The Use of Alum and Aluminum-based Products in Lake and Pond Restoration in New Jersey

The original intent of using alum in lake restoration was to provide a means of inactivating the internal (i.e. sediments) phosphorus load in deep lakes with low flushing rates. In these cases the objective of applying alum to a lake was to dose in enough alum and allow it to settle to the bottom to cover the sediments with an "alum blanket". Under anoxic (no oxygen) conditions in the bottom waters, substantial amounts of phosphorus are released from the sediments. An alum blanket would allow aluminum ions to bind with the phosphate ions, rendering the phosphorus unavailable for algal growth. Thus, the use of alum was thought to only be cost effective in large, deep lakes that receive most of their annual phosphorus load from internal regeneration. However, over the past 10-15 years, alum and aluminum-based products have been utilized in a variety of ways to inactivate the phosphorus load of shallow waterbodies, as well as reduce external phosphorus loads. This presentation is a general overview of these relatively recent innovations in the use of alum in lake and pond restoration. 9 pp.