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Floating Islands

River sanitation in San Cristóbal de Las Casas with floating islands of bioremediating plants.

Millions of years of evolution demonstrate that natural systems hold the solution to the vast majority of anthropogenic problems. Ojos de Agua is focusing its efforts on counteracting the negative consequences for human health stemming from the lack of water sanitation in San Cristóbal de Las Casas (SCLC), Chiapas. We propose to mimic nature using so-called ‘floating wetlands’. The core idea is to use the same local plant species (with the capacity to absorb organic and inorganic pollutants) that are being used in a constructed wetland wastewater treatment plant elsewhere in Chiapas and place them in floating structures in the rivers of San Cristobal de las Casas. The installation of floating islands housing these aquatic or semiaquatic plants also create a healthier habitat for the flora and fauna. There is ample empirical and scientific evidence that this type of sanitation works.

The rivers in SCLC are the recipients of sewage dumped from thousands of clandestine sewage pipes originating from both domestic households and businesses, amongst other sources of pollution. Due to the high level of pollutants, low retention times (current is approximately 2m/s) and above all the number of islands we can install, our challenge is to achieve significant results in the selected sites, and to ensure that the community is involved and becomes convinced that such a system provides many benefits, such as:

  • VISUAL: the rivers will look cleaner, greener and filled with life instead of garbage.
  • OLFACTORY: once we start installing more islands and implement the many strategies necessary to maintain river cleanliness (e.g. environmental education), we will no longer have to cover our noses when walking across the bridges of the city or alongside the riverbanks
  • HEALTH: The rivers, currently open sewers whose waters are used to irrigate the city vegetable supply, will no longer carry and cause water-borne, preventable diseases.
  • SOCIAL COHESION: a solution that is visually attractive, affordable, easy to construct, simple to maintain, ready to be implemented by anyone, can bring people together. When this solution beautifies our environment it also provides new spaces to socialize.
  • LOW CONSTRUCTION COST: Each floating island costs 4,000MXN (including material, labor and everything needed for the construction). Materials are largely recycled.
  • LOW MAINTENANCE COST: the maintenance of a traditional wastewater treatment plant costs around 500,000 pesos per month (mainly electricity). Floating islands need to be periodically checked (to ensure they are in place, without damage or garbage build-up), pruned twice a year (with proper disposal of pruned vegetative tissue) and the plant filters need to be replaced as necessary. We believe that, were the municipal authorities to extend this sanitation treatment throughout the rivers of San Cristobal de las Casas wherever possible, the salaries of the maintenance crew required would come to far less than this amount.


Here it is a long version:


We are developing strategies for public outreach that involve information campaigns (via all possible outlets we can get access to), workshops (for all ages), public talks and events that require active participation, such as floating island construction fiestas. We are approaching governmental agencies to establish collaborations and ensure sustainability for this type of river sanitation.

Through the installation, maintenance and monitoring of floating islands with bioremediating plants and citizen participation actions, we envision cleaner rivers and happier, healthier citizens.