 380 liters of drinking water were compared. In addition two of the filter media were compared with 1,900 liters of drinking water. The filter media evaluated were MF nitrocellulose membranes (293 mm), AA Cox M-780 epoxy-fiberglass-asbestos disks (267 mm), K-27 yarn-wound fiberglass cartridges + AA Cox M-780 disks (127 mm), and Balston epoxy-fiberglass tubes (24.5 by 63.5 mm). The filters were used to concentrate seeded poliovirus from 380 liters of finished drinking water. Sodium thiosulfate was added to the drinking water to neutralize chlorine, and hydrochloric acid was added to adjust the pH to 3.5. Virus was eluted from the filters with glycine-NaOH buffer at pH 11.5. In terms of virus recovery efficiency, the filter media ranked Balston greater than Cox 267-mm greater than MF 293-mm congruent to K-27 + Cox 127-mm, but differences were slight. The Balston filters and holders were also superior to the other systems in terms of size, weight, cost, and handling factors. Experiments with 2- and 8-mum porosity Balston filters showed no statistically significant difference in virus recovery. Virus was readily detected by the Balston and the MF 293-mm systems at input levels of 12 to 22 PFU/1,900 liters. Preliminary experiments indicated that an elution pH lower than 11.5 may be satisfactory.

In plain English

This was a laboratory experiment comparing four microporous virus-adsorbent filter media for recovering poliovirus from finished drinking water; asbestos appears only as a filter material, not as a health exposure. Cincinnati tap water was conditioned with hydrochloric acid to pH 3.5 and sodium thiosulfate, seeded with attenuated poliovirus type 1 (LSc2ab), and passed through MF nitrocellulose membranes (293 mm), AA Cox M-780 epoxy-fiberglass-asbestos microfilters (267 mm), K-27 yarn-wound fiberglass cartridges plus Cox 127-mm disks, and Balston epoxy-fiberglass tubes. Virus was eluted with glycine-sodium hydroxide buffer at pH 11.5. Across 12 runs with 380-liter samples, mean recoveries were 30.9% (MF 293-mm), 45.3% (Balston) and 28.8% (K-27 plus Cox 127-mm); the Cox 267-mm mean of 39% came from only six of those runs, and the authors excluded it from the statistical analyses. Comparing 2- and 8-micrometre Balston filters gave no statistically significant difference. With 1,900-liter samples, both the MF 293-mm and Balston systems detected virus at inputs of 12 to 22 PFU. The authors concluded all systems could concentrate low levels of poliovirus, with the Balston system advantageous for size, weight, cost and handling.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Laboratory comparative experiment: four virus-adsorbent filter systems run simultaneously on seeded drinking water
• Who was studied: Not people: 380-liter and 1,900-liter volumes of Cincinnati finished tap water seeded with poliovirus, sampled over about 3 months; 12 comparative runs (Cox 267-mm included in only six of them) plus further trials (26 samples with MF 293-mm, 6 with Cox 267-mm, 31 with Balston, 12 with K-27 + Cox 127-mm)
• Exposure: Filter media tested, one of which contained asbestos: AA Cox M-780 epoxy-fiberglass-asbestos microfilters, alongside nitrocellulose membranes, yarn-wound fiberglass cartridges and borosilicate glass microfiber-epoxy tubes; water seeded with poliovirus type 1 LSc2ab
• Main results:
  • In the 380-liter comparison, mean virus recovery was 30.9% for MF 293-mm, 39% for Cox 267-mm, 45.3% for Balston and 28.8% for K-27 + Cox 127-mm; Table 2 lists 12 experiments, with the Cox 267-mm recorded in only six and 'not done' in the rest
  • The authors excluded the Cox 267-mm data from the statistical analyses because of the small number of experiments including it, but judged its efficiency intermediate between MF 293-mm and Balston
  • By the Wilcoxon matched-pairs test, Balston recovered significantly more virus (P less than 0.05) than MF 293-mm and than K-27 + Cox 127-mm; MF 293-mm versus K-27 + Cox 127-mm was not significant (P greater than 0.05)
  • Ranking of the four media for recovery efficiency, with the asbestos-containing Cox 267-mm disk second
  • Balston filters of 2- and 8-micrometre porosity: more virus recovered with 2-micrometre filters in 8 of 10 trials, but not statistically significant
  • With 1,900-liter samples, both MF 293-mm and Balston systems detected virus at inputs of 12 to 22 PFU per 1,900 liters (1 PFU per 86 to 158 liters)
  • Elution at pH 9.8 versus 11.5: MF 293-mm recovered more at pH 11.5 in each of four trials; Balston recovered more at pH 11.5 in two of four trials
  • Among the handling comparisons, the authors listed the asbestos-containing Cox 267-mm holder as the heaviest of the filter holders, while the Balston system had the lowest values for size, weight and cost
• The authors' conclusion: The authors concluded that all four systems could concentrate low levels of poliovirus from 380 liters or more of finished drinking water, that differences in recovery were slight, and that choice could rest on other factors, with the Balston system advantageous for size, weight, cost and handling
• Limitations the authors state:
  • The authors said the small number of experiments with the Cox 267-mm filter meant those data were left out of the analyses
  • The authors noted that random (Poisson) distribution of virus in the additive container could cause one system to receive more virus than another, and that variations in water quality could explain the wide range of recoveries
  • The authors said studies with other human enteric viruses are needed, as only poliovirus was tested

Related studies

• Detection of virus in water: sensitivity of the tentative standard method for drinking water — W.F. Hill, W. Jakubowski, et al. (1976)
• Modified membrane-filter procedure for concentration of enteroviruses from tap water — P.A. Shields, S.A. Berenfeld, et al. (1985)
• Efficiency of beef extract for the recovery of poliovirus from wastewater effluents — E.F. Landry, J.M. Vaughn, et al. (1978)
• Three potential sources of microfungi in a treated municipal water supply system in sub-tropical Australia — N.B. Sammon, K.M. Harrower, et al. (2011)
• Drinking water and cancer — K.P. Cantor (1997)
• Asbestos fibres in beverages and drinking water — H.M. Cunningham, R. Pontefract (1971)

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