Avaliação do ciclo de vida - ACV de um sistema de wetland construído de fluxo vertical para o tratamento de esgoto doméstico

Abstract

The wastewater treatment system by constructed wetland takes into account the basic principles of natural wetlands for modification of water quality, however, it has controlled hydraulic flow and is constructed according to the desired treatment efficiency. At the Federal University of Santa Maria a vertical flow constructed wetland was designed to treat 1500 liters of wastewater per day, equivalent to that generated by 10 inhabitants of the House of College Student II, in the city of Santa Maria - RS. As every environment-modifying activity, the construction and operation of the constructed wetland result in environmental impacts, which may be positive or negative. To assess these impacts a Life Cycle Analysis - LCA was held on the wastewater treatment system. Considered one of the most complete tools for assessing environmental impacts, the LCA aims a detailed study of possible emissions from a process or product. The LCA of UFSM s constructed wetland was performed using the survey data of all building materials used in the work and the wastewater treatment parameters, and followed the steps defined by the ISO 14040 and 14044 (ABNT, 2009). For impact assessment, Ecoinvent data library and SimaPro 8® software were used. The interpretation of the results of the constructive phase was performed by ReCiPe method and the operation phase by CML method. Besides, analysis of the energy consumed in the manufacture of all construction materials was performed by Cumulative Energy Demand. The results showed that the bricks, steel and concrete were the most striking materials in all categories examined, with PVC, lime and sand the less striking materials. The bricks and cement represent 42.7% and 29.5%, respectively, of the impact of climate change category. Methane and nitrous oxide generated during the wastewater treatment are responsible for the occurrence of the environmental impact of climate change, cause by the 95% and 5% methane by nitrous oxide. COD, TKN and TP cause eutrophication representing 8.8%, 26.53% and 64.63% of impacts, respectively. Methane is related to the formation of photochemical oxidants. The energy consumed in operation during the life cycle of the system has an impact in all environmental categories analyzed by the software, with minimum impacts, taking into account the system s low power consumption.