[00:00:00] Bridget Scanlon: Welcome to the Water Resources Podcast. I am Bridget Scanlon. In this podcast, we discuss water challenges with leading experts, including topics on extreme climate events, over exploitation, and potential solutions towards more sustainable management. I'm delighted to welcome Doug Owen to the podcast.
Doug will talk about wastewater reuse, including the evolution of technology and economics. Thanks. with a focus on the San Diego Pure Water Program. Doug is a Senior Principal at Stantec and consults with utilities on water treatment and with the U. S. EPA and American Water Works Association on policy issues.
He was elected to the National Academy of Engineering last year for his contributions to drinking water quality, expansion of potable reuse and integration of sustainability in water treatment plant design.
So today I hope we will talk about the Pure Water Program in San Diego that when fully implemented will provide up to half of San Diego's water supply.
And then I hope that you will educate us on the history of wastewater treatment. Recent technology advances and comparison with other water sources for San Diego, including the Carlsbad Desal project and Colorado River water. Thank you so much for joining me today.
[00:01:30] Doug Owen: Well, thank you for having me.
[00:01:32] Bridget Scanlon: So Doug, you've been in this industry all of your career and made huge contributions.
I think wastewater use is increasingly being considered in many regions, especially in urban areas as part of a portfolio for water management. California, you've seen long term droughts, multi year droughts, and then floods. So having a source of water that's a reliable and sustainable is becoming increasingly important.
Globally, Michelle Van Vliet and her colleagues estimate that about 360 cubic kilometers of wastewater are produced each year globally. And a cubic kilometer is similar to a million acre feet, 1.2 cubic kilometers per million acre feet. So of all that wastewater that is produced, 63 percent is collected. And 50 percent is treated and 11 percent is reused. So that the, that's about 40 cubic kilometers that's reused. And that's similar to the volume of water that's desalinated globally also that they estimate. So I would love to hear your ideas on the status of wastewater reuse in the U. S. and how it compares to the global numbers and what you hope it achieves in terms of water sustainability.
[00:02:51] Doug Owen: I'm going to use a little bit different numbers, but I'll put it in a percentage standpoint compared to the global metrics. In the United States, we generate about 34 billion gallons a day (~ 38 maf/yr, 47 km3/yr). And that's about 13 percent of the total wastewater production that you just talked about globally.
But interestingly that with 4 percent of the population. So in the United States, it's, we're a very heavy water usage on a per capita basis, which is not surprising in developed countries in general. We see that throughout, I mean a little bit of reduction in Europe and elsewhere, but it's mostly the more economically disadvantaged communities that have, much lower water usage and accordingly less wastewater production and less, less wastewater treatment.
In the United States, we collect and treat almost all the wastewater that we have. Certainly, there are, there are certain locations where. Small communities or individual households have their own septic systems and things like that. But in general, we don't have raw sewage going into waterways. And the Clean Water Act that came in 1972 basically put out the admonition that all waters had to be fishable and swimmable. And that really drove the United States into an entire different and higher level of treatment for all of our wastewater.
And through that process began our journey where we can begin to think about reusing that water for beneficial purposes. In terms of reuse in the United States, The picture's getting better, but it's still relatively low. The percentages are about, I'd say a decade ago they were probably about 11%. Now they're up to 15% By 2027, they may be up to 19% or close to 20% 'cause there's been a bit big acceleration on reuse overall. And some of that driver is what we're gonna talk about today, which is potable reuse.
[00:05:17] Bridget Scanlon: Right. And I think there's increasing interest in this one water concept. So we, consider the full cycle. And some people may be a bit allergic to water reuse, but we are reusing water all the time,
And so when you discharge it treated wastewater to a river and then further downstream you pull that water out. So it's, it's, it is just different type of reuse really, that we are thinking about. Right. And so. There is maybe there was the concept toilet to tap, or I don't know what the, what the word is that you use now, the verbage you use to reflect complete potable water reuse.
And so that's becoming achievable because of the technology advances, right?
[00:06:05] Doug Owen: That’s right. And, and to step back for a second, I don't think that people often think about the fact there is no new water on the planet. All the water that we have on the planet is here right now and has always been here.
So every drop of water that we use, that we consume, that we use in our daily lives is already reused. It's just whether it's happening through some natural processes or we're accelerating those kinds of processes through technology overall. And I really want to get away and we might have a chance to talk a little bit about public outreach and, and all of that, but I'd really like to get away from that toilet to tap concept because it really, it really is a misnomer and isn't true because it, everything that happens, you talked about technology, everything that happens in between.
It's, it's really wastewater collection to treatment. To your tap and and so it's really important to understand the The ability of the technology to do exactly the same thing that nature does, but just do it in a more accelerated manner in denser population areas.
[00:07:33] Bridget Scanlon: Right. Right. So I think San Diego, the Pure Water project that you are heavily involved with, that is a huge project to treat the wastewater. And I think when I, yes. I spoke with Bill Alley earlier in an earlier podcast. I guess maybe when they were looking at the wastewater treatment system, it made sense to do the advanced treatment then economically to provide maybe drought resilient water source for San Diego and more reliable source of water for San Diego.
