Survival ofEnteroviruses andColiform Bacteria ina Sludge

viruses was followed during detention ofsludge inthelagoon andafter application ofsludge tolandfordisposal. Whiledigested sludge was being addedtothelagoon, enteroviruses were readily detected ingrabsamples of sludge fromthelagoon. Sludge-associated viruses dropped tolowor undetectable levels after disposal ofsludge on landandduring periods whenaddition of digested sludge tothelagoon was suspended. Changes inthelevels offecal coliforms inthelagooned sludge paralleled changes inthenumbersofenteroviruses.Enteroviruses were notdetected inwaterfromdeepwells located on the sludge disposal site or near thelagoon. Duringtheinitial partofthestudy, poliovirus serotypes accounted forgreater than90%oftheviruses identified. Later, poliovirus serotypes comprised less than40%ofthevirus isolates, and echoviruses andCoxsackieviruses were themostcommon enteroviruses identified. Wastewater treatment bytheactivated sludge process results intheproduction oflarge amounts ofexcess sludge. Thissludge maycontainparasitic helminth eggs, protozoan cysts, bacterial pathogens, andviruses (2, 9,11). Since anaerobic sludge digestion isnotsufficient for total virus inactivation (2, 6), thepossible spread ofviruses during disposal ofsludge mustbe considered. IntheUnitedStates, theWater Pollution Control Actof1972(PL92-500), as recently amended, requires acceptable methods fortheutilization anddisposal ofwastewater sludge. Amongthevarious altematives available, landapplication isanattractive oneinmany cases. Sludge disposal bylagooning amountsof 264,000 drytons(c.237,600 t)peryearwithin theUnited States (P.K.Bastian, unpublished data). Thisamountrepresents 4.5%ofthetotal sludge. However, sludge lagooning isatbesta temporary disposal methodsince thelagooned sludge isoften applied tolandfordisposal. Inthepresent study, thefate ofviruses associated withsludge during lagooning andafter disposal ofsludge onlandwasdetermined. Survival ofcoliform bacteria during lagooning was also followed.