The problem of lead in drinking water has been top of mind since the crisis in Flint, Michigan, which began in 2014. Exposure to lead impacts children’s brains and nervous systems, and there is no safe level of lead in the blood.
Since April 2019, Pittsburgh Water, then PWSA, began treating drinking water with orthophosphate to prevent corrosion of lead pipes.
A new study looks at how this chemical is getting into urban streams.
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“We have discovered that it is leaking into Pittsburgh’s streams at [an] alarming rate,” said the study’s first author, Anusha Balangoda, Ph.D., assistant teaching professor in geology and environmental science at the University of Pittsburgh.
In collaboration with PWSA, she and the other researchers studied five streams in Pittsburgh before and after orthophosphate was added to the city’s drinking water. After treatment, they found high levels of phosphorus.
“Phosphorus increased over 600 percent after treatment began,” Balangoda said.
She said manganese also spiked over 3,000 percent, copper over 300% percent and iron over 400 percent. These are corrosion byproducts.
According to the study, one reason for the increase is leaky water pipes.
Balangoda said in 2019, Pittsburgh Water lost around 40 to 50 percent of treated water, or around 28 to 35 million gallons of treated water daily. That includes unmetered use and water main breaks. The agency couldn’t confirm that figure, but said in an email, “Due to the age of our infrastructure and a historic lack of investment, the distribution system does experience a high percentage of water loss.”
The leaking water takes the chemicals and metals with it, and Balangoda said they can infiltrate deep into groundwater. From there, phosphate can move into streams.
“This finding suggests that our underground infrastructure isn’t as sealed off from the environment as we often assume,” Balangoda said.
Orthophosphate can also get into urban streams through greywater – the treated water we cook and shower with – when the city’s combined sewer system overflows into the rivers and streams during rainstorms.
The impact of phosphorus in waterways
Phosphorus, Balangoda said, is a nutrient. It feeds microorganisms and algae in streams.
Most healthy streams have few nutrients.
“So any sources of nitrogen and phosphorus can be utilized by the microbes, the algae living in these systems, and result in blooms and toxic blooms,” said John Stolz, a professor in the Department of Biological Sciences and the Department of Civil and Environmental Engineering and Science at Duquesne University. “In some cases, they just consume all the oxygen, and everything dies because of not being able to breathe essentially.”
That is called eutrophication. Low-oxygen water can harm fish and other aquatic life. Some of the algal blooms may also be toxic.
These urban streams feed Pittsburgh’s rivers, Balangoda said, which provide drinking water.
“Drinking water treatment plants have to remove those toxins before they send water into their customers,” she said. “Eventually, we have to pay additional costs to drinking water treatment plants to remove the toxins.”
Recommendations for keeping phosphate out of streams
The study makes some suggestions for how to prevent phosphate migrating from leaky water infrastructure into urban streams. One is to replace old pipes more quickly. Another is to optimize orthophosphate in treated water.
“Find the minimum phosphate level that prevents lead exposure,” Balangoda said, “without overwhelming local streams.”
Pittsburgh Water said orthophosphate is a common solution to protecting water customers from lead pipes. It is used by other “water systems across the country, including neighboring water utilities like Pennsylvania American Water that provides drinking water services to some Pittsburgh neighborhoods,” the agency said in an email.
By adding orthophosphate and replacing lead service lines, Pittsburgh Water said this October it reached a historic low lead level – 2.0 parts per billion — in the latest round of water testing certified by state regulators. The agency said it has optimized the corrosion control program and that orthophosphate levels in drinking water are different from when the study was conducted in 2019 and 2020.
Another recommendation by the study authors is to upgrade the process for phosphorus removal at the wastewater treatment plant. Currently, the Allegheny County Sanitary Authority (ALCOSAN) treats wastewater for phosphorus in its secondary stage of cleansing. The authors recommend a third stage.
But in an email, ALCOSAN said tertiary treatment is not required and that it “conducts all testing in accordance with PA DEP and EPA permitting requirements, which are based on water quality criteria set by regulatory agencies.”
Finally, Balangoda said streams should continue to be monitored to determine if phosphorus and metal levels persist over time.
A wider problem
This isn’t just an issue in Pittsburgh. Lead in drinking water, associated with aging water infrastructure, is happening across the northeast, midwest, and Great Lakes area, according to Balangoda.
“This is a widespread problem,” she said.
Water treated with orthophosphate could be leaking into waterways elsewhere.
“We can have both safe drinking water and healthy streams,” Balandoga said. But it will require investment.
She said this is the first study to try to understand how drinking water from water pipes leaks away and ends up in urban streams.
“We absolutely need to protect people from lead in drinking water,” said co-author Emily Elliott, Ph.D., co-founder and chair of Pitt’s Pittsburgh Water Collaboratory and professor in Geology and Environmental Science. “But we also need to understand how these treatments affect our rivers and ecosystems.”
The study was published in the journal PLOS Water. Sarah-Jane-Haig, an associate professor, and Isaiah Spencer-Williams, a doctoral student in Civil and Environmental Engineering, were also co-authors on the study.
