Rising Salinity Cause for Concern at North Carolina Desalination Plant

An increase in salinity levels at the North Reverse Osmosis Water Plant in Kill Devil Hills (yes, that’s the town name) that had been creating stress for some local officials has been explained in a recent study. Researchers from nearby Duke University found that the rising salinity levels at this coastal aquifer are the result of fossil seawater and not seawater intrusion, as had been feared. Since the well’s installation in the late 1980’s salinity has more than doubled from about 1,000 mg/L to about 2,500 mg/L. There was much cause for relief however, when researchers were able to attribute the rise to fossilized seawater and not to seawater leaking in from the coast.

According to the director of the study, Duke Professor Avner Vengosh, knowing the source of the salinity increase is important because fossil seawater raises salinity, “At a relatively slow and steady rate that is more manageable and sustainable than the rapid increase we’d see if there was modern-day seawater intrusion.” As a result of this study the community will be able to rely on this aquifer for decades to come without having to resort to more expensive seawater desalination techniques which require more energy and advanced filtration methods.

Current treatment for groundwater desalination includes the use of reverse osmosis (RO) membranes to separate dissolved salts from potable water. Even with the rising salinity level these membranes remove around 96 to 99 percent of the dissolved salts. RO membranes also remove between 16 and 42 percent of the boron and 54 to 75 percent of the arsenic from the groundwater. Additional treatment following reverse osmosis desalination continues to remove arsenic until it is within safe drinking levels (10 parts per billion, according to the EPA).

Because seawater consistently has more salt than groundwater it requires more energy to treat, and therefore the cost is higher. Per this report on desalination from the Pacific Institute, “Energy is the single largest variable cost for a desalination plant, varying from one-third to more than one-half the cost of produced water.” The report also states, “At these percentages, a 25% increase in energy cost would increase the cost of produced water by 11% (for RO plants).” In looking at these percentages, it’s easy to see why the plant was concerned about seawater intrusion. Thanks to this research, the local citizens can drink easier knowing they have a supply of healthy, affordable water for a long time to come.

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EPA Creates 4 New Clean Air Research Centers

Today the Environmental Protection Agency awarded $32 million to 4 universities around the country to study the health impacts of air pollution. These centers will answering questions like, "does air pollution effect a child's learning ability?" "Are obese people more susceptible to health effects of air pollution?" "How does your commute effect your health?"

We work with a number of environmental labs to provide filtration materials, and one of the most common requests we get from them is for our 0.45 micron, 25mm silver membranes to comply with NIOSH methods for testing airborne contaminants such as silica and bromine. 

Here is a breakdown of what the four new centers are focusing on:

• University of Washington - Effects of roadway pollution on on cardiovascular health.
• Michigan State University - The relationships between obesity and air pollution.
• Emory University / Georgia Institute of Technology - Characterize health risks of air pollution mixtures, research how social factors (living location, commute, etc.) impact health. 
• Harvard University - Investigate health effects of short-term and long-term exposure to pollutants on specific health functions, including cognitive function, birth weight, and mortality. 

See also:
"EPA Awards $32 Million to Understand Health Impacts of Air Pollution"

EPA Clean Air Research Centers Home