Maybe you can describe the Pure Water Project and what it involves. I think that would be great. Thanks.
[00:08:13] Doug Owen: Yeah, well, first of all, there's a twofold benefit to doing what we're doing here in San Diego.
One is we're producing a safe, reliable, cost competitive water supply.
The second thing is, is we're reducing discharges to the ocean.
And that, and of course, the Pacific Ocean is such an important resource. Important economic and recreational and environmental asset for California. We really need to do everything we can do to protect it. So by diverting wastewater and producing purified water, we're reducing those ocean discharges.
And so so there's a lot of value on both sides of that. In San Diego right now, we import 85 percent of our water. And it comes from one of two locations. It comes primarily through the Colorado River aqueduct that's to the east, but it also comes from the state water project from the north to a lesser extent.
And those aqueducts, they, they cross earthquake fault lines, as we all know, what's happening with extended droughts and what's going on in Lake Mead with the Colorado River where we really have over allocated the Colorado River to seven states. And so the question is, is, is what can we do in places where it's economically feasible in order to create a more local, sustainable, reliable supply?
And that's and that's where Pure Water, San Diego comes in. So ultimately for the program right now, there's there's a couple of phases and we're in construction past 50 percent construction on the first phase. Ultimately, when that's fully implemented, it will be up to half of the city's water supply.
And and that that is a very significant reduction on the dependence of imported water that ultimately can allow some of that water to be available for areas that that don't have the kind of opportunities that we have. Here in San Diego, in order to use our technology and, and create potable reuse. So that was, that was how the project has been envisioned and how it's going forward.
And we use a very high level of treatment to do this. We start, as we talked about before, we talked about the Clean Water Act. And the fact that all waters had to be fishable and swimmable, and that meant that we created a certain level of wastewater quality to begin with. That once you add a little bit of, add some filtration to that, is good for non-potable reuse.
So you can use it in the commercial industrial area, you can use it for irrigation. And depending on the quality, you can use it for food crops or non food crops.
The city, back in the late 1990s, established two treatment plants for, collectively, for 45 million gallons a day to produce that kind of water. The non potable reuse. But there's, there's always a balance that's associated with demand for non potable and, and getting the piping to where it needs to go. And we realized that there were times when that we really need to think of that wastewater as a water resource, just like you were talking about, Bridget, in the one water concept.
It's a resource. And we really need to think about how we most fully utilize that resource. And so it that's where Pure Water came in. And we said, we can produce 24 hours a day, 365 days a year. We can provide a resource, a water supply by taking that wastewater. That is, is underutilized in the non potable approaches and creating through advanced treatment of supply.
So the treatment is really extraordinary and I will offer that a science advisory board from the National Academies, a report in the National Academies that came out in 2012 indicated that this was feasible. And there'd been a lot of talk about it for a long time, but they went to the academies and they said, and got the best scientists and engineers together and said, do we really think it's ready for primetime?
And the answer was yes. And that, and that really helped support and accelerate the movement to potable reuse that we're seeing throughout California and was a very strong supporting document for what we're doing here in San Diego. And the treatment uses the same basic concepts that we've always used for drinking water, multi barrier treatment.
And we use a number of different approaches to that treatment. We have physical separation through sedimentation filtration. We have oxidation through ozone and and we have disinfection and oxidation through UV light. We have diffusion through reverse osmosis, and we have multiple barriers that we use.
So we have filtration in the terms of granular media filtration. We also have adsorption in through biologically active carbon, and then we have physical separation in membranes and through membrane filtration, which is literally a straining, except the pores that those are going through or are about 0.01 to 0.1 microns. That's anywhere from one one thousandth to one ten thousandth the thickness of a hair. So you, you put the water through that, and then it's prepared to go through reverse osmosis, which is really the same process that we use to desalinate seawater, which, which removes individual molecules down to chloride and sodium and monovalent ions like that.
And then we disinfect it with a very high, powerful disinfectant, UV. advanced oxidation, so we use creating hydroxyl radicals that will destroy and remove and oxidize pharmaceuticals and personal care products and 1, 4 dioxane and a host of individual contaminants that often are removed in the previous processes.
But just in case there's anything left, we do that. And then it goes, and in our case. It goes to a surface water reservoir. But interestingly, there was still a concern was, is that going to be enough? The the microfiltration, reverse osmosis, UVAOP being advanced oxidation process, is a standard approach in California.
It's not that way everywhere. There are some GA, granular activated carbon based systems elsewhere, but that's the standard in California. But they're, because this was the first going to a surface water reservoir and not going to the groundwater. They asked whether we could put in another treatment process, and that's where we put in ozone preceding activated carbon which brings in another oxidation step, and an adsorption step. And there's been a lot of benefits to that that I could talk about. I don't want to take up all the time on the technology here, but that I could talk about. But just to close on the technology aspect, the real key that's associated with that in the sequence and how this is being implemented across the country is whether or not you're gonna have that reverse osmosis step. The RO step is very helpful in terms of removing total dissolved solids, and it is an excellent barrier, but it produces a brine. Concentrate reject that you have to deal with and for inland and landlocked areas. The question is, what do we do with that?
