The partial nitritation (PN) and anaerobic ammonia oxidation (anammox) process is an energy-efficient innovative biotechnological revolution for nitrogen removal from wastewaters. The high-stress susceptibility of PN and anammox process towards fluctuations in temperature is an impediment for full-scale deployment under mainstream conditions. Here, we investigate the response of microbial biofilm for PN-anammox activity to temperature gradients (35°C, 21°C & 13°C). The average NH4+-N removal declined with a decrease in temperature. At 13°C, the PN-anammox process was deemed unstable with high nitrite (&gt;20mgN L-1). The genes and transcripts of metagenome-assembled genomes (MAGs) were used to investigate the stress response of PN and anammox process. Briefly, a 9-L batch PN/A reactor, fed with reject water from anaerobically digested sludge, was exposed to temperature gradients of 35°C, 21°C & 13°C. RNA & DNA were extracted from biomass collected at each gradient post acclimatization period. The DNA sequences were assembled into contigs using SPAdes & subsequently binned into MAGs using MetaBAT. The RNA-Seq data were mapped to the gene of MAGs with BBMap. Sixty-seven MAGs were recovered from the PN-anammox reactors. The community-wide expression of genes differed with the different temperatures. The specific activity and transcriptional response of ammonia-oxidizing bacteria and anammox bacteria declined at low temperatures. At 13°C, low temperature, the number of MAG genes expressed reduced by three-folds, crippling the partial nitritation and anammox process. The genome-based analysis reveals that anammox species and other vital microbes differ in their gene expression responses to different temperatures. The metabolic pathways inferred from MAGs indicate that PN-anammox bioreactor microbes are metabolically versatile and exhibited novel opportunities for metabolic cooperation.

Low temperature crippled the distributed metabolism of partial nitritation/anammox (PN/A) reactor

ACS Fall 2021

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