Where MNA Might Go From Here

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Из курса от партнера Rice University

Natural Attenuation of Groundwater Contaminants: New Paradigms, Technologies, and Applications

111 оценки

Rice University

Natural Attenuation of Groundwater Contaminants: New Paradigms, Technologies, and Applications

111 оценки

Cleaning up the large number of groundwater contamination sites is a significant and complex environmental challenge. The environmental industry is continuously looking for remediation methods that are both effective and cost-efficient. Over the past 10 years there have been amazing, important developments in our understanding of key attenuation processes and technologies for evaluating natural attenuation processes, and a changing institutional perspective on when and where Monitored Natural Attenuation (MNA) may be applied. Despite these advances, restoring groundwater contaminated by anthropogenic sources to allow for unrestricted use continues to be a challenge. Because of a complex mix of physical, chemical, and biological constraints associated with active in-situ cleanup technologies, there has been a long standing focus on understanding natural processes that attenuate groundwater contaminant plumes. We will build upon basic environmental science and environmental engineering principles to discover how to best implement MNA as a viable treatment for groundwater contamination plumes. Additionally we will delve into the history behind and make predictions about the new directions for this technology. Any professional working in the environmental remediation industry will benefit from this in-depth study of MNA. We will use lectures, readings, and computational exercises to enhance our understanding and implementation of MNA. At the completion of this course, students will have updated understanding and practical tools that can be applied to all possible MNA sites.

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New Directions for MNA

This final series of lectures will cover a mélange of interesting MNA topicsl We start with the brand new ESTCP BIOPIC tool, then talk about the broad universe of MNA that extends to a lot of different contaminant classes. Then some new developments in the LNAPL world: Natural Source Zone Depletion, both with conventional methods and a new method based on thermal monitoring. Then we talk a little bit about low threat closures and transition assessments, and end up with a brief conversation with the three instructors. And then you are done!

BioPIC: Bio Pathway Identification Criteria Screening Tool for MNA9:54

Applicability of MNA for Different Contaminant Classes11:31

Natural Source Zone Depletion (NSZD)10:27

Thermal Monitoring of Natural Source Zone Depletion (Thermal NSZD)8:48

Low Risk Sites, Transition Assessments, and MNA10:33

Where MNA Might Go From Here6:22

Познакомьтесь с преподавателями

Pedro Alvarez
George R. Brown Professor of Civil and Environmental Engineering
Department of Civil and Environmental Engineering
Charles Newell
Vice President
GSI Environmental Inc.
David Adamson
Senior Environmental Engineer
GSI Environmental Inc.

We're here on set for the last of about 55 lectures,

about monitored natural attenuation.

I'm Elizabeth Pina, an engineer at GSI Environmental.

A recent graduate of Rice University and a manager for this project.

Today, we'll have a short discussion where I ask three question to each of our

instructors and we'll all have a brief discussion following each question.

So we'll go ahead and get started with our first question.

After about 20 years of applying MNA is our underlying philosophy still valid?

Are there any other factor that might makes us less

likely to do MNA in the future?

Pedro, you want to get started?

>> Yes, absolutely the philosophy is valid.

There is no question that some priority pollutants at some sites will degrade

faster than they migrate and that makes monitor natural attenuation,

the most logical and most cost effective approach in those cases.

But we have to remember, that the burden of proof that these process

are proceeding at an acceptable rate lies on the deeper opponent.

And we have learned organized last nine weeks or so, many techniques and

scientific principles to demonstrate that is the case and

enhance your decisions to select or reject natural attenuation.

>> Yeah, that's a great answer I'm thinking about the first part

of your question was is the philosophy still valid?

And I think back to a earlier lecture where I went on record saying that we're

all MNAers, so, yeah I believe the question to that is yes as well.

And then in terms of other factors to overcome, one thing that comes to

mind is this idea that there are still emerging contaminants out there and

it's PFAS, these per- and polyfluoroalkyl substances,

are of particular concern because I don't think we've really got the proper

conceptual model built for those in terms of how they behave in the environment.

