Avaliação da produção de odor na estação de tratamento de esgoto Paranoá e seus problemas associados




The Federal District of Brazil has been suffering problems of emanations of odors proceeding from sewage treatment plants (STP). For this reason, this work has the objective of evaluating the production of odor in the Paranoá sewage treatment plant (Paranoá STP), in Federal District, and its associated problems, employing hydrogen sulfide (H2S) as an indicator of mal odor. In order to doing this, we used a procedure composed of the following actions: (1) analytical determinations in the liquid phase (pH, temperature, electric conductivity, total sulfide, hydrogen of sulfide, sulfate, elementary sulphur, DO, COD and BOD); (2) determination of the H2S concentrations in the gaseous phase through a specific sensor; (3) determination of the H2S emission rates using a mathematical model for odor emission and (4) application of questionnaires in the surrounding area of the Paranoá STP. The H2S concentration presented variability with regard to the collection schedules, presenting maximum values of 9,30, 14,87 and 5.81 mg/L (morning, late and night) in the anaerobic reactor effluent. This variability in the H2S concentration is credited, mainly, to the external variable (temperature, pH, sulphur concentration, potential redox, etc.) and to the proper process of treatment. The concentration of H2S emitted for the atmosphere next to the place of the exit of the anaerobic reactor effluent was always above of the threshold of odor of 0,0005 mg/L. The emitted loads of H2S for the atmosphere in the preliminary treatment, in the anaerobic reactor, and in the lagoon had been of 0,03 g/s; 0,30 g/s and 0,45 g/s (observed) and of 0,05 g/s, 0,04 g/s and 0,38 g/s (predicted by the emission model), respectively. Sulphate and DQO had shown to be good pointers of the reduction of sulphate to sulfide. Sulfide formation by dissimilatory sulphate reduction was verified in the lagoons during the night, since concentrations of oxygen dissolved in these lagoons were low along the majority of the time, (0.1 to 1,0 mg/L). It was observed that perception of odor for the surrounding inhabitants to the STP occurred, with consequent non-satisfaction, since 78% of the interviewed people felt the bad smell proceeding from the STP and 60% had said that the odor intensity was very strong. It was possible to conclude that H2S was formed in the anaerobic reactor and that H2S reduction occurred in the preliminary treatment and in the lagoon.


sulfeto de hidrogênio - aspectos ambientais esgotos lago paranoá (df) recursos hidricos

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