Nitrogen removal in anaerobic reactors

Abstract

The use of anaerobic reactors for wastewater treatment has been growing and consolidating in Brazil due to a number of favorable socioeconomic and environmental factors. In this scenario, this project proposes to evaluate pre-denitrification and partial denitrification combined with Anammox in anaerobic reactors, aiming to contribute to nitrogen removal in sewage treatments plants. Therefore, a set of Anaerobic filters and UASB reactors will be inoculated with sludge from an anaerobic reactor that has been operating at UNICAMP for 10 years and another set of reactors will be inoculated with the same sludge, combined with Anammox sludge. Both sets will be operated under various hydraulic retention times (12, 8, 6 and 4 hours) and fed synthetic effluent enriched with various nitrate concentrations (0, 25, 50, 75 e 100 mgL-1) and with various organic matter concentrations (COD equal to 400, 300, 200, 100 mgL-1). All reactors will be evaluated for usual environmental parameters and also for changes in biogas production and microbial community. In the latter case, the modern technic of large-scale sequencing will be employed for biodiversity analysis. When the definition of ideal operational conditions for pre-denitrification and partial denitrification combined to Anammox regarding nitrate concentration, affluent COD and minimum hydraulic retention time is concluded, the life cycle assessment (LCA) will be conducted. As determined by ISO 14.000 series (ISO, 2002), this LCA will take into account all the treatment system, including the nitrification stage. This analysis will offer a general view of the environmental impacts of the treatment plant as a whole, considering the mass balance and energy balance. With its application it will be possible to infer which treatment process applied in nitrogen removal (pre-denitrification and partial denitrification combined to Anammox) will be the most adequate considering all environmental aspects and not only the final effluent quality. (AU)