Secondary wastewater treatment requires providing oxygen to bacteria in wastewater so that they remove the dissolved contamination from it. Providing this oxygen to the bacteria is called aeration. In general, there are two types of aeration: mechanical surface aeration, which uses a mechanical impeller to spray water into the air and tends to be inefficient and to suffer from maintenance and health and safety issues, and fine bubble aeration, which involves releasing tiny bubbles from diffusers fixed to the bottom of a reactor. The Israeli company Mapal Green Energy, based in Kibbutz Yagur, has come up with a new take on the latter method. Its floating fine bubble aeration (FFBA) system uses an easily removed floating device to inject wastewater with fine bubbles from above through diffusers that are suspended from the water surface. This system is significantly more efficient than surface mechanical aeration and is easier to maintain than a floor-fixed system. 

In this interview, Mapal’s cofounder and chief executive officer (CEO), Zeev Fisher, tells Municipal Water Leader about the benefits of FFBA and Mapal’s work around the world. 

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Municipal Water Leader: Please tell us about your background and how you came to be in your current position. 

Zeev Fisher: I’m a mechanical engineer. I grew up in Israel and graduated from Ben Gurion University in Beersheba. All my experience is in the infrastructure business, including water, wastewater, and desalination projects. About 10 years ago, I identified an interesting technology which was still at an early stage. Because of my experience, I realized its potential for the wastewater treatment process, and I decided to found Mapal, which I did with a partner who is no longer active in the company; to raise money; and to slowly penetrate the global market. 

Municipal Water Leader: Please tell us about Mapal as a company. 

Zeev Fisher: We’re a small company with 10 employees, based in Kibbutz Yagur in northern Israel. We are not a big engineering, procurement, and construction contractor that does everything; we are a niche company with a specialty in aeration technology for municipal and industrial biological wastewater treatment. We have developed a technology that we call FFBA. 

Municipal Water Leader: Is the company owned by the kibbutz? 

Zeev Fisher: No; I founded the company and the raised money from private investors in the United Kingdom, who now own the company. The kibbutz is just where our office and manufacturing facility are located. Many water technology and irrigation companies have grown up in kibbutzim because they address the needs of these largely agricultural communities. 

Municipal Water Leader: How does FFBA work? 

Zeev Fisher: Aeration is the core of biological, or secondary, wastewater treatment, both municipal and industrial. During biological treatment, we supply oxygen to the bacteria that naturally exist in wastewater, and the bacteria multiply and eat the dissolved contamination. 

Wastewater contains two types of contamination: solids, or particles, and dissolved contamination. The solids and particles are removed during pretreatment, which is a simple process that uses the physical parameters of the particle: If the particles are light, they float and can be skimmed off the surface; if they are heavy, they sink and can be collected from the bottom; if they’re in between, they are called suspended solids and can be filtered or screened away. 

Wastewater also contains dissolved contamination, including biological load, biological oxygen demand (BOD), chemical oxygen demand (COD), ammonia, etc. That is removed by bacteria. This is a much more complicated process than the removal of solids, because the bacteria that are used are microorganisms—living creatures. You have to control the water for pH, temperature, retention time, oxygen, etc. There is a direct link between the amount of oxygen that the bacteria consume and their performance. To remove 1 kilogram (kg) of BOD, you need 1.1 kg of oxygen. If you supply more than that, you waste energy; if you supply less than that, you won’t meet the effluent consent set by the local regulator or government. 

There are two types of technology that are used to aerate wastewater. One is what we call mechanical surface aeration. This involves a mechanical device that floats or is fixed on a bridge or another structure. It has an electrical motor and a gearbox that drives an impeller that sprays wastewater into the air. The oxygen in the air then dissolves into the wastewater. The main problem with this system is that it consumes a lot of energy or, in other words, has a low oxidation efficiency. The other problem is that the electromechanical equipment is in the wastewater, so to maintain or repair it, you need to get in the water. That creates maintenance issues and health and safety issues. Finally, there are odor issues, since you’re spraying wastewater into the air. 

Recognizing these problems, about 15–20 years ago the industry developed a new technology, fine bubble aeration. Instead of bringing the water to the air, it brings air to the water. A blower sits outside the water, takes atmospheric air, and pushes it through piping that is fixed to the concrete floor of the reactor and through rubber diffusers, usually made of high-density polyethylene membrane, creating hundreds of billions of fine bubbles that go up to the water surface. As the air bubbles rise, the oxygen in them dissolves into the wastewater, supplying the bacteria with the right amount of oxygen needed for the process. The oxidation efficiency of fine bubble aeration is about twice as high as that of mechanical surface aeration. There are no moving parts in the water, so maintenance is minimal. Moreover, there is no spray, so there is less odor. 

Where does Mapal come in? There are many existing lagoons and wastewater treatment plants that suffer from a lack of oxygen and in which the original equipment doesn’t work properly or needs to be upgraded to deal with increased loads caused by population growth. For these and many other reasons, there is demand for a device that can increase the oxidation capacity of an existing treatment site. However, upgrades to existing sites can be expensive. Our FFBA device can be installed in any existing reactor or lagoon with minimal investment and bring it all the advantages of fine bubble aeration. Today our technology is mature, and we have global experience. In addition to Israel, we have worked in Australia, Brazil, Indonesia, South Africa, and the United Kingdom. 

Municipal Water Leader: Is the FFBA device used primarily to upgrade installations that previously used mechanical surface aeration? 

