[Studies on the dynamics of Salmonella organisms in raw sewage treatment plants].

The dynamics of Salmonella organisms in raw sewage treatment plants was studied over a period from July 1987 to August 1989. An experiment where Salmonella ser. Havana NAr was introduced into raw sewage was also performed over 2 days during this period. The results are as follows. 1) A number of strains of Salmonella could be isolated usually from samples drawn from raw sewage influent and up to the activated sludge stage of sewage processing. 2) After Salmonella ser. Havana NAr was introduced into raw sewage, the number of the organisms decreased in the activated sludge process to 1/1000 and the organisms were not found in the treatment plants after about forty days. 3) These results suggest that Salmonellas are adsorbed to activated sludge or other sludges, and are not discharged into rivers from this treatment plant. 4) The possibility of being able to determine the strain of Salmonella in regional epidemics by serovars of Salmonella detected in raw sewage treatment plants was suggested.