How Saline Uses Corrosion Control to Keep Drinking Water Safe

 01/28/2016 - 16:01
in

Saline Water Superintendent Bob Scull monitors the water plant operation through a computer interface.

Abundant drinkable water is something many of us take for granted. But if it looks clear and tastes OK that does not mean it is safe. In view of the recent Flint water fiasco, it is appropriate for all communities to take a closer look at the safety of their water.

The Flint problem is that water emerging from people’s taps had dangerously high levels of lead, an element that can cause irreversible brain damage, particularly in children. The lead was not in the source water; it was leached from lead piping in older homes and old supply lines because the water was corrosive.

The crisis in Flint happened because of a perfect storm of poor choices and negligence. Many officials and organizations deserve a share of the blame.

Although the Flint City Council voted in March 2013 to change their water source from Detroit to the Karegnondi Water Authority (KWA), either an appointed emergency manager or Governor Snyder himself appears to have made the decision to use Flint River Water until the KWA pipeline was completed. Government officials also ignored a recommendation to use corrosion controls.

A primary way the state monitors corrosivity is to look for its consequence – elevated lead and copper concentration in water that has sat in lead-containing pipes. The water authorities collecting samples in Flint homes apparently were not careful to follow the proper protocol in collecting those samples. This helped hide the problem.

The Michigan Department of Environmental Quality (MDEQ) analyzed the samples for lead. They asked Flint officials to exclude two samples that showed alarmingly high concentrations of lead, deeming them erroneous outliers. Doing this lowered the average concentration to just under the action level.

Afterward, the MDEQ, the Michigan Department of Health and Human Services and the regional office of the EPA all appear to have contributed to downplaying concerns as various individuals raised them. For more on the history of Flint’s water woes visit Flintwaterstudy.org

In older cities throughout Michigan there are pipes that contain lead. Is Saline also in danger of lead poisoning?

160125-saline-013.jpg

Saline Well House #6 is one of five wells serving the city's water needs.

Saline’s water mains range in age from less than one to about 100 years old according to City Manager Todd Campbell. He says most are 40 to 60 years old. The 100-year-old main in Michigan Avenue will be replaced this summer as part of the 2016 reconstruction project.

The mains are made of ductile iron and some of cast iron and are considered to be in good shape. However older homes may have lead service lines connecting to the main. Many also have lead solder on copper pipes in their homes.

In 2005, a new water system went on line in the City of Saline. In contrast to the situation in Flint, care was taken to control corrosivity.

“When we went to the reverse osmosis plant they made us do additional corrosive studies, which we did and we passed,” said Saline Water Superintendent Bob Scull. “I’m not sure why or if they did that in Flint. That stuff should have been done. It seems like somewhere down the line something broke down.”

There was one good reason that the state closely monitored Saline’s new water system. The reverse osmosis system greatly reduces the hardness of the water and soft water is more corrosive.  

Saline dealt with this problem in two ways. First, they mixed treated water with water that has not been treated by reverse osmosis - three parts processed to one part unprocessed. This increased the hardness to about 100 ppm (measured as total CaCO3). This would be rated “moderately hard.”

Unlike Flint, they also added orthophosphate, a corrosion inhibitor. Phosphate interacts with the metal in the pipes forming an insoluble protective layer on the surface that blocks leaching of copper and lead.

Since the protective layer builds up over time, new homes are also at risk for contamination by metals leached from pipes.

Saline gets its water from underground. Before 2005, Saline water was very hard. It also had high levels of iron that caused discoloration.

In 1997, the city contracted with an engineering consultant, McNamee, to design upgrades to the water system. The plan included two new wells, a new water tower, replacement of some mains and a new treatment facility.

The new system cost nearly $9.4 million and was paid using low interest loans from the state Drinking Water Revolving Fund (DWRF). The city will be paying these off until 2025.

The iron problem was handled by running the water through “greensand” filters. All of Saline’s water is treated in this way. Next, the reverse osmosis system removes many kinds dissolved contaminants in the water, including the calcium and magnesium ions that cause hardness.

The city increases water hardness by adding back about 25 percent of the water treated for iron but not treated by reverse osmosis. The city also adds phosphate to inhibit corrosion, chlorine to control microbial contamination, and fluoride.

To assure purity, the water is periodically tested.

“We test on a schedule dictated by the state and we check for a wide array of things given whatever schedule the state puts us on,” Scull said.

These things include pesticides, herbicides, industrial chemicals, various metals, nitrates, fluoride, arsenic, coliform bacteria and other potential contaminants. These tests have consistently show concentrations well below action levels, the level at which remediation is required.

A water quality report can be viewed on-line by visiting the Department of Water Production and Wastewater Treatment website.

Tests for lead and copper are done every three years. Since these contaminants come from piping systems, they are tested at individual homes.

According to Scull, the samples are collected by homeowners who volunteer and are asked to follow a specific protocol. Collected properly, the water should be allowed to sit in the pipes overnight before collection so that leaching can take place.

Twenty homes are tested, a number based on Saline’s population. These homes are scattered throughout the city based on state criteria.

In 2014, no homes were found to be above the action level. In fact, lead was below limits of detection and 90 percent of homes had copper levels below 298 ppb, less than a quarter of the action level.

For those concerned about fluoride, a 2015 report gives the level as 0.4 mg/L. This is somewhat below the Public Health Service recommendation of 0.7 mg/L for optimal dental protection.

Saline has redundancy built into their water supply system. There are five wells, so that if one has a problem the others can supply the needed water. There are even backup generators at the wells to provide power in the event of an outage.

The city delivers over a million gallons a day to homes and businesses. A high percentage goes to industry, the largest user being American Soy Products, Inc.

Those who have concerns about their drinking water should of course contact the city water department. Also the Environmental Protection Agency has a detailed list of recommendations for those concerned about lead.

 

 

Robert Conradi
Bob Conradi Is a retired pharmaceutical scientist who has redefined himself as a photographer and journalist. He has lived in Michigan for 36 years and in the Saline area for 10. He enjoys researching and learning about new ideas. Follow him on Twitter at @RobertConradi.