The principle objective of this study was to evaluate the spray freezing process as a treatment alternative for industrial wastewater. It included the investigation of the ice nucleation characteristics of pulp mill effluent, piggery wastewater and oil sands tailings pond water droplets, the freezing behavior of freely suspended wastewater droplets and impurity rejection and concentration phenomena occurred in the freezing and melting process.

The laboratory experiments showed that wastewater droplets made from different wastewaters froze at different temperatures when they were tested under the same experimental conditions. When a water drop was freely suspended in the cold air, the freezing started at the bottom of the drop and then spread over the entire surface enveloping the drop in an ice shell. The freezing temperature of a droplet was influenced by the nature of the wastewater, the ambient air temperature, the droplet size, the impurity concentration and the pH of the wastewater.

When wastewater was sprayed into a cold atmosphere, the contaminants in the wastewater were rejected by the growing ice crystals and were concentrated in the liquid phase as part of the sprayed water froze. The unfrozen water generated in the spray freezing process could carry away more than 50% of the impurities in the source water from the ice mound. The spray ice impurity concentration could be predicted by a mathematical model based on the mass balance of the impurity in the continuous spray freezing process.

Impurities remained in the spray ice would redistribute and were concentrated in the early meltwater. Experimental results indicated that the fractionation of impurities from melting ice column was affected by the nature of the wastewater, the impurity concentration in the spray ice, the age of the ice (or storage time), the distribution of the impurities within the ice column and the ice column density. The initial 30% of the meltwater removed between 50% and 80% of the total impurities (indicated by TOC, COD, color, conductivity, Cl⁻ − and SO²⁻₄ concentrations) in the ice columns. The meltwater impurity concentration can be predicted using empirical equations.