Performance Of Advanced Nitrogen Removal And Microbial Characteristics Via FeS-driven Autotrophic Denitrification Coupled With Anammox

The synergy among members in a complex microbial community to transform elements is a key ecological regulation strategy in nature.Making full use of this phenomenon and achieving functional combinations of different microorganisms may have a significant effect on developing new wastewater treatment processes.Numerous coupling processes centered on Anammox technology are useful attempts to exploit this strategy,but they do have certain limitations that restrict their use as prefect,including the accumulation of nitrate,competition among microorganisms for rate-limiting substrates,effects of toxicity and sludge discharge on accumulation of Anammox.Based on the analysis of relevant theories,this paper proposes a novel autotrophic nitrogen removal mode which is based on the metabolic synergy of Anammox and autotrophic denitrification,the experimental and theoretical studies for related to chemical information and microbial characteristics were carried out.In this study,nitrogen-containing pollutants in static batch experiment were used as research objects.The dosage of FeS,the ratio of NO₃^--N/NO₂^--N and the ratio of Anammox to autotrophic denitrification biomass were taken as reaction control conditions.The cooperation mechanism resulted from the metabolic complementation between Anammox and autotrophic denitrification was discussed.This study showed that excessive dosage of FeS could ensure the more thoroughly reaction of autotrophic denitrification,without significantly affecting the metabolic activity of Anammox bacteria.Complex microbial community was involved in the competition with metabolic substrates when the proportion of NO₂^--N in the electron acceptor was increased,resulting in a negative impact on the removal of TN.The increase of Anammox biomass was contributed to strengthening the cooperation between Anammox and autotrophic denitrification.When the stoichiometric ratio of NH₄⁺-N to NO₃^--N was less than0.85,TN could be completely removed.The results showed that a more reasonable wastewater treatment process may be established by understanding the interaction between microorganisms and manipulating or regulation of complex microbial community,which could achieve the efficient removal of pollutants under the condition of low material consumption.Based on batch multifactor experiments,a continuous flow biological fluidized bed reactor was established to explore the long-term denitrification performance and microbial community structure evolution of Anammox and autotrophic denitrification coupling system.When the influent nitrogen load was 8.33 mg N·?L·h?^-11 and NO₃^--N/NH₄⁺-N ratio was 1.0,the removal rates of NO₃^--N and NH₄⁺-N could reach 100%and 72.63%in the reactor,respectively.The autotrophic denitrification provided sufficient NO₂^--N for the Anammox process and ensured the complete removal of NO_x^--N in the reactor,while the Anammox process ensured a high removal rate of the influent TN,whose contribution rate to TN removal was kept above 80%.During long-term operation,Thiobacillus was performed autotrophic denitrification function,while the Candidatus Kuenenia was potentially contributing the most to Anammox.Both of autotrophic denitrification and Anammox bacteria was achieved satisfactory retention in the reactor,which relative abundances were20.32%-23.64%and 3.52%-8.67%,respectively.In addition,the reactor could maintain a stable pH and produces less by-product of SO₄^2-,due to the two elements of FeS provide electronic propertie,while the FeS which covering the surface of sludge had gradually transformed into the sheet-like secondary mineral of FeOOH.The research word has the potential of energy saving and low consumption in treating low C/N ratio wastewater to completely remove TN.