Henry: Hello, I'm Henry Borrebach, training coordinator with the Reef Resilience Network we call ourselves RRN, and host of this, our brand-new podcast. For almost 20 years, the Reef Resilience Network, a partnership led by The Nature Conservancy, but made up of dozens of partners and hundreds of global experts, has been a global leader in training marine managers and other practitioners to effectively manage, protect, and restore coral reefs.
We do this by turning scientific information and in the water experience into operational knowledge, tools, and guidance to help those who are tasked with caring for the world's reefs. This podcast is one of the new ways we're trying out to bring the latest science and strategies to marine managers for effective management of critical coastal areas.
Thanks for joining us. Let's dive on in!
As we get started, I should also mention that this episode is brought to you by not just the Reef Resilience Network, but also by our partners at The Nature Conservancy's Wasted Water Podcast. If you're interested in learning more about the impacts of wastewater pollution on humans and aquatic environments, and in exploring solutions for sustainable sanitation, please be sure to keep an eye out for the new Wasted Water Podcast, coming soon.
Today, I'll be joined by my colleague Kristen Maize, strategy lead for the Reef Resilience Network, and Rob McDonald, lead scientist for nature-based solutions at The Nature Conservancy, as well as lead scientist for the Europe region. We'll be discussing nature-based solutions for managing wastewater pollution.
Nature based solutions provide an alternative to traditional grey infrastructure. For me, I think of the cement vats of wastewater tucked never quite out of sight and never ever out of smell just outside of so many of the cities where I've lived, uh, versus the gray water gardens and eco properties where I've also worked before.
Beyond the wastewater pollution sector, nature-based solutions are emerging as an important tool to combat climate change, from urban greening projects to living shorelines and more. For wastewater pollution mitigation, nature-based solutions use natural processes involving plants or microbes to capture and treat contaminated water before discharging to the ocean or waterways.
Using nature as infrastructure can be a great way to reduce risk from wastewater pollution while also providing important ecological benefits to animals and humans. Rob researches the impact and dependencies of communities on the natural world, studying how nature can increase resilience in the face of climate change while also improving human health and wellbeing.
He recently led the SNAPP, that's Science for Nature and People Partnership, the SNAPP Working Group on Water, Sanitation, and Nature. Nature based solutions are still a relatively novel concept, but Rob is here to talk with us about the crucial role that they can play in protecting our reefs and our communities, and to share some strategies on how we can make the case for their implementation.
So, welcome, Kristen and Rob. I'm so excited you're here. Um, maybe Kristen, I'll hand it off to you.
Kristin: Thanks, Henry. And thanks, Rob, for joining us. And thanks, everyone. Welcome. Rob, we're really eager to hear from you about nature-based solutions for ocean wastewater pollution. But before we dive in, as Henry said, is there anything else you'd like to say about yourself by way of introduction?
Rob: Thanks for having me. First of all, it's delightful to be here. Um, you know, as was mentioned, I work as lead scientist for nature-based solutions. So I think about all of those different benefits nature provides to people, um, from wellbeing mental and physical to filtering water to reducing heat. Um, by training, I'm a terrestrial plant ecologist, actually, so it's a little intimidating joining a podcast about reefs and reef managers.
But one of the benefits that nature provides is this filtration of water, getting pollutants out of water. And so that's going to be the link that we talk about today to, to freshwater and then to the marine system.
Kristin: Awesome. Well, we're really glad that you're here, Rob, um, and bring the expertise and background that you do.
So if you've made it to this podcast, you probably understand a little bit about the impacts that wastewater can have of our on our oceans and coral reefs in particular. But just in case as a little reminder, you know, wastewater can transport pathogens, nutrients and contaminants like pharmaceuticals and personal care products into the ocean and that can cause coral bleaching and disease for corals, fish and shellfish.
Wastewater can also alter ocean temperature, pH, salinity and oxygen levels, disrupting biological processes and physical environments that are essential to marine life. Um, and Henry, even though you introduced the concept of nature-based solutions as a potential replacement for or complement to gray water, it’s actually really important to keep in mind that in many places there is no wastewater treatment at all.
It's estimated that 80 percent of wastewater globally is discharged into the environment without any treatment. So in many places, a nature-based solution could be the first solution that is implemented. So those are just a few points to serve as context for our conversation with Rob. Um, so Rob, uh, could you please start off by telling us a little bit more about the ways nature-based solutions are being used around the world to treat wastewater?
Rob: Yeah, sure. Um, so first of all, when you think about nature-based solutions for treating wastewater, people tend to think first, when you say nature-based solutions about trees and grass and shrubs and, but actually the important part of nature that we're really talking about is often soil and bacteria.
So those are the, the natural elements that play a big role in treating wastewater and removing pollutants. The reason nature-based solutions as a complement to gray infrastructure is that it usually reduces the use of chemicals usually reduces the use of energy. There's sometimes some lower cost, especially the capital cost of, of building the nature-based solution.
