What is Phosphorus?
Phosphorus is a nutrient vital to human, animal, and plant life that occurs naturally in our food, water, and bodies, as well as, in human and animal waste. In nature, phosphorus usually exists in the form of phosphate molecules that are formed from plant or animal tissue. Both organic and inorganic phosphate can be dissolved in water or become attached to other particles in water.
Why is too much phosphorus bad?
Too much phosphorus in freshwater systems can set off a whole chain of undesirable events including accelerated plant growth, algae blooms, low dissolved oxygen, and the death of fish, invertebrates and other aquatic animals.
Phosphorus and Algae
High phosphrous levels could make algae spread across the water surface in floating blooms that prevent sunlight from reaching the underlying plants. As a consequence, plants die and decompose and micro-organisms that feed on dying plants could also consume too much of the oxygen in the water body, leaving fish and other aquatic life to die.
Phosphorus and the Thames River
Like most rivers in Southern Ontario, background levels of total phosphorus exceed the Provincial Water Quality Objectives (PWQO). In London, total phosphorus levels are about 3.4 times higher than the PWQO concentration enterning the City and by about 4 times the concentration leaving the City. Accordingly, the Thames River is designated as a " Policy 2" river which means that waters should not be degraded further until all practical measures are taken to upgrade the water quality to the Objectives. In recognition, London's Pollution Control Plant Discharge Strategy lead to a decision to reduce the quantity of phosphorus discharges with future treatment plant expansions.
A high percentage of the loading occurs during significant snow melt/rain events. In February 2018, there were peak flows of 1,000 m3 per second in the Thames River near Byron. The flow for the 4 days of peak flows was estimated to be about 10% of the annual flow (based on 2017 flow data) and sample analysis for phosphorous was 0.35 mg/L. The phosphorous loading was estimated to be about 21% of the annual phosphorous loading of 342 tonnes in the Thames River. This shows the significant impact of peak flows to phosphorous loadings.
A 2018 report was done on Monitoring to Quantify Phosphorous Loadings.