Abstract
Stormwater runoff related inputs of nutrients, suspended solids, heavy metals and bacteria have
caused severe degradation and deterioration of water quality across the United States. New land
development projects in many states are now required to utilize stormwater management practices
such as retention or detention ponds to minimize post-development discharge of pollutants to
receiving water bodies. Unfortunately, the majority of existing land development occurred before
implementation of current stormwater regulations and, therefore, contain no facilities for
stormwater runoff management. Many of these areas are highly urbanized and fully developed,
with little space available for retrofitting activities using traditional stormwater management
techniques.
In 1986, a prototype stormwater alum treatment system was introduced in a lake restoration
project on Lake Ella in Tallahassee, Florida, based on the flow-weighted injection of liquid
aluminum sulfate, Al2(SO4)3.18 H2O, commonly
called alum into the runoff flow inside the stormsewer lines before discharging to the lake.
Alum treatment of stormwater runoff has been shown to consistently reduce concentrations of
orthophosphorous and total phosphorus by 85%-95%, heavy metals by 80%-90%, suspended solids by
95%, total nitrogen by 50%-80%, and coliform bacteria by more than 99%. Since Lake Ella, six
additional alum stormwater treatment systems have been constructed. These innovative systems
typically require no land acquisition or stormwater basin construction, thus greatly reducing
the capital cost of stormwater retrofit projects.
Alum stormwater treatment combines an extremely cost-effective method of retrofitting direct
discharge stormwater systems with high removal rates of nutrients, heavy metals, and bacteria.
This method of stormwater treatment is not only applicable to Florida but any area needing
stormwater treatment and surface water quality improvement.
Return to Technical Papers