So, as we'll get into it, it's not a panacea but it, they can serve important purposes, especially for certain kinds of wastewater. So that's another big concept we should keep in mind today. There are at least three kinds of gray water or cranes of wastewater. One is gray water. So, this idea of water from showers and baths and, you know, your washing machine, that's only a little bit dirty. It's an easier type of wastewater to clean up. And then there's what's sometimes called black water. So, this is your toilet waste, basically. And there's all kinds of human health issues dealing with black water. So, it's harder to use nature-based solutions to treat that. And then the third category people talk about is industrial wastewater, which sometimes has really high concentrations of heavy metals or other toxic chemicals.
So, the sewage that a sewage treatment plant gets It might be a mix of all those. And how dirty it is determines how much nature can do. I think the other big thing to think about is what kind of treatment you're doing. So, a typical sewage treatment plant first does primary removal. So primary treatment is there's like solid waste floating in the water, sediment, you know, bits of toilet paper, those have to settle out.
Then you have secondary treatment. So, you're removing some kind of organic matter that's floating in the water that's dissolved in the water and here, bacteria plays a really big role. So, if nature-based solutions are going to come in, it's often algal tanks or tanks with bacteria that's treating and dissolving that organic matter.
Um, then there's what's called tertiary treatment and that is removal of other pollutants, especially excess nutrients or too much nitrogen, for instance. That is probably most often in the U. S. and Europe, where you see nature-based solutions playing a big role is in that tertiary treatment process.
So anyway, in a nutshell, think about what kind of wastewater is coming in and what role you want nature to play when you're planning for nature-based solutions.
Kristin: Awesome. Thanks, Rob. And you started off by just sharing a little bit that, you know, what jumps to mind most often for folks at plants, and that's definitely the case for me.
I always just picture rain gardens. It's like my default. And as you were describing some things to us, there was a visual of a tank, but could you just give us a few other visuals of, you know, what these solutions look like in in real life.
Rob: Yeah, so they definitely vary. And for the project that we're talking about today, we were working with engineers from around the world sort of collecting what are the different kinds of nature-based solutions for wastewater treatment and there's dozens and dozens of types. But I think a lot of them look like wetlands kind of constructed wetlands.
You might have fragmites, you know, cattails growing. And then they you have some plants growing on top of often sand or gravel. And the water, their designs of water flows through that system. So, the water is flowing slowly through the wetland and through that filtration, uh, system or material at the bottom.
Uh, so has a lot of the function of a natural marsh, but they're usually man made with a uh, kind of a, an impermeable barrier at the bottom or at least engineered so that the water flow is controlled. But yeah, people want to have something in mind. Just think about a marsh if you've ever seen one with, with cattails.
That's what a lot of these, uh, look like. Or short grasses. They can be short grasses..
Kristin: Awesome. Super helpful. And could you just talk a little bit, I know we said your a plant guy, terrestrial based, but just talk a little bit more about how nature-based solutions can address wastewater pollution issues for the ocean.
Rob: Yeah. So, in a way, nature, nature-based solutions for wastewater treatment are the same whether you're thinking about just protecting fresh water streams or the ocean. The task that you want nature to do, cleaning up the wastewater is kind of the same. What makes marine systems more vulnerable, right, is that there are these hotspots for biodiversity and also that in many cities, human settlements are near coastlines. And in fact, intentionally dump untreated sewage just a bit offshore. So, there's been a tendency in past decades to think of kind of oh, well, we're just going to put it out into the sea and this problem will go away. And obviously the pollution doesn't go away. It just ends up impacting marine systems.
So, nature-based solutions really are just one tool to clean up some of that gunk that we're dropping into the ocean. And from the perspective of protecting those reef systems, you shouldn't really care too much if it's nature-based solutions or gray solutions or some hybrid. You just want to find an efficient solution that's going to, um, reduce the amount of pollution getting into the ocean.
Henry: Yeah. That makes a lot of sense. As I'm imagining these, like the marshes are sort of, you've put this idea of like the tanks or sort of semi manmade marsh systems for the treatment. Is it scale? Does it scale up and down pretty readily? Like does it, does it function similarly at, at like the small scale, say for like even a village or a small population versus what you'd need for a city or.
Rob: You know, I guess that, yeah. So, the size that you need, the space you need to use nature-based solutions for wastewater varies a lot on at least two things. The first is the amount of wastewater that's there. And so that has to do with the number of people. Obviously, if you're designing something just for one house or one apartment building, very different than for a whole town.
Um, the other big thing is climate. Which, which might surprise folks, but if you're in a fairly cold climate, a lot of the bacterial processes are moving pretty slow. There's not a lot of, you know, energy in the system. Conversely, if you're in the tropics, the bacterial processes move really quickly.
Organic matter breaks down really quickly. That can pose some problems for management, but you need a little bit less space all else equal. So those are kind of the two big factors. And I guess the third factor that has to do with scale is how dirty the water is. So gray water is easier to treat.
Especially if your goal is to just get to a point where you can use it for watering plants and lawns and you know, it's not meant to be potable. Things like, um, black water, it takes more space, right? Because you're often needing a whole treatment train from primary to secondary to tertiary and maybe to advanced treatment to get back to a place where you can use it safely and there isn't that human health risk.
