Phosphorus Loading

Reducing your Facility’s Phosphorus Loading


Water must be clean and healthy to sustain aquatic life and provide recreational use. Although phosphorus is a nutrient for plant growth, excess phosphorus can speed up the aging process of lakes and streams by over stimulating algae growth. Algae blooms are unsightly and create high biochemical oxygen demand (BOD) as the algae decomposes and uses up available oxygen supplies, sometimes threatening the survival of fish and other aquatic organisms.

During high rainfall periods, the majority of phosphorus loading comes from non-point (non-specific wide-spread) sources caused by significant runoff from agricultural lands. The Minnesota Pollution Control Agency’s (MPCA) monitoring data has documented during these high flow periods that only 10% of total phosphorus comes from point sources.

Point sources contribute as much as 64% of total phosphorus to  Surface waters during low flow or low rainfall conditions. These point sources include wastewater treatment plants and industrial dischargers. Industrial sources of phosphorus include food processing, phosphatizing, and cleaning operations.

Public wastewater treatment facilities (WWTF) that have or anticipate phosphorus effluent limits  are turning to their commercial and industrial users  to reduce the volume of phosphorus in sewered wastewater. Facilities need to first identify and then reduce sources of phosphorus in your facility in order to  limit the amount of phosphorus  discharged to  the treatment facility. Point source phosphorus reduction  can help the WWTF minimize the amount of chemicals needed to treat the phosphorus before discharging to  lakes and streams.

Identify and Reduce Sources of Phosphorus

Many kinds of businesses are likely to contribute phosphorus to the WWTF. These can include agricultural co-ops, car/truck washing facilities, dairies, food processing plants, meat packing plants and lockers, metal finishing facilities, municipal water treatment plants that add phosphorus to drinking water, nursing homes, restaurants, schools, and other institutions. Additionally, industrial cleaning and sanitizing operations in any facility may result in high discharge levels of phosphorus. The MnTAP  fact sheet, Phosphorus: Reducing Releases from Industrial Cleaning and Sanitizing Operations addresses this concern and provides information about alternatives.

Identifying what processes contain phosphorus is a good place to start. Once those have been identified, you may be able to talk to your chemical supplier to discuss alternatives that either contain low levels or no phosphorus at all. MnTAP has helped several facilities reduce their phosphorus. Examples are found  in the following section.

Wastewater treatment facilities should develop a Phosphorus Management Plan. MnTAP and the Minnesota Pollution Control Agency (MPCA) jointly developed the Phosphorus Management Plan Guide (2006) to help WWTFs develop their management and reduction plans. The guide outlines steps to work with local businesses.

Process-Specific Fact Sheets and Case Studies

These fact sheets and case studies provide information about specific processes and facilities with high levels of phosphorus, like metal phosphatizing and food processing operations that typically generate high levels of phosphorus in wastewater.

Fact Sheets

Case Studies