Estudo da autodepuração de um riacho após lançamento do efluente de estação de tratamento de esgoto

Abstract

Brazil is experiencing a moment of valorization of the basic sanitation sector, the number of works and the value of investments in the sector has only been increasing in the last years, in search of the so desired universalization of sanitation services in the national territory. The need then arises to adopt more modern methods of effluent treatment that are more flexible in their possible applications, and that the receiving water bodies have the capacity to receive these treated effluents. In this expansion process, a WWTP that uses MBBR (Moving Bed Biological Reactor) technology was built in Maceió with a capacity of treating up to 360 L/s of effluent and discharging said effluent in its treated state into a basin in the process of urbanization with a flow rate around 0.06 m³/s. In this context the present work sought to understand what is the impact of this effluent and how it behaves along the course of the receiving body, which presents a flow rate between 0.02 m³/s and 0.06 m³/s. To this end, the raw and treated effluent of the WWTP was characterized, the efficiency of the WWTP was evaluated, a qualitative/quantitative analysis of the receiving water body was performed, and the selfdepuration phenomenon was modeled by applying the Streeter-Phelps mathematical model. The results revealed that the raw sewage has typical characteristics of effluents of medium to high concentration, with data pointing out a BOD concentration of around 280,16 mg.O2/L, that the WWTP presents efficiency of organic load removal above 95%, that the creek is already in a state of degradation, as shown by its BOD going up more than 10 mg.O2/L above what the current legislation recommends and that the release of the treated effluent can be considered as positive and even as a mitigating action, as the receiving body is able to increase its oxygen and BOD concentrations to adequate values in less than 250 meters by self-depuration.