Natural freeze concentration of wastewater for nutrient recovery

Abstract

Water and food are vital needs for all humans and animals living on the earth, and intensive crop cultivation that requires plentiful nutrients and water has evolved to meet food production demands. As population grows and the supply of raw material nutrient deposits and clean water begin to run out, effective recycling becomes increasingly important. However, recovering nutrients from urban waste streams is not yet technically or economically feasible. New energy efficient separation technologies are needed to meet the demand. Making use of the colder climates of polar regions is an opportunity to achieve a more efficient and economical transition to a circular economy. Hence, this study focuses on a natural cold-climate freeze concentration technique that enables the recovery of both water and material concurrently in a single process.Experiments were carried out in a winter simulator device using various waste streams originating from landfill and a biogas production plant. Average partition coefficients between 1.5 and 3 for the concentrates and 0.08 and 0.4 for the ice were achieved for different concentrate mass yields with different water quality measures, essential ions, and elements, including harmful metals. These results confirm that freeze concentration is a potential option when developing new technologies that combine water and material reclamation from wastewater towards sustainable circularity.