Temperature and De-icing Salt, Effect on the Activated Sludge Respiration

The respiratory activity of microorganisms in sewage sludge is affected by several physicochemical factors, and a considerable amount of information concerning the influence of individual factors has been recorded. However, very little is known about their effects in combination. In the recent past, the concentration of chlorides entering wastewater has increased greatly and the major source is sodium chloride, which is used in large quantities to de-ice roads in winter. In this article, the effects of various concentrations of sodium chloride at different temperatures on the respiratory activity of the micro-organisms have been examined. It is found that low temperature (6 degrees C) and high concentrations of NaCl (1 M) had drastic effects on the metabolism of the microorganisms in activated sludge; the acclimation phase of activated sludge is 117 h. Not only is their respiratory activity strongly depressed but also the length of their acclimation period is greatly magnified.