Erosion and creeping shores threaten landmasses. Many scientists believe that global warming may be behind rising sea levels and flooding, which in turn destroys the coastlines.
Yet when we harvest drinking water from aquifers over periods of years, land levels decrease, accelerating the pace of seawater intrusion.
Communities in the coastal areas surrounding Virginia Beach, Norfolk, and Newport News, Virginia enacted the Sustainable Water Initiative for Tomorrow, or SWIFT. It aims, in part, to return treated wastewater into ground reserves, helping to raise the ground water level and prevent land subsidence and seawater intrusion.
Fluorescence spectroscopy plays a vital role.
SWIFT is a water treatment project in eastern Virginia designed to protect the region’s environment, enhance the sustainability of the region’s long-term groundwater supply, and help address environmental pressures such as Chesapeake Bay restoration, rising sea levels and saltwater intrusion.
The process includes the use of highly treated water from water treatment plants that would otherwise discharge into local rivers, and puts it through additional rounds of advanced water treatment to meet drinking water quality standards. In the Virginia Beach, Norfolk, and Newport News area, plants empty the SWIFT water to the Potomac Aquifer, the primary source of groundwater throughout eastern Virginia.
Typical water treatment includes several stages: Allowing heavy solids to settle in the bottom of holding tanks, which is then taken away; removing dissolved and suspended biological matter using filtration systems; and chemically treating of physically disinfecting the treated water in lagoons.
Under the SWIFT initiative, engineers reduce the nutrients discharged into the Chesapeake Bay from the wastewater by treating it with advanced methods. Those include ozonation, biofiltration and adsorption to convert the treated wastewater into drinking-quality water.
It’s basically putting advanced water treatment on the back end of the wastewater plant.
In ozonation, engineers infuse the water with ozone, which acts as a disinfectant.
Biofiltration and adsorption captures and biologically degrades pollutants into smaller, biologically degradable molecules. SWIFT uses granular activated carbon for biodegradation and adsorption of dissolved organic matter on the surface of the granular activated carbon media.
Scientists use fluorescence spectroscopy to monitor dissolved organics in the water as it goes through the various steps of treatment. Engineers measure samples of the effluent before, during and after the various stages of the advanced water treatment process using fluorescence spectroscopy. It allows scientists to determine the effectiveness of different treatment techniques.
One SWIFT plant uses a HORIBA Aqualog® spectrofluorometer to test for dissolved organic matter in the effluent. The Aqualog is the only instrument that, through its exclusive A-TEEM™ technology, simultaneously measures both absorbance spectra and fluorescence Excitation-Emission Matrices (EEMs). It acquires EEMs up to a 100 times faster than with other instruments.
With the Aqualog, the plants can get a full spectrum at different wavelengths quickly and inexpensively, giving operations an idea of the organic distribution before and after treatment.
The Aqualog generates fluorescence data in a 3D plot with excitation and emission. And that tells operators how much light is fluorescing – giving them an idea about the organics in the water as it goes through the treatment processes.
Results showed that ozonation decreased total fluorescence. The Aqualog also determined biofiltration and granular activated carbon absorption removed the organics still further, resulting in even lower fluorescence values.
Plant operators have shown that the SWIFT initiative’s advanced water treatment and aquifer replenishment might be a viable alternative in the battle against coastal erosion. As additional plants adopt this method, the evidence could become more compelling. And one key to fighting the loss of shorelines might come from the water we throw away.
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