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Given the increasing use of nanoscale zero-valent iron (NZVI) particles for environmental remediation and wastewater treatment, their potential impact on anaerobic ammonium oxidation (anammox) bacteria was investigated in this study using anammox sludge. Batch assays showed that NZVI concentrations up to 200 mg L −1 did not affect anammox activity, reactive oxygen species production, and cell membrane integrity. The nitrogen removal efficiency of the continuous-flow reactor fluctuated in the presence of 20 or 50 mg L −1 NZVI, but it could return to normal over time, even at 200 mg L −1 NZVI. 16S rDNA-based high-throughput sequencing indicated that although the presence of 10, 20, 50, and 200 mg L −1 NZVI to some extent affected microbial composition, the anammox bacteria ( Candidatus Kuenenia ) never lost its dominance. The abundance of gene families that are related to the assimilation and utilization of iron was down-regulated in response to the stress of high-level NZVI. [ABSTRACT FROM AUTHOR]

Previous studies investigating the risk of engineered nanoparticles (NPs) to biological wastewater treatment have primarily tested NPs individually; however, limited data are available on the impact of NPs on the anaerobic ammonium oxidation (anammox) process. In this study, the toxicity of CuNPs on anammox granules was investigated individually and in combination with CuONPs or ZnONPs. Exposure to CuNPs at 5 mg g −1 suspended solids (SS) decreased the anammox activity to 47.1 ± 8.5%, increased the lactate dehydrogenase level to 110.5 ± 3.4% and increased the extracellular N 2 H 4 concentration by 16-fold but did not cause oxidative stress. The presence of CuONPs or ZnONPs at 5 mg g −1 SS did not significantly aggravate or alleviate the toxicity of the CuNPs; however, the introduction of EDTA or S 2− could attenuate the adverse effects of the CuNPs, CuONPs and ZnONPs on the anammox granules. EDTA captured Cu ions, whereas S 2− shielded and deactivated Cu ions and passivated CuNPs. Therefore, our results indicated that the toxicity of NPs was dependent on the amount of active metal reaching the anammox cells. Overall, the results of this study have filled knowledge gaps and provided insights into the combined toxicity of NPs on anammox biomass. [ABSTRACT FROM AUTHOR]

The increasing application of engineered nanoparticles (NPs) has posed an emerging challenge to wastewater treatment processes. The short-term impacts of CuNPs, CuONPs, ZnONPs and AgNPs on anaerobic ammonium oxidation (anammox) process were investigated firstly in this study. CuONPs, ZnONPs and AgNPs up to 50 mg g −1 suspended solid (SS) did not affect anammox activity, reactive oxygen species (ROS) production or cell membrane integrity. However, 1.25 mg g −1 SS CuNPs significantly inhibited the anammox activity and the loads that caused 50% inhibition were 4.64 ± 1.24 and 3.27 ± 0.79 mg g −1 SS for anammox granules and flocs, respectively. 5 mg g −1 SS CuNPs caused serious accumulation of the toxic intermediate N 2 H 4 . Furthermore, CuNPs interacted with extracellular polymeric substances by specifically bonding to tyrosine or tryptophan-containing groups, C-O-C in polysaccharides and –OH in polymeric compounds. Therefore, this study calls for more attention to the risks of NPs to the anammox-based processes. [ABSTRACT FROM AUTHOR]

This paper examined the influence of magnesium on denitrifying sludge. Two up-flow anaerobic sludge bed (UASB) reactors were used in the study. R 1 was continuously supplied with 50 mg L −1 of divalent magnesium in the wastewater and R 0 was used as a control without magnesium. On the 258th day, the sludge properties in R 0 and R 1 were analyzed when the nitrogen loading rates were both 36.0 kgN m −3 d −1 and the nitrogen removal rates of R 0 and R 1 were 33.8 and 34.6 kgN m −3 d −1 , respectively. The diameters of R 0 and R 1 were 0.95and1.35 mm, settling velocity (74.5 ± 20.8 and102.0 ± 22.6 m h −1 ), extracellular polymeric substance (60.8 ± 2.1 and76.0 ± 2.7 mg g −1 VSS)and specific denitrifying activity (794.4 ± 9.6 and825.6 ± 4.9 mgN d −1 ) were also compared. These results addressed that the addition of magnesium to denitrifying reactor is an effective alternative to enhance sludge properties. [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 metal oxide nanoparticles (MONPs) in consumer products raises great concerns about their environmental impacts, but their potential impacts on anaerobic ammonium oxidation (anammox) process in wastewater treatment remain unclear. In this study, the presence of MONPs (1, 50, 200 mg L −1 ) exhibited no visible effects on the nitrogen removal performance of anammox reactors, but high levels (200 mg L −1 ) of SiO 2 NPs, Al 2 O 3 NPs and CeO 2 NPs had a distinct effect on shaping the anammox community. Long-term exposure of MONPs caused different responses in the relative abundance of Ca. Kuenenia , the level of functional gene Hzs A and the activities of three key enzymes involved in anammox metabolism, but no significant inhibition effects on specific anammox activity were detected. Overall, the effects of MONPs on anammox community structure and sludge properties depended on their types and levels and followed the order SiO 2  > CeO 2  > Al 2 O 3  > TiO 2 . [ABSTRACT FROM AUTHOR]

The increasing use of engineered nanoparticles (NPs) in consumer and industrial products raises concerns about their environmental impacts, but their potential influence on anaerobic ammonium oxidation (anammox) process in wastewater treatment remains unknown. In this study, the response of granule-based anammox reactor to different loads of ZnONPs was investigated. The introduction of 1–5 mg L − 1 ZnONPs did not affect reactor performance, but 90% of the nitrogen removal capacity was deprived by a shock of 10 mg L − 1 ZnONPs within 3 days. Anammox activity was significantly inhibited, but no significant stimulation of intracellular reactive oxygen species (ROS) production or extracellular lactate dehydrogenase (LDH) activity was observed. The inhibition was thus mainly due to the accumulation of toxic Zn(II) ions in anammox biomass. However, the resistance and resilience of this anammox reactor to ZnONPs were enhanced by intermittent perturbations in the mode of “shock-recovery”. The up-regulated abundance of Zn(II)-exporter ZntA might contribute to the enhanced resistance. In addition, these repeated transient disturbances improved the functional specificity of the anammox community despite the reduction of its diversity. Overall, these results may provide useful references for evaluating and controlling the risk of NPs to anammox process. [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]