Pulsed Burst Systems is a Milwaukee-based startup that has developed a simple yet effective device called the MegaBubble that creates large air bubbles that can be used to mix large quantities of water or even pump water through a pipe. With help from The Water Council in Milwaukee and its BREW business accelerator program, Pulsed Burst is finding potential clients across the country, including wastewater treatment plants and municipal water districts.
Charles Otis, chief operating officer of Pulsed Burst Systems, spoke with Municipal Water Leader Managing Editor Joshua Dill about his background in the water industry, his company, and what the U.S. water industry could do to boost innovation.
Joshua Dill: Please tell us about yourself, your background, and how you ended up in your current work.
Charles Otis: I went to the University of Minnesota and got a degree in child psychology. The field wasn’t a good fit for me, and after working a stint as a loan officer, I moved home to Madison and got a degree in civil engineering from the University of Wisconsin–Madison, focusing on wastewater from the beginning. My dad was prominent in wastewater treatment, so I was familiar with the field. I got my degree at the depths of the recession, making figuring out my next step difficult, until in 2011 I got an opportunity to move to Norway to pursue a master’s degree in environmental technology.
I moved over there at the beginning of 2012 and started school. The education was quite good, and free, and I got to be involved with several different companies. I worked with Salsnes Filter for my master’s on a project called Slam til Energi (which translates to sludge to energy). I then worked for a consulting firm called Aquateam, which is now Aquateam COWI. Through Aquateam, I worked for several different companies on all sorts of different projects. My job ended up being to set up pilot systems designed to test out different theories and independently test out technology; I was building a lot of things with PVC and plastic, with data collection, controls, and automation. I also consulted with a company called Biowater, which makes moving bed bioreactors (MBBRs). One of our projects, which was called continuous flow, intermittent cleaning, involved cleaning MBBR biomedia by using air to bump off the biomasses that had collected on them. It was difficult to do effectively because of the nature of the experiments: There was a very high fill percentage of this plastic media. We had to fluidize the bed in order to let the air get enough momentum to move the media and clean it. That stayed in the back of my mind. I’d do it differently now.
At the end of 2015, I moved back to Wisconsin for family reasons; I chose Milwaukee specifically because of The Water Council and because it was close to home in Madison. I ended up working for a bacillus manufacturer just south of Milwaukee where I did research on a couple
of biological systems, looking for novel bacteria. I built lab-scale pilot devices out of PVC in a lab. It was fun, but I was more interested in the physical workings of the systems than the biology itself.
Just when I was thinking of moving on to a new job, I got a call from Ken Neu, a friend of Bjørn Rusten, who I had worked for on many projects while at Aquateam in Norway—it turns out he lives near Eau Claire half the year because he married an American woman. Ken had got hold of some intellectual property for this bubble device, and he and his business partner asked if I would join them to be their representative in The Water Council’s Business, Research, and Entrepreneurship in Water (BREW) program and work toward equity in the company. It was perfect timing—kind of serendipitous.
The bubble device technology made me think of my work with Biowater, and I thought that it might work well to mix the sorts of things I had had trouble mixing in the past. I came up with a novel way to build the mixers with economics in mind. That was all made possible through the BREW program. They supplied us with some money and put us through classes designed to turn engineers into entrepreneurs. They’ve been putting us in front of lots of different people to present our tool and the various applications in wastewater management it could be used for.
That’s actually how I ended up meeting Shane Leonard of the Roosevelt Water Conservation District. He and several others, who I think were all associated with the National Water Resources Association, came to Milwaukee for a tour of The Water Council. We, as startups, were given an opportunity to pitch our products to the group. Frankly, I wasn’t all that excited about it, since it didn’t really seem like it was a market we’d have much luck in. I mentioned that we were able to mix large volumes of water with our mixers, and that if you put a pipe on top of one of our mixers, it turns into a pump that can pump sediment, using nothing more than a small blower. The airless pump is a relatively old technology, but using a large bubble is an efficient way of mixing and pumping, and it is cost effective because it doesn’t need high pressures. I offered to show a few people, Shane included, a small demo I had in my office after the presentation. They were impressed by how simple the technology was and wanted to discuss it further.
