Phosphorus is an element with the chemical symbol P and occurs in water as phosphate (PO43-). Phosphorus is essential to life and is described as a macronutrient.
Phosphates are washed into water as it passes over rocks. Phosphates come from rocks and are non-renewable, so must be recycled. Globally there is a drive to ensure phosphates from effluents and soil runoff are recycled.
Although phosphate is not harmful to humans, man-made inputs of phosphorus are well known to have a significant impact on our ecosystems and can damage the health of rivers and lakes.
Phosphates are present in a variety of applications. Below we outline where you may find phosphates and why they should be monitored.
Phosphate must be monitored because it is undesirable in pools and spas as it promotes the growth of algae. This is especially important for outdoor pools and spas. The level of total phosphates in pool and spa water should be 0.01 mg/L or below. Other key tests for pool and spa include pH, chlorine and turbidity.
For an overview of key testing parameters, guidance on recommended levels and the effects of poor water monitoring download our pool chemistry guide.
Phosphates are widely used in fertilizers to increase crop yield and health, which contributes to phosphate in the environment. Phosphate is an important parameter for soil testing because it is essential for plant growth; it is a macronutrient. If phosphate levels are too high or too low in soil, plants can show stunted growth, especially in their leaves and roots.
Phosphates are added to drinking water to combat leaching of lead from the pipes into the water. The phosphates form a layer over the inside surface of the pipes known as a passivation layer, which protects the water from the lead. Monitoring of phosphates is therefore critical, with sufficient quantities required for coating the pipes and ensuring that no lead leaches into the water. To find out me about lead in water click here.
Phosphates in effluents are monitored as they can cause eutrophication which can have a negative impact on the aquatic ecosystem. This can increase the growth of aquatic plants, known as algal bloom, which covers the water surface. Plants below the surface are then killed as light and oxygen cannot reach them. As the plants decompose, oxygen they use up all the dissolved oxygen in the water, and eventually suffocate the aquatic life
The EU Wastewater Directive released in 2018 tightened laws with regards to phosphorus removal from effluents prior to release, meaning more phosphorus testing is required.
Polyphosphates are used in boiler and cooling tower systems to prevent scale formation. Phosphate must be monitored because if levels are too low, scale will form on the equipment.
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Eutrophication is a type of water pollution caused by the addition of sewage or fertiliser. This is caused when fertilisers are washed off the land by rainwater into rivers and lakes.