Avaliação de diferentes diluições para aplicação do processo Anammox na remoção de N-amoniacal de efluente da indústria de fertilizantes

Abstract

Anaerobic Ammonium Oxidation (Anammox) is one of the most promising biological processes for the treatment of ammonium-rich effluents, as Anammox-active bacteria oxidize ammonium ions directly to nitrogen gas, using nitrite as the final electron acceptor. In this way, oxygen is not required, leading to lower energy consumption and eliminating the need for external carbon sources. In this context, testing with domestic and industrial effluents is encouraged in the literature. However, the development of research and its application to the treatment of effluent from nitrogen fertilizer industries, as well as the evaluation of the best operational conditions for reactors with Anammox activity, have not been the main focus of studies. This research evaluated, on a laboratory scale, the performance of the Anammox process in a Sequencing Batch Reactor (SBR) for 403 days, applied to effluent from a nitrogen fertilizer industry, containing approximately 10,000 mgNH4 + .L-1 , testing different dilutions and nitrogen loading. In this study, dilution of nitrogen fertilizer in domestic anaerobic effluent was used as a strategy to prevent process inhibition, with three different conditions being evaluated: Phase 1 - 1:100 dilution, Phase 2 - 1:50 dilution, Phase 3 - 1:16.7 dilution of fertilizer effluent in domestic anaerobic effluent, respectively, with nitrite supplementation to the reactor. In addition to the physicochemical parameters, the microbial community was evaluated using qPCR techniques in real-time and 16S rRNA amplicon massive sequencing. Phases 1 and 2 showed simultaneous consumption of ammonium nitrogen and nitrite for 101 days, with high average nitrogen removal efficiency (80.69% - Phase 1) (98.06% - Phase 2) and nitrite removal (85.50% - Phase 1) (99.41% - Phase 2), with nitrogen loads of up to 42.75 g.m³.d-1 . COD removal, supported by the microbial consortium with heterotrophic denitrifying bacteria, without compromising Anammox activity, was also observed. In Phase 3, the Anammox process was inhibited with no signs of performance recovery during the assessed period. In Phases 1 and 2, the abundance of Anammox bacteria was 3.12 x 10⁸ and 4.49 x 10⁸ copies/g of sludge of the 16S rRNA gene of Anammox, respectively. In the SNG, the genus Ca. Brocadia was identified at low relative abundance (0.15%) in Phase 1. This study revealed the potential of using the Anammox process for effluents from the nitrogen fertilizer industry at high dilutions (1:100 and 1:50). The study also showed that applying the Anammox process under direct use conditions was unfeasible for lower dilutions (1:16.7). Pre-treatment of this effluent, aiming at the degradation of high loads of nitrogen compounds and other substances with inhibitory effects on the process, should be considered as an alternative combined with the Anammox process