London's sewage is treated at six pollution control plants. Phosphorus concentrations are reduced to levels well below the approved limits allowed by the Ontario Ministry of the Environment. Phosphorus enters our treatment plants in concentrations of about 5.8 mg/L and about 90% is removed before discharge at about 0.5 mg/L. On average about 17% of the phosphorus loading to the river is from wastewater treatment plants.
A Pollution Control Plant Discharge Strategy (March 2008) Master Plan was completed with the recommendation to minimize phosphorus loading to the Thames River by reducing concentration limits with future plant expansions.
Phosphorus can also enter waterways from septic systems. Owners of septic systems are encouraged to ensure the systems are functioning properly and that septic tanks are regularly cleaned out.
The Ontario Minister of Agriculture, Food and Rural Affairs website provides some tips for the care and maintenance of septic systems.