Análise espacial do aproveitamento energético de biogás e lodo seco de estações de tratamento anaeróbio de esgoto sanitário da região de Curitiba

Abstract

This study evaluated the energy utilization of sludge and biogas from the anaerobic treatment of wastewater treatment plants (WWTP), and aimed to spatially analyze the feasibility of implementing energy recovery technology of biogas and sewage treatment plants of dry sludge in the metropolitan area from Curitiba. Biogas and sludge are sub products generated during anaerobic treatment that have characteristics and potentials to generate energy from the use of technologies. Proper disposal of these by-products is necessary to reduce the environmental impacts they can cause, such as the emission of greenhouse gases (GHG) and solid waste generation. A survey of technologies for the use of biogas and technologies for the use of sludge was carried out to analyze its technical and economic viability. The study area consisted of 24 WWTP in the metropolitan region of Curitiba in the current scenario (year 2017) and 29 treatment plants in the 2043 horizon, with the forecast of nine new plants and deactivation of four existing ones. The simulated 2043 horizon is due to a study developed for the metropolitan region of Curitiba (Plano Diretor prepared by the water and sewage services provider of Paraná). The types of treatment and characteristics that were used to estimate the generated volume of biogas and the volume of anaerobic sludge to be dehydrated and later burned to generate energy were collected in each WWTP. An analysis was made of the energy utilization potential for the biogas generated and for the dry anaerobic sludge in each WWTP in the two scenarios (2017 and 2043). Two thermal drying technologies were evaluated using biogas and dry sludge as fuel and the motor generator technology for the biogas energy utilization. In each technology the necessary investment and electricity consumption avoided by the energy utilization in each WWTP in the two scenarios (2017 and 2043) were verified. Finally, indicators and evaluation indices of the proposed strategies for the 2017 and 2043 scenarios were calculated to assist managers in decision making. It was possible to identify which WWTPs make feasible the implantation of a system of energy utilization and which energy sources (biogas, dry sludge or both) for each use in each WWTP of the study area. In the current scenario (year 2017) the 6 sludge management units added can avoid the consumption of 840 MWh.m-1, and by the 2043 horizon the same units can avoid up to 1680 MWh.m-1. For the medium-sized ETEs, the technological alternative of motor generators was proposed and together they could avoid up to 655 MWh.m-1 in the horizon of 2043. The evaluation index was calculated from indicators financial and productivity growth, and resulted between 0,18 and 0,43, so that the indexes above 0,3 were classified as high viability and resulted in an acceptable energy use, but they need to deepen the analysis of the technologies.