Selección y evaluación de impactos ambientales de un sistema descentralizado para el tratamiento diferenciado de las aguas residuales domésticas en una vivienda en la Ciudad de México

Abstract

In this work, different decentralized wastewater treatment systems were evaluated, preselected for the treatment of gray water generated in a house in Iztapalapa of the type "Unique house on land with average occupants of 4”. Housing defined as a case study, taking as a reference the Mexico City mayor's office that presents greater problems of availability of piped water and coverage of wastewater treatment. The evaluation of the systems was carried out through the following phases: Phase 1. Indicators that contribute to the sustainability of the systems were identified and pondered, these being: demand for the system area, as well as its robustness, pollutant removal efficiency, investment costs, energy requirements, greenhouse gas emissions, landscape damage, odor emission and generation of byproducts whit economic or reuse value. Phase 2. The possible systems to be installed in the case study were pre-selected: sequential batch reactor, membrane biological, upflow anaerobic, as well as constructed wetlands and septic tanks. Based on these systems and the previously defined indicators, the available technical information was compiled. Phase 3. A decision matrix comprised the indicators, their weighting, and the preselected systems. Based on the information obtained in Phase 2, the systems were evaluated according to their compliance with each indicator. Once the evaluation was settled, it was weighted to obtain the qualification by alternative. Thus, the upflow anaerobic reactor obtained the highest rating (72.4 points), followed by the sequential batch reactor with only 2.8 points below. Given this result, the systems were compared based on the following criteria: a) Effluent quality and greenhouse gases from the systems operation products: where the sequential batch reactor presented better quality effluents and lower greenhouse gas emissions. b) Environmental impact of the treatment of gray water from the case study: the results showed that the sequential batch reactor was the most environmentally sustainable option.