We have the option here in California on urban areas near the ocean to release it through treatment to the ocean, but many places inland don't have that option. That's why they go, they're using the more GAC granular activated carbon based options, which won't get the same total dissolved solids removal.
But, you don't have to deal with that brine concentrate, which that's, we always make some kind of residuals when we treat something. We can't, we can't get rid of, can't take everything to 100 percent treatment, and so that's an important element of everything that we do here.
[00:17:20] Bridget Scanlon: Right. So I guess the message is that wastewater reuse has two fundamental advantages.
One is you're producing a water resource that we're using more and more now or considering more, but also that you're avoiding contaminating other sources. And, and I see this a lot because wastewater treatment plants. are, are not really at the level of water treatment plants. It seems like in many areas, the wastewater doesn't get the same level of attention because maybe utilities are not incentivized or the economics is not there to treat the wastewater, especially in developing countries.
So, so then you're, you're losing out on the source of water and you could be contaminating surface reservoirs or other sources of water. So it's a double whammy then if you don't do it. And then as you describe the treatment technologies. I guess they get the impression of redundancy. So many different things to, to make sure that you develop a pure water source.
And I guess the water that you develop is so pure that you actually have to remineralize it or add stuff back into it before you discharge it and augment the surface water source. And then. Okay.. Always when we treat, as you say, we develop a concentrate. So what do we do with it? I talked to some Israelis about seawater desal and they discharge the concentrate to the ocean with the long diffuser systems and things like that. So, and mix it with power plant water. So it's not really that elevated in salinity. So that's always an issue is managing the concentrate. So there are a number of advantages, two basic advantages. You're providing a water source and you're avoiding contaminating, releasing nitrates or phosphates, the surface water bodies and all of these things from wastewater.
So wastewater, you mentioned the Clean Water Act. And so wastewater treatment technologies have evolved over time. I hear the terms primary, secondary, tertiary. Advanced. And I know you've probably alluded to these when you've talked about these things, but maybe you could just spell out what we mean by primary treatment, secondary or tertiary, and then the Pure Water system I presume is the advanced system for wastewater reuse.
[00:19:44] Doug Owen: That’s right. And if we go back in history and we go and we think about urban areas in those locations, a lot of people had their waste and we're dumping them in the streets over time. And then there were different ways for someone to come and collect that manually and take it to some location and release it.
But over time, as as people Areas became more dense. It was obviously clear from a public health standpoint that you couldn't have that kind of waste in the streets. And so, I mean, the classic sewers in Paris and London where they effectively move the wastewater from directly being adjacent to the population, but into a water course.
Where a waterway, which with the concept, well, it'll be diluted. And when your waterway is large enough and your waste discharge is small enough. That may work to some degree, but the problem is, as these urban areas get larger and larger, the assimilative capacity of, of the receiving water can't possibly tolerate it.
So the concept when it was, we have to have some level of treatment now, primary. And so it started very simply with primary treatments and basins called Imhoff Cones where they take wastewater, put it in to a large settling basin and the solids would say, I mean, it was kind of a cone with a with a V bottom on it and that solids would settle down to the bottom and they would digest a little bit.
Just the way that you think about if you leave food on the kitchen counter for a long period of time, it starts to digest and and produces a little bit of gas and things like that. And then they took those solids and they and they took them somewhere. And that's one level of treatment. And you can get a reasonable amount of treatment of suspended solids removal in that maybe up to 60 percent suspended solids, and there'll be some other solid. But the key here in that is there's this remaining soluble material that is that can't be settled, but creates an oxygen demand. And that's, and, and you'll get some of that out. There's some of that oxygen demanding organic substance is associated with the solids.
But the remainder of, of that soluble that doesn't get settled, if we just put that into a receiving water stream, it's going to consume oxygen somewhere. So it consumes it in the stream and when you, when it or whatever the receiving body is, reservoir or the ocean, so you put the, the wastewater there after some level of treatment, but you don't have, you're not taking a lot of the oxygen out of the water or oxygen out of the way.
Or the demand, the oxygen demand out of the waste. Well, then it's going to exert itself in the receiving stream. And when it exerts itself in the receiving stream, the dissolved oxygen in that receiving stream goes down. You get eutrophication and what's hard for living organisms, this fish and other things to survive in there.
So the next step was, how do we do that? And so what we did is basically as a popular, is we developed systems where. You again accelerated that natural process. You built basins, you put oxygen into it. It grew microorganisms. It's called activated sludge. That's the term for it. And you grow them in those bugs in the basins eat all that soluble material, and then you send it into a settling, another settling tank, you settle out the bugs, you let the treated wastewater move on, which now has a much, much lower oxygen demand. And these are really very efficient basins where you're, you're putting the oxygen and then you bring the bugs back, so that they can continue to be effective, but just like, When you give up bugs, a bunch of food, you grow bugs.
