The First Non-Research Phosphorous Sorbing Filters

Treated Slag Phosphorus Filter

This was one of the first projects in Maryland to utilize iron slag treated with an acid-bath patented by Dr. Chad Penn of Arizona State University. Ridge to Reefs installed a bed filter approximately 12' wide by 100' long and 2' deep, lined the pit and filled it with 60 tons of treated iron slag. The slag absorbs approximately 50% of dissolved phosphorus for a period of approximately 2 years before there is any decline in percent absorption.

Fair Hill Dairy Farms 

Fair Hill Dairy is located in Chestertown, in the Middle Chester River subwatershed of the Chester River watershed.  The farm manages 500 head of cattle and has a production area that includes several large barns, a milking parlor, an office building, a single-family home, and a grain storage area. These impervious areas drain to a degraded grass waterway that flows approximately 2,355 linear feet before emptying into a pond. The pond receives drainage from approximately 335 acres, most of which is cropland in a corn and soybean rotation. 

The farm is in the process of implementing a center-pivot irrigation rig, which will irrigate much of the pond’s drainage area with liquefied waste.  As is typical of dairy operations, there are many opportunities for sediment and nutrients to leave the farm.  Stormwater from the production area can be contaminated with nutrients, sediment, and bacteria and the leachate from grain storage is highly acidic. Application of the phosphorous filter will greatly reduce runoff, improve local water quality, and reduce the farm’s impact on the watershed.