How does public water use influence the amount of phosphorus in the environment?

Human activity has led to excess phosphorus concentrations and the continued over-enrichment of coastal and fresh waters across the United States. Alongside colleagues from Union College in New York and Lancaster University, BGS scientists are researching the biogeochemical cycling (how specific chemicals cycle through the biological and geological components of the Earth) of nutrients in aquatic environments in the USA.

What is eutrophication?

Eutrophication is the process by which water becomes progressively enriched with minerals and nutrients, for example phosphorus and nitrogen. It can affect both coastal and fresh waters and can be caused by excess phosphorus entering the water system. Natural eutrophication is a very slow process, but it can occur much more rapidly when pollution accumulates from human sources such as sewage and fertilisers. Eutrophication can cause harmful algal blooms, leading to oxygen depletion in the water and damage to local ecosystems.

Previous and new research

This new research follows on from studies initially undertaken in the UK in 2016 (Gooddy et al., 2015; Ascott et al., 2016) that looked at mains water leakage and the associated inputs of phosphate that this causes. However, these studies only considered mains water leakage: the new study employs an innovative way of determining previously unaccounted-for phosphorus sources at a much bigger scale. It estimates, for the first time, the amount of phosphorus that enters the environment from the US public water supply.

Phosphorus in US public water supplies

Public water systems across the United States widely dose water with phosphate (PO₄) to control the corrosion of lead and copper within water distribution networks. When pipes leak or people water their lawns, this phosphate enters the environment and can find its way into rivers and groundwater. About 5 to 17 per cent of this phosphate-dosed water leaks out of water mains, whilst 5 to 21 per cent is used outdoors. In some parts of the US, the amount of phosphorus entering the environment from the water supply exceeds that coming from point sources like wastewater treatment plants, or from agriculture and fertilisers.

Developing a more effective phosphorus management policy requires a comprehensive understanding of phosphorus sources and routes into the environment, which are known as fluxes. These fluxes should be considered in relation to other sources of phosphorus in the aquatic environment (Gooddy et al., 2017) and can inform localised phosphorus management practices.

Future work

The next step is to look at carbon cycling and greenhouse gas emissions from water use in the US. A sister study, which was published by the same authors in 2022, looked at how water supply processes are responsible for significant nitrogen fluxes (Flint et al., 2022).

Researchers and funding

BGS is the lead on this research with PhD candidate Elizabeth Flint supervised by Dr Matthew Ascott and Prof Daren Gooddy. There has also been input to the work from Dr Mason Stahl from Union College, NY, USA and Dr Ben Surridge at Lancaster University, UK.

This work has been funded through ENVISION DTP with supervisor support provided through the BGS BUFI programme and National Capability funding through Groundwater Processes.

Further reading

• US public water supply is a local source of phosphorus pollution

References

About the author

Prof Daren Gooddy

BGS Groundwater Processes team leader

BGS Wallingford

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