And so you have to take some of those bugs out periodically to keep a stable system all the time. And you take those and you end on many wastewater plants. And certainly in the United States, we digest them. You put them in digesters that don't have any oxygen in it. They eat each other up. You end up with methane gas that you can capture in order to produce energy to support all the processes that you're using. And then you end up with a little bit of volatile solids when you're left and a lot of bug bones. And those are the things that you can, you can take that sludge and depending on the level of treatment, you may be able to use it for landfill, landfill cover, or use it overall to as, as a crop amenity, soil amenity. So that's secondary treatment.
Now, tertiary treatment means we'd like to take this waste, this wastewater and use it for some other beneficial uses potentially. So let's, let's filter it. Get some remaining of the remaining solids out of it. We're also going to disinfect it. And by the way, many, many discharges, almost all discharges that actually go out to receiving streams often are disinfected as well.
But we're going to disinfect this and, and then we can use it for irrigation or we can use it for commercial industrial facilities. Industry may have some general needs, cooling towers, things like that, that have no public contact kind of things we can use it there and that's the tertiary treatment And then we then we may say well, we want to get the nutrients out.
We work and we're concerned about hypoxia in the in the areas where we have nitrogen and phosphorus and we're growing a lot of algae the area in the south of the Mississippi River as it goes into the Gulf of New Mexico is a classic area. And these areas are found throughout the world, near urban areas where you have a lot of nutrients going in.
So the question is, do we need to remove the nutrients? And that's another act, a type of activated sludge, but it's additional work where you actually grow specialized bugs. You can do this through the way that you design your system. You grow specialized bugs that will take the nitrogen and, and turn it into nitrate, and then other bugs that'll take that nitrate and use it and convert the nitrogen to nitrogen gas, which then is totally, is completely removed, well, removed atmospherically from the system.
And that's how you get rid of nitrogen. And those bugs also take up a lot of phosphorus. They need that phosphorus for energy. So they take up a lot of phosphorus. So you end up with a very concentrated phosphorus rich sludge. And now you've removed nutrients as well. And so where we need to do that and how we need to do that is very closely related to what we'll call the assimilative capacity of the receiving water. There's very high levels of nitrogen and phosphorus removal need required in Chesapeake Bay, for example, on the East Coast, because it's a very sensitive ecosystem.
On the other hand, in deep ocean discharges, where you have a large amount of mixing and very, and a great deal of ocean monitoring that's going on. For example, example, here in San Diego, we have the Scripps Institute together with San Diego. There's an incredible level of ocean monitoring that goes on with all that and has found that nitrogen removal is not required in this case. Second, we have very high level of advanced chemically enhanced primary treatment, but even requiring secondary treatment and it isn't necessary.
There's actually a waiver that's allowed through the Clean Water Act, and we get that here because of the assimilative capacity and what we're doing with all of that. So, so, so that's the, that's the kind of the, the wastewater odyssey, the time frame and how you have to fit into how, how does our treatment match where we're going to put the water and, and the capacity of that water to be able to manage different levels of treatment and then just to close.
We take that tertiary and in, in our case, we remove a lot of nitrogen from our waters because we're putting it into a surface water when we're all done with this. So we, so we're upgrading our secondary treatment plants that already filtered and provided irrigation water and industry water. We remove nutrients from that as well.
And then we go into the advanced treatments that has the ozone and the biological activated carbon, the membrane filtration, the reverse osmosis, the UVAOP (UV Advanced Oxidation Process). And as you indicated, we then there's nothing in this water when you get done. It's almost demineralized as well. And we have to put minerals back in the water in order to bring the pH, to buffer the water, to bring the pH back up again, and to make sure that as it goes in, it blends well with other potential sources that will be treated at the drinking water.
[00:29:40] Bridget Scanlon: That's fascinating. It's really, we don't, many of us are not aware of the early systems in London and Paris and these sorts of things. But even in developing countries, I was seeing some documentaries, they manually collect the wastewater and the sewage and things like that and, and, and put it in different places.
And then you mentioned early on, maybe you were discharging and you relied on dilution. And I think we had, The mantra long ago, dilution is the solution to pollution, but then, as you say, that depends on the assimilative capacity and how much flow you have in the rivers or, or how much buffer you have in the oceans and things like that.
So that's an important aspect, but then the, the basic, it's interesting to hear that maybe you don't even need so much secondary treatment to discharge to the ocean in San Diego, because you've got such a large assimilative capacity in the system. And then that chemical demand and eutrophication that can occur because of the oxygen demand of the waste.
And so it has evolved over time then, but we're still seeing it hasn't evolved that much or it's not being utilized as much in developing countries. And, and so we still need to help them try to, to develop these wastewater treatment systems to avoid contaminating other water sources and to have a, an additional water source there.
So as you describe all of these processes, then what comes to mind is how much energy it takes to treat the water. And I guess economics, there are two basic aspects. Maybe you can discuss those a little, Doug.
