Journal of Cold Regions Engineering

LOW temperature has significant effects on many processes of water and wastewater treatment systems. Practically all operations and processes are affected by low temperature through viscosity changes in the water or changes in chemical or biochemical reaction rates. In the arctic regions, temperatures of most water sources are below 4 °C and frequently at or near 0 °C and wastewater temperatures are low. Such low temperature conditions call for adjustments in design, construction, operation, and maintenance of water and wastewater systems, to those adopted in temperate climates. Thus, a knowledge of the effects of low temperature on various unit processes becomes important for a proper design and operation of these treatment systems. A review of literature on the low temperature effects on the performance of aeration, sedimentation, filtration, disinfection, and the removal of chlorination byproducts such as trihalomethanes through water treatment systems is presented briefly. The review also includes low temperature effects on gas transfer, sedimentation, ozonation, and adsorption in wastewater treatment.

The depth of frost and ground temperatures were monitored on a regular basis between 1983 and 1985 at 12 locations in Tumbler Ridge, British Columbia. The soil is dry gravel which has a moisture content of 1.5 to 4%. The maximum depth of frost recorded was 3.98 m for a winter having 1,430 ° C‐days. Back calculation using the Stefan equation yielded n factors relating air and ground freezing indices to be generally within the range of those quoted in the literature. However, in heavily traveled cleared roadways, the value of n was higher than that reported in the literature. Values of unfrozen thermal diffusivity were calculated from both the temperature dissipation with depth and the time lag that the maximum temperature was recorded with depth. The results of these analyses compare well with typical values quoted in the literature for dry gravel.

Fiber composites are an attractive class of materials for construction in the remote and desolate terrains of cold regions and the Arctic. Data on the cold weather performance of these materials is sparse. High residual stresses occur in composites at low temperatures because of large differences in coefficients of thermal expansion of the constituent elements. Results of cold and cold thermal cycling on a number of composite materials are presented. Results have shown strength degradation at low temperatures for unidirectional composites. Low temperature thermal cycling degraded the strength when the fibers were oriented off‐axis. These changes at low temperatures must be considered in designing with composite materials in cold regions.