Joshua Dill: Tell us about the company you work for today.
Charles Otis: The company I work for is called Pulsed Burst Systems. There are three of us, Ken and me and a silent partner, plus a couple of people who give us indispensable help. We’ve been in business for about a year and a half: We started with the BREW program last August. We started out with the technology and no concrete way to market it, but we’ve been learning with the BREW program, and The Water Council has been putting us in front of people to pitch our ideas to in the larger water community.
Right now we’re small, but we’re making really cool stuff. We have a pilot at a wastewater treatment plant in Oak Creek, Wisconsin, where we’ve turned an aerobic zone into an anaerobic zone using air, though that might seem counterintuitive. We’re able to use air the plant already uses to aerate the activated sludge, mixing it anaerobically instead of using electric motors or mixers, and without introducing much oxygen to the water. That is the niche we have found on the wastewater side of things.
Joshua Dill: Would you explain, in layman’s terms, the physics of the MegaBubble device?
Charles Otis: Sure. It uses an accumulator—basically an airtight, upside-down dome, which you can pump air into. It has one outlet: a hole near the bottom of the dome. You fill up the vessel with air that is just over the pressure of the water at that depth, and once it reaches a certain point, all the air is evacuated out of that hole as water rushes back in to replace the volume. There are no moving parts. It functions on two different principles: pressure and a siphon effect. One way to think of it is as an upside-down toilet. It works just like the siphon on your toilet: When you flush, the water gets going down the pipe and creates a vacuum that pulls down the rest of the water. The air works in a similar way, just the opposite. When the air is released, it creates a big bubble. That bubble has velocity gradients that pull water behind it, as well as displacement effects that create eddies as the bubble rises through the column. So it is a simple small pump that is pretty effective at mixing. What we’ve found is that the radius of its area of influence is roughly the same as the depth of the pump. If it’s 15 feet deep, it has roughly a 15-foot radius of influence.
If you put a pipe on top of the outlet and direct the bubble into it, the bubble creates an air piston in the pipe with a siphon effect. The water isn’t able to get around the bubble because of its speed and because of the cohesive forces. The siphon effect pushes water out of the pipe and sucks water
up from the bottom. We can pump water effectively just by using air. The force is great enough that we can pump solids as well. It’s a neat tool.
Joshua Dill: You mentioned that wastewater treatment was one possible use of your tool. Are there other potential applications for municipal water districts?
Charles Otis: Mixing is one of the big ones. There’s evidence that we can increase the efficiency of aeration by using a large bubble in conjunction with aeration devices. There’s also pumping.
One of the things we’re looking at is de-icing marinas and docks. In the northern climes, when winter sets in, ice dams start to form. Marina owners are trying to protect their docks. We put our devices down in specific locations, and the bubbles keep the ice from forming on top.
They can also be used to keep reservoirs and irrigation plants free of silt or to mix and destratify bodies of water. You can also use the mixers or pumps to destratify them. If you have a large, stratified body of water, you can keep cold water pumping from the bottom to the top to keep the lake mixed. The devices could potentially prevent turnover from happening, but for that you’d need quite a few of them, especially in a large body.
The real advantage of it is that we’re using low-pressure air. There are no moving parts in our system. Basically, all you have to do is break the static pressure of the water with a blower, so if the device is at a depth of 15 feet and the water at that depth is at a pressure of roughly 7 pounds per square inch (psi), we can use 7 psi air to pump and mix. This makes the process cost effective both from an energy standpoint and from a maintenance perspective, since there’s nothing moving but air and water. The advantage of that in a wastewater-treatment system, for example, is that they’re already going to be using blowers for microbiological reasons, adding air as fine bubbles to activated sludge, for example, in order to have the oxygen that the bacteria and protozoa need to treat the waste. So instead of adding an electronic propeller mixer or something like that, we can use the same air that’s already being used, and we’re able to do that without adding oxygen. That cuts down on equipment and motors to maintain. Also, you can pump. You don’t necessarily need to pump all that much water, depending on the volume of our accumulators, but over time you can pump quite a bit of water with what you’re already using. This may not be something that a large plant needs, but its simplicity makes it attractive for decentralized systems.
