In arid Region south of Mexicali, where the pale desert dominates the landscape, the wetland of Las Arenitas looks like a mirage. But it is real and is an oasis for endemic and migratory birds that cross the Colorado River Delta. Here, just south of the American-Mexican border, the water used in the city of Mexicali obtains a second life. Half goes to the neighboring Hardy river, in order to relaunch ecosystems that were considered irreparable.
Historically, the waterways here have been rinsed full of wastewater –especially the New RiverWho fled from the Colorado river to the north, crossing from Mexico to the United States and ending in the Salton Sea in California. For many years, this watercourse has received untreated wastewater from Mexicali, render it One of the most polluted rivers of its size in the United States. In the 1990s, the American and Mexican authorities could no longer ignore how bad the problem had become, and they started to collaborate in infrastructure to reduce pollution. And therefore, in 2007, south of Mexicali, the Las Arennitas treatment plant began its operations.
Mexicali, which is right at the border, generates more than 80 million cubic meters of sewers per year. Of this total, 90% is collected, with 46% of this going to Las Arennitas.
In the wastewater plant, solids and sediments are first removed from wastewater. Then, airy lagoons on the surface are used, where air is injected into water to stimulate the growth of aerobic bacteria, which decompose organic matter in the presence of oxygen. The water then switches to optional lagoons, where aerobic and anaerobic bacteria complement each other, the last degrading organic matter that the first could not. Finally, the water reaches the maturation lagoons, where the remaining solids are deposited.
When it was launched, this new system worked. “At the beginning, the factory did not occur ideally,” explains Edith Santiago, assistant director of the Delta program from the Colorado River in Mexicali to non -profit conservation of the Sonoran Institute. To fight against this, some organizations have offered the water management agency that they should use the surrounding land, which housed a lake ago, to create an artificial wetland that would give water an additional cleanliness.
Such a plan, as well as to help the city's wastewater problem, would also help to partially restore the local landscape to its old state. Before the overexploitation of the Colorado river, its delta crossed Baja California and Sonora until it encounters the waters of the Gulf of California, resulting in more than 400,000 hectares of wetlands. Although the river course has become a ghost, around 15% of these wetlands have survived, hosting invaluable biodiversity of plants and animals. Seeking to imitate this force, the artificial wetland of Las Arennitas is a break from the devastation of the local landscape.
