Microbiology of domestic wastes. II. A comparative study of the seasonal physiological activity of bacteria indigenous to a sewage lagoon

Abstract

A comparative study was made of the physiological activity of bacteria seasonally present in a sewage lagoon which experiences warm summers and very cold winters. Bacteria recovered from surface samples of lagoon water during summer were able to metabolize glucose, acetate, palmitate, creatinine, vitamin-free casamino acids, egg albumin, and urea aerobically at 25 °C, the highest prevailing temperature of the lagoon during summer. Under anaerobic conditions, acetate and palmitate were the only substrates not metabolized. Bacteria recovered from samples of lagoon water taken during winter were able to metabolize aerobically glucose, acetate, palmitate, creatinine, and urea at 2 °C, the prevailing temperature of lagoon water under ice cover, but casamino acids and egg albumin were not metabolized aerobically at 2 °C or 25 °C. Acetate, palmitate, casamino acids, and egg albumin were not metabolized anaerobically by bacteria in winter samples. Urea was hydrolyzed much more rapidly by bacteria in winter samples than by those present in summer samples and is probably the preferred nitrogen source for growth under winter conditions. The optimum pH for oxidation of acetate and casamino acids by bacteria in summer samples was 7.0; only 50% of the maximum activity was obtained at pH 9.0, virtually the highest pH that was found in the lagoon under natural conditions.The results show that bacteria active at low temperatures contribute appreciably to the stabilization of domestic wastes by the lagooning method even under severe winter conditions.