Municipal Water Leader: Please tell us about your background and how you came to be in your current position.
Eli Cohen: I was born and raised in Israel and studied physics, thermodynamics, and materials science engineering. About 35 years ago, I was working for a high-tech company as its research and development leader. At that time, I bought a farm in the Galilee region as a place to live, but when I got to the land, I realized, “This is my destiny—I want to be a farmer.” I decided that I would slowly move into agriculture, but it happened faster than I expected, and I quickly got into growing aquatic plants to sell to Japan and Europe.
Dealing with aquatic plants and water, I started facing a lot of issues. To grow these plants, you need water that meets specific quality standards, because they normally grow in clean streams in the Amazon, Southeast Asia, or Africa. Moreover, I wanted to do it in the semiarid climate of Israel. I ended up learning all about water and how to keep the environment adaptive. My education, together with intuitional learning and long field experience, helped me with the tasks of treating water, managing the environment, and farming.
Today, what’s written on my business card is Sustainability Expert. A sustainable ecosystem is one that can live by itself like any living creature. The aim of our company is to create sustainable systems that can run by themselves, and the only way to do that is to rely on nature. We’re working with nature to help nature—and to help ourselves. This isn’t about hugging trees, it’s about living our lives and doing our work, but with less energy, less chemicals, and less human dependence.
The world today is facing two main development issues. One is the lack of fresh water. There is a huge need in many parts of the world for good, fresh water; meanwhile, only 1–2 percent of sewage water is being recycled. At the same time, we need to reduce our carbon footprint, which results primarily from burning fossil fuels. Burning fossil fuels is only 15–30 percent efficient; the remaining heat and gases contribute to air pollution and the greenhouse effect. It’s obvious that we need to use less energy. In fact, a big chunk of our energy usage goes to water treatment and transport. If we can treat and recycle more water in a natural way that does not require much energy, then we can change the entire game without changing our way of life.
Municipal Water Leader: When did you found Ayala?
Eli Cohen: Ayala as a company was established in 2002, but I’ve been working on the same things independently since 1989.
Municipal Water Leader: How many employees do you have today?
Eli Cohen: Today we have 12 employees, but I also work with freelancers and contractors, including architects and engineers.
Municipal Water Leader: Would you tell us about the NBS technology?
Eli Cohen: It is designed to mimic nature and uses natural elements, both biotic and abiotic. It behaves like a wetland. Wetland plants, like all plants, develop a root zone, a highly efficient net of roots that supports huge communities of microorganisms that live in perfect harmony and full symbiosis. The importance of aquatic plants lies in their ability to transfer oxygen, which is absent in water, to the root zone and to release gases through the stem. The plants’ roots and the microorganisms come into contact with the contaminants in the water and break them down and remove them. However, natural wetlands cannot cope with the amount of contaminants that humans are discharging into the environment, and that is why they’re collapsing. The NBS is an artificial wetland designed to treat specific contaminants and a specific organic load. It is made far more effective than a natural wetland by adjusting the hydrology, the carrying substrate, and the types of plants. We have also developed different kinds of natural additives that stimulate the work of the biological system.
Physically, the NBS is a pond about 1 meter in depth that has a special substrate and is planted with different aquatic plants. Water flows through it in any of a number of water regimes—upstream, downstream, horizontal, free flow, etc. These parameters are chosen depending on the kind of contaminant a client wants to treat. Some create more aerobic conditions; others more anaerobic conditions. Different types of gravel can also help treat different types of contaminants. Limestone, for example, is good at absorbing phosphate from the water. We make the water flow through gravel filters, creating a kind of natural chemical filtration. Most importantly, the plants you plant in the gravel perform a powerful biological filtration function. Their root zones support huge communities of microorganisms, like fungus and microbes, which use the contaminants as a source of food and energy. All the contaminants break down to the mineral level and accumulate in the gravel or in the plants themselves. What results is clean drinking water of high quality in all parameters, not only organics and solids, but also heavy metals, hormones, pathogenic elements, and biota.
