IESF - Iron-Enhanced Sand Filters

Stormwater Runoff Treatment Innovation

A cost-effective method of cleaning up the nation's stormwater runoff, centered on phosphorus reduction through the use of elemental iron mixed with sand.  Research conducted at the University of Minnesota has pioneered the IESF methodology.  When sand is mixed with 5% iron filings by weight, the iron captures 88% phosphate for at least 200m of treated depth, significantly greater than a sand without iron filings.  It works through a chemical process where phosphorus molecules in water bind to iron particles within the sand filter as water passes through the filter.



  • Removal of several colloidal and dissolved constituents, including color and phosphates

  • High pollutant removal rates

  • Use as a retrofit for existing ponds and other stormwater BMPs

  • Good for nutrient impaired water

  • Could be used at sites with certain types of restrictions where infiltration is not appropriate or feasible

  • Little maintenance needed following installation


Iron-Enhanced Sand Filter Design

Iron-Enhanced Sand Filter Basin - Photo courtesy of Barr Engineering.

Iron-Enhanced Sand Filter Basin - Photo courtesy of Barr Engineering.


(-8 + 50 MESH)

4                  (4.75 mm)               100
8                  (2.36 mm)           98.5 - 100
16                (1.18 mm)             45 - 80
30                (0.600 mm)            5 - 40
50                (0.300 mm)            0 - 20

100              (0.150 mm)            0 - 10

Specification Sheet CC-1004 Download

Connelly-GPM, Inc.    (773) 247-7231