Enhanced microbial metabolism in one stage partial nitritation-anammox system treating low strength wastewater by novel composite carrier.

One stage partial nitritation-anammox (PN-A) process has attracted more and more attention due to the low investment cost but the instability in treating low strength wastewater. In this study, for producing a novel composite carrier that could provide high ammonia microenvironment in low strength wastewater, the zeolites and floating materials were combined in the spherical shell and distributed evenly by the spherical polyhedron. And a moving bed biofilm reactor (MBBR) with the composite carriers and ordinary carriers without zeolites as control group was operated for nearly 120 days. The PN-A process were realized in 53 days, and the total nitrogen removal efficiency reached around 85% at influent ammonium concentration of 50 mg/L finally. Analysis of 16S rRNA gene sequencing revealed that the composite carriers showed significant promotion on the proliferation of ammonium oxidizing bacteria (AOB) and enrichment of anaerobic ammonium oxidizing bacteria (AnAOB), accounting for 19.14% and 41.65% on the surface, respectively. Moreover, the existence of relative higher abundance of ammonia on the composite carrier surface was validated by the metabolite biomarker of glutamate and especially spermidine. The metabolomics analysis and 16S rRNA function prediction showed that the protein synthesis pathway was obviously upregulated on the composite carriers surface compared with that on the ordinary carriers surface. The higher abundance of glutamate and putrescine indicated that the composite carrier could stimulate the metabolism and growth of bacteria. The present study provided a functional carrier to realize the transformation of activated sludge system into PN-A system treating low strength wastewater, which is significant to the application of the process in mainstream.