Henry: Great. Thank you for that. Um, and then maybe kind of along these same lines thinking about the efficiencies and costs, and also, I guess the potential benefits. Could you talk a little bit more about sort of, like the, yeah, I guess just a cost benefit comparison of a nature-based solution versus a more traditional gray infrastructural option.
Rob: Yeah, so on the cost side nature-based solutions take some more space than gray infrastructure. And maybe it's a bit of a newer technique. There are a lot of engineers working on it, but you need to work with engineers who are skilled in using nature to treat wastewater. What is generally cheaper is that nature-based solutions often cost less to construct on the front end, so there's often lower capital costs.
They take less energy, less chemicals. And so there's often kind of less, some less maintenance costs. There still are some main costs to be clear. It's sometimes you have to go in and dredge out the wetland or whatever. Um, so there's kind of a human time cost that can be considerable, but overall for certain tasks, especially that sort of tertiary treatment I was talking about of removing, uh, nitrogen, say they're quite cost competitive ways to, to do that compared with the grain infrastructure solution, uh, again, as long as you have that, that space.
Henry: And then I guess following from that as well. I mean, honestly, when I was looking and reading about some of this stuff ahead of recording this I think that comes up a lot is that nature-based solutions get dismissed as being like too costly or that they don't balance out against gray infrastructure.
And so I guess in two pieces of question here is one, is that, do you feel like that is accurate? And whether or not that's true, how have you been finding ways to make the case for, for implementing nature-based solutions?
Rob: Yeah, what we were doing in this project was assembling really case studies from hundreds of places around the world where nature-based solutions were being used to treat wastewater, and then synthesizing that information into a website and a decision support tool for where we are planning for how to use nature to treat wastewater.
So hopefully we can have the link on your website, but it's snapp.icra.cat. So if you go there, what you see is lots of different technologies and then there's a button that says, find your NBS and you can start to plug in the factors we were just talking about. So, how dirty is the water? How many people is this wastewater coming from? What climate are you in? And it helps you narrow down to a few kinds of nature-based solutions. And then for each of them, you can click and see a sort of schematic, but also have examples. For a lot of them, we have linked kind of case studies to a real world example that talks about the cost and the benefits of that site.
So that's my little way as a scientist that I'm making the case for this technology. There are definitely colleagues of mine at The Nature Conservancy who are then out trying to implement some of these solutions in the real world, right, and are kind of making that case in an on the ground practitioner kind of way, too.
Kristin: Great. Thanks, Rob. And we'll definitely make sure that that resource link is available. And anytime there's any resource that has a breakdown between nature-based solutions and more traditional great infrastructure kind of pros and cons to each could be a really useful tool. But along the same lines of just continuing, you know, kind of the building content to make the case or, you know, demonstrate the effectiveness for nature-based solutions where we're often hearing from practitioners that it can be difficult making the case when we're thinking about nature-based solutions, really, because of the lack of long term data on how these solutions function and the benefits they provide, especially because gray infrastructure, you know, despite some of the faults or the cons that you just outlined, it has years of monitoring to demonstrate its effectiveness. Um, so just wondering if you've run into this challenge in your research. And maybe just any thoughts you have around how to overcome this, you know, shorter, shorter amount of data for nature-based solutions.
Rob: Yeah, I always feel like in some ways, the phrase nature-based solutions. Um, uh, can be sometimes misleading. Well, because it is a new term, just the last four or five years, really. And it can make everything nature related sound quite new. Um, in this particular domain of using nature to clean wastewater, certain things like having algal palms and using bacteria and soils to treat water or constructed wetlands for tertiary treatment—those have been around for decades, decades and decades. And so there are engineering standards for how you build them. They vary a little bit between country and that was countries. That was one of the things I learned during this project. I thought was interesting is the way the French do them is a little different than the way the Americans do them.
But, but there are standard ways to do them and there's some long term data. Now there are other kind of newer, hipper types of nature-based solutions. You see people trying to use integrated gray water systems that then filter gray water through plants growing on a wall, for instance.
There's a lot of, um, really interesting work happening now with green facades. So those are really new, and we don't know as much about the long term costs or how you maintain those systems, but for the, the basic stuff we're talking about, about building constructive wetlands or. using bacteria and soil to treat water, there's quite a lot of long-term data. And when I did this project, I'm an ecologist, but was co-leading this project with people from the International Water Association, IWA. And they have a whole commission of engineers who just work on this topic of MDS fresh sanitation. And for a lot of them, it's been their business for most of their career.
And for folks, anyone listening to this podcast who's seriously thinking about this, building a nature for sanitation facility, the IWA commission is there in part to answer questions, right? So people can email them and get questions answered.
Kristin: Fabulous. So great, great to hear. There is long-term data and it sounds like it's more about kind of reframing and repackaging and make sure all the. You know, I love using nature for sanitation solutions. It feels innovative and novel. We remind people that it's not that new. So that's a really important takeaway for me from this. So thanks, Rob and just go in a step further because you just gave some great advice. Do you have any additional advice to a marine manager who's trying to make the case for using nature-based solutions to address environmental issues? Ocean wastewater pollution. So here I'm envisioning a manager making a pitch to their local or state government and particularly thinking of our managers in regions with more limited resources available. What advice would you have for them?