[00:31:19] Doug Owen: Sure, sure. And over, overall, just to touch, as I move into this, to touch briefly on, on the developing country issue, it is an issue of economics and affordability and, and the economic support you can have for it, but it's kind of a related thing.
You can spur your economy if you have better water sources, but you have to spend in order to be able to have those water sources. And so getting the system moving in order to be able to create those large, those true infrastructure benefits, it's a conundrum for people smarter than me to figure out, but as we think about here in San Diego, obviously a much higher developed economy here, it takes a lot of energy to move water, water is heavy. It's, it's 8.34 pounds a gallon, and when you move water from the Colorado River or the State Water Project to the north, hundreds of miles over mountains, you're using a lot of energy in order to bring that water to where we are. And so the desire to be able to create instead of using that energy in order to import water from another location, maybe use that same amount of energy.
And it's actually They're the same or a little bit less energy for us here to treat the wastewater to potable reuse level, and distribute it. It uses less energy than trying to import this water from a lot of locations, or at least the equivalent amount. It's a little less energy coming from the Colorado River than from the state project, but overall, they're about the same.
And the other thing that we always want to remember when we talk about it is there's kind of two pieces to the energy use equation. One piece has to do with how much energy do we use to treat the wastewater, or to treat to potable purified water standards? The second thing is we have to get it somewhere.
We have, once it's treated, we have to move it to a place where it can be stored as a water supply. Or, or actually ultimately through direct potable reuse to be blended with other drinking water supplies and go into the system and the way that that water systems are designed reservoirs were already put it always put at higher elevations because you wanted to use gravity to flow downstream.
So you put your reservoir at a higher level, you put your treatment plant up there, and then you use gravity to be able to distribute to the population. So when we get done, we have to pump the water up to the reservoir, but even then, even then, when you add in the energy usage for treatment and the energy usage to go to the reservoirs, it's not different than importing the water from elsewhere.
The other thing I would say from a treatment standpoint. Is you're using reverse osmosis in this process and reverse osmosis uses a lot of energy and, and it can, and it does, but the amount of energy reverse osmosis uses depends on the salinity or the dissolved solids of, of the water. I mean, that's why it's called reverse osmosis.
In normal osmosis the water is going to move from a pure location to, to one that is saltier. Well, what we're doing is we're basically reversing that process and taking the saltier water and creating a more purified water and the energy that you need to do that is proportional to the difference between the purified water that you're producing and what you're starting with in the salinity because you're, you're going against that natural osmotic pressure and process.
So, for example, the total dissolved solids, we will call it salinity for an easy term, of wastewater, might be 1500 milligrams per liter or thousand milligrams per liter. In the ocean, it's 32,000 to 36,000. So the energy that you need in reverse osmosis to desalinate water is much greater than the energy need through reverse osmosis, in the processes that we use.
The trade off there is we have more pre treatment processes, much more pre treatment processes that are energy intensive in wastewater treatment. You're pumping oxygen in, you're creating, there's a lot of energy to do that. You don't have that in desalination. So, so there's trade offs there. But we would use probably from an energy portfolio side on the, on the treatment side, maybe about a half to two thirds the amount of energy you'd use to desalinate ocean water on the treatment side. But then of course, it all depends on where you're putting the, where that water goes to. We have to put, take the water to a reservoir. If. A desalinated plant can go directly into the distribution system at a certain pressure, or in the case of the Carlsbad desalination facility, which is the large 50 million gallons a day, the largest in the Western Hemisphere, it pumps up to a location where there's a drinking water treatment plant.
For the county water authority, by the way, then this is there's the San Diego County water authority and there's the city of San Diego Pure Water project. San Diego is the city of San Diego. The desal plant is the county of San Diego, but we're all providing water in the same area, but they have to pump up to a location there as well.
So, so just looking strictly at how much does it take to treat doesn't really take in the full energy portfolio that you need in order to be able to get the water to where you want it to be. You want to treat it. You have to get the water. Then you have to, which in our case is relatively straightforward because we're collecting the wastewater or in the case of the desal is because the oceans right there, but imported water, that's where all the energy is. Then you have to treat the water and we've just talked about that and then you have to move the water to the place where it's going to go to the customers. So, I will, I will offer, we'll be the first surface water augmentation in California. And there's some very specific rules, but there are some systems that have been doing groundwater augmentation for a long time.
The largest in the world and very notable is Orange County Water District, which is just north of here in Orange County, which is the county that's south of Los Angeles, where Disneyland is. Actually, it's not far from there. They do 135 million gallons a day. They've been doing that for a year. Well, they just they've just expanded their plant, but they've been recharging groundwater for years, and they've got a great system for energy conservation, so to speak, and how they distribute it, because they put it, they put it out to spreading basins.
They have to pump to spreading basins, but those spreading basins just, Or, infiltrate water into the ground, or they pump it into the ground, and the energy that's required in that kind of distribution system network is much less than trying to pump it all the way up to a reservoir, to higher elevations, or in the case of desal, pumping it into the distribution system.
