Treating eutrophic stagnant surface water - by covering the sediment with a semipermeable film to encapsulate pptd. phosphate

摘要

Process for restoring stagnant eutrophic surface water by covering the sediment with a gas-permeable film or membrane which is water-impermeable in the direction from the sediment to the body of water, e.g. where the covering layer is of GORE-TEX (RTM). The semi-permeable film layer may be covered with a gas- and liq.-permeable felt followed by a stabilising layer of sand, gravel, heavy slag or other material with a low nutrient content and esp. an Fe-contg. material. USE/ADVANTAGE - The layer of semi-permeable film prevents the phosphate present in the sediment from re-dissolving in the body of water and gives a progressive mineralisation of the phosphate in the sediment, esp. in the presence of Fe which promotes formation of Fe(III) phosphate. Pref. the eutrophic water is treated in spring or autumn by addn. of a precipitating agent for the phosphate, if possible with supplementary aeration, and the phosphate is encapsulated in the resulting sediment by covering the sediment with the semipermeable film layer.