Viabilidade econômica de estratégias de conservação de água em edificação comercial de grande porte

Abstract

The technical and economic evaluation for the implementation of water conservation systems that address the use of alternative sources for non-potable purposes is an essential tool in decision-making to determine the most appropriate configuration for each building. Thus, this research sought to evaluate the technical and economic feasibility of reusing sanitary sewage to meet non-potable demands in relation to the reuse of greywater at Shopping Center Vila Velha. Scenarios for the reuse of sanitary sewage associated or not with the use of rainwater and condensate water were established and evaluated, in comparison with the reuse of greywater associated with the use of rainwater and condensate water. The technical evaluation was carried out with the aid of the STAN software (subSTance flow ANalysis), through the preparation of three hypothetical water balances for the building. The economic evaluation was carried out through budgets for the implementation of eight settings for the collection, storage, treatment and distribution of the four alternative sources of non-potable water. The results obtained in the technical feasibility assessment indicated that the reuse of sanitary sewage offers better performance in meeting the demands for non-potable water, when compared to the reuse of greywater. In addition, the scenario in which only sanitary sewage is used as an alternative source is the one that guarantees greater water security for the building, so that all the demand for non-potable water could be met only with the supply of sanitary sewage. The results obtained in the economic viability assessment indicated that all the scenarios evaluated have economic viability, with NPVs between R$ 7,184,956.17 and R$ 11,736,080.62, IRR between 52% and 182% and payback period between seven months and two years and two months. In addition, despite presenting higher initial investment and operation and maintenance costs, systems that consider the reuse of sanitary sewage have NPV, IRR and Pay Back discounted better than that of the system with reuse of greywater, when considering similar treatment solutions. Thus, for the Shopping Center Vila Velha, the reuse of sanitary sewage showed better technical and economic feasibility than the reuse of greywater.