Good bad phosphorus Phosphorus is an essential structural component in almost every forms of life. In human body phosphorus is needed all the way from cell and bones formation to energy production (1). So how something so essential to us can also be dangerous? Well, in natural phosphorus cycle plant captures phosphorus as a nutrient from soil then insect or algae eats the plant. After this animal consumes insects and algae as nutrient and eventually animal dies and its body and phosphorus in the body decomposes back to soil. But modern agriculture is another story… Phosphorus in agriculture The problems with phosphorus appear when phosphorus is mined and used as a fertilizer in order to guarantee good crop which can feed our growing population. From soil phosphorus leaches to river and lake waters due to over use and rains. This leads to growth of algae population that used to be limited by lack of this nutrient. Even though algae is just as important in the food chain as phosphorus, when its population grows oxygen consumption in the water raises hand in hand with it. Lack of oxygen leads to fish mortality (2). The beautiful irony in the fact that we destroy our food resources, at the same time as we are trying to make it bigger has been troubling minds of scientist and engineers for a while. Luckily answer have been also found. Collecting phosphorus with Päästösieppari (Discharge catcher) Phosphorus has been collected from our waste water in treatment plants for tens of years already by making water dissolved phosphorus form precipitate in reaction with ferric sulphate. But collecting it from lakes with tolerable costs has been much trickier. 1.8.2012 Project RAKI was started in order to decrease amount of phosphorus in lake waters. Just like in water treatment plants, Päästösieppari (discharge catcher) is mainly based on sedimentation reaction between ferric sulphate and phosphorus. In All-season chemical feeding picture (below) you can see the whole process of eutrophicated water turning back into natural water and valuable phosphorus turning into sludge that we can re-use in farming again. And all this is powered by gravity (3). Results and future
The results from RAKI project have been successful. Reduction of dissolved phosphorus has been excellent medians from two lakes has been 94,8% and 85,2%. Nutrient rich sludge that comes as a ‘’side product’’ of cleaning the lake is not capable in competing with commercial fertilizers but when phosphorus mines of our planet start to dry out recycled phosphorus comes more and more valuable (4). References
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May 2019
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