Rob: I would say first focus on your goal and which may very well just be preventing wastewater from impacting your marine system, whether it's gray or green and sort of start with that. Departure point. Nature-based solutions might just be one way to do that, but it is likely going to have to be complimented by other gray infrastructure, especially in the U.S or Europe, where there's some pretty strict rules about how you have to treat gray water. So, it's actually hard. In those two countries to just treat wastewater with, like, especially black water with just nature-based solutions. I think the situation in developing countries is different. There's often a lot less resources.
And some really significant health problems from sewage, right? And you do see some situations where nature-based solutions are, you know, one of the only options because they're cheaper to implement. And I, yeah, I think people should be aware that there one potential solution. And that there are these, they're very good for some things like for moving nutrients, you know, sediment, certain kinds of pollutant and they're not so good for other things, right? And, and so that, that tradeoff is something to keep in, keep in mind.
Henry: Yeah, I find myself thinking that as long as you've got the space, the, since the startup costs are lower that's the crux of the case would be, if we've got the space to, to implement this kind of system, it's going to be cheaper to start. And also, being really clear about the objectives that it will deliver on.
And I think this is actually we're covering what we were hoping to. I wanted to pivot a little bit with maybe just one more question here. And I don't really know what the answer is at all, but I was wondering if you could talk a little bit about sort of the intersection between whether it's wastewater treatment or nature-based solutions and climate change.
Rob: Yeah, that's it's such a interesting complex question. So on the one hand, climate change is making the wastewater challenge a lot harder. So many cities around the world have combined sewer system. So, the stormwater flows in with the sewage and then all of that water combined goes to the sewage treatment plant.
Those systems are usually designed so that when it rains a lot, uh, that mass of sewage and stormwater gets dumped into rivers, right, and then impacts the ocean. There, climate change is making that problem worse because it is, it seems to be making what rains do occur more intense. And so you're getting potentially more of these sewer overflow events.
Climate change also will, of course, change how the nature-based solution functions when it's when it's treating the wastewater. So, in some ways, you know, having warm temperatures actually speeds up that bacterial action I talked about. That can be climate change is, um, Helpful, especially if you live in the colder climate right now.
Um, but if you start to get really extreme droughts that can kill the grasses or the marsh plants growing there. Or conversely, if you get really big flood events water can move too fast through those systems and that that can reduce their ability to reduce the pollutant load. So, climate change is something that you'll have to plan for in this area of human society, just like probably everything we do now.
Henry: Yeah, that, that, that's true for sure. Well, that's really great. Cause I, I think about that too, in terms of if you're in a context where there's really no particular infrastructure in place yet, that if you do go the route of a nature-based solution and, and are thinking ahead to future climate scenarios that you might have a system that can be more resilient in that kind of way too, or ready to absorb some of those shock events as they come. But with that, unless either of you have anything else really that you need to get out before we end here. I think that's about what we've got. So I'll, I'll wait a beat to see if either of you say anything else.
Kristin: I'll just say thanks, Rob. Appreciate it. I learned a lot. I don't know why I'm hung up on the, you know, in warmer climates, bacteria works better and it can be more efficient. It seems so obvious, but it's just not anything I've thought about before. So, I don't, I don't know that that's sticking with me, but, but really appreciate your time.
Rob: Oh, it's a pleasure. It was a pleasure to be here. Yeah, I mean, I view this as, um, this interesting intersection of nature and then a public health challenge, right, which is avoiding sanitation failures and wastewater pollution. And, so it's fun for me to talk about it. It's fun for me to think about how nature can be one small part of solving that problem.
Kristin: Yeah, and Henry, I'll just add, I mean, I think this is a great conversation, Rob, and really important for marine managers to be learning from the terrestrial folks and with a really this huge and complex problem of wastewater pollution in the ocean. It is really important to work across sectors, both marine to terrestrial.
We've been talking a lot. And just getting more familiar with this topic and kind of understanding each other's language helps have conversations across those sectors. And really helps can help our managers begin to address wastewater issues at their site. So, so thanks for helping us understand more today.
Henry: Yeah. Thank you both very much for joining us here. And thanks to all you listeners that listened to us here. And as we stumbled through our very first podcast I thought it was a really great conversation. And as we mentioned earlier any links or additional resources along with RRN's own wastewater pollution toolkit can be found on our website at reefresilience.org.
Kristin: Thanks for bringing up the toolkit. I will just say for those listeners who aren't already familiar and maybe haven't taken the course, Reef Resilience Network in response to you guys asking for years for some resources to start to begin to tackle this topic, we developed some introductory resources. So, there's the wastewater pollution toolkit that Henry mentioned. So, it's webpages summarizing, you know, the basics of impacts to marine and human health, what management of wastewater is currently looking like, um, what it could look like and some resources and tips related to collaboration and communication.
Our online course is a deeper dive on all of that content. It's free, self-paced. There's two lessons. You can access it through our website. We also have case studies. I think there are about 15 now on focused on wastewater pollution, highlighting management strategies that your colleagues are using across the world. And then we have summaries on the latest science related to this topic. So thanks, Henry, for that reminder. And yeah, hope you can explore those resources and please always give us feedback and ideas for what we should be sharing.
