This study is the first to report the start-up and the nitrogen removal performance of a single-stage PN/A/PD MABR without a heating system. It was found that the lumen pressure difference significantly affected the total nitrogen removal efficiency (TNRE), and the dissolved oxygen (DO) changed markedly with the lumen pressure difference. When the lumen pressure difference decreased, the DO tended to decrease, and (partial) denitrification can be enhanced, thus, the TNRE was further improved. And the highest removal efficiency of NH 4 + -N and TN can reach 100 % and 88.03 %, even at 8.7 °C-19.1 °C. At the low temperatures and C/N ratio 3-4, it was found that the relative abundance of Candidatus_Brocadia increased from 3.99 % to 8.64 % from day 45 to day 99 in the PN/A/PD MABR, showing Candidatus_Brocadias low-temperature adaptability, based on 16S rRNA and metagenomics technology. Carbohydrate metabolism and nitrogen metabolism were also analyzed according to the Kyoto Encyclopedia of Genes and Genomes (KEGG) metabolism pathway. The study achieved NO 2 − -N accumulation through partial nitrification and partial denitrification processes in a single-stage Anammox MABR with low-intensity substrates and had engineering application guiding value for mainstream Anammox MABR. • This reactor was easy to achieve NO 2 − -N accumulation by simple operation. • PN/A/PD MABR was firstly established by the lumen pressure difference control. • The NH 4 + -N and TN removal efficiency can reach 100 % and 88.03 % in 8.7°C to 19.1°C. • Candidatus_Brocadia is able to adapt to the low-temperature environment. 

Achieving efficient nitrogen removal in a single-stage partial nitrification-anammox-partial denitrification (PN/A/PD) membrane aerated biofilm reactor (MABR)

Enhanced benzofluoranthrene removal in constructed wetlands with iron- modified biochar: Mediated by dissolved organic matter and microbial response.

To investigate the effect of oxygen, pH shock, and H2S inhibition on the competition between sulfate-reducing bacteria (SRB) and methane-producing archaea (MPA), a UASB reactor treating wastewater containing sulfate, ethanol and acetate was operated for 360 days. With micro-oxygenation performed at a flow rate of 100 mL/min in the upper part of the up-flow anaerobic sludge blanket (UASB) reactor, the sulfate removal and total sulfide concentration increased to 68.6% and 500 mg S/L, while the methane production rate slightly reduced from 2.5 to 2.1 L/L/d. However, methane production was still the main reaction in the reactor. The pH shock and high H2S concentration finally changed the competition results between SRB and MPA. Sulfate reduction was not affected while methane production was completely inhibited at H2S concentration more than 200 mg/L. Complete sulfate reduction (99.0%) was maintained over the long term with a stable organic COD removal (70.4%). The experimental results proved that in the complete sulfate-reducing stage, ethanol was mainly utilized by incomplete-oxidizing SRB for sulfate reduction. 

Effects of operational variations of micro-oxygenation and pH shock on the competition between methane production and sulfate reduction in a UASB reactor

Shewanella sp. strain F1, isolated from a lab-scale Fe(II)−dependent anaerobic denitrifying reactor, could reduce nitrate by oxidizing Fe(II). Its nitrate reduction rate and Fe(II) oxidation rate were 0.48 mg/(L·h) and 5.05 mg/(L·h) at OD600 of 0.4786 with a five-fold diluent. Shewanella sp. was popular in Fe(III) reduction. Fewer studies about its ability for Fe(II) oxidation are available. The low pH was determined to be the switch for Shewanella sp. strain F1 to perform Fe(III) reduction or Fe(II) oxidation. Even under a low pH, the produced Fe(III) precipitated around cells from iron encrustation. By observation of the morphologies of strain F1, two corresponding microbial mechanisms were proposed. One was named Cyc 2−based Fe(II)-dependent denitrification, in which Fe(II) was oxidized by Cyc 2 in the outer cell membrane, and the produced Fe(III) precipitated on the cell wall surface to form tiled iron encrustation. The other was named Cyc 1−based Fe(II)−dependent denitrification, in which Fe(II) was oxidized on the existing iron precipitation on the cell wall surface to form towery iron encrustation, and the electron was transported to Cyc 1 in the periplasm. The efficiency determination and mechanism investigation of strain F1 will promote the development of autotrophic denitrification technology and meet the requirement of a low−carbon policy.

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Efficiency Determination and Mechanism Investigation of Autotrophic Denitrification Strain F1 to Promote Low-Carbon Development

Ultrasonic-assisted hypochlorite activation accelerated volatile fatty acids production during sewage sludge fermentation: Critical insights on solubilization/hydrolysis stages and microbial traits.

Effect of asparagine, corncob biochar and Fe(II) on anaerobic biological treatment under low temperature: Enhanced performance and microbial community dynamic

The start-up process, microbial communities, and metagenomic features of a micro-aerated anaerobic reactor for the treatment of sulfate wastewater were investigated. At a COD/SO42- ratio of 1.0 of the influent, the average COD, SO42- and NH4+-N removal rate in the micro-aerated anaerobic reactor was 93.43%, 34.97%, and 28.88%, respectively. However, with the COD/SO42- ratio increased from 1.0 to 1.5, the average COD removal rate reduced by 15.55% and the average removal rate of SO42- increased by 2.85%. When the COD/SO42- ratio was 1.5, the activities of sulfite reductase, acetate kinase, and coenzyme F420 were highest in the sludge, with average concentrations of 0.12 Um/L, 0.089 mol/L, and 0.00913 mmol/g, respectively. During the whole experiment, the fluorescence peak of coenzyme F420 appeared in the LB-EPS, while the peaks of tryptophan-like protein and tyrosine-like protein appeared in TB-EPS. Proteobacteria was the main phylum in all three stages, with relative abundances of 28.17%, 22.74%, and 19.94%, respectively. Methanosaeta was the main genus, with relative abundances of 8.98%, 5.64%, and 7.08%, respectively, in stages A, B, and C. Meanwhile, the relative abundance of the dissimilatory sulfate reduction modules was 0.0083%, 0.0189%, and 0.0115%, which ensured the removal of sulfate in the micro-aerated anaerobic reactor. 

Mariam Bibilashvili

Papers

Effect of asparagine, corncob biochar and Fe(II) on anaerobic biological treatment under low temperature: Enhanced performance and microbial community dynamic

Performance and metagenomic analysis of a micro-aerated anaerobic reactor for biological sulfate-rich wastewater treatment