The water in Mexico City today flows from the surrounding volcanic ranges to the center, past the airport, through and around the mountain ranges on the north of the city, to end up in Tula and Mezquital Valley. From the Aztec Empire and the separation of fresh and saline water surrounding Tenochtitlan, to the Spaniards and their attempt to drain Lake Texcoco in order to control flooding, the issue of water management has always been vital for Mexico City. Nowadays, only a few remnants of the former Lake Texcoco persist throughout the year, as rivers and canals funnel wastewater out of the valley.

The Tula and Mezquital Valley is now a vast agricultural region, irrigated by the wastewater of Mexico City. This relationship between wastewater and agriculture has existed since the time of Tenochtitlan, when the chinampas were invented and proliferated in an attempt to feed the city. In addition to the farmlands and the urban sprawl, nature reserves and airports are also entering the discussions around water in Mexico City, as conservation and globalization manifest themselves spatially within the valley.

Three architectural projects explore the intersection of wastewater and agricultural practices in the greater region of Mexico City, through specific organizational structures. From the government to the cooperative, these three different organograms dictate Mexico City’s future perspective on wastewater as both an input and output for the metropolitan metabolism.

The Axolotl and the Chinampero

Sequestering the heavy metals in the chinampas through alien species and future technology.

Where the water from the volcanic ranges sprung is the hiding place of an Aztec god, Xolotl. Now in the form of an adorable amphibian, the disappearance of these axolotls would signify the end of Xochimilco. Since the time of Tenōchtitlan, feeding the growing city was a challenge. These axolotls were one source of food, but the highly productive land where they make their home now was what the Aztecs relied on. The chinampas were invented and proliferated by the Aztec Empire throughout Lake Xochimilco and Chalco. Referred to as “floating gardens,” the creation and upkeep of these artificial islands integrated land reclamation, food production, and water management.

The islands kept together by stakes and willow trees (ahuejotes) established the soil bed for agriculture along with a filtration apparatus for waste. As a grid-like pattern of development was established, the remaining lake in between became natural waterways (acalotes) and irrigation channels (apantles). Maintenance of both these landscape infrastructures is done by collecting the mud from the lake bed and placing it on the chinampas along with other biomass. This process clears the waterways while fertilizing the soil and maintaining the plot until the ahuejotes can fully mature to bind the whole structure to the landscape.

The landscape now is nothing like what it used to be. A series of new interventions along with developmental shifts completely altered the contents of this region, leaving the remains of the chinampas as both the land and water deteriorate. The changes all began in the water. The source changed after the lakes and aquifers were drained, which required water from Cerro de la Estrella WWTP to be brought in. The habitat changed after carp and tilapia were introduced as alternative food sources and the water hyacinth made its way up from the Amazon basin. Now the tilapia and water hyacinth dominate the aquatic life in a lake with rising concentrations of heavy metals from the waste water and runoff.

However, these alien species provide a new opportunity for the chinampas. Water hyacinths can rapidly absorb the heavy metals in water thanks to their aggressive growth rate. As heavy metals accumulate most in the roots of a plant, by removing the roots before using the tops for fertilizers the soil and water can immediately be improved. Starting from this labor intensive method, new experimental methods can later be introduced. Electrokinetic Phytoremediation is a process that takes advantage of the natural process of heavy metal absorption, like with the water hyacinths, by increasing the absorption rate through an electrical current around the plant. If successful, the ahuejotes would no longer just bind and protect the individual chinampa and instead become a pillar of water quality for the whole of Mexico City.

The electricity can be generated within the chinampa system by introducing a biogas digester. This Fish Digester would promote the catching of tilapia and carp to be turned into biogas and fish emulsion. The fish emulsion can be used to fertilize not just the chinampas but be made available to the greenhouses and nurseries to mitigate the use of agrochemicals that are currently adding heavy metals to the system. Most importantly, the Fish Digester will promote the return of fishermen to the chinampas. With their help the biodiversity in Xochimilco, Tlahuac, and Milpa Alta can improve through their management of the tilapia and carp population. Then as the waters become clearer and the axolotl population recovers, even they could return to their original status as food sources. The stabilization of all species reliant on the chinampas sprouting from the ahuejotes.