The NBS requires zero energy: It all works by gravity. In fact, with the plants, you’re actually sucking carbon from the atmosphere. We don’t use flocculants, so there is no sludge. Big and heavy solids are separated by gravity, given adequate retention time. Moreover, the systems are part of your landscape. Imagine that the park near your house cleans the sewage that comes from your home. You can jog or play with your children there and never know that sewage is being treated under your feet. We call it an active landscape. We convert city parks into active parks. That eliminates the need to build a long pipe or pumping station to send the sewage far away to a treatment center.
The NBS does much more than just treat sewage. Because it’s part of your landscape and watershed, it can collect storm water and treat it as well. Rainwater, unfortunately, is often not especially pure, so you can treat it and then use it to recharge the aquifer or discharge it into a river. Holding and catching rainwater upstream can also help prevent floods downstream. Today, we see more and more floods in cities around the world because of urbanization. The land is all covered with asphalt and cement, so water flows down the road and into drains and ends up causing floods. Our system holds, treats, and releases rainwater at a more moderate rate.
Municipal Water Leader: How long does it take the water to go through the system?
Eli Cohen: We call that retention time, and it can range from half a day to 3 full days, depending on the quality of the inlet and the quality you want in the outlet.
Municipal Water Leader: When you build an NBS installation, how long does it take for the plants to grow and mature before they are ready to treat water?
Eli Cohen: The system starts working from day 1, but the plants need some time to develop their root zones. After 1 year, the system is mature; after 2 years, it’s even better. At 1 or 2 years, it produces water of a higher quality. We design NBS installations to treat the target amount of water almost from day 1, so after 1–2 years it can actually treat more water than it was designed for.
Municipal Water Leader: Does the NBS need any sort of maintenance once it’s been built?
Eli Cohen: Because it doesn’t have any moving parts and doesn’t use any chemicals, the maintenance is mostly gardening.
Municipal Water Leader: Does the water that your system produces meet government-set water quality standards?
Eli Cohen: We can meet any standard. If you want to meet high standards, you might need to increase your retention time. We can also play with the hydrology of the system and use our special natural additives to make it more efficient.
Municipal Water Leader: Would you tell us about some of your applications and clients?
Eli Cohen: Our largest system is in New Delhi, India. We finished the design for that about a year ago. It will serve about 8 million people and will treat around 250,000 cubic meters (202 acre-feet) of water a day, which is a lot of water. New Delhi tried a number of other methods. It had problems with its large sewage treatment plants because they required a lot of energy. The bigger problem was conveying the sewage to the central treatment plant. Building pipes and pumps through the middle of the city would be expensive and logistically impossible. Today, most of the sewage just runs freely into the Yamuna River. That’s why they asked us to design a sustainable, nature-based solution. We created a design called the Tree of Life, which will be like a park that actually joins the city and the river and also treats sewage by gravity. This active park will also harvest, treat, and recycle storm water, preventing floods downstream and reducing the city’s carbon footprint.
Municipal Water Leader: Who are your other clients?
Eli Cohen: We do a lot of work with industrial clients. We’re working with a lot of food factories and we have also worked with cosmetic companies like L’Oréal and with pharmaceutical companies. We have done work for the City of Nice, France, cleaning water from its entire watershed. We won an international competition to get that project. We have many other clients besides.
Municipal Water Leader: Have you worked at all in the United States?
Eli Cohen: Yes and no. I was invited to give some talks in New York City in 2007 and met people from the city government and even got two jobs there. One had to do with a lake near LaGuardia Airport and another was at a complex in Long Island City. I was also in touch with a big manufacturing company in California regarding the design of one of their logistics centers and with a company from Texas about water flowing out of a meat processing plant. Unfortunately, the 2008 market crash killed all those projects.
Last year, I was in Washington, DC, and met some utilities at a meeting with the World Bank. My impression is that the technology is interesting to them and has the potential to save them a lot of money. The Potomac River receives a lot of unclean water from a local sewage treatment plant. If we can create a buffer zone at the outlet, we can change the face of the river. A few weeks ago, I got a call from Colorado from a city that doesn’t want its water chlorinated. Our system can dramatically reduce pathogenic elements without chlorine, instead using complex natural processes in the substrate media aided by a natural additive in the last flow zone that has been proven to eliminate pathogens completely.
We believe that these are the solutions of the future. They can enable us to improve the environment and our lives without changing our daily habits. Climate change’s effects are knocking on our door, and all we need is more attention and awareness and a willingness to change our mindset.