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Conversion of dissolved phosphorus in runoff by ferric sulfate to a form less available to algae: Field performance and cost assessment
- Uusitalo, Risto, Närvänen, Aaro, Kaseva, Antti, Launto-Tiuttu, Aino, Heikkinen, Janne, Joki-Heiskala, Päivi, Rasa, Kimmo, Salo, Tapio
- Ambio 2015 v.44 no.Supplement 2 pp. 286-296
- algae, cost analysis, cost effectiveness, dispensers, ferric sulfate, phosphorus, risk, runoff, watersheds, Finland
- Conversion of dissolved P by ferric sulfate into a particulate form sparingly available to algae was studied in 15 ditches in Finland using stand-alone dispensers for ferric sulfate administration. Ferric sulfate typically converted 60–70 % of dissolved P into iron-associated form, a process which required 250–650 kg per kg dissolved P. Mean cost was 160 EUR per kg P converted (range 20–400 EUR kg⁻¹). The costs were lowest at sites characterized by high dissolved P concentrations and small catchment area. At best, the treatment was efficient and cost-effective, but to limit the costs and the risks, ferric sulfate dispensers should only be installed in small critical source areas.