News

New natural freezing method offers energy savings in water purification

Freezing winter temperatures can be put to good use in improving the cost and energy efficiency of wastewater purification.

The ice that is formed when wastewater freezes naturally in the winter is cleaner than the residual waste water itself. The purity of the ice is a function of the rate of the freezing process: the slower the freezing process, the greater the purity of the resulting ice. Research is underway under the Academy of Finland’s Arctic Research Programme to develop sustainable working methods that are suited to the unique and fragile Arctic environment.

Associate professor of Chemical Engineering Marjatta Louhi-Kultanen is running a research project aimed at developing energy-efficient methods of wastewater purification by taking advantage of seasonal temperature variations and natural water freezing.

The process of freezing wastewater requires no additional energy input in the winter. The ice layer is mechanically removed from the residual wastewater, which then becomes more concentrated. Energy is only required for breaking and transporting the frozen wastewater.

Contaminants in the ice samples collected in both laboratory conditions and natural winter conditions were well below environmental permit standards. Contaminant levels in ice samples extracted from mine water reservoirs were up to 65–90 per cent lower than in the mine water itself. The results indicate that natural freezing is a particularly effective method for purifying large volumes of weak aqueous solutions.

“Although the mine ice was clearly purer than the mine water, its measured mechanical strength values were clearly lower than those of clean lake water. The mechanical collection of ice from mines would therefore not require expensive special equipment,” says Dr Mikko Suominen from the Aalto University research team studying marine and Arctic technology.

The research project has also used a winter simulator that makes it possible to adjust and fine-tune the freezing process by controlling aqueous solutions and the temperature and velocity of cooling air. It is important to have an in-depth knowledge of the strength and other mechanical properties of ice so that the process of ice collection can be optimised. The results of the research have important application in developing systems for breaking and collecting ice.

The project is a joint effort of teams from Aalto University and Lappeenranta University of Technology. Their key areas of focus include freezing kinetics, mathematical modelling and the development of mechanical processes, such as breaking, analysing, collecting and transporting ice. Furthermore, they have applied the tested purification method to both landfill waters and municipal wastewater. Tests have also been carried out on mine water reservoirs in Sotkamo, in two peat bog areas and on the ice on Lake Saimaa.

Inquiries and more information:

Marjatta Louhi-Kultanen, Aalto University
[email protected], tel. +35850 324 5780

Mikko Suominen, Aalto University
[email protected], tel. +35850 433 1338

 

On 6–7 June 2018 the Academy of Finland will be hosting an international conference on the topical theme of “Emerging Pollutants in Freshwater Ecosystems” as part of the European Water JPI network. The Helsinki conference will be attended by more than 200 researchers, decision-makers and partners in the field. During the two days of the conference, keynote lectures and presentations will be held among others on the hazardous pollutants threatening our drinking water and on how chemicals and pesticides, for instance, enter the water cycle. The effects of pollutants on the ecosystem and human health as well as new methods for monitoring and preventing pollutants are also included in the programme. www.aka.fi/waterjpi2018 – www.aka.fi/arktiko

 

  • Published:
  • Updated:
Share
URL copied!

Read more news

Future Digital Mobility Management
Research & Art Published:

Do you drive a car in metropolitan area? Come and test how to make motoring routes smoother and safer.

During the autumn, an international Code the Streets pilot will be implemented in metropolitan area, where motorists will be offered alternative driving routes with a navigator. We are now looking for testers for the navigation app who have an Android phone.
Ths picture shows Assistant Professor Ciprian Domnisoru and Professor, Nobel Laureate David Card.
Research & Art Published:

Research co-operation with a Nobel Laureate

According to Assistant Professor Ciprian Domnisoru, David Card is a meticulous, hard-working, kind, and fun co-author who often uses a Finnish painting as his Zoom background.
Speaker photos of How to win with platform strategy with Tero Ojanperä, Bengt Holmström, Timo Vuori, Maija Hovila, Matias Järnefelt, Michael Tushman
Research & Art Published:

Recording and Q&A now available from the Platform Strategy Seminar 5 October, 2021

The Aalto University seminar "How to Win with Platform Strategy" with top experts from MIT, Harvard, Aalto University, and industry took place on 5 October, 2021 both online and onsite at Aalto campus in Espoo. On this page you can find the recording of the event and Q&A.
Kimchi and Chips
Research & Art Published:

Artist talk: Kimchi and Chips

We are pleased to welcome you to an artist talk by Kimchi and Chips!