A problem that is common for cities around the world is what to do with their wastewater. In western societies the most common way to treat wastewater is through a wastewater treatment plant where chemicals and biological elements are added to treat the water. However, for a lot of the world these plants are too expensive and they lack the expertise required to run the plant. A cheaper and more ecofriendly way to treat wastewater is by using the environment, and since 1950 researchers have been working to investigate how this is done. Now, 60 years later they have figured it out, and today artificial wetlands are being used all over the world.
The other day I was watching a video on sanitation and I was surprised to learn that there is an artificial wetland here in California that is treating wastewater. The Arcata Wastewater Treatment Plant is part of the Arcata Marsh and Wildlife Sanctuary in…you guessed it…Arcata, CA and treats all of the waste from their roughly 18,000 citizens. What use to be abandoned mills and a dump site is now 307 acres of beautiful marshland, freshwater ponds, and mudflats populated by different types of marine animals and migratory birds. Here’s a very basic description of how the process at the treatment plant works. The primary treatment includes removing all solid matter from the water and eventually using it to produce compost and methane. The second phase sends the water into oxidation ponds where algae adds oxygen to the water and removes up to 50% of the BOD from the water (Don’t know what a BOD is? Click here bit.ly/aRM241). It then continues into the treatment wetlands where the algae settles out of the water and microorganisms living in the roots of the plants further reduce the BODs. Next you have what is called the tertiary treatment phase, and during this phase excess nutrients such as nitrogen and phosphorus are removed. The process for doing this is as simple as releasing the water into the marshes and letting the water flow
through all of the plants. From here the water is chlorinated to remove any bacteria or pathogens, and then part of it is sent back into the marshes and the rest is sent out into Humboldt Bay. Although this process may sound complicated it is nothing compared to what a traditional treatment plant goes through to get clean water. And besides cleaning the water it provides an wilderness area where birds and other animals can go to thrive, a beautiful area where people go to take go for a run or just relax in the beauty of the marsh (and unlike traditional systems, there’s no smell). Because of their achievements the Arcata Marsh and Wildlife Sanctuary was awarded the Innovations in Government award from the Ford Foundation/Harvard University Kennedy School of Government. Let’s move on and look at another example of using the environment to clean wastewater from Nepal.
In Nepal most of their treatment plants are non-functioning due to various reasons, and so they are using an alternative treatment called reed bed wastewater treatment units (RBWTUs). Reed bed units use the same idea as the wetlands in Arcata except the water is not treated with chlorine; the water flows in, the solids are separated, oxygen is transferred into the roots of the reeds which cause micro-organisms to grow, and as the water slowly moves through the roots it is treated by these micro-organisms, and comes out on the other side clean. Here are a couple of simple diagrams showing how the reed bed system could be made:
The last example comes from Egypt where they found themselves with a twofold problem; stopping the pollution to Lake Manzala, and treating the wastewater that has been polluting it. Egypt couldn’t afford to install traditional wastewater treatment facilities so they started looking for other options. Based on the facts that Egypt is a water scarce country, they have a lot of open land, and they required a low cost technology to deal with their waste they decided wetlands were the way to go. This wetland works pretty much like the others; water goes into a pond and the solids are pulled out and the sediment settles, then it is put through several different wetlands, the microorganisms in the roots kill the bacteria and virus’, and then the water is released. The difference with this situation is that when the water is released it is put in a pond where they have a fish farm. Here the people from the community can farm their fish and make a living off of it. They plan to expand and add more fish farms and eventually have enough stock that they can start re-populating the lake. The Project Director, Dr. Diaa el Quosy knows that the project is a great success. The water comes out 75% cleaner than it goes in, the project was 10% of the cost of a traditional facility, it’s good for the environment because they don’t use any chemicals, the maintenance is relatively easy, and they’re saving the lake from pollution. Sounds like they’re happy with the choice they made, and hopefully Eqypt will decide to build more artificial wetlands to help with their pollution problem. Here’s a quick 5 minute video showing the lake and the project.
There are a number of benefits of artificial wetlands over traditional treatment facilities. As far as the treatment side the systems are simple and so they are generally less expensive to build and operate, maintenance is easier, wetlands can tolerate different levels of water flow, and obviously they produce clean, but non-potable, water. Other than these benefits the wetlands provide a habitat for many animals and therefore promote biodiversity, it is environmentally friendly, and they turn areas that may have been otherwise polluted or unused into beautiful open spaces to be enjoyed by the public. Thanks for reading, and i’ll leave you with two other diagrams showing what it takes to treat wastewater at a typical traditional treatment facility vs an artificial wetland.