Zeev Fisher: Our clients and potential clients fall into several markets. One of those markets is upgrading existing sites and lagoons to use fine bubble aeration. Another market is plants that are going to be upgraded but need a short- or medium-term solution until that upgrade occurs. A third market is newly built plants for which the consultant and the client engineer specify that they want fine bubble aeration, but don’t want to have those plastic pipes and diffusers fixed to the floor. If you do have a problem with a plant like that—if a pipe or membrane breaks—you need to drain the reactor to fix it. The Mapal FFBA device, on the other hand, is designed to be a completely retrievable system that can be lifted out of the water with no need to stop the process or to drain the reactor. That is a major advantage of our system. We’ve done a project for TasWater in Blackmans Bay, Tasmania, Australia, for which that was the specification. The general contractor won the design bid contract and chose our technology, and we designed a system that is completely retrievable with no winch or rails on the reactor walls whatsoever. The system is manufactured in Israel and shipped like a kit, and after it is assembled, the client lifts the device with a crane and puts it in the water with no need to stop the process. It is simple and easy. That allows the operator to increase oxidation immediately. 

Municipal Water Leader: Are all the units manufactured in Israel? 

Zeev Fisher: At the moment, yes. We find it most cost effective to manufacture in Israel, but when foreign markets grow, in Australia for example, we may begin to manufacture locally. Presently, everything is manufactured in Israel and shipped inside a shipping container. 

Municipal Water Leader: Can the operator of a reactor or a lagoon add more Mapal units to the reactor to make their process more efficient, or is there an optimal number of units that should be used? 

Zeev Fisher: The efficiency of secondary biological treatment depends on several parameters, so it can’t necessarily be improved just by adding more oxygen. Other factors include retention time, the size of the lagoon or reactor, and the flow and load that are coming in. We can design a system that can be integrated into an existing plant given its constraints. 

You should understand that the wastewater treatment industry is driven primarily by regulation. If there were no regulation, nobody would do anything. Regulations also need to be enforced and monitored to make sure that the effluent that is discharged to the environment meets the effluent consent parameters determined by local regulations and laws. When the final effluent does not meet the effluent consent parameters and a local regulator fines a plant manager or takes them to court, there is an immediate demand to solve the problem. In our experience, most of the time the problem is a lack of oxygen, and that is something we can help with. There are two kinds of solutions we can provide in that type of situation. One is capital expenditure on a project that exactly meet the client’s requirements for many years to come. The other is that we have rental units that can increase oxidation and increase the performance of the bacteria quite dramatically. We’ve done it in both the municipal and industrial sectors. 

For example, there is a semiconductor manufacturing facility in Israel that has been having an issue with its effluent ammonia value. The operators came to us and said they urgently needed extra oxygen. We manufactured and supplied two units on a rental basis for 6 months, and that gave the operators enough time to plan a permanent solution. Right now, we’ve got rental units operating in Australia, Israel, and the United Kingdom. 

Municipal Water Leader: Do you currently have any clients in the United States? 

Zeev Fisher: Not currently, though we have received several inquiries. The investigations that we’ve made suggest that there is a lot of potential for our technology in the United States, mainly in the Midwest, where there are a lot of lagoons that use mechanical surface aeration technology. Replacing the surface aeration with our FFBA system could reduce their energy and maintenance costs. However, penetrating into new territory takes time and a lot of money: You have to convince people of the usefulness of a new technology, you have to meet a lot of consultants, and you have to go to conferences. At the moment, Mapal is concentrating on its existing territory, but when we have the funds and the right financial structure to support going into the United States, we will be very happy to. 

Municipal Water Leader: In what ways does Mapal’s solution save energy? 

Zeev Fisher: As I said before, there are two types of aeration: mechanical surface aeration and fine bubble aeration. If we dive a little bit into the numbers, under standard conditions, mechanical surface aeration supplies 0.9–2.1 kg of oxygen per kilowatt (kW) and fine bubble aeration supplies 3.6–4.8 kg of oxygen per kW. This is what we call standard oxygen transfer efficiency. Just by looking at the numbers, you can see that fine bubble aeration delivers 1.7 to 5.3 times more oxygen per kW. There is a direct link between the oxygen requirements of the bacteria and their performance: To remove 1 kg of BOD, you need 1.1 kg of oxygen; to remove 1 kg of ammonia, you need 4.2 kg of oxygen. When a process engineer receives the requirements for a plant, they calculate its actual oxygen requirements, and from that, they calculate the standard oxygen requirements. That states how much oxygen needs to be supplied to the process to meet the effluent consent requirements. Since the oxygen demand is fixed by the process requirements, using a more efficient method of aeration saves energy. Based on our experience and the case studies we’ve done, we save 40–50 percent of the energy used by mechanical surface aeration. 

Municipal Water Leader: What is your vision for Mapal? 

Zeev Fisher: The issue of lack of oxygen is present all around the globe—it’s an endless market. We haven’t even touched China, India, or Latin America yet. There is demand in all those places for this sort of service because lagoon treatment is common there. Any industry that needs to treat contaminated water before discharging it is a potential client. We have experience in a wide range of industries: We’ve done oil refineries in Haifa, Israel; pulp and paper in South Africa and Indonesia; food and beverage in Israel and the UK; chicken abattoirs in South Africa; and pig-breeding plants in Israel. Although we are a small company, our technology meets an important need that exists in municipal and industrial plants all over the world. 

Zeev Fisher is the cofounder and CEO of Mapal. He can be contacted at