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BalticSea2020 is funding two new projects to reduce eutrophication in the coastal bays of the Baltic Sea

To find alternative ways of reducing eutrophication in coastal bays, BalticSea2020 is launching two projects. “Permanent binding of phosphorus in the bottom sediments of the Baltic Sea” is being carried out at Stockholm University under the direction of associate professor Sven Blomqvist. At the Royal Institute of Technology (KTH), “Reactive sorbents for fixing of phosphorus in Baltic Sea bottoms” is being carried out under the direction of Professor Gunno Renman.

An effective way of dealing with eutrophication in the Baltic Sea may be to increase the -binding capacity of phosphorus to the bottom sediments. This capacity has been largely lost in recent decades as the bottoms have become anoxic, and phosphorus levels have increased in the bottom water. This is a key problem for the deeper areas of the Baltic Sea as a whole, but also for its coastal bays.

Permanent binding of phosphorus in the bottom sediments of the Baltic Sea
The project “Permanent binding of phosphorus in the bottom sediments of the Baltic Sea” is directed by Sven Blomqvist, an associate professor in the Department of Systems Ecology at Stockholm University. This project aims to develop a granular material that will permanently bind phosphorus in the bottom sediments of the Baltic, be cheap to produce, be based on waste products, and be harmless to the environment.

Waste products and by-products from industrial activity today are often dumped in landfill sites. On the island of Gotland this applies in particular to the lime industry. Other mining and quarrying industries, particularly metal extraction, also pass on various waste products and by-products to landfill.

- Waste products from the lime industry may have the potential to bind phosphorus in the anoxic environment that prevails in the bottom sediments, and the binding can probably become even more effective and long-term if the many properties of the lime material can be fully utilised, individually or in combination with other substances, says Blomqvist.

The project’s main focus is thus on examining waste products from the lime and mining industries, and how they can best be developed into a suitable granular material. The main by-products under investigation are marl, fine-particle limestone and red sludge, each of which, alone or in combination, could form a phosphorus-binding granular material that would strengthen the phosphorus-binding capacity of the bottom sediments in the coastal bays. Laboratory tests will follow, and, later, controlled field experiments. Cost-effectiveness will be evaluated as well as binding capacity.

The project will take one year to complete, starting in 2012.

Reactive sorbents for fixing of phosphorus in Baltic Sea bottoms
To find more phosphorus-binding substances, Gunno Renman at the Department of Land and Water Resources Engineering at the Royal Institute of Technology is studying whether reactive sorbents – compounds with a strong phosphorus-binding capacity – can be used to fix phosphorus in the bottom sediments of the Baltic Sea in the long term. The materials may be by-products from the steel industry and from concrete production, or may be entirely new products made from lime-rich rocks. Some such materials have already demonstrated significant phosphorus-binding capacity, and one that was developed a few years ago has been commercialised for use in private sewerage systems (Polonite®).

- The aim is to study the ability of the chosen reactive sorbents to bind phosphorus in the bottom sediments of the Baltic Sea in the long term and thus limit the release of phosphorus into the water. The idea is to create a barrier between sediment and water that will persist for a long time, says Renman.

Initial laboratory tests have investigated the phosphorus-binding capacity of the selected materials, and they are also assessed in terms of whether, for example, they are suitable for adding to sea bottoms. Binding experiments will be performed using sediments collected from anoxic and oxygenated bottoms. The lifetime of the reactive sorbents will also be studied, to see how long they continue to be effective before their ability to bind phosphorus declines or simply ceases.

The project will last one year (2012–2013).

- The hope with these projects is to find cost-effective products that can bind phosphorus on a large scale at reasonable cost in order to permanently bind phosphorus in the coastal zones of the Baltic Sea, says Conrad Stralka, executive director of BalticSea2020.

Read more about the projects on the Baltic2020 website

For further information, please contact:
Sven Blomqvist, associate professor at the Department of Systems Ecology of Stockholm University, telephone: +46 (0)8 16 42 60, or e-mail: sven.blomqvist@ecology.su.se.
Gunno Renman, Professor of Cultural Engineering, in particular Ecotechnology, at the Royal Institute of Technology (KTH), telephone: +46 (0)8 7906350, or e-mail: gunno@kth.se.