1. How do the islands work?
The phytoremediating islands, installed in rivers and lakes, are floating structures that function as artificial wetlands which serve as wastewater treatment plants, with a capacity of 5 m2 of wetland / person (Cooper and Breen, 1998). The installation of floating islands also creates a habitat or refuge for the surrounding flora and fauna.
They work as a natural water-cleaning machine that is aesthetic and easy to build. The island or raft is the means to have and retain the plants where we need them, because we are replicating the natural processes of water cleaning. The main idea is to copy what the so-called "floating wetlands" do, using local plants placed in floating structures within the SCLC rivers.
Our islands hold more than 130kg and house local, aquatic and semi-aquatic plants like bullrush (Typha latifolia), native grasses (Cyperaceas), reed (Phragmites sp.), common rush (Juncus effusus), false water clover (Marsilea ancytopoda), whorled pennywort (Hydrocotyle) verticilata) and horsetail (Equisetum giganteum), capable of absorbing organic and inorganic pollutants.
2. The islands filter small quantities of water, right? Why did you choose islands and not barriers/dams?
We chose floating islands because intervening in the river is not trivial. To construct a dam or barrier, detailed studies of hydrology, hydraulics, topography, environmental impact, possible risks, among other evaluations and a big amount of paperwork, are required. You need to have concessions and permits emitted by CONAGUA, because rivers are federal zone.
We have informed CONAGUA about this pilot project and they have given permission to test the idea on a small scale, since the simulations we have done demonstrate that the islands pose no risk to the population or to the river itself. For example, there is no risk of flooding if we place 20 islands in the Amarillo River.
The next step is to show the population and the municipality that this is one of many viable solutions. We are at that stage now. Subsequently, all relevant studies and paperwork will be required.
3. So, the idea is to monitor the quality of water to know if there is any positive effect of the islands?
Originally, the idea was to analyse water samples of water prior to entering the islands stretch and water coming out of the islands stretch to provide evidence of their efficiency. However:
- there are clandestine downloads of sewage even within the sections where the islands will be installed,
- the retention time of particles is very short (the river runs at 2m/s) and it is unlikely that we will be able to capture an improvement in water quality (especially having few islands),
- there is an enormous body of literature (based on scientific studies) that demonstrates the phytoremediation capacity of many plants (including the ones we use). That is why we know that they work,
- We believe that it would be great to analyse the vegetative tissue of the plants in our islands, but for the moment we have no budget to do so. Although this is not a scientific project, it would be very helpful to have hard, qualitative and quantitative data. Would you like to contribute? .
The monitoring we do consist of visual inspection and evaluation of the health of the plants that are on the islands and determining the lifespan of the islands, because what interests us the most with this pilot project is that people get to know the solution that we propose, knowing that it works and that they can adopt this idea.
4. It would be more convenient to have a dam similar to those that beavers construct or the so called Chinampas (typical of Xochimilco), using different filters if one wants to clean a river.
Our idea is to copy the natural system of wetlands for filtering and cleaning water.
The islands we propose are like floating micro-wetlands that contain wetland plants, which are local and purify the water.
Without doubt we require different approaches or ideas to solve the big problem of the lack of sanitation in SCLC. A beaver-type dam could be viable, but it is essential to do the hydrological, hydraulic and topographic studies (and all what is mentioned in question 2) of the rivers to ensure that it would not cause problems upstream or downstream (such as floods).
5. If I cannot help in the construction of floating islands, how else can I contribute to this project?
Ask six friends to give you $ 5. Every pallet costs $ 15 and we need 2 per island. With your help we can get the base for one island. Do you want to contribute? .
Spread the word about our projects among your acquaintances or share with us the contacts that would be interested in knowing more about how floating islands work and why they are one of many viable solutions (@ojosdeaguaSCLC).
Donate materials for the construction of floating islands. Do you want to donate?
Use less quantity of cleaning products, since they are one of the most consumed products and they pollute our rivers.
Separate solid waste into organic and inorganic piles.
There are many sites in SCLC where you can take waste that is recyclable (paper, metal, glass, plastics). La Albarrada accepts remains of food and transforms it into compost but if you can not go there to leave your organic waste, make your own. If you live in one of those lucky neighbourhoods where waste collection is already being implemented by the municipality, find out how to do a proper separation of solid waste.