A multiple extraction–centrifugation method for the recovery of viruses from waste water treatment plant effluents and sludges

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Abstract
Absorption of 14C-labelled poliovirus-2 to sedimentable solids of primary sludge samples collected from a secondary treatment facility during a 6-month period averaged 94%; for anaerobically digested sludge, 99%. The extent of virus adsorption was influenced by the amount of solids. Maximal adsorption occurred at or above 0.5% solids with sludge diluted with deionized water and above 1.5% solids when diluted with the respective particle-free sludge supernatants. A Tris–HCl buffer containing NaCl, glycerol, and serum was found to efficiently elute poliovirus-2 from primary sludge solids. By means of re-extraction and concentration by centrifugation (the TEC procedure), the average recoveries of poliovirus-2 were 92–94% based upon either infectivity or radioactivity analyses. Similarly, recoveries were 90–92% for poliovirus-2 in digested sludge. Maximum elution was dependent upon all four TEC buffer components and the restriction of solids to≤ 1.0%. The procedure was found to be more efficient than glycine–NaOH and Freon procedures or elution with beef embryo extract. As adapted for effluents the procedure increased the yield and improved the consistency of virus recovery. The arithmetic mean titers obtained during a monitoring study for primary and digested sludge were 4.2 × 105 and 5.1 × 103 plaque-forming units (pfu)/L; for primary, secondary, and final effluents 2.3 × 105, 4.7 × 103, and 4.7 × 102 pfu/L, respectively.