Phosphate in tap water ‘looks’ very different from the phosphate coming out of waste water treatment works or from that used in agricultural fertilisers.

Researchers at Lancaster Environment Centre and the BGS have used small variations in the chemistry of phosphate as a label, based on analysing the isotopes of phosphate. This label makes it possible to differentiate between the phosphate getting into the environment from leaking mains and phosphate from other sources.

Dr Ben Surridge, a lecturer who leads research with phosphate isotope analysis at Lancaster University, said: “Lancaster Environment Centre and the BGS are at the forefront of research that is developing this isotopic label for phosphate. The label provides new opportunities to understand the sources and the fate of phosphorus in the environment. These are important challenges and our work with phosphate in drinking water is one example of the highly novel research we are undertaking in this area.”

In the UK, phosphorus is routinely added to drinking water supplies in a form known as phosphate. It is added to effectively prevent any lead entering the water supply, which can come from the corrosion of old piping. Lead is a toxic metal and adding phosphate has proven to be very successful in reducing human exposure to it. But just what is the fate of this phosphate?

Latest statistics show that the biggest UK water utilities lose around 25 per cent of drinking water to leakage – or around 40 litres per customer per day. Based on the amount of phosphate which is presently added to tap water, this is equivalent to around 1200 tonnes of phosphorus entering the environment every year.

Although phosphate is not harmful to humans, anthropogenic, or man-made, inputs of phosphorus are well known to have a significant impact on ecosystems, and can damage the health of rivers and lakes (known as eutrophication). What ultimately happens to phosphate after leakage is currently unknown. However, as the UK water industry focuses on lowering the amount of leakage that is acceptable, this may also cut down any negative effects on the environment of phosphate leaking from drinking water.

The study has shown the potential to differentiate between phosphate in tap water, fertilisers and waste water using isotopes. This means that in the future we may be able to better understand the sources of phosphate in the environment and target measures and investments for better environmental benefit. The latest technical advancements described above give us some of the tools necessary to do this.

Professor Rob Ward, Director of Groundwater Science at the BGS, commented on the research: “This study has for the first time estimated the amount of phosphorus entering the environment directly from leaking water pipes. Whilst the addition of phosphorus to drinking water is beneficial to our health by reducing our exposure to lead from old pipes, its leakage can have a very damaging impact on the environment by affecting the ecology of streams, rivers and estuaries.”

Dr Daren Gooddy, a scientist at the BGS who led the research, said: “Previous studies considering inputs of phosphate to the environment have not considered leaking mains water. Consequently, considerable efforts have been put into reducing phosphate inputs from agriculture and, in particular, from waste water treatment plants. This means that as we reduce phosphate loading from these sources, under the current practice, the relative contribution of phosphate dosed drinking water will increase.”

The research has recently been published in the journal Environmental Science and Technology, to access the paper click here.