Avaliação técnica-operacional e monitoramento de um sistema descentralizado de tratamento de esgotos domésticos como proposta de reúso de água em áreas isoladas

Abstract

The lack of supply of sanitary sewage services is a socio-environmental problem that affects even more intensely the populations of isolated areas, who need to apply decentralized alternatives to have sewage treatment. The aim of the study was to evaluate the performance of the decentralized domestic wastewater treatment system - Engineered Ecosystem (EE), installed at the CEADS of the Rio de Janeiro State University (UERJ) in Ilha Grande – Rio de Janeiro for proper final disposal and/or use of treated effluent. The EE is formed by the combination of conventional treatment, such as grease trap, septic tank, submerged aerated filter and mixed biofilter, with the biotechnology of 3 constructed wetlands (E. crassipe, T. domingensis, grasses) and algae tank, with a treatment capacity of 1440 Lday-1, occupying a total area of 25 m2. The system was operated and monitored in 3 phases (system startup, phase I and phase II of operation) from February/22 to February/23, with 10 campaigns being carried out to evaluate the efficiency of treatment of physical-chemical parameters (pH, DO, BOD, COD, Temperature, Turbidity, EC, TSS, TDS, SedS, Ammonia, Nitrite, Nitrate and Phosphorus) and microbiological (Thermotolerant Coliforms) in order to meet the standards for the release of liquid effluents of the Rio de Janeiro Regulation - NOP INEA nº 45/2021. Also, were evaluated the contribution of removal of organic loads and nutrients by macrophyte biomass and the potential for removal of emerging pollutants, including drugs, hormones, and plastic additives. The results indicated good efficiency in the removal of organic compounds, with a final effluent with an average concentration of BOD of 57.2 mg L-1 (74% removal efficiency), 13 mg L-1 of TSS (90%), meeting the current legislation. However, the removal of nutrients was not so satisfactory, presenting a final effluent with a concentration of 41.4 mg L-1 of Ammonia and 16.20 mg L-1 of phosphorus, requiring an adjustment in the EE for improvements in the routes of removal of these compounds. The removal of thermotolerant coliforms was 99.9%, 91.9% and 42.5% in different campaigns at the end of treatment. The average growth rate of macrophyte biomass was 24.12 g m-2 day-1, with a total absorption of 10.41 g C m–2 day-1, 1.01 g N m–2 day-1, 0.15 g P m–2 day-1. The emerging compounds showed a reduction in chromatographic peak area of 32-99%. However, the final effluent still presents chronic toxicity for microalgae. The proposals for water reuse were for restricted use applications, due to the quality of the final effluent generated, and the application of some barriers was recommended to allow greater viability of the practice. According to our results, the EE model is a viable alternative to universalize access to domestic wastewater treatment in isolated communities, being a treatment efficiency, low energy consumption, simple operation, low maintenance and high resilience. Toward to increase treatment efficiency, some adjustments are recommended, such as the installation of photovoltaic panels, to provide more electricity autonomy.