Henry: And again, thank you for joining us and we'll hope you, you tune in next time as well.
We do this by turning scientific information and in the water experience into operational knowledge, tools, and guidance to help those who are tasked with caring for the world's reefs. This podcast is one of the new ways we're trying out to bring the latest science and strategies to marine managers for effective management of critical coastal areas.
Thanks for joining us. Let's dive on in!
As we get started, I should also mention that this episode is brought to you by not just the Reef Resilience Network, but also by our partners at The Nature Conservancy's Wasted Water Podcast. If you're interested in learning more about the impacts of wastewater pollution on humans and aquatic environments, and in exploring solutions for sustainable sanitation, please be sure to keep an eye out for the new Wasted Water Podcast, coming soon.
Today, I'll be joined by my colleague Kristen Maize, strategy lead for the Reef Resilience Network, and Rob McDonald, lead scientist for nature-based solutions at The Nature Conservancy, as well as lead scientist for the Europe region. We'll be discussing nature-based solutions for managing wastewater pollution.
Nature based solutions provide an alternative to traditional grey infrastructure. For me, I think of the cement vats of wastewater tucked never quite out of sight and never ever out of smell just outside of so many of the cities where I've lived, uh, versus the gray water gardens and eco properties where I've also worked before.
Beyond the wastewater pollution sector, nature-based solutions are emerging as an important tool to combat climate change, from urban greening projects to living shorelines and more. For wastewater pollution mitigation, nature-based solutions use natural processes involving plants or microbes to capture and treat contaminated water before discharging to the ocean or waterways.
Using nature as infrastructure can be a great way to reduce risk from wastewater pollution while also providing important ecological benefits to animals and humans. Rob researches the impact and dependencies of communities on the natural world, studying how nature can increase resilience in the face of climate change while also improving human health and wellbeing.
He recently led the SNAPP, that's Science for Nature and People Partnership, the SNAPP Working Group on Water, Sanitation, and Nature. Nature based solutions are still a relatively novel concept, but Rob is here to talk with us about the crucial role that they can play in protecting our reefs and our communities, and to share some strategies on how we can make the case for their implementation.
So, welcome, Kristen and Rob. I'm so excited you're here. Um, maybe Kristen, I'll hand it off to you.
Kristin: Thanks, Henry. And thanks, Rob, for joining us. And thanks, everyone. Welcome. Rob, we're really eager to hear from you about nature-based solutions for ocean wastewater pollution. But before we dive in, as Henry said, is there anything else you'd like to say about yourself by way of introduction?
Rob: Thanks for having me. First of all, it's delightful to be here. Um, you know, as was mentioned, I work as lead scientist for nature-based solutions. So I think about all of those different benefits nature provides to people, um, from wellbeing mental and physical to filtering water to reducing heat. Um, by training, I'm a terrestrial plant ecologist, actually, so it's a little intimidating joining a podcast about reefs and reef managers.
But one of the benefits that nature provides is this filtration of water, getting pollutants out of water. And so that's going to be the link that we talk about today to, to freshwater and then to the marine system.
Kristin: Awesome. Well, we're really glad that you're here, Rob, um, and bring the expertise and background that you do.
So if you've made it to this podcast, you probably understand a little bit about the impacts that wastewater can have of our on our oceans and coral reefs in particular. But just in case as a little reminder, you know, wastewater can transport pathogens, nutrients and contaminants like pharmaceuticals and personal care products into the ocean and that can cause coral bleaching and disease for corals, fish and shellfish.
Wastewater can also alter ocean temperature, pH, salinity and oxygen levels, disrupting biological processes and physical environments that are essential to marine life. Um, and Henry, even though you introduced the concept of nature-based solutions as a potential replacement for or complement to gray water, it’s actually really important to keep in mind that in many places there is no wastewater treatment at all.
It's estimated that 80 percent of wastewater globally is discharged into the environment without any treatment. So in many places, a nature-based solution could be the first solution that is implemented. So those are just a few points to serve as context for our conversation with Rob. Um, so Rob, uh, could you please start off by telling us a little bit more about the ways nature-based solutions are being used around the world to treat wastewater?
Rob: Yeah, sure. Um, so first of all, when you think about nature-based solutions for treating wastewater, people tend to think first, when you say nature-based solutions about trees and grass and shrubs and, but actually the important part of nature that we're really talking about is often soil and bacteria.
So those are the, the natural elements that play a big role in treating wastewater and removing pollutants. The reason nature-based solutions as a complement to gray infrastructure is that it usually reduces the use of chemicals usually reduces the use of energy. There's sometimes some lower cost, especially the capital cost of, of building the nature-based solution.
So, as we'll get into it, it's not a panacea but it, they can serve important purposes, especially for certain kinds of wastewater. So that's another big concept we should keep in mind today. There are at least three kinds of gray water or cranes of wastewater. One is gray water. So, this idea of water from showers and baths and, you know, your washing machine, that's only a little bit dirty. It's an easier type of wastewater to clean up. And then there's what's sometimes called black water. So, this is your toilet waste, basically. And there's all kinds of human health issues dealing with black water. So, it's harder to use nature-based solutions to treat that. And then the third category people talk about is industrial wastewater, which sometimes has really high concentrations of heavy metals or other toxic chemicals.
