Factors affecting salmonellae repopulation in composted sludges

The repopulation potential and recovery of Salmonella sp. and their close relatives Arizona spp. and Citrobacter spp. in sewage sludge which had been composted was examined. Salmonellae growth in previously composted sludge was found to occur in the mesophilic temperature range (20 to 40 degrees c), require a moisture content of greater than or equal to 20%, and require a carbon/nitrogen ratio in excess of 15:1.