Characterization of virucidal agents in activated sludge

Abstract

A comprehensive study was carried out to determine the properties of agents responsible for loss of virus infectivity in mixed-liquor suspended solids (MLSS) of activated sludge. Initial experiments revealed that model enteric viruses (poliovirus-1 and rotavirus SA-li) were irreversibly inactivated in MLSS and released their RNA genomes. Enteric viruses belonging to other genera (echovirus-12, coxsackievirus A13, reovirus-3) were also shown to lose infectivity in MLSS. Although the virucidal activity decreased at reduced temperatures, MLSS still retained significant activity at 4°C. The virucidal agents in MLSS were stable for months at 4°C, but their activity decreased approximately 50% during 4 days of aeration at 26°C. Primary effluent, the nutrient source for activated sludge, also contained virucidal activity. After centrifugation of MLSS, almost all virucidal activity was found in the particulate fraction because of inhibitory substances retained in the supernatant fraction. Decreasing or increasing the solids concentration of the particulate fraction did not increase the virucidal activity of the fraction. The effects of heat and antibiotics on the virucidal activity of MLSS, coupled with the finding that the activity can be produced in autoclaved primary effluent seeded with MLSS, strongly support the conclusion that microorganisms are responsible for this activity. Attempts to characterize the virucidal microbial components of MLSS indicated that treatments that resulted in the inactivation or removal of microorganisms also caused a loss of virucidal activity. Thus, it appears that the virucidal components of microorganisms are either short-lived or active only while bound to the organisms themselves.

An Antiviral Agent (46NW-04A) Produced byPseudomonassp. and Its Activity against Fish Viruses

“…This finding suggests the possibility that the antiviral activity observed in aquatic ecosystems may be due to the production of low-molecular-weight substances. The antiviral substance 46NW-04A described in this report was different from the proteolytic enzymes described by Ward et al (1986) and Knowlton and Ward (1987) because 46NW-04A has a molecular weight of 1,126. Negative ninhydrin reaction suggested that 46NW-04A was a peptide blocked in its N-terminal residues.…”

“…However, there have been no reports on antiviral substances actually isolated and characterized from microorganisms indigenous to aquatic environments. Several investigators have suggested that the causative agent of viral inactivation was proteolytic bacterial enzymes (Toranzo et al 1982(Toranzo et al , 1983Ward et al 1986;Knowlton and Ward 1987), but few compounds with antiviral action have been isolated from microorganisms in aquatic environments. Most reports are limited to antibiotics active against bacteria or fungi (Rosenfeld and Zobell 1947;Grein and Meyers 1958;Burkholder et al 1966;Doggett 1968;Ballester et al 1977;Wratten et al 1977;Lemos et al 1985).…”

“…This antiviral activity seemed to be related to microorganisms inherent in these environments (Magnusson et al 1967;Fujioka et al 1980;Toranzo et al 1982Toranzo et al , 1983Ward 1982;Ward et al 1986;Knowlton and Ward 1987). It has been reported that this inactivation was caused by proteolytic enzymes produced by bacteria (Cliver and Herrmann 1972;Toranzo et al 1982Toranzo et al , 1983Ward et al 1986;Knowlton and Ward 1987). These proteolytic enzymes were not characterized or isolated from the bacteria, although some properties were studied by heat treatment, dialysis, and release by solubilizing agents.…”

Ammonia as an In Situ Sanitizer: Influence of Virus Genome Type on Inactivation

“…Furthermore, the water content of sludge can be an important parameter, as it determines the mobility and concentration of inactivating or protective agents, and water evaporation itself can lead to virus inactivation during the dewatering process (90)(91)(92). Finally, microbial or related enzyme activity may also enhance inactivation during sludge digestion (93)(94)(95)(96).…”

Inactivation of animal viruses during sewage sludge treatment

“…The viruses tested here can be grouped into thermolabile viruses that are comparatively chemoresistant (rotaviruses, enteroviruses) and thermostable viruses that are chemolabile (parvoviruses). In this connection chemoresistance means that viruses are relatively insensitive to chemical factors such as ammonia and detergents (19)(20)(21) or to microbial factors (10) present in the sludge.…”