The world’s population depends on clean drinking water. Methods for measuring contaminants in wastewater, including dissolved organic matter are evolving with the use of proven techniques, improving the processes’ efficiency, effectiveness, and economics.
But varying regional economic conditions still pose challenges.
Just ask Professor Shane Snyder, Ph.D. He is a world-renowned wastewater contaminant expert. He oversees a staff of 300 people as the Executive Director of the Nanyang Environment & Water Research Institute (NEWRI) at Nanyang Technological University (NTU) in Singapore. He’s also a Professor of Civil and Environmental Engineering there.
Prof. Snyder spent the last two decades conducting research on the identification, fate and health relevance of emerging water pollutants. He and his team have published hundreds of manuscripts and book chapters on emerging contaminant analysis, treatment, and toxicology. That work produced over 30,000 citations thus far.i
So, when he talks about ways to detect wastewater contaminants, people pay attention.
“There's several fronts that we're working on,” he said. “My Ph.D. was on trying to identify estrogen compounds and complex mixtures of wastewater that were having an impact on the fish population. I started that work back in the 1990s, and I think we've progressed a long way. I've always worked with in vitro cellular bioassays to screen complex mixtures in the environment, and then usually using mass spectrometry to try to identify contaminants.”
Today, the area that he works on the most is how to do things faster and online, using sensor technologies and simpler measurements that can be representative of the broader classes in a tiered structure.
“I think the work that we're doing today will help us to maintain safe and reliable water consistently, but also if there is a new contaminant or something formed in the water, we have a structure that allows us to more rapidly identify that compound and predict its impact to human or environmental health.”
There’s been a barrier to that in the past.
The process that he’s worked on for a very long time is, first of all, trying to extract organic contaminants from water. So, he must have a way to isolate these or to measure it directly.
And then he needs a way to identify it. Up until the last decade, it’s been done generally with different kinds of mass spectrometry.
He also screens it for toxicity using human cell lines.
“That's the workflow to identify specific new contaminants,” he said
Yet new tools play a huge role, which is in rapid screening to look for changes or patterns of changes, and how he can control the water treatment systems to make sure that these are running optimally when it comes to attenuating trace contaminants. It's a multi-pronged approach.
One of his key tools is the HORIBA Aqualog™ Spectrofluorometer, with simultaneous Absorbance-Transmission fluorescence Excitation and Emission Matrix acquisition (A-TEEM). This novel approach is a fast and inexpensive optical technique for quantitative molecular fingerprinting with high specificity and ultrahigh sensitivity.
Challenges crop up, like novel contaminants in our water supply.
“How do you address the unknown or these new types of contaminants, and how do you have a system that's faster? If something is awry, then the old way of taking a sample, maybe is a mass spectrometer that’s being used, and you’re getting data back a week later. But that could be way too late, depending on the type of water system. If there's a failure in that system, it has to be corrected or shut down immediately.”
“There's a whole series of methods. In fact, the methods are often referred to as standard methods. There's standardized methods and EPA regulatory methods, which must be used. There's some leeway within the methods, but these are dictated to meet the regulations.”
There are protocols that utilities must follow to meet the regulations to do that. And there's a lot of new ideas that are being proposed. But how do you address the unknown or these new types of contaminants, and how do you have a system that's faster?
That’s where Snyder has deployed the Aqualog, both in research and industrial use at water treatment facilities.
“Aqualog has a really interesting feature,” Snyder said. “That's its ability to scan a broad spectrum of wavelengths of light. Its spectroscopy results in patterns. And those patterns can be deconvoluted mathematically to look for changes. And those changes can correspond to different types of contaminants. It’s more for us in knowing that the treatment process is operating effectively.”
“So, we use it very heavily in that domain, to optimize the water treatment system and to use the data from the Aqualog to predict how well the system is actually working. Because (Aqualog is) so much faster, we can get data by the hour versus by the days or even weeks.”
The speed, sensitivity, ease of sample preparation, cost to use and A-TEEM technology give the Aqualog an advantage over the slower, more expensive mass spectrometry method.
“It's being used to look at coagulation optimization and chemical feeds. It's more on the treatment side, as a surrogate measure of the treatment.”
Snyder sees a trend towards fluorescence EEMs in wastewater treatment.
“In California, we have recommended fluorescence, as we call it, ‘delta fluorescence.’ So basically we are looking at the intrinsic fluorescence of the water before and after a particular unit process,” he said. “For instance, when we're recycling wastewater, that water will have a quite strong fluorescent signal. And after a process such as reverse osmosis, that signal changes dramatically. Most of it's removed because most of the aromatic or conjugated bond organics that are removed, but we can actually use it to make sure that the membranes still have integrity.”
“We're using fluorescence in different processes. That's just one example, but it's being used even in what we call natural recycled water, where we infiltrate wastewater into the ground. Then we withdraw that water for drinking water. The natural bacteria in the soils are very, very good at degrading most organic contaminants. So, we can actually look at the change in that fluorescence pattern as a surrogate for the process.”
The technique is being proposed and is employed at many water utilities.
In recycled water and in ocean desalination, membranes are critical. It’s one of the primary barriers or treatment tools. And the fluorescence EEMs are an extremely good indicator of whether the membrane is performing as it should. The fluorescence EEM pattern before the membrane and after the membrane is quite distinct. If something changes, operators know there could be an integrity breach within that.
In Singapore, Snyder and his team are looking at a new application for the HORIBA spectrofluorometer — how they can use the Aqualog to optimize ocean desalination.
“We struggled with ocean desalination efficacy because the seas have changed dramatically around Singapore, both from construction and land reclamation, but also from climate change,” he said. “And by looking at the spectral pattern in the water, we can actually predict how much pretreatment we will need. And then we can also subsequently monitor the water after the pretreatment to make sure it's adequate, and that helps protect the (treatment) membranes, making the ocean desalination more efficacious.”
Economics plays a vital role in wastewater treatment integrity.
Singapore is a small country with strong finances to build high-tech wastewater treatment facilities. But geography often determines how good those facilities are.
“We are surrounded by countries,” Snyder said. “(There are) 650 million people in Southeast Asia, 80 percent of whom don't have adequate sanitation. So, if you're asking it from the point of a modern city, like Singapore or Los Angeles, I think the emphasis is really on making the systems efficient, lowering the energy and getting as much resource recovery as possible.”
“But, all I have to do is cross one bridge into Malaysia, and it's a much, much different situation where they are just bringing on the most basic kinds of wastewater treatment. They still have a lot of issues with nutrients and incomplete wastewater treatment, which is loading nutrients into the water, which causes algal blooms, and puts some of the water at risk for contaminants.”
One of the real challenges for Singapore is sludge. When you treat wastewater, it's a biological process and generates sludge. That leaves the problem of how to get rid of the sludge, and how to extract nutrients, maybe biogas or hydrogen from that. But, these are the high-tech versions of wastewater treatment.
The Aqualog and fluorescence spectroscopy is achieving significant penetration in the wastewater treatment industry, as its operational costs, ease of use, speed, and sensitivity gives it a competitive advantage over traditional methods.
Meanwhile, when Snyder analyzes certain types of samples through traditional methodologies, it’s extremely expensive and time-consuming.
A new trend is achieving online monitoring to make the process even faster and not have to wait to get the data back. He’s looking at that now.
“That’s one of our biggest challenges,” he said.
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