So, the sewage that a sewage treatment plant gets It might be a mix of all those. And how dirty it is determines how much nature can do. I think the other big thing to think about is what kind of treatment you're doing. So, a typical sewage treatment plant first does primary removal. So primary treatment is there's like solid waste floating in the water, sediment, you know, bits of toilet paper, those have to settle out.
Then you have secondary treatment. So, you're removing some kind of organic matter that's floating in the water that's dissolved in the water and here, bacteria plays a really big role. So, if nature-based solutions are going to come in, it's often algal tanks or tanks with bacteria that's treating and dissolving that organic matter.
Um, then there's what's called tertiary treatment and that is removal of other pollutants, especially excess nutrients or too much nitrogen, for instance. That is probably most often in the U. S. and Europe, where you see nature-based solutions playing a big role is in that tertiary treatment process.
So anyway, in a nutshell, think about what kind of wastewater is coming in and what role you want nature to play when you're planning for nature-based solutions.
Kristin: Awesome. Thanks, Rob. And you started off by just sharing a little bit that, you know, what jumps to mind most often for folks at plants, and that's definitely the case for me.
I always just picture rain gardens. It's like my default. And as you were describing some things to us, there was a visual of a tank, but could you just give us a few other visuals of, you know, what these solutions look like in in real life.
Rob: Yeah, so they definitely vary. And for the project that we're talking about today, we were working with engineers from around the world sort of collecting what are the different kinds of nature-based solutions for wastewater treatment and there's dozens and dozens of types. But I think a lot of them look like wetlands kind of constructed wetlands.
You might have fragmites, you know, cattails growing. And then they you have some plants growing on top of often sand or gravel. And the water, their designs of water flows through that system. So, the water is flowing slowly through the wetland and through that filtration, uh, system or material at the bottom.
Uh, so has a lot of the function of a natural marsh, but they're usually man made with a uh, kind of a, an impermeable barrier at the bottom or at least engineered so that the water flow is controlled. But yeah, people want to have something in mind. Just think about a marsh if you've ever seen one with, with cattails.
That's what a lot of these, uh, look like. Or short grasses. They can be short grasses..
Kristin: Awesome. Super helpful. And could you just talk a little bit, I know we said your a plant guy, terrestrial based, but just talk a little bit more about how nature-based solutions can address wastewater pollution issues for the ocean.
Rob: Yeah. So, in a way, nature, nature-based solutions for wastewater treatment are the same whether you're thinking about just protecting fresh water streams or the ocean. The task that you want nature to do, cleaning up the wastewater is kind of the same. What makes marine systems more vulnerable, right, is that there are these hotspots for biodiversity and also that in many cities, human settlements are near coastlines. And in fact, intentionally dump untreated sewage just a bit offshore. So, there's been a tendency in past decades to think of kind of oh, well, we're just going to put it out into the sea and this problem will go away. And obviously the pollution doesn't go away. It just ends up impacting marine systems.
So, nature-based solutions really are just one tool to clean up some of that gunk that we're dropping into the ocean. And from the perspective of protecting those reef systems, you shouldn't really care too much if it's nature-based solutions or gray solutions or some hybrid. You just want to find an efficient solution that's going to, um, reduce the amount of pollution getting into the ocean.
Henry: Yeah. That makes a lot of sense. As I'm imagining these, like the marshes are sort of, you've put this idea of like the tanks or sort of semi manmade marsh systems for the treatment. Is it scale? Does it scale up and down pretty readily? Like does it, does it function similarly at, at like the small scale, say for like even a village or a small population versus what you'd need for a city or.
Rob: You know, I guess that, yeah. So, the size that you need, the space you need to use nature-based solutions for wastewater varies a lot on at least two things. The first is the amount of wastewater that's there. And so that has to do with the number of people. Obviously, if you're designing something just for one house or one apartment building, very different than for a whole town.
Um, the other big thing is climate. Which, which might surprise folks, but if you're in a fairly cold climate, a lot of the bacterial processes are moving pretty slow. There's not a lot of, you know, energy in the system. Conversely, if you're in the tropics, the bacterial processes move really quickly.
Organic matter breaks down really quickly. That can pose some problems for management, but you need a little bit less space all else equal. So those are kind of the two big factors. And I guess the third factor that has to do with scale is how dirty the water is. So gray water is easier to treat.
Especially if your goal is to just get to a point where you can use it for watering plants and lawns and you know, it's not meant to be potable. Things like, um, black water, it takes more space, right? Because you're often needing a whole treatment train from primary to secondary to tertiary and maybe to advanced treatment to get back to a place where you can use it safely and there isn't that human health risk.
Henry: Great. Thank you for that. Um, and then maybe kind of along these same lines thinking about the efficiencies and costs, and also, I guess the potential benefits. Could you talk a little bit more about sort of, like the, yeah, I guess just a cost benefit comparison of a nature-based solution versus a more traditional gray infrastructural option.
