Separation efficiency of air-cooled freeze crystallization in wastewater purification

Freeze crystallization has potential for numerous technical applications for example in production of fruit juice concentrates (freeze concentration) as well as in waste water purification. The present study evaluates the feasibility of air-cooled natural freezing to purify real wastewaters. In natural freeze crystallization pure ice layer is formed on the liquid surface and thus the contaminants are concentrated in the residual liquid. The composition of wastewaters can vary significantly; wastewater can contain varieties of contaminants with varying concentrations over time. Freeze separation process enables also purification of non-biodegradable and toxic waters in an energy efficient way without added chemicals. Within this experiment separation efficiency of freeze crystallization was studied with real wastewaters collected from municipal wastewater treatment plant and landfill site.