Joshua Dill: Please tell us a little about your work with the Roosevelt Water Conservation District in Arizona.
Charles Otis: So far, it’s very preliminary. We’ve only been talking. It looks like in December or January I will go out there and see what they have and how we might be able to help. They have large pumps that go down into sumps, but in low flow times, apparently the silt and sand in the irrigation tunnels settle out and accumulate in the sumps. When sand and silt get in the pumps, they wear on the pump vanes. However, there is a possibility that we can drop our small pump units in and use them to push the sand and silt back out of the sumps and protect the pumps. I’m pretty sure we can do that. Our devices will create a cone of depression; if placed right below the pump intake, they can prevent the silt and sand from ever getting into the pumps, increasing pump life. I want to say they’re using 5-horsepower pumps, or maybe 15-horsepower—large pumps that are moving a lot of water. Using our devices in this way could decrease maintenance costs significantly over time.
Joshua Dill: How did you find out about The Water Council?
Charles Otis: In 2013, when I was living in Norway and deciding whether to stay there, a good friend of mine in Milwaukee sent me a link about The Water Council. This was right around when it got started. I thought it sounded so cool—something like that in my home state. When I moved back, I decided to be as close to it as possible. I figured that with my background in water it might provide good opportunities for finding work. It was close to home, which is important. I had been trying to get my foot in the door for a couple of years after moving back until it serendipitously happened last year.
Joshua Dill: Are there any big contrasts that stand out to you between how the water industry functions in Norway and in the United States?
Charles Otis: There’s a lot of innovation in Norway. The wastewater-treatment systems, for example, tend to be a lot smaller than our municipal systems. The buildings are smaller. If you’re going to build there, you’re building on bedrock, so you have to blast a lot. It’s a lot more decentralized in terms of where the water industry is. They also have, of course, the offshore oil industry, which has the same sorts of issues with space. It is not necessarily cheap equipment by any means, but it is small and effective. In Norway, and in Europe in general, they’re used to spending a little bit more money on the treatment, although Norway especially has quite a bit of money from the oil that they invest wisely.
Quite a few companies have come out of Norway: Salsnes Filter is one, which is now owned by Trojan UV, a Canadian company. Another is Biowater, which was actually formed by the people who were originally Kaldnes. Kaldnes was bought by the German company Krüger, and then sold to Veolia for $100 million about 10 years ago. Biowater was formed after they sold because there was still more they could do with their technology than just simple wastewater treatment. Another company is Cambi, which does sludge hydrolysis and power generation from waste. There are a quite a few more, especially on the produced-water treatment side of things for the offshore oil industry. It’s innovative, which I think is partly a function of being so close to the other EU countries where there are a lot of small companies that are nimbler and less consolidated than the ones inthe United States.
Joshua Dill: Do you think there’s any one big lesson that the U.S. water industry could learn from Norway?
Charles Otis: More speculative research and development money would be good. In the United States, large companies like Xylem, Evoqua, and Suez get big contracts because they are established. There’s nothing wrong with that, but there is a lot of innovation in small companies because they are nimbler and have to adjust to the market.
Joshua Dill: Is there anything else you wanted to add?
Charles Otis: The Water Council is doing a fantastic job right now. What they’re doing is really making Milwaukee and the Global Water Center a magnet for water businesses. I think they’re going to do quite well in the future as things start to coalesce and the cluster starts making more waves. I would never have met Shane Leonard without them. I went into that presentation at The Water Council with no expectations at all. The exposure we got there will help our business quite a bit. I’m happy to be a part of it.