Rob: Yeah, so on the cost side nature-based solutions take some more space than gray infrastructure. And maybe it's a bit of a newer technique. There are a lot of engineers working on it, but you need to work with engineers who are skilled in using nature to treat wastewater. What is generally cheaper is that nature-based solutions often cost less to construct on the front end, so there's often lower capital costs.
They take less energy, less chemicals. And so there's often kind of less, some less maintenance costs. There still are some main costs to be clear. It's sometimes you have to go in and dredge out the wetland or whatever. Um, so there's kind of a human time cost that can be considerable, but overall for certain tasks, especially that sort of tertiary treatment I was talking about of removing, uh, nitrogen, say they're quite cost competitive ways to, to do that compared with the grain infrastructure solution, uh, again, as long as you have that, that space.
Henry: And then I guess following from that as well. I mean, honestly, when I was looking and reading about some of this stuff ahead of recording this I think that comes up a lot is that nature-based solutions get dismissed as being like too costly or that they don't balance out against gray infrastructure.
And so I guess in two pieces of question here is one, is that, do you feel like that is accurate? And whether or not that's true, how have you been finding ways to make the case for, for implementing nature-based solutions?
Rob: Yeah, what we were doing in this project was assembling really case studies from hundreds of places around the world where nature-based solutions were being used to treat wastewater, and then synthesizing that information into a website and a decision support tool for where we are planning for how to use nature to treat wastewater.
So hopefully we can have the link on your website, but it's snapp.icra.cat. So if you go there, what you see is lots of different technologies and then there's a button that says, find your NBS and you can start to plug in the factors we were just talking about. So, how dirty is the water? How many people is this wastewater coming from? What climate are you in? And it helps you narrow down to a few kinds of nature-based solutions. And then for each of them, you can click and see a sort of schematic, but also have examples. For a lot of them, we have linked kind of case studies to a real world example that talks about the cost and the benefits of that site.
So that's my little way as a scientist that I'm making the case for this technology. There are definitely colleagues of mine at The Nature Conservancy who are then out trying to implement some of these solutions in the real world, right, and are kind of making that case in an on the ground practitioner kind of way, too.
Kristin: Great. Thanks, Rob. And we'll definitely make sure that that resource link is available. And anytime there's any resource that has a breakdown between nature-based solutions and more traditional great infrastructure kind of pros and cons to each could be a really useful tool. But along the same lines of just continuing, you know, kind of the building content to make the case or, you know, demonstrate the effectiveness for nature-based solutions where we're often hearing from practitioners that it can be difficult making the case when we're thinking about nature-based solutions, really, because of the lack of long term data on how these solutions function and the benefits they provide, especially because gray infrastructure, you know, despite some of the faults or the cons that you just outlined, it has years of monitoring to demonstrate its effectiveness. Um, so just wondering if you've run into this challenge in your research. And maybe just any thoughts you have around how to overcome this, you know, shorter, shorter amount of data for nature-based solutions.
Rob: Yeah, I always feel like in some ways, the phrase nature-based solutions. Um, uh, can be sometimes misleading. Well, because it is a new term, just the last four or five years, really. And it can make everything nature related sound quite new. Um, in this particular domain of using nature to clean wastewater, certain things like having algal palms and using bacteria and soils to treat water or constructed wetlands for tertiary treatment—those have been around for decades, decades and decades. And so there are engineering standards for how you build them. They vary a little bit between country and that was countries. That was one of the things I learned during this project. I thought was interesting is the way the French do them is a little different than the way the Americans do them.
But, but there are standard ways to do them and there's some long term data. Now there are other kind of newer, hipper types of nature-based solutions. You see people trying to use integrated gray water systems that then filter gray water through plants growing on a wall, for instance.
There's a lot of, um, really interesting work happening now with green facades. So those are really new, and we don't know as much about the long term costs or how you maintain those systems, but for the, the basic stuff we're talking about, about building constructive wetlands or. using bacteria and soil to treat water, there's quite a lot of long-term data. And when I did this project, I'm an ecologist, but was co-leading this project with people from the International Water Association, IWA. And they have a whole commission of engineers who just work on this topic of MDS fresh sanitation. And for a lot of them, it's been their business for most of their career.
And for folks, anyone listening to this podcast who's seriously thinking about this, building a nature for sanitation facility, the IWA commission is there in part to answer questions, right? So people can email them and get questions answered.
Kristin: Fabulous. So great, great to hear. There is long-term data and it sounds like it's more about kind of reframing and repackaging and make sure all the. You know, I love using nature for sanitation solutions. It feels innovative and novel. We remind people that it's not that new. So that's a really important takeaway for me from this. So thanks, Rob and just go in a step further because you just gave some great advice. Do you have any additional advice to a marine manager who's trying to make the case for using nature-based solutions to address environmental issues? Ocean wastewater pollution. So here I'm envisioning a manager making a pitch to their local or state government and particularly thinking of our managers in regions with more limited resources available. What advice would you have for them?
