Within the arid area south of Mexicali, the place the pale desert dominates the panorama, the Las Arenitas wetland appears like a mirage. However it’s actual, and is an oasis for endemic and migratory birds that cross the Colorado River delta. Right here, simply south of the US-Mexico border, used water from town of Mexicali will get a second life. Half of it goes to the close by Hardy River, in an try to revive ecosystems that have been considered irrecoverable.
Traditionally, waterways right here have been flushed filled with sewage—significantly the New River, which runs off from the Colorado River northwards, crossing from Mexico into the US and ending within the Salton Sea in California. For a few years, this water course acquired untreated sewage from Mexicali, rendering it one of many worst-polluted rivers of its dimension within the US. Within the Nineties, American and Mexican authorities may not ignore how dangerous the issue had turn out to be, they usually started collaborating on infrastructure to reduce the air pollution. And so, in 2007, south of Mexicali, the Las Arenitas therapy plant started operations.
Mexicali, which sits proper on the border, generates greater than 80 million cubic meters of sewage a yr. Of that whole, 90 p.c is collected, with 46 p.c of that going to Las Arenitas.
Within the sewage plant, solids and sediments are first faraway from the wastewater. Subsequent, surface-aerated lagoons are used, the place air is injected into the water to stimulate the expansion of cardio micro organism, which decompose natural matter within the presence of oxygen. The water then passes to facultative lagoons, the place cardio and anaerobic micro organism complement one another, the latter degrading natural matter that the previous couldn’t. Lastly, the water reaches the maturation lagoons, the place the remaining solids settle out.
When it launched, this new system labored. “To start with, the plant didn’t carry out ideally,” says Edith Santiago, deputy director of the Colorado River delta program in Mexicali on the conservation nonprofit the Sonoran Institute. To fight this, some organizations proposed to the water administration company that they need to use the encompassing land, which a long time in the past housed a lake, to create a man-made wetland that may give the water further cleanliness.
Such a plan, in addition to serving to with town’s sewage downside, would additionally assist partially restore the native panorama to its former state. Earlier than the overexploitation of the Colorado River, its delta crossed Baja California and Sonora till it met the waters of the Gulf of California, leading to greater than 400,000 hectares of wetlands. Though the river’s course has turn out to be a ghost, about 15 p.c of these wetlands have survived, harboring a useful biodiversity of vegetation and animals. In search of to imitate that energy, the Las Arenitas synthetic wetland is a pause to the devastation of the native panorama.
