Enhanced shortcut nitrogen removal and metagenomic analysis of functional microbial communities in a double sludge system treating ammonium-rich wastewater.

Biological nitrogen removal processes based on partial nitrification are promising for ammonium-rich wastewater treatment. In this study, a partial nitrification-denitrification double sludge system was applied to treat synthetic ammonium-rich wastewater. Metagenomic analysis of functional genes and metabolic pathways was conducted, also with the evaluation of system performance and nitrous oxide (N2O) emission. In the nitrifying sequencing batch reactor (SBRPN), the removal percentage of ammonium nitrogen reached to 99.98% with a high nitritation efficiency of 93.24%, and the N2O emission factor was 0.88%. In the denitrifying sequencing batch reactor (SBRDN), there was almost no nitrate nitrogen and nitrite nitrogen in the effluent, and the maximum N2O emission was 0.078 mg N/L. The dominant ammonia oxidizing bacteria was Nitrosomonas in SBRPN (13.6%), and the main potential denitrifiers in SBRDN were Thauera (14.6%), an uncultured genus in the Comamonadaceae family (4.0%), an uncultured genus in Rhodocyclaceae family (2.4%) and Comamonas (1.1%). Metagenomic analysis revealed that amo mainly distributed in Nitrosomonas eutropha (38.3%), Nitrosomonas europaea (27.1%), Nitrosomonas sp. GH22 (20.5%) and Nitrosomonas sp. TK794 (15.0%), and Bacteroidetes had the N2O reduction potential in SBRPN.

System performance and microbial community in ethanol-fed anaerobic reactors acclimated with different organic carbon to sulfate ratios.

Sulfate influences the organics removal and methanogenic performance during anaerobic wastewater treatment. System performance, microbial community and metabolic pathways in ethanol-fed anaerobic reactors were investigated under different COD/SO42- ratios (2, 1 and 0.67) and control without sulfate addition. The sulfate removal percentages declined (99%, 60% and 49%) with decreasing COD/SO42- ratios, and methanogenesis was completely inhibited. Acetate accumulated to 903-734 mg/L, though propionate was constantly lower than 30 mg/L. Without sulfate, acetate and propionate did not accumulate, despite the extended time for propionate degradation. Incomplete oxidizing sulfate reducing bacteria (Desulfobulbus and Desulfomicrobium) and hydrolysis-acidification genera (Treponema and Bacteroidales) predominated but could not degrade acetate. Desulfobulbus was the key genus for propionate degradation through the pyruvate & propanoate metabolism pathway. Pseudomonas and Desulfobulbus, possessing genes encoding Type IV pili and cytochrome c6 OmcF, respectively, potentially participated in the direct interspecies electron transfer in sulfate-rich conditions.