Microbial Aspects of the Inuvik Sewage Lagoon

A facultative sewage lagoon in Inuvik, N.W.T. was studied in August (ice free) and November (ice covered) 1984. Emphasis was placed on the microbiological aspects and their relation to lagoon performance. Analyses performed included, pH, total alkalinity, total solids, suspended solids, volatile solids, COD and BOD5 determinations. The microbiological tests included total plate counts (20°C) and psychrotrophic counts (1°C). Results indicated that the Inuvik sewage lagoon system achieved removal efficiencies, ranging from 90% BOD5 removal in summer to about 80% in winter. The total bacterial count was found to decrease in the liquid of the primary cells in the winter, but the bacterial count in the secondary cell was similar under both winter and summer conditions. No significant difference existed in bacterial counts in the sludge samples between primary and secondary cells. The total bacterial number decreased by one order of magnitude in the winter in sludges from all cells. A shift from mesophilic to psychrotrophic bacteria occurred in the winter. The percentage of psychrotrophs increased from less than 1% to over 80% with the change in season. The role of psychrotrophs in lagoon performance is discussed.