Removal of Enteric Viruses from Sewage by Activated Sludge Treatment

Abstract

The activated sludge process appears to be effective in removing at least 2 enteric viruses, and probably others, from sewage. Using a bench model activated sludge unit into which sewage and virus were fed for a 48-hour period, the treatment removed 90% of type I poliovirus when the unit was seeded with 400-4000 ppm of activated sludge. At a 600-1500 ppm seeding, it removed about 98% of Coxsackie A9 virus. Coliform removal averaged 97% and fecal streptococcus, 96%. Primary sewage treatment (settling) had no appreciable effect on virus during a 3-hour settling period, although some loss occurred during 6 to 24 hours of settling. It was also demonstrated that type I poliovirus was reduced by 60% when sewage and virus were mixed 6-7 hours in the unit wihtout activated sludge. Other experiments suggests that virus removal is an adsorption phenomenon and that the sludge-virus complex is extremely stable or that most adsorbed virus is in-activated in some way.