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Internationally recognised waste-water research on the precipitation of phosphorus



"The precipitation of phosphorus is important for two reasons: phosphorus accelerates the eutrophication of waterways and is also a non-renewable resource that, once it has dissolved into the waters, is not easily recovered," Toivakainen crystallises.

Why, then, is phosphorus so important that so much attention is suddenly being paid to its depletion?

"Phosphorus is the number one fertiliser of agriculture. Intensive farming would be impossible without fertilisers containing phosphorus."

In the photo Sakari Toivakainen presents the equipment he uses in laboratory conditions that enables the modelling of a waste water treatment plant at a pulp mill in six basins simultaneously.

"One of my most essential findings is that the amount of phosphorus added as a nutrient at the waste water treatment plant at the pulp mill is larger than necessary. The amount of phosphorus coming to the waste water treatment plant in timber alone is vast," Toivakainen sums up.

Towards more efficient processing of waste water

Toivakainen has considered the existing waste water treatment process in pulp mills from a more comprehensive perspective. According to him, the whole operating principle of the waste water treatment plant must be rethought in terms of energy consumption and the efficiency of the treatment process. The current plants were designed for pulp mills in the 1980s, a time when energy was cheaply available.

"The aeration time is long, which consumes huge amounts of energy. At the time, the aim was to create a waste water treatment plant that functions as efficiently as possible, which meant that the basins were scaled rather large."

Improvements regarding environmental performance and energy consumption can be made without adding new treatment stages.

"In the context of my research, it all started with phosphorus, as the emission limits have become increasingly stringent. Finland is an inland waterway area where eutrophication poses a significant problem.

Researcher almost by accident

 Toivakainen ended up as a researcher almost by accident. The topic of his Master’s thesis seemed to have a life of its own, and the research work continued after graduation. Already in his Master’s thesis he had focused on improving the efficiency of the biological waste water treatment process at a pulp mill. He expects to gain his doctorate a couple of years from now.

"Turning my back on the research just wasn’t an option, so I had to stick with it," comments the doctoral candidate.

Read more about Toivakainen’s successful conference presentation and waste water treatment at the pulp mill in the June edition of Water21, the magazine of the International Water Association.

Further information on the research:

Sakari Toivakainen, M.Sc. (tech.), firstname.lastname(at)

Clean Technologies Research Group



The waste water treatment plant is modelled using pilot equipment, after which tests can be carried out in full scale at the waste water treatment plant in the pulp mill.




Page content by: verkkotoimitus [at] aalto [dot] fi | Last updated: 21.02.2014.