Poliovirus inactivation by activated sludge.

Abstract

Enteric virus iNACTivATiON during the treatment of municipal wastewater by the activated sludge process has been re ported extensively in the literature.16 Carl son et aV used polio virus in the form of a suspension of infected mouse cords and brains to inoculate a batch activated sludge system and found that, after 6 hr of aera tion, the virus was removed or inactivated to a point at which infectivity for mice was greatly reduced. Clarke et al.6 showed that the removal of Coxsackie A-9 virus in a batch activated sludge system conformed to the Freundlich isotherm, and they al luded to adsorption as the mechanism of removal. Because all infective virus par ticles could not be recovered from the sludge, however, they suggested the possi bility of the toxic effects of municipal waste water on enteric viruses. Kelly et al.3 re ported that the removal of enteric virus by activated sludge was effective only under aerobic conditions. However, Flavobac terium, Klebsiella, Aerobactor, and other coliform strains that were capable of rapid poliovirus inactivation were isolated from the activated sludge.3 Cliver and Herr mann 8 reported that some enteroviruses are susceptible to proteolytic enzymes, but, of the eight enzymes tested, none had a sig nificant effect on poliovirus-1. The results of experiments to characterize the antiviral action of P. aeruginosa against Coxsackie A-9 indicated that the inactivation was rapid, viral protein was incorporated into cells, and the nucleic acid was not suf ficiently degraded to be used by the cells.8 The poliovirus-1 and P. aeruginosa system confirmed the above results. Higher microbial forms also affect virus survival. Nematodes and ciliates ingested picornavirus, which is digested within an hour.9 Chang and Kabler 10 observed sig nificant numbers of nematodes in the efflu ents from aerobic treatment units. The activated sludge is a complex biological mass with a considerable population of ciliates. Therefore, one of the mechanisms of enteric virus inactivation may be the ingestion and subsequent degradation by protozoans. In summary, activated sludge has been found to reduce the infective virus titer in the wastewater, but the ultimate fate of the removed viruses has not been clearly de fined. The results of the experiments of Kelly et al.,3 Cliver and Herrmann,8 and Chang ? indicate that the activated sludge could permanently inactivate the adsorbed enteric virus. The objective of the investi gation reported herein was the evaluation of the permanent inactivation of virus in the activated sludge process. Activated sludge was inoculated with tritium-labeled polio virus ( Mahoney ) in batch reactors, and the fate of the virus was followed by tracing the radioactive label and infectivity with time.