Contribution by Jin Young Chang

Terminal Reclamation

Sociedad Holística y Tecnológica.

Combining the useful with the beautiful, allotment gardens provide healthy physical activity while offering organized members the pleasure of experiencing the garden and the production of food. Going beyond merely recreational, 'Sociedad Holística y Tecnológica' aims to offer an alternative model for urban development and land reclamation, in which modern citizens can take part in sustenance farming and the process of land reclamation.

Following the canceled airport and building upon the current plans for a recreational park, a land reclamation project is proposed. By experimenting with traditional agricultural practices and directly participating in a largely enclosed waste and water cycle on-site, members slowly transform the former site of Texcoco Airport, while nourishing themselves both physically and spiritually. From producing and fertilizing to consuming and composting, organic matter is accumulated to enrich soil and improve the water retention of the site.

Central to this development is the re-imagined toilet unit, challenging members to rethink the way in which they use the toilet. While behavioral adjustments might take some effort, human bodies already separate urine from manure by default. Collecting waste separately requires less processing, produces less smell, and attracts less pests, while allowing it to be composted and percolated directly. From simple low-tech buckets for footloose individuals, to sophisticated high-tech thrones for established communities, the new toilet can be constructed and used regardless of income level, user volume, pre-existing infrastructure or site.

Today, the site exists on a variety of topologies, presenting plots for a range of new members. Most of the terrain is vacant, ready to accept new chinampa developments. Elsewhere, Texcoco Airport is partially constructed, and the existing airfield has been graded with tezontle and concrete. In this area, the airport's foundations are in place together with hyperboloid structures. For these parcels, partners and tenants are sought out to be part of a research and innovation center for gardening and composting. By embracing its liquid infrastructure, Mexico City is to expand without negatively impacting its natural resources.

Contribution by Michael Tjia

W.C. The Wastewater Cooperative

A New Productive Infrastructure for the Mezquital Valley

“All smell of decomposing matter may be said to indicate loss of money”  Hugo Chadwick 1846

As part of the metabolic functioning of the metropolis, Mexico City’s wastewater is expelled to The Mezquital Valley, where it is used to irrigate the crops that return to the city in the form of food. The valley’s farmers and communities are economically dependent on sewage, a resource that both creates wealth and diseases.

As Atotonilco WWTP is able to treat only the 70% of the wastewater coming from the city, the contribution proposes a decentralized cooperative to treat the remaining 17m3/s ensuring a balance between health, agriculture and landscape, through five mission statements:

1. Scattered through the three irrigation districts of The Mezquital Valley, seven infrastructural rings connected to the valley drainage system composed of dams and rivers, treat the wastewater which is used for irrigation and then is filtered back into the aquifer.

2. The configuration of the valley composed of hills, plains, towns and rivers, suggests a radial geometry as a solution that works in two directions. While the ring cleans the water from inside to outside, the centrifugal shaft adapts to the context.

3. The main use of the W.C. system is 6000 Ha of wetlands necesary to purify water in the existing territory without altering it. However, Biomass plants, logistics centers, and worker facilities are the adjoining programs fundamental for an optimal relation between water, food and energy.

4. As part of the existing ejidos, the radial grid combines the minimum size of the hectare with the linear system of water purification to configure the width of the ring. While the first stage of the cleaning process provides water to irrigate the interior formed by drought tolerant crops,  the second stage provides water for the exterior formed by water intensive crops.

5. With an ideology based on the organic vision coined by the nineteenth-century socialist Pierre Leroux, the project turns waste into an agent of regeneration, creating a new social order to transform our anthropocentric society.

Contribution by Ana Herreros Cantis