Ultimately, somebody has to pump it out of the ground. And there's an energy cost associated with that. But if you look at the energy requirements specifically for treatment and distribution for groundwater recharge versus surface water recharge, sometimes the balance is a little bit different because of where you're taking the water.
[00:39:32] Bridget Scanlon: That's fascinating. And I really appreciate your comprehensive answer because California gets quite a lot of water from the Colorado. I think 4. 4 million acre feet out of the seven and a half million acre feet from the lower basin. And, and I guess San Diego, you're getting it from Imperial Irrigation District or it comes through there to San Diego and maybe in the early 2000s, you were paying the Irrigation District to use more irrigation conservative processes so that you could get more water from the Irrigation District.
So comparing water transfers from the Colorado and the energy takes, because we're becoming more aware of greenhouse gas issues and stuff like that. So any solution that we develop for sustainable water resources needs to consider greenhouse gas emissions and economics and all of these different things.
So it was great to hear the comparison then. And in San Diego, then with the wastewater reuse and the Pure Water project that you have taking wastewater and augmenting surface water because you don't have suitable aquifers to do what they're doing in Orange County and so augmenting the surface water and then the seawater desal. So you've got quite a portfolio then to have a resilient system when you have to deal with these multi-year droughts, 2012 to 2016 was multi-year drought in California. And then of course, you've got atmospheric rivers and it's, it's either too much or too little. But so the energy requirements and the cost of these different things is, is very important to look at the tradeoffs in different solutions.
In China, they have the same South to North water diversion, where they're taking water from the Yangtze and taking it up to Beijing and other urban areas. And along the way, then they have a lot of water treatment plants and everything and, and reservoirs and stuff. So there's no free lunch, but it's trying to optimize, I think, looking at these different options.
[00:41:34] Doug Owen: Yeah, in general, I believe there's a movement to try to be watershed centric, and this is the One Water concept that you were talking about. we all, we all live within a certain watershed, and how do we manage our water? The best that we can and reuse it the best that we can within the, the boundaries where we can collect that water rather than trying to go track trans boundary in order to be able to do that.
And, and, yeah, with the drought cycles, we, the interesting thing about the Colorado River is that when it got allocated in the 1st place that it got allocated historically during a very wet period. So even when it was initially allocated more water was allocated than was really going to be available over the long term that had already happened.
But some of the some of the states were using less water than their allocation, and the remainder was available for other states using higher allocations, one of which is California. But now you like, as you indicated, Bridget, you, you put climate change on top of that. And you have these periods of drought and and it exacerbates this situation extraordinarily and really puts a focus on our ability to to capture and store and reuse the wastewater that we will have readily available to us.
And there's there's a In California, of course, there's a food security issue to this. The Central Valley grows 90 percent of the fruits and vegetables, many types of fruits and vegetables, nuts, that are used throughout the country. And we're all aware of the groundwater basin there, lowering, and the famous pictures of, of people with poles that are 15 feet high showing where the surface, the of the ground used to be, and how much it has depressed or compressed as a result of using that groundwater.
So, so in the long-term concept, the ability for the, for our large urban areas to be able to capture and use and reuse the water within our watershed so that the water that remaining from the state project, for example, can be used to recharge the central basin and provide more security there for the farmers is really important.
And, and with the cost of energy and the types of improvements in technology, the economics are getting much better, but you used a really key word there and that's groundwater. We in San Diego would love to buy a groundwater basin, and we just, we just can't get one. And the advantage is Orange County does that, Los Angeles was, has a big stormwater program that they're putting in place where they can recharge groundwater. Those, those kinds of things give a lot more latitude to be able to reuse. And in San Diego County here, we, we have, we have a, a reasonable reservoir system, but it, it doesn't have nearly the capacity that large groundwater basins do.
So we're all, we're always going to have to kind of manage our way there and build the portfolio the best that we can. In a portfolio concept, you've, you use that word, Bridget, I think it's a really good word. It's, it's really important because people say, well, why don't we just reuse all the wastewater and then we don't need to desalinate water and everything.
You can't reuse yourself out of a drought. You can't conserve yourself out of a drought. If you have no other water resources, there are just consumptive sources that through evaporation or bodily function or crops or whatever, you can't get that water back. So you have to have some amount through your natural rainfall, or in the case of San Diego, desal, you have to expand the portfolio in order to be truly be able to count on everything in the watershed.
Yeah. And then there are just these agreements like you talked about with farmers as, as two thirds or up to 70 percent of the water globally is used for agriculture. The extent to which we can make farming more sustainable. Water efficient frees up water for other kinds of uses and similarly that exchange with the Imperial Irrigation District in order to purchase water rights from them to bring it to urban areas, but also allow them to be more efficient from a farming standpoint is an example of that.
And again, in that case, just to be clear, that was the County Water Authority. The county, not the city, we're all together here in San Diego proper.
[00:46:27] Bridget Scanlon: Right. So, you're relying on a wastewater feedstock, and how reliable is that? I think we're hearing more about in home water reuse and businesses being required to, to reuse their wastewater within the building and stuff like that.