Rob: I would say first focus on your goal and which may very well just be preventing wastewater from impacting your marine system, whether it's gray or green and sort of start with that. Departure point. Nature-based solutions might just be one way to do that, but it is likely going to have to be complimented by other gray infrastructure, especially in the U.S or Europe, where there's some pretty strict rules about how you have to treat gray water. So, it's actually hard. In those two countries to just treat wastewater with, like, especially black water with just nature-based solutions. I think the situation in developing countries is different. There's often a lot less resources.
And some really significant health problems from sewage, right? And you do see some situations where nature-based solutions are, you know, one of the only options because they're cheaper to implement. And I, yeah, I think people should be aware that there one potential solution. And that there are these, they're very good for some things like for moving nutrients, you know, sediment, certain kinds of pollutant and they're not so good for other things, right? And, and so that, that tradeoff is something to keep in, keep in mind.
Henry: Yeah, I find myself thinking that as long as you've got the space, the, since the startup costs are lower that's the crux of the case would be, if we've got the space to, to implement this kind of system, it's going to be cheaper to start. And also, being really clear about the objectives that it will deliver on.
And I think this is actually we're covering what we were hoping to. I wanted to pivot a little bit with maybe just one more question here. And I don't really know what the answer is at all, but I was wondering if you could talk a little bit about sort of the intersection between whether it's wastewater treatment or nature-based solutions and climate change.
Rob: Yeah, that's it's such a interesting complex question. So on the one hand, climate change is making the wastewater challenge a lot harder. So many cities around the world have combined sewer system. So, the stormwater flows in with the sewage and then all of that water combined goes to the sewage treatment plant.
Those systems are usually designed so that when it rains a lot, uh, that mass of sewage and stormwater gets dumped into rivers, right, and then impacts the ocean. There, climate change is making that problem worse because it is, it seems to be making what rains do occur more intense. And so you're getting potentially more of these sewer overflow events.
Climate change also will, of course, change how the nature-based solution functions when it's when it's treating the wastewater. So, in some ways, you know, having warm temperatures actually speeds up that bacterial action I talked about. That can be climate change is, um, Helpful, especially if you live in the colder climate right now.
Um, but if you start to get really extreme droughts that can kill the grasses or the marsh plants growing there. Or conversely, if you get really big flood events water can move too fast through those systems and that that can reduce their ability to reduce the pollutant load. So, climate change is something that you'll have to plan for in this area of human society, just like probably everything we do now.
Henry: Yeah, that, that, that's true for sure. Well, that's really great. Cause I, I think about that too, in terms of if you're in a context where there's really no particular infrastructure in place yet, that if you do go the route of a nature-based solution and, and are thinking ahead to future climate scenarios that you might have a system that can be more resilient in that kind of way too, or ready to absorb some of those shock events as they come. But with that, unless either of you have anything else really that you need to get out before we end here. I think that's about what we've got. So I'll, I'll wait a beat to see if either of you say anything else.
Kristin: I'll just say thanks, Rob. Appreciate it. I learned a lot. I don't know why I'm hung up on the, you know, in warmer climates, bacteria works better and it can be more efficient. It seems so obvious, but it's just not anything I've thought about before. So, I don't, I don't know that that's sticking with me, but, but really appreciate your time.
Rob: Oh, it's a pleasure. It was a pleasure to be here. Yeah, I mean, I view this as, um, this interesting intersection of nature and then a public health challenge, right, which is avoiding sanitation failures and wastewater pollution. And, so it's fun for me to talk about it. It's fun for me to think about how nature can be one small part of solving that problem.
Kristin: Yeah, and Henry, I'll just add, I mean, I think this is a great conversation, Rob, and really important for marine managers to be learning from the terrestrial folks and with a really this huge and complex problem of wastewater pollution in the ocean. It is really important to work across sectors, both marine to terrestrial.
We've been talking a lot. And just getting more familiar with this topic and kind of understanding each other's language helps have conversations across those sectors. And really helps can help our managers begin to address wastewater issues at their site. So, so thanks for helping us understand more today.
Henry: Yeah. Thank you both very much for joining us here. And thanks to all you listeners that listened to us here. And as we stumbled through our very first podcast I thought it was a really great conversation. And as we mentioned earlier any links or additional resources along with RRN's own wastewater pollution toolkit can be found on our website at reefresilience.org.
Kristin: Thanks for bringing up the toolkit. I will just say for those listeners who aren't already familiar and maybe haven't taken the course, Reef Resilience Network in response to you guys asking for years for some resources to start to begin to tackle this topic, we developed some introductory resources. So, there's the wastewater pollution toolkit that Henry mentioned. So, it's webpages summarizing, you know, the basics of impacts to marine and human health, what management of wastewater is currently looking like, um, what it could look like and some resources and tips related to collaboration and communication.
Our online course is a deeper dive on all of that content. It's free, self-paced. There's two lessons. You can access it through our website. We also have case studies. I think there are about 15 now on focused on wastewater pollution, highlighting management strategies that your colleagues are using across the world. And then we have summaries on the latest science related to this topic. So thanks, Henry, for that reminder. And yeah, hope you can explore those resources and please always give us feedback and ideas for what we should be sharing.
Henry: And again, thank you for joining us and we'll hope you, you tune in next time as well.