So I think we're still a few years in terms of using MNA for

those types of sites.

>> Okay.

>> Well, good points, Pedro and Dave but Emily did

your question about what might makes use MNA less frequently in the future.

And it sort of taught three things.

So, they going back in time, 20,

maybe 25 years ago when the MNA was first being developed.

Some people said, there's going to be a failure, well, people get sick and

that's going to really reduce the use of this.

And I don't think that happened yet, but that's still possible in the future.

And that can be one constraint of big event where if people get sick,

because the emanate failed and, hey, we're going to use less of it.

Number two is changing exceptual models.

And this is happening a little bit things like vapour intrusion,maybe we're going to

have to reopen sites, you talked about those perfluorinated compounds.

If those are in a lot of sites and they're not amenable to MNA,

maybe we can't use it, because we've got to think about those compounds.

Number three, what about the silver bullet.

An intensive,

active remediation technology that can really remove most of these mass.

In that case, maybe we wouldn't need MNA.

So those are the three things that I thought about.

>> Great. Well, let's go ahead and

move to the second question.

Under what circumstances are we confident enough in MNA processeses and

our predictions about MNA,

that we can close sites before they meet drinking water standards.

Chuck, you want to go ahead and get us started?

>> Well, sure as I think many of you guys know that

there's many regulatory programs now that have these conditional closures out there.

That under certain circumstances,

you can watch this and understand, disseminate and then close this site.

But I think maybe with some of the new stuff that's coming out, and

we've talked about this in one of our lectures.

There's a lot of vary building in groundwater data and

instead of just having two years of data,

maybe we need longer records to really get that confidence in there.

So that's what I was thinking.

>> Yeah, and I think that I agree with you because we also went

through in one of the lectures there's policy, there's state policy out there

that allows you to actually sort of designate things as low risk sites.

Where concentrations might be above the MCL but

if you can demonstrate he distance to the receptor, and the concentrations,

are low enough that you can, actually, go out there and get these sites closed.

So, I think we're definitely transitioning that way.

>> Yeah, that's right.

I mean, nothing beats field data, showing that or

long terms, the plume is no longer expanding, that it might be stable,

or shrinking, and that's highly unlikely to ever reach a receptor.

But, we gotta be weary of unintended consequences when for

example, you try to accelerate Sorenson bioremediation and

in doing so, you end up either hindering microbial activities or

mobilizing some priority pollutants faster.

>> Great. And for a third and final question,

what new emerging technologies or techniques are you most excited about?

What new technologies will make our MNA projects better in the next few years?

Dave, you want to get us going on this one?

>> Well, I'm excited about all the advances that we've done in terms of high

resolution site characterization.

It's become pretty common place to actually use these at our sites and

we talked a lot about how sort of low permeability zones and matrix

diffusion and storage of this containment mass can impact the way the MNA works.

So we're actually got all these great tools now that we can use to build

the proper conceptual site model, sort of understand these things and

actually enhance the applicability of MNA.

>> Neat, neat.

Well, for me, I'm relished in this sort of Internet of things and

arrays of cheap sensors that are out there that are monitoring these sites.

I'm part of this team with some Colorado State to develop and

commercialize this thermal NSZD, Natural Source Zone Depletion technology.

Putting all of the thermocouples and measuring the heat,

generated by these bacteria to get these natural sources on the pollution rates.

Think it's really neat.

>> Yeah, those are really cool areas.

I am most excited about the molecular biology and

bioinformatics revolution that is sweeping across many different disciplines.

This is making gene pearls being easily accessible for many applications, and

significantly enhancing our forensic analysis capabilities.

Our abilities to assess performance assessment, for example,

when in support of these decisions to accept or reject natural attenuation.

In the not so distant future, I foresee the use of even

genes to augment the capabilities of indigenous bacteria and

accelerate this intrinsic bioremediation process.

>> Dr. Alvarez, Dr. Newell, Dr. Adamson, thank you so much for your time.

And to the viewer, thanks for listening.

Now, this conclude our nine week long course on monitored natural tenuation.

All you have left are quizzes and homework.

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