Method for determining virus inactivation during sludge treatment processes

Abstract

A simple and reliable method is described which allows determination of virus inactivation rates during sludge treatment processes in situ. Bacteriophage f2 was adsorbed onto an electropositive membrane filter which was then sandwiched between two polycarbonate membranes with pores smaller than the virus diameter. The resulting sandwich was fixed in an open filter holder, and several such devices were connected before being exposed in sludge-digesting tanks. The device described prevented uncontrolled virus escape, but allowed direct contact of the various inactivating or stabilizing substances present in the environment tested with the virus adsorbed to the carrier membrane. After exposure to an environment, the surviving fraction of virus was eluted from the inner filter and determined by plaque counting. By using polycarbonate membranes without pores for sandwiching, the influence of temperature alone on virus inactivation could be measured. Thermophilic fermentation at 60 degrees C and at 65 kPa pressure led to a bacteriophage f2 titer reduction of 3.5 log10 units per h, whereas during thermophilic digestion at 54.5 degrees C titers decreased 1.2 log10 units per h. During mesophilic digestion an inactivation rate of only 0.04 log10 units per h was observed. Under these latter conditions, temperature had only a minor effect (19%) on virus inactivation, whereas at 54.5 degrees C during thermophilic digestion heat accounted for 32% of the total inactivation, and during thermophilic fermentation at 60 degrees C temperature and pressure were 100% responsible for virus denaturation.

Full‐Scale Class A Biosolids Production by Two‐Stage Continuous‐Batch Thermophilic Anaerobic Digestion at the Hyperion Treatment Plant, Los Angeles, California

“…This is an important finding, because inactivated cells may be nonculturable during analysis (Gibbs et al, 1997;National Research Council, 2002) and hence be nondetectable, but still cause noncompliance with the Class A requirements after reactivation. Other factors that may potentially contribute to preventing the recurrence of fecal coliforms in postdigestion biosolids are the production of ammonia, VFAs, and possibly other compounds, such as proteases and antibiotics, by the indigenous thermophilic culture (Kato et al, 2001;Traub et al, 1986;Ward and Ashley, 1977;Ward et al, 1999).…”

Inactivation of animal viruses during sewage sludge treatment

“…Sandwich technique to determine virus inactivation during exposure in reactors. The method for monitoring virus inactivation during sludge treatment processes has been described previously (18). Briefly, the virus was adsorbed to an electropositively charged Zetapor filter membrane with a pore size of 200 nm (AMF, Cuno Div., Meriden, Conn.) sandwiched between two polycarbonate membranes (Nuclepore Corp., Pleasanton, Calif.) with pores of 15-nm size to prevent loss of virus.…”

“…Within the scope of a Swiss National Research Program we therefore examined the fate of human and animal viruses during various sludge treatment processes. The technique used had been established with bacteriophage f2 (18). In this study we tested a human rotavirus, as the most important causative agent of viral gastroenteritis in infants, and coxsackievirus B5, as a representative of the widespread enteroviruses.…”

Occurrence and levels of phages proposed as surrogate indicators of enteric viruses in different types of sludges

“…Information on bacteriophages in sludges is scarce. However, the data available indicate that they may be a useful tool with which to model the fate of human enteric viruses in sludges (Ohgaki et al 1986;Traub et al 1986;Williams et al 1988;Ketranakul and Ohgaki 1989;Ketranakul et al 1991). In addition, information on the elution of bacteriophages from either sludges or sediments is rare, although both kinds of eluants mentioned above have been used (Williams et al 1988;Jofre et al 1989;Ketranakul and Ohgaki 1989).…”