Release of contaminants from melting spray ice of industrial wastewaters

This study was carried out to investigate organic and inorganic contaminant removal from melting spray ice produced from aerated stabilization basin treated pulp mill wastewater and the oil sands tailings pond water. The influence of the feedwater characteristics and the ice column contaminant concentration and distribution patterns induced by the degree of freezing during the spraying on the release of impurities were examined. The contaminant separation efficiency was not significantly influenced by the characteristics of the wastewaters. A dramatic decrease of chemical oxygen demand, total organic carbon, conductivity, color (pulp mill effluent), and Cl- and SO42- (oil sands tailings pond water) concentration in the early meltwater occurred in all ice columns produced with drainwater formation during spraying. Most impurities entrapped within the ice columns had moved to the bottom of the columns, therefore a greater volume of high-quality meltwater was produced. Release of impurities from these ice columns was best described using a power equation. Reduction of meltwater impurity concentration was much slower when the impurities were distributed uniformly in the ice columns as occurred when no drainwater was produced during spraying. In this case, the decay of the meltwater impurity concentration was best predicted using an exponential function. Preferential release of one type of contaminant over others occurred under some experimental conditions.