Comparison of phosphorus (P) removal properties of materials proposed for the control of sediment P release in UK lakes.

Of growing interest in the control of sediment phosphorus (P) release in lakes is the use of solid phase P-sorbing products (PSPs) including industrial by-products and naturally occurring or modified mineral complexes. However, there is a need to report on novel PSPs proposed by suppliers for use in lake remediation projects at the national scale. We comparatively assessed the elemental composition and P sorption properties of six industrial waste-products (waste-products from treatment of abandoned mine waters - 'red ochre' and 'black ochre'; waste products from building practices: 'gypsum', 'sander dust', 'mag dust' and 'vermiculite') and one commercially available modified lanthanum (La) bentonite product (Phoslock®), all of which have been proposed for use in remediation projects in UK lakes. P sorption was well described (r(2)>0.70) by Langmuir isotherms for all products with the exception of 'gypsum' for which no significant P sorption was reported. P sorption capacities ranged from 4 mgPg(-1) dry weight (d.w.) PSP ('black ochre') to 63 mgg(-1) d.w. ('sander dust'), with products composed mainly of calcium oxide (CaO) and silicon dioxide (SiO(2)) (i.e. 'vermiculite', 'mag dust' and 'sander dust' PSPs) having significantly higher sorption capacities than all other PSPs. Estimates of the equilibrium P concentration (EPC(0)) from Langmuir isotherms indicated that all PSPs, with the exception of 'gypsum', were capable of reducing soluble reactive P (SRP) concentrations to <5.1 μgL(-1). Further research and development required to underpin regulatory policy decisions regarding the use of PSPs is discussed. Dose estimates for each PSP required to treat a eutrophic shallow loch (40.6 ha) with persistent internal loading issues are reported.