WWTP Phosphorus Loadings 

In 2008, the WWTP removed approximately 273,000 pounds of the phosphorous in the wastewater entering the plant. The WWTP consistently removes 90-95% of the phosphorus in wastewater.   Source: Wastewater Treatment Services

Note: In 2008, there was a two-month gap in data collection for phosphorus concentration of WWTP influent. The 2008 value for pounds of phosphorus removed is an estimate that was calculated using three-year averages for November and December.  

What are phosphorus loadings?

Loading refers to the total amount of a particular pollutant contained in a waterbody. Loading limits have been set for various water quality parameters in the City’s wastewater effluent by state and federal authorities. Limits are set at levels that comply with water quality standards, and can vary seasonally.

How does phosphorus affect the environment?

Excess phosphorus is one of the biggest water quality challenges facing urban areas like Ann Arbor. Phosphorus is a naturally occurring mineral in the earth’s crust. It is also present in many foods, fertilizers, detergents, and human, animal and industrial waste. Both point and non-point sources of pollution will contain phosphorous.

Phosphorous is an essential nutrient for plants and animals, but too much phosphorous in our lakes and streams can cause excess plant growth and algal blooms. The excess growth and blooms create vegetative mats that make recreation difficult. In addition, certain types of algae also contain toxins that can be harmful to humans and animals. The algal blooms also blocks sunlight needed by other organisms and depletes the available oxygen for fish and other aquatic species’ survival.

More information

• Ann Arbor Wastewater Treatment Services
• Huron River Watershed Council's Middle Huron Cooperative Agreement for Reduction of Phosphorus Loading to the Middle Huron River Watershed (2004-2009)
• Ann Arbor Phosphorus Fertilizer Ordinance 
• Michigan Department of Environmental Quality

Last Updated July 2009