Phosphate inactivation with iron chloride during sediment resuspension: Fid-Bau Portal

Phosphate inactivation with iron chloride during sediment resuspension

Wísniewski, Ryszard

The present study undertook laboratory and in situ experiments in two hypertrophic lakes in order to determine the possibilities for the effective PO₄ precipitation by means of FeCl₃, applied directly to organic sediments (at a specific depth) previously subject to resuspension. The study also aimed to test, modify and improve a device constructed previously. This made the direct application of FeCl₃ to organic sediments possible, while generating resuspension in the surface layer of sediments to a specified thickness. The results of both laboratory and field experiments, and tests of the prototype device, showed that linking a dosage of FeCl₃ with the initiation of controlled resuspension led to a decrease of seven‐fold in the concentration of PO₄ in interstitial water, and changed other physical and chemical parameters in the water only slightly. The effectiveness of PO₄ precipitation relied mostly on initial conditions in the interface of water–organic sediment phases, and especially on the sorption capacity of sediments for phosphates, on the gradient of PO₄ concentration, and on the concentration of oxygen in the layer of water above the sediment. It could be an effective method of over‐eutrophied lakes reclamation, and an alternative to the expensive removal of sediments.