Phosphorus and Cyanobacteria Precipitation and Sediment Capping in Lake Water Using Alum and Natural Minerals

Abstract

The objective of this study was to evaluate the use of natural minerals to enhance the precipitation of phosphorus and cyanobacteria during alum coagulation, and to reduce phosphate release during sediment capping in eutrophic lakes. Laboratory coagulation experiments were conducted on lake water spiked with Anabaena sp. using alum and four natural minerals (zeolite, calcite, limestone, and sand) to determine the effect of natural minerals on chlorophyll a, phosphate, and turbidity removal. Long-term column sediment-capping experiments were also conducted using different minerals after alum coagulation to evaluate their effectiveness in reducing phosphate release. The results showed that alum coagulation effectively removed phosphate and chlorophyll a from lake water samples. The added natural particles did not substantially affect coagulation performance during combined alum and particle treatment. However, natural particles increased the floc settling kinetics during coagulation. The combined treatment with alum and particles also increased the resistance of the sediment to disturbance by mixing. The long-term sediment-capping experiments showed that capping with natural minerals reduced the levels of phosphate released from the sediment.