How might that impact the source of wastewater for your, that you will be using?
[00:46:48] Doug Owen: Yeah, that conservation and other reuse has a very large impact on the wastewater that's available for these centralized kind of facilities. As a matter of fact, we looked at the plans. There was a concept in 2012 about how all this is would come together for Pure Water San Diego in these different phases, and now we're seeing through water conservation that the amount of wastewater, although it's a little more concentrated, still very treatable, but still more concentrated, is a lower flow. And so, we want to make sure that we have enough wastewater where we think we're going to have it, and we will, and have it into the future in order to be able to meet our overall commitments and desires to produce half of the water supply.
So all those things there, there are economies.
And we might talk a little bit about decentralization. There are economies of scale at some level in the wastewater treatment and to an extent, to an extent in the advanced treatment that if you try to reproduce a lot of this and, but they're doing it effectively in San Francisco and other areas in, in building reuse, and matching it.
It, if you look at the cost versus the amount of water produced. Typically, it, it's more effective to try to do it in, in a, in a more centralized fashion. But not always. It depends. And, and we may, you may have a question about the centralization, decentralization issue as well.
[00:48:28] Bridget Scanlon: Right. Yeah. So you mentioned you, you really wish you had a suitable aquifer to, to work with.
And I think these aquifers are being considered like batteries now and folks at Scripps are looking at forecast informed reservoir operations and then the Prado dam trying to move that water into groundwater storage and then they can use it during drought. So, so there are a lot of ways that we're adapting to these extremes and to managing them.
And I think it's a really interesting to see how we are coping with those extreme atmospheric rivers and long-term droughts and things like that. So, a couple of questions about the system in San Diego. Why do you think San Diego did not choose to expand their non portable reuse, like commercial, industrial or irrigation, rather than provide this extra treatment for potable reuse?
[00:49:21] Doug Owen: That's a, that's a really great question. And, and there's, there's a couple, and you mentioned them both. There's a couple of kind of key areas where you look to reuse. One is commercial, industrial, often in cooling towers and things like that. And the other is in irrigation. And if you, if you have a commercial industrial customer that's very large, that's going to use your water continuously, that can offer very favorable economics for what we'll call non potable or non drinking water reuse.
And as an example of that, in Phoenix, Arizona, They, the 91st Avenue Wastewater Treatment Plant has a customer, the Palo Verde Nuclear Power Plant. And they use a lot of recycled water from the reuse plant for cooling water. And they need that 24/7/365. It's great. But a lot of times, in urban areas, you don't have a customer that large, or you don't have those customers all in the same area.
There may be a little, a, a business district that has groups of, but, but they don't use that much water and you, and like we just talked about, you've got to pipe the water out there and you're running those pipes through city streets that are very crowded now with, with utilities and underground energy utilities and fiber optics and all that kind of stuff.
It's really, it's hard to find any open space under the ground. And you never know where, I mean, my favorite statement about that, we always try to minimize how much, how far we, we move water in, in the streets under these kinds of plans, because everything that you can't see is not where it's supposed to be.
And once you start digging up underneath there, you find things. So, so you don't want to be shooting all these pipelines out every everywhere. But if you have a good industrial customer, you should take advantage of it.
The second thing is so it's not sure how much of your total wastewater you can use in that.
The second thing is you can use a lot for irrigation and and the city has been relatively successful with that. We use an average of about 10 or 11 MGD overall in the reuse portfolio, but when it rains, and it does still rain in California, we get about 10 inches a year, 25 centimeters a year here in San Diego and sometimes more.
And we have the last couple of years, nobody, nobody needs it. Nobody wants it, so they shut it off, understandably. And so you have this water resource, and you can't do anything with it. And off it goes, through treatment and off to the ocean. And so what potable reuse really allows you to do is fully utilize the resource 24/7/365, on a beneficial way in order to produce a source that you can store and then use for drinking water.
[00:52:12] Bridget Scanlon: And you bring up an important point with economics. You need a stable customer. You, you don't need just a fair weather customer. And I've been hearing about this in, even in developing countries, sometimes when they have surface water, then they don't want to pay for the other system and, and then the utilities have a difficult time managing through those times when they cannot sell the water, but so oftentimes you have a take or pay contract. And so if you had a long-term contract with a commercial facility with a take or pay contract, then that would help. And in Israel, when they developed a lot of their desalination projects, the government guaranteed the price of the desalinated water for 20 years.
That allowed them to develop it. And that's what you need sometimes to develop these options. So the Pure Water project, what are the economics associated with that? What is the capital costs or the operational costs to develop this Pure Water system for San Diego?
[00:53:10] Doug Owen: Yeah, the way that we often do that is we, and this isn't unusual, this is how it's done in the industry, is you take the capital costs, you develop some kind of debt service approach associated with interest rates and the borrowing that you have, and you annualize that cost, and you add that cost to whatever your annual operating and maintenance costs are, and you come up with a unit cost, and that cost is usually a dollar per share.
