(117a) Reversing Eutrophication with a Low-cost Chemisorbent – from Lab Research to Industrial Scale and Field Studies

The Baltic Sea suffers from a high phosphorus (P) load, which has led to severe eutrophication and the loss of aquatic life. P-removal is installed in many sewage water treatment stations around the Baltics, but there are large amounts of historic P in the seabed that is reactivated cyclically. Hence, a dynamic treatment is sought, and activated limestone¹ is a promising adsorbent to sequester mobile P in the seabed. The thermally activated limestone is produced from a cheap side product (marl) of the lime quarries. Here, we show that activated limestone can speed up the recovery of the Baltic Sea by binding P in to the sediment. The hypotheses are that the activation enhances the specific surface area and that this area is defining the action of the sorbents. The phosphate ions chemisorb on the calcium carbonate fraction or co-precipitate with a dissolving fraction of calcium hydroxide. We demonstrate that when activated limestone are prepared and used at the 30+ ton scale, it lowered the phosphate level in the deep water in a local bay in the Baltics significantly immediately after spreading. It should be noted that the use of marl, to produce the activated limestone, also reduced the amount of dumped marl on land, as this is commonly regarded as waste. The use of activated limestone could potentially lead to the revival of the Baltic Sea, benefiting the fishing, tourism, and limestone mining industries and creating new business opportunities. There are numerous other lakes, rivers, and arms of oceans that suffer from P-related eutrophication, where this approach could be relevant for remediation.

This project was initiated in 2012 by Assoc. Prof. Sven Blomqvist Stockholm University, (who unfortunately is no longer part of the project).

¹ SE1951309 (A1) ”Binding of phosphorus in the bottom sediment” Björkman, E., Person, H., Ekeroth, N., and Blomqvist, S.