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Waste Water Treatment in Mexico. Hugo Fernando Palacios González. Introduction. Hydrologic resources in Mexico 780 mm of pluvial precipitation (1 532 million m3) Superficial runoffs of an annual average volume of 410,164 million m3. Runoffs distributed in 320 drainage basins
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Waste Water Treatment in Mexico Hugo Fernando Palacios González
Introduction Hydrologic resources in Mexico • 780 mm of pluvial precipitation (1 532 million m3) • Superficial runoffs of an annual average volume of 410,164 million m3. • Runoffs distributed in 320 drainage basins • Some of the most important rivers: Yaqui, Lerma-Santiago, Balsas, Bravo, Pánuco, Grijalva, Usumacinta.
Yaqui Bravo Lerma Grijalva
Water distribution problem- 80% of hydrological resources under 500 m (over sea level). 70% of total population over this level, 80% of industrial activity as well. • 55% of industrial activity is developed in the valley of Mexico at more than 2000 m over sea level.
Water Quality • 3 main pollution sources classified as follows: • Social sector. Mexico 23%, Monterrey 4.1%, Guadalajara 4%. Only 50% of the population has sewerage infrastructure. • Industrial sector. Generates 43% of waste water in the country. • Agricultural sector. 92 500 million m3 are used in this sector. Produces 12% of waste water. Water with high levels of particles in eutrophication state.
Waste Water Treatment • 361 municipal WWT plants. Installed capacity of 25 m3/s. (Unfortunately they only have capacity to treat 24%) • 282 industrial WWT plants. Capacity of 20 m3/s. (Only treats 25%) • It’s been estimated that only 50% of these plants operate regularly
There’s an index of water quality used by scientists to classify treated water. • It’s known as the ICARen (Índice de Calidad de Agua Renovada) which would literally mean Quality Index of Renewed Water • ICARen of 0- drinkable water • ICARen >38- useless water
Water Purification Stations • Conventional treatment methods • Basic Physical and chemical procedures, such as decantation, sedimentation and coagulation • Elimination of wastes, oils, greases, sand • Elimination of inorganic and organic materials by decantation • Elimination of biodegradable organic matter • Stabilization and disposition of sludge extracted in the processes
Reverse Osmosis • Membranes made out of synthetic materials
Coagulation • Addition of electrolytes (Alum or Lime) • Charged particles of waste water combine with ions neutralizing the charges • The neutral particles combine to form greater particles • E.G. Ca(OH)2 -> Ca(aq)2+ + 2 OH- (causing pH change)
Flocculation • Use of starch or multiply charged ions to attract or trap the particles and settle down together. • Other salts such as iron sulfates Fe2(SO4)3 and FeSO4, chromium sulfate Cr2(SO4)3, and some special polymers are also useful
Sedimentation • Used after coagulation and flocculation • A settling tank with inlets and outlets is used • The settled particles and sludge must be removed Settling tank
Filtration • Removal of solids from water, passing them by a porous medium • Artificial membranes, nets, sand filter and high technological filter systems
Aeration • Main purpose: Oxygenation • Removal of volatile organic substances , hydrogen sulfide, ammonia and volatile compounds • Diffused aeration- air bubbles through water • Spray aeration • Multiple tray aeration- water flows through many trays to mix with air • Cascade aeration • Air stripping- combination of multiple tray and cascade techniques
Bioaugmentation • Introduction of a group of natural microbial strains or a genetically engineered variant KB-1 Dechlorinator. Used to introduce Dehalococcoides to sites where they are absent
Activated Sludge • Atmospheric air or pure oxygen is bubbled through sewage combined with organisms to develop a sludge, which reduces the organic content of sewage.
Industrial Effluent Recycling • Clonal poplar as recycling engine • Transpiration function driven by weather characteristics • Plantation supplied with water according to needs • Monitoring of parameters every 10 minutes: • Solar radiation • Air temperature • Air relative humidity • Wind speed • Rainfall
Parameters monitored by a station equipped with a micrologger (environmental data logger) • Data is retrieved and evapotranspiration is calculated for every 10 min. interval • These amounts are summed until they reach the amount of a watering (Pre-established based on soil water)
Effluent recycling plant Poplar plantation
Sewerage Infrastructure • Old infrastructural designs • Old facilities • New Projects: “TúnelEmisorOriente” (Mexico city). Interior diameter of 7 meters. Extension of 62 kilometers at more than 200 meters under ground level. Investment of 13 million pesos (19.5 million Kč approximately). Avoid Future floods.
Present Day Problems • In the Valley of Mexico only about 6% of their waste water is treated (against legislation) • Immediate response to the problem: • Permits for the construction of 6 new WWT plants in Mexico city • Investment of 37 million pesos (55.4 million Kč approx)
Leading WWT companies • ACS MedioAmbiente(Monterrey, NL) • Aguas Latinas México S de RL de CV (México, DF) • Alianza con la Biosfera (AliBio) (México, DF) • Bio-Ingenieria Ingeniería SA de CV (La Paz, BCS)
References • www.sagan-gea.org/hojared_AGUA/paginas/8agua.html • http://www.imacmexico.org/ev_es.php?ID=17461_201&ID2=DO_TOPIC