Okay. some currency amount, in our case, U. S. dollars, divided by the amount of water that you're producing. And, and it can be done. Often, you see things on the East Coast in dollars per thousand gallons or dollars per million gallons. Out where we are here in the West, we use, we use dollars per acre foot.
And it's an agricultural term that was, if you planted a certain crop, how, how many feet of water or inches of water did you need for that crop in order to be able to grow it? And how many acres do you have? And you multiply those two things together, and that's how many acre feet of water that you need.
If we put that in urban terms, an acre foot of water might support a couple families a year. A family of three or four depending. We're getting a lot more efficient. You go back 20, 30 years ago, or even longer, an acre foot might support one family. Now we're at two. And in some instances where conservation is very good, it can be three, but, but that is so we often do things here in dollar in dollars per acre foot.
And when you look at the imported water rates, and you look at the at the San Diego County Water Authority, and they they have wholesale prices. In other words, we'll give you untreated water. We'll get the imported water that comes in. We have a price for that that we provide to you through the Metropolitan Water District of Southern California up in Los Angeles.
We'll give you that and you treat it. That's what the city of San Diego does. We often for the most part, if we're buying water from the county water authority, we're we're treating it. The city's treating it at its own drinking water treatment plants. There's a cost for that. And then there's also a cost if it's already treated.
So The county water authority will sell you water that they have treated at their Twin Oaks treatment plant or from the Carlsbad desal plant where it blends at the Twin Oak plants and then moves into that and into the whole distribution system for for its customer. There's 20 plus member agencies that are associated with the County Water Authority, San Diego, which is one and the city, which is the largest, but there's many so so we look at we look at and balance on all those.
And if you look at the latest prices for water, the all in cost for water from the County Water Authority. For, for treated water is about 1,500 an acre foot or something in that category. They have a take and, and embedded in that is the take or pay contract. Just as you said, they have a take or pay with Carlsbad Desal as that's run.
That's a design owner financed operated system that sells the water to the County Water Authority That is sensitive to the energy costs. So the latest cost of that water, it's specific water, is about 3,200 an acre foot. If you look at our water, our water is, and there's two pieces to this, and this is another thing. If you look at the water that we're doing, there's a wastewater cost to it and there's a water cost to it. And of course, the agreement that we had is we didn't have to expand our wastewater system for the Point Loma Wastewater Treatment Plant because of all the benefits we talked about with ocean mixing and all the monitoring that Scripps and the city does.
We don't have to increase the treatment there to a great extent as long as we divert and reduce the flows to the ocean. Through this purified water. So but so if we weren't producing purified water, there'd be a wastewater cost that we would have. And even as such, there's a wastewater cost that we incur that gets and that cost is borne not only by us but by 12 other member, not by the city, but by 12 other member agencies that use the collection system. So we have to keep our wastewater costs separate from our water costs.
Our water costs are, are, are getting to the point, I mean, this advanced treatment cost. It's, it's very cost competitive and, and meaningfully lower than what desal water is and getting closer to the cost for, for treated water that's coming from the county water authority. And even both, you could take the wastewater and the water, the advanced water costs. And you add those together. Those are still, those are still very cost competitive and lower than desalinated water. But I want to make sure here that we don't demonize the cost of desalinated water because we always compare to what's the cost of imported water.
Okay. But what if we don't have that imported water? That's the whole issue. I mean, the issue is not, should we be comparing it to the cost of a resource that at the moment is a little bit over allocated, and that, and, and with drought, you never know whether you're going to really have it available or not, and you have to move that water.
Should we be comparing it to that? Or should we be comparing it to the cost of the next new water supply? So, from our, from my perspective, comparing it to what would it cost to develop a new water supply, and desal is a very good example, is a way to determine the cost competitiveness of potable reuse.
And in that case, potable reuse is very cost competitive.
[00:59:11] Bridget Scanlon: Right. Right. Well, it's great that you put all of these things in context because that is so, so important. And what would it, what would the economic impacts be if you ran out of water?
[00:59:23] Doug Owen: You know, the statement that I loved, I've always heard about is we spend a lot of time talking appropriately, talking about energy and alternative forms of energy.
There is no alternative to water. Right. This is what we have. This and it is singly the most important resource. I know I'm probably a little biased here, but it's singly the most important resource on the planet and there's no alternative to it. So we have to, we have to figure out how to be good.
and stewards of this resource.
[01:00:01] Bridget Scanlon: Right, right. Very important to be good stewards of the water resource. And I really appreciate your time today, Doug. It's great to have you in the Academy and providing all of your input into different issues that we are dealing with. And you mentioned earlier that the Academy report on wastewater reuse really helped your program.
And I wish you the best in the Pure Water initiative. And, and it seems like it's going well. It's progressing very well, and, and thanks for explaining all of those things to us, the differences between desal and, and wastewater and imported water. So really appreciate your time and good luck with your work.
[01:00:42] Doug Owen: Well, thank you for having me and really enjoyed the dialogue here, and we're excited about everything that's happening in San Diego, so we can't wait to turn it on.
