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Phosphorus Filters

Phosphorus Filter Project

Funded by the Canadian Agricultural Partnership Environmental Stewardship and Climate Change Group Program

Mitigation technologies to reduce agricultural runoff nutrient contributions to improve water quality

Agricultural runoff can contribute to algae blooms in lakes, reservoirs, and dugouts which affects water quality and increases water treatment costs. To improve water quality the County of Warner Agriculture Service Board has partnered with Alberta Agriculture and Forestry, and the East Raymond Colony to conduct a research project to install and evaluate a multi-stage phosphorus and biological filter to remediate agricultural runoff from a confined cattle feeding operation.

The phosphorus filter is comprised of a wooden channel that diverts runoff downslope into three excavations. The first excavation is filled with three different sizes of gravel which will filter out the coarse organics and manure, from this filter the water flows into a biofilter which is a lined excavation filled with flax straw. The flax straw provides a carbon source and home to bacteria which consume nitrogen, This bacteria will decrease the nitrogen concentration in the runoff. As this filter fills with water it will flow into a third excavation that is filled with metal slag, the metal slag is about 50% calcium oxide, 40% iron oxide, and 10% silicon oxide with trace amounts of magnesium, manganese, and sulphur. The metal slag will bind with phosphorus and decrease the phosphorus concentration in the runoff.

The goal of this project is to reduce the nutrient contributions to surface water in order to improve water quality. Improving water quality within Warner County can decrease costs in water treatment, and improve water availability to livestock, agricultural projects and our communities. The lessons learned in this project can be applied to other agricultural businesses, communities, and recreational facilities such as golf courses.

Flax filled bioreactor

Project site, showing the gravel filled roughing filterProject site, showing the constructed berms and wooden runoff channel

The project is funded through the Canadian Agricultural Partnership and is part of a larger research initiative within central and southern Alberta toward improving water quality. The County of Warner would like to thank the Canadian Agricultural Partnership Environmental Stewardship and Climate Change Group Program for funding the project, Alberta Agriculture and Forestry for project assistance, and the project team for your expertise, hard work and dedication.

Wooden runoff channel inlet

Wooden runoff channel inlet and fenced perimeterPhosphorus filter, filled with slag material with PVC water distribution system

Special thanks to Ken Janzen, for your excellent technical expertise and expert knowledge, the project construction would not have been a success without your assistance.

Phosphorus filter

In 2015, A project to install a phosphorus filter at Tributary 4, of the Milk River Ridge Reservoir was initiated.

The filter uses a filter media called BioMax, which is a formulation of fibrous organic material and small particles of iron. The iron binds to the dissolved phosphorus, while the organic material would provide a carbon source for denitrifying bacteria which remove nitrogen. 

The project has been operational since June 2017, a interim progress report further describes the project.

The application of phosphorus filters to other land-uses

Phosphorus filters can be used in urban areas such as golf courses and stormwater systems. The USGS has applied the technology to golf courses to prevent the runoff of dissolved phosphorus from turfgrass into the downstream watersheds. Golf courses are known to be lush, green, and uniform, to accomplish this, the consistent applications of fertilizers are a regular occurrence. These fertilizer nutrients can sometimes be migrated off-site by increased precipitation or irrigation watering.

The USGS installed a phosphorus system at Northland Country Club in Duluth, Minnesota, the system removes the dissolved phosphorus from golf course runoff, thereby reducing phosphorus contributions to downstream watersheds. Generally, these systems are a catchment structure which holds the steel slag material, as water flows through the system, the dissolved phosphorus bind to the slag which decreases the concentration of dissolved phosphorus in the runoff, thereby reducing the contributions to downstream watersheds. 

These structures can take many forms, such as vertical above-ground,  or buried tanks. While the aforementioned project is quite complex as it was designed to be a research prototype, these systems do not have to be as technical, the vessels can be as simple as a stock water holding tank or clean chemical totes filled with slag material. Providing the vessel contains the binding material and facilitates the flow-through of water, the objective is accomplished. 

The County of Warner is currently pursuing grants and partnerships to install one of these smaller-scale systems at a suitable location at the urban-agricultural interface. 

Relevant publications

Penn, Chad & McGrath, Joshua & Bowen, James & Wilson, Stuart. (2014). Phosphorus removal structures: A management option for legacy phosphorus. Journal of Soil and Water Conservation. 69. 51A-56A. 10.2489/jswc.69.2.51A. 

Penn C, Chagas I, Klimeski A, Lyngsie G. A Review of Phosphorus Removal Structures: How to Assess and Compare Their Performance. Water. 2017; 9(8):583.

Feyereisen, G.W. & Christianson, Laura. (2015). Hydraulic flow characteristics of agricultural residues for denitrifying bioreactor media. Applied Engineering in Agriculture. 31. 89-96. 10.13031/aea.31.10552. 

Guanghui Hua, Morgan W. Salo, Christopher G. Schmit, Christopher H. Hay, Nitrate and phosphate removal from agricultural subsurface drainage using laboratory woodchip bioreactors and recycled steel byproduct filters, Water Research, Volume 102, 2016, Pages 180-189, ISSN 0043-1354,

Wegelin, M.(1996).Surface water treatment by roughing filters : a design, construction and operation manual, SANDEC report. No.2/96

USGS Phosphorus Filter Video