Multi-faceted effects and mechanisms of granular activated carbon to enhance anaerobic ammonium oxidation (anammox) for nitrogen removal from wastewater
Zhufang Wang, Chunxia Jiang, Mac-Anthony Nnorom, Claudio Avignone–Rossa, Kai Yang, Bing Guo
Abstract
• GAC boosted SAA by 12.97 mg-N·g-VSS -1 ·d -1 although not increasing AnAOB abundance. • GAC increased hzs abundance, slightly improved hdh abundance. • GAC inhibited Nitrosomonas / Castellaniella in nitrification/full denitrification. • GAC enhanced DNRA and partial denitrification conducting by Anaerolineae members. • GAC prevented system breakdown, a potential advantage for engineering implementation. Nitrogen removal via anammox is efficient but challenged by their slow growth. Adding granular activated carbon (GAC) increased the total nitrogen removal rate to 66.99 g-N/m 3 /day, compared to 50.00 g-N/m 3 /day in non-GAC reactor. Both reactors dominated by Candidatus Brocadia (non-GAC: 36.25 %, GAC: 35.5 %) but GAC improved specific anammox activity. Functional metabolic profiling from metagenomic analysis unveiled that GAC enhanced pathways associated with electron shuttle production, potentially promoting intra/extracellular electron transfer. In nitrogen metabolism, GAC is indicated to facilitate anammox N 2 H 4 synthesis process, and inhibit nitrification and full denitrification processes, functioned by Nitrosomonas and Castellaniella which are more abundant in the non-GAC reactor. GAC also enhanced dissimilatory nitrate reduction to ammonium and partial denitrification processes, providing anammox with NH 4 + /NO, which was conducted by Anaerolineae members (29.7 % in GAC-reactor and 7.8 % in non-GAC reactor sludge). This research illuminated the intricate microbial nitrogen cycling networks affected by GAC in anammox systems.