Minnesota’s waters 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.
The majority of phosphorus loading comes from non-point sources during high rainfall periods causing significant runoff from agricultural lands. During these high flow periods, the Minnesota Pollution Control Agency's (MPCA) monitoring data has documented that only 10% of total phosphorus comes from point sources. But during low flow or low rainfall conditions, point sources contribute as much as 64% of total phosphorus to the river basin.
These point sources include wastewater treatment plants and industrial dischargers. Industrial sources of phosphorus include food processing, phosphatizing, and cleaning operations.
As public wastewater treatment facilities (WWTF) receive or anticipate phosphorus effluent limits they are turning to their commercial and industrial users and asking them to reduce the volume of phosphorus in their wastewater. To do so, it is important that you first identify and then reduce sources of phosphorus in your facility. This can help you limit the amount of phosphorus you are discharging to your local treatment facility. In turn, this can help the WWTF minimize the amount of chemicals needed to treat the phosphorus before discharging to Minnesota’s lakes and streams.
Identify and Reduce Sources of Phosphorus
Business users that are likely to contribute phosphorus to the WWTF 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. MnTAP developed a fact sheet, Phosphorus: Reducing Releases from Industrial Cleaning and Sanitizing Operations (2009), to address this concern and provide information about alternatives.
If you are concerned with the amount of phosphorus your facility is discharging to the WWTF, 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 and we provide those examples for you in this section.
If you are a wastewater treatment facility, you should develop a Phosphorus Management Plan. MnTAP and MPCA jointly developed the Phosphorus Management Plan Guide to help POTWs 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. Most notably, metal phosphatizing and food processing operations typically generate high levels of phosphorus in wastewater.
- Metal Finishing: Metal Phosphatizing Operations (2009). This fact sheet provides information on processes that result in high levels of phosphorus discharge and provides examples of alternatives including equipment, chemicals, and treatment options.
- Food Processing: Phosphorus: Reducing Releases from Dairy Processing Facilities (2009) and Phosphorus: Reducing Releases from Meat Packing Operations (2008). In dairy and meat packing operations, cleaning production lines, scraping food preparation vats, cleaning and rinsing equipment, and rinsing product and floor cleaning chemicals down the drain are all ways phosphorus enters wastewater.
- Food Processing: Phosphorus: Reducing Releases from Poultry Processing Plants (2008). This fact sheet outlines a number of steps that can be taken to reduce phosphorus discharge from poultry processing plants.
- Other: Reducing Phosphorus on University & College Campuses (2009). This fact sheet provides a number of ways to assess and reduce phosphorus use in various campus departments.
- Coating Process: Minnesota Elevator Benefits from Switch to a New Coating System (2010). MEI evaluated alternatives to the iron phosphatizing chemical and switched to zirconium oxide (nano-ceramic) conversion coating, which is phosphate free, used at ambient temperatures, and does not require a seal rinse.
- Coating Process: Intern at Artic Cat Reduces Water, Energy, and Chemical Use (2009). The company reduced their phosphorus concentration in the iron phosphate stage by limiting chemical additions to the system and using just the chemical that was already in the tank.
- Food Processing: Sunny Fresh Foods (2006). This food processor worked with its cleaning and sanitizing vendors to reduce its phosphorus effluent by 80%.
- Other Manufacturing: Ver-tech Labs Reduces Phosphorus in Wastewater Discharge (2008). The facility engaged employees and worked with the City of Rockford to reduce phosphorus in wastewater.
- Other Manufacturing: Electrolux Reduces Phosphorus 86% (2005). Electrolux converted the wash stage on its two paint systems to non-phosphorus chemical cleaners and sealant solutions to reduce the phosphorus going to its POTW.
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