Granular Sludge Coupling Nitrate/Nitrite Dependent Anaerobic Methane Oxidation with Anammox: from Proof-of-Concept to High Rate Nitrogen Removal

This work developed a novel Membrane Granular Sludge Reactor (MGSR) equipped with a gas permeable membrane module for efficient methane delivery to cultivate nitrate/nitrite dependent anaerobic methane oxidation (n-DAMO) microorganisms in granular sludge. As proof of concept, the MGSR was fed with synthetic wastewater containing nitrate and ammonium to facilitate the growth of nDAMO microorganisms. The granular sludge of n-DAMO and Anammox was gradually developed and achieved a nitrogen removal rate of 1.08 g NO3--N L-1 d(-1) and 0.81 g NH4 (+)-N L( -1 )d (-1). Finally, enriched granular sludge was successfully applied for nitrogen removal from the synthetic partial nitritation effluent. The combined dominance of nDAMO archaea, Anammox bacteria, and n-DAMO bacteria in the microbial community was confirmed by 16S rRNA amplicon sequencing. Fluorescence in situ hybridization revealed that a layered structure was formed in the granular sludge with Anammox bacteria in the outer layer and n-DAMO microorganisms in the inner layer when granules were fed with nitrite and ammonium. The high performance of nitrogen removal (16.53 kg N m(-3) d(-1)) with satisfactory effluent quality (similar to 8 mg N L (-1)) and excellent biomass retention capacity (43 g VSS L--(1)) make the MGSR promising for the practical application of n-DAMO and Anammox in wastewater treatment.