It’s no longer a dirty secret.
Rising sea levels and flooding are among the largest issues facing coastal areas. Many point to climate change as the force behind these shifts.
But it’s not the only cause.
This is particularly true in the Hampton Roads, Virginia area. It’s dotted with sailors and aircrew from nearby naval and air force bases. It’s also located close to sea level in the costal southeastern portion of the state. Erosion and creeping shores threaten the landmasses.
Part of that problem is harvesting drinking water. The land level decreases over periods of years because users are pumping so much water out from the ground. That hastens the pace of seawater intrusion.
The Hampton Roads Sanitation District treats wastewater effluent with advanced treatment techniques. New research is showing that the process can actually have a positive effect on subsidence - land sinking or gradual downward settling - and intrusion of seawater. As well as cost effective ways to purify the effluent.
HRSD covers the areas surrounding Virginia Beach, Norfolk, and Newport News, Virginia.
Wastewater management is the process of disposing of human and industrial sewage without danger to human health or unacceptable damage to the natural environment. Yet, the discharge of the plant’s effluents can affect the health of surrounding waterways, and consequently the adjoining landmasses.
HRSD is fighting back against these environmental challenges with the Sustainable Water Initiative for Tomorrow, or SWIFT. More on that later.
Ramola Vaidya is a research intern and Ph.D. student at Virginia Tech, also known as Virginia Polytechnic Institute and State University. She is doing some novel research at the Hampton Roads Sanitation District.
Vaidya and her team are developing methods of advanced water treatment that not only returns the wastewater to a healthy level, but raises the ground water level, and prevents land subsidence and seawater intrusion.
Vaidya grew up in India, in Pune. It’s a city in the Maharashtra state in the western part of the country. She moved to Virginia to pursue her masters and then doctoral degree.
“I loved growing up in India and love the Indian food and culture,” she said. “I did my undergrad in chemical engineering in India. There are water shortages in India, and one day I would love to work on some of the water problems there.”
Vaidya’s work follows the SWIFT initiative. 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, sea level rise and saltwater intrusion.
SWIFT takes highly treated water that plants would otherwise discharge into local rivers, and puts it through additional rounds of advanced water treatment to meet drinking water quality standards. The plants empty the SWIFT water to the Potomac Aquifer, the primary source of groundwater throughout eastern Virginia.
Wastewater treatment generally involves three stages:
Most reuse facilities use some sort of membrane system and reverse osmosis or ultrafiltration, Vaidya said. That involves a semi-permeable, thin membrane with pores small enough to pass pure water through. It blocks larger molecules such as dissolved salts, and other impurities such as bacteria.
“If you look in the West coast where water scarcity is the driver, that's where they've been using membranes,” she said. “We are trying to go the no-membrane approach. We have actually shown that it's equally effective and it’s cost effective. Not just for the water quality, but it's cost effective for us to use.”
SWIFT’s objective is to reduce the nutrients discharged into the Chesapeake Bay from the wastewater by treating it with advanced methods. Then the plant would inject the effluent into the aquifer to provide a sustainable solution for the decreasing ground water levels in the aquifer.
Vaidya’s team use the additional steps of ozonation, biofiltration and adsorption to convert the treated wastewater into drinking-quality water.
“We basically have put advanced water treatment on the back end of the wastewater plant,” Vaidya said. “And then we're recharging the (Potomac) aquifer with this drinking water-quality SWIFT water. We are also preventing all the nutrients that are currently being discharged from going to the Chesapeake Bay.”
Vaidya’s team demonstrated it achieved good water quality with its treatment, comparable to drinking water, and complied with all the regulations. That includes the National Secondary Drinking Water Regulations. It showed that the treatment is sufficient, even from a pathogen standpoint.
The experiment began in one of Hampton Road’s 16 treatment facilities as a pilot program. That lasted a year and a half.
“Then we scaled up to a one million gallon per day facility, which is still a research facility, but it's on a much bigger scale,” she said. “And now we are recharging that water into the aquifer. This facility has been operating for a year now.”
As an added benefit, the team has observed an increase in the ground level on a small scale.
Vaidya uses fluorescence spectroscopy to monitor dissolved organics in the water as it goes through the various steps of treatment.
Her research focuses on ozone and biofiltration. She takes samples of the effluent before, during and after the various stages of the treatment process.
“When you're sampling during the process, you're looking for the effectiveness of different treatment operations,” she said.
Vaidya 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.
Vaidya prefers fluorescence spectroscopy with the Aqualog to other methods.
“UV254 analysis can be done on any other machine as well,” she said. “The really good thing about the Aqualog is you can get a full spectrum at different wavelengths, and that gives you an idea of the organic distribution before and after your treatment.“
Spectrum produced by the Aqualog
“The fluorescence that the Aqualog generates gives you a 3D plot with excitation and emission. And that tells you how much light is fluorescing - it gives you an idea about the organics.”
Vaidya reported that the total fluorescence decreased after ozonation. Once the effluent was sent to biofiltration and granular activated carbon absorption, her team was able to remove the organics even further, resulting in even lower fluorescence values.
Vaidya hopes to write up her dissertation and defend it over the summer of 2020 to finish her Ph.D.
“It has been challenging and exciting at the same time. We started with nothing and now we have a 1 MGD (million gallns a day)-scale facility that has been recharging the aquifer. Soon we will have full scale SWIFT plants,” she said. “And it's not just me. It's a big team of people working on this project that has made this possible.”
So, what’s her next move after earning a doctorate in civil and environmental engineering?
“I'm an engineer, so I'm going to get into consulting,” she said. “I don't want to go into academia. I want to work for a consulting firm that works for these different utilities such as Hampton Roads. That way I can continue working on reuse projects like SWIFT that involve wastewater and drinking water treatment.”
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