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To facilitate the application of partial nitritation (PN) – anaerobic ammonium oxidation process in nitrogen removal from livestock wastewater, the inhibition of roxithromycin (ROX) and Cu(II) on the PN sludge was examined using a respirometric method. The results showed that the IC 50 of ROX and Cu(II) on PN sludge were 346 and 74.3 mg L −1 , respectively. The relative specific respiration rate (SRR) of ammonia-oxidizing bacteria (AOB) decreased from 87.4% to 17.7% with the ROX concentration increased from 0 to 500 mg L −1 . When the concentration of Cu(II) increased from 0 to 160 mg L −1 , the SRRs of AOB and nitrite-oxidizing bacteria decreased by 85.5% and 11.2%, respectively. According to the isobole plots analysis, combined suppression by ROX and Cu(II) was synergistic. Fourier transform infrared spectroscopy analyses showed that ROX exposure altered the positions of C O bonds, and the intensity of the absorption peak at 2100 cm −1 changed under Cu(II) exposure. [ABSTRACT FROM AUTHOR]

The combined anammox (anaerobic ammonium oxidation) and autotrophic desulfurization–denitrification (AADD) process represents a promising innovative technology for biological nitrogen and sulfur removal. In this study, an up-flow anaerobic sludge blanket reactor, which was started with anammox and methanogenic granules, was operated for 245 days to evaluate the co-treatment of wastewater containing nitrogen and sulfur. The reactor demonstrated good performance in terms of nitrogen and sulfide removal and exhibited excellent behavior for removal of NH 4 + -N, NO 2 − -N and S 2− -S exceeding 252, 333 and 330 mg L −1 , respectively. The highest nitrogen removal rate and sulfide removal rate attained were 4.00 kgN m −3 d −1 and 2.39 kgS m −3 d −1 , respectively, which were also the highest reported values for a coupling-system. The influent NH 4 + -N:S 2− -S and NO 2 − -N:S 2− -S ratios set at 1.74 and 2.20–2.27 are suitable for maintaining system stability. The specific activities of anammox and autotrophic desulfurization–denitrification (SAA and SADD), extracellular polymeric substance (EPS), heme c (an important cofactor of some anammox bacterial enzymes) and the diversity of anammox and autotrophic desulfurization–denitrification (ADD) bacteria were investigated during the operation. The SAA and SADD are regarded as key factors for high efficiency. The granules contained many EPS (128.4–204.5 mg g −1 VSS) and minor heme c content (1.17 μmol g −1 VSS). The dominant bacteria belonged to members of Brocadiaceae and Hydrogenophilaceae , a majority of which were anammox bacteria and ADD bacteria, respectively. These observations suggest a new removal process for ammonia, nitrite and sulfide utilizing an uncommon mechanism involving simultaneous anammox and ADD. [ABSTRACT FROM AUTHOR]

An anaerobic ammonium oxidation (anammox) reactor was operated with two feeding regimes. In stage 1, the reactor was operated as a common anaerobic baffled reactor (CABR) (constant flow direction), whereas in stage 2, the reactor was modified as a flow switched anaerobic baffled reactor (FSABR) with the flow direction switching every 10 days. Adjusting the feeding regime resulted in an increase in the average nitrogen loading rate (from 1.62 to 1.80 kgN m −3 d −1 ) and nitrogen removal efficiency (from 75.4 to 83.1%). In addition, a maximum nitrogen removal rate of 3.49 kgN m −3 d −1 was obtained in stage 2, compared with 3.00 kgN m −3 d −1 in stage 1. The sludge properties were also enhanced; from stage 1 to stage 2, the specific anammox activity increased by more than 5-fold, the settling velocity increased from 64.1 to 71.9 m h −1 , and the average particle diameter increased from 0.8 to 2.3 mm. However, there was minimal variation in the heme c content. The maximum substrate removal rates in stages 1 and 2 were 4.28 and 46.38 kgN m −3 d −1 when fitted by the Stover-Kincannon model, respectively. The results indicate that the FSABR performance was significantly enhanced compared with the CABR. [ABSTRACT FROM AUTHOR]

Metal and metal oxide nanoparticles (NPs) show differences in antimicrobial activity due to different chemical and physical properties. Using copper as a representative example, this study compared the NP effects on anaerobic ammonium oxidation (anammox) bacteria in wastewater treatment. Long-term exposure to 5 mgCu L −1 CuNPs reduced the physiological activity and abundance of anammox bacteria, thereby causing deterioration of reactor performance. However, anammox granules exhibited stronger resistance and resilience to perturbation by 1–160 mgCu L −1 CuONPs, and no adverse effects on performance were observed. Moreover, the level of Cu(II) released from NPs in the influent exhibited good correlations with variations of the community structure and sludge properties. Therefore, the effects of Cu-based NPs on anammox sludge properties are dependent on their forms and levels, and their discrepant effects are partially attributed to their ability to release ionic copper. [ABSTRACT FROM AUTHOR]

The increasing use of engineered nanoparticles (NPs) poses an emerging challenge to biological wastewater treatment. The long-term impact of CuNPs on anaerobic ammonium oxidation (anammox) process was firstly investigated in this study. The nitrogen removal capacity of anammox reactor was nearly deprived within 30 days under the stress of 5.0 mg L −1 CuNPs and the relative abundance of anammox bacteria (Ca. Kuenenia ) was decreased from 29.59% to 17.53%. Meanwhile, copper resistance genes associated with the Cus, Cop and Pco systems were enriched to eliminate excess intracellular copper. After the withdrawal of CuNPs from the influent, the nitrogen removal capacity of anammox biomass recovered completely within 70 days. Overall, anammox biomass showed susceptibility, resistance and resilience to the stress of CuNPs. Therefore, the potential impacts of ENPs on anammox-based processes should be of great concern. [ABSTRACT FROM AUTHOR]

Given the prospective application of anaerobic ammonium oxidation (anammox)-based processes in treating the ammonium-rich and phosphate-containing wastewaters, the effects of phosphate on anammox process were investigated considering the roles of phosphate forms and biomass geometry in this study. Batch experiments showed that phosphate lower than 155 mg P L −1 stimulated the specific anammox activity (SAA) of granules or flocs, whereas 310 mg P L −1 phosphate inhibited the SAA by 10% and the inhibitory effects were further enhanced with phosphate concentrations increasing. The half-maximal inhibitory concentrations of anammox granules and flocs were estimated as 1664.7 ± 114.7 and 1205.9 ± 77.5 mg P L −1 , respectively. The inhibitory effect may be mainly attributed to the dihydrogen phosphate ion (H 2 PO 4 − ) in weakly basic conditions. However, when the influent phosphate level of the granular sludge reactor gradually increased from 2 to 500 mg P L −1 , no adverse effects on the nitrogen removal performance were observed during a 195-day operation. The microbial community diversity and the relative abundance of anammox bacteria were reduced, but no shift in dominant anammox strain was recorded by high throughput sequencing. These results will trigger a rational reevaluation regarding the effects of inorganic phosphate on anammox process. [ABSTRACT FROM AUTHOR]