Survival of S. Typhi in Sewage Oxidation Ponds

Tests indicate that Salmonella typhi survive for longer periods in anaerobic than in facultative lagoons. Laboratory tests on the survival of Salmonella typhi were made in several columns, some of which simulated conditions in anaerobic lagoons, other facultative (or aerobic) lagoons. Lagoons which were in use were used as a source of test media to fill the columns. During the tests on the facultative columns, daily additions of sterile settled sewage were made at a biochemical oxygen demand (BOD) loading of 50 lb per acre per day. Nutrient addition continued after inoculation with Salmonella typhi. The anaerobic column loadings were varied from 500 lb to 6,000 lb of BOD per day, by addition of sterile raw sludge. After inoculation of these columns with Salmonella typhi no further nutrient was added. Survival in the facultative case (low loadings) was of the order of 30 hr. Survival time in the anaerobic columns increased with increases in initial (or interim) loadings to 4,000 lb of BOD per acre per day. Preliminary tests using Serratia Marcescens as an indicator organism in place of Salmonella typhi were unsuccessful. Bismuth sulphite agar proved suitable as a differential media for enumeration of Salmonella typhi in sewage lagoons.