Aluminum application to restore water quality in eutrophic lakes: maximizing binding efficiency between aluminum and phosphorus

Abstract

ABSTRACTHuser BJ. 2017. Aluminum application to restore water quality in eutrophic lakes: maximizing binding efficiency between aluminum and phosphorus. Lake Reserv Manage. 33:143–151.Aluminum (Al), typically added to lakes to reduce internal cycling of legacy phosphorus (P) in sediment, was added to the littoral zone of Lake Harriet (Minnesota) to inhibit the uptake of sediment P by buoyancy regulating species of plankton. Analytical results from sediment collected over an 11-year period showed that the added Al (32 g/m2) started to move outside the treatment zone almost immediately after treatment, with <5% remaining within the treatment area after 6 months. Although the original treatment design failed, the application method was, unexpectedly, a success with respect to binding efficiency between Al and P in the sediment. As the Al drifted to deeper areas of the lake, internal P release in non-treated, deeper areas of the lake declined and the binding ratio between Al and Al-bound P decreased, reaching 2.1 (molar) in profundal sediments 10 years after treatment. The increased contact with available (mobile) sediment P increased binding efficiency, resulting in a 163–581% increase of P bound per unit Al compared to previous whole-lake aluminum treatments. The binding efficiency exceeded expectations showing that, in addition to the amount of Al added, treatment location and subsequent translocation of the Al floc can substantially affect binding efficiency and treatment effectiveness.