New Tech Simulates Winter To Purify Wastewater

Researchers are trying to perfect a quirky way to purify wastewater: freezing it.

When wastewater freezes, "it is purified through the formation of a cleaner layer of ice. Then the clean layer of ice can be removed from the rest of the wastewater, and the remaining wastewater is more concentrated, which can be treated as needed with a lot less outside processing. Energy is required only for breaking the ice and transporting it from the waste water pool," Science 2.0 reported.

Scientists at the Lappeenranta University of Technology in Finland are attempting to apply that method to purifying wastewater from mines. The wastewater is left to freeze in special pools, and the cleaner part is removed by breaking the ice. "Then the treated waste water would be recycled, or undergo further treatment using membrane filtration, reducing the amount of fresh water that is used," the report said.

"Equipment developed by LUT chemical technology researchers includes a winter simulator which makes it possible to study how the temperature of cooling air affects freezing. The simulator has been used to study the growth rate of the layer of ice that emerges, and the degree of purity when salt solutions of different concentrations are used," the report said.

Chemtech Professor Marjatta Louhi-Kultanen, a crystallization expert, explained the effort.

"We took samples of both the lake water and the ice and we examined the amount of impurities that they contained. The result was that the lake water contained about ten times more impurities than the ice. Another finding in the research was that the slower the layer of ice grows, the cleaner the ice is. Therefore, the purity of the ice is directly dependent on its rate of growth," Louhi-Kultanen said, per an announcement from the university.