The following article was submitted by Ocean Lakes High School student Sarah Scharf.
Eutrophication and Why it Matters
Eutrophication is caused by excessive amounts of nutrients in bodies of water. An increase in nutrients can cause an increase in phytoplankton, or algae, which can grow very rapidly, sometimes forming algae blooms. Once the algae die and decay, oxygen is depleted in the water which can kill aquatic animals. Eutrophication has damaged roughly two-thirds of our estuaries and bays in the United States. Wastewater treatment plants clean the wastewater that is created at homes, businesses, and industries across Hampton Roads and then send highly treated water, called effluent, into waterways. This effluent is safe for our waterways, but it still contains some nitrogen, a nutrient that contributes to eutrophication. Scientists and HRSD are researching other methods for nutrient removal during wastewater treatment to better protect our waterways.
History on Wastewater Treatment
Traditional wastewater treatment plants use a process that only removes certain forms of nitrogen. As a result, organic nitrogen, termed effluent dissolved organic nitrogen (EDON), still makes its way into waterways. Some scientists now think that EDON could contribute to increases in phytoplankton, so researchers at the Virginia Institute of Marine Science (VIMS) investigated the effect of EDON on the environment. Here is what they did:
The Experiment
During the summer of 2016, VIMS researchers tested different nitrogen removal treatment methods and their effect on phytoplankton in saltwater and freshwater collected from the Upper York River and Lower York River. Wastewater was treated four different ways to remove nitrogen, resulting in four groups with different nitrogen levels. Each of these groups were then disinfected three different ways. Disinfection is the final step at a wastewater treatment plant to remove anything harmful, like pathogens that may still be remaining before the water is sent out into waterways. At HRSD, most treatment plants disinfect with chlorine and some use UV light.
This aerial shot of VIMS shows the pier (center) where saltwater was collected for the experiment.
At this point, the experiment had twelve sample groups. Researchers then added a control group with no treatments, and another group with extra nitrogen added in. These two groups would provide a comparison on the effects of each of the treatments. Each of the fourteen groups were then split once more to be combined with either a freshwater sample or a saltwater sample to simulate effluent being discharged into a waterway. Now with a total of 28 groups, researchers tested the chlorophyll levels caused by phytoplankton over a period of four days. If chlorophyll levels increased in this smaller, lab-controlled environment, then researchers would have cause to investigate potential impacts in the environment. Here is what they found:
- Out of the four different nitrogen treatments, the two that removed the most nitrogen resulted in lower levels of chlorophyll, which may indicate that less EDON in the water will lower the threat of eutrophication.
- Results were different between freshwater and saltwater, which is probably because freshwater and saltwater contain different species of phytoplankton that react to nutrients in different ways. Chlorophyll levels typically only increased in freshwater, not saltwater, for the two treatments that removed the most nitrogen.
- Water disinfected with chlorine may leave behind different nutrients than water disinfected with UV light or not disinfected at all.
This research has the potential to aid HRSD in achieving their vision of ensuring future generations inherit clean waterways and are able to keep them clean. Currently, HRSD is using at least five different nutrient removal methods across their 16 treatment plants and is working on about seven special projects that focus on nutrient removal.
HRSD is also leading an initiative to eliminate almost all of the nutrients that enter our waterways from wastewater treatment plants. It’s called the Sustainable Water Initiative for Tomorrow (SWIFT) and it will take highly treated water that would otherwise be discharged into local rivers and put it through additional rounds of advanced water treatment so that it is clean enough to drink. The SWIFT Water will then be added to the Potomac Aquifer, the primary source of groundwater throughout eastern Virginia. This will help the Chesapeake Bay by reducing the nutrients we currently discharge into local rivers, as well as replenish our dwindling groundwater supply and help fight the impacts of sea level rise.
Sarah (second from right) and the VIMS team.
About the Author Sarah Scharf
I am a student at Ocean Lakes High School who worked with the researchers at VIMS. As this was my first time working in a professional lab, the researchers took me under their wings despite my lack of experience. All the researchers immediately accepted me into the VIMS community. I really enjoyed the challenges they gave me, which included learning to use new equipment that I didn’t have at school. The experience has helped me in my science classes during the past couple of years and I’m very excited to see how I will use the same skills in college.
Outside of school, I enjoy many water-related activities, including kayaking and snorkeling. A few years ago, I visited California and went snorkeling with leopard sharks and stingrays. Fantastic activities like that show me again and again that protecting our water resources is important both for our health and our happiness.