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[Display omitted] • UDB and DB at different pyrolysis temperatures played contrasting roles. • DB800-amended group displayed superior nitrogen removal performance. • DB at lower pyrolysis temperature imposed suppression. • Properties of dissolved organic matter released by DB were tracked at molecular level. Biochar has attracted increasingly attention in the biological wastewater treatment owing to its unique environmental behavior. However, the differential effects of undissolved and dissolved fractions of biochar (hereafter named as UDB and DB, respectively) on the anaerobic ammonium oxidation (anammox) process remain unclear. The study evaluated the nitrogen removal performance of anammox system in response to UDB and DB prepared at different pyrolysis temperatures (300 °C, 550 °C and 800 °C). The DB800-amended group displayed superior nitrogen removal performance with the total nitrogen removal efficiency (TNRE) of 92.8 ± 1.4 %. Compared with CK, TNRE was changed by +5.0 % (UDB300), +0.4 % (UDB550) and −22.3 % (UDB800) for UDB-amended groups, and by −16.0 % (DB300), −9.4 % (DB550), and +9.2 % (DB800) for DB-amended groups, respectively. The differences were closely related to the physicochemical properties of UDB and DB. Particularly, dissolved organic matter released by DB were tracked at molecular level, which revealed that CHO occupied the highest proportion of 70.3 % and lignin-like and carboxylic rich alicyclic molecules were dominant in DB800. This study would facilitate the understanding of the differences between the nitrogen removal performance of UDB and DB-amended anammox, thus providing deeper insights for the comprehensive assessment of the impacts of biochar on the anammox process. [ABSTRACT FROM AUTHOR]

The response of anaerobic ammonium oxidation (anammox) process and granular sludge in the upflow anaerobic sludge blanket reactor was analyzed under long-term exposure to MnO 2 nanoparticles (NPs) (1–200 mg L−1). The addition of 200 mg L−1 MnO 2 NPs had a significantly positive effect on nitrogen removal and this system exhibited excellent performance, with a total nitrogen removal efficiency of 93.1%. Moreover, the specific anammox activity enhanced with increasing concentrations of MnO 2 NPs up to the maximum value of 657.3 ± 9.3 mg TN g−1 VSS d−1 under MnO 2 NPs concentration of 200 mg L−1. This value was approximately 1.6-fold higher than that of the reactor in the absence of MnO 2 NPs. The extracellular polymeric substances and settling velocity were both increased with MnO 2 NPs addition. Meanwhile, the high-throughput sequencing results revealed that MnO 2 NPs increased the relative abundance of dominant bacteria (Candidatus Kuenenia) from 17.3% at the absence of MnO 2 NPs to 23.9% at 200 mg L−1 MnO 2 NPs, which resulted in a higher efficiency of biological nitrogen removal on the anammox system. These results indicated that MnO 2 NPs enhanced nitrogen removal performance of anammox process. Image 108286 • Long-term effects of MnO 2 NPs on the anammox system were firstly evaluated. • MnO 2 NPs in a wide concentration range enhanced the anammox performance. • The SAA, EPS and V S had the similar variations to NRR. • " Ca. Kuenenia " dominated the community under the tested MnO 2 NPs levels. [ABSTRACT FROM AUTHOR]

Abstract Given the increasing applications of NiO nanoparticles (NPs) in battery products, the potential effects of NiO NPs on anaerobic ammonium oxidation (anammox) systems were studied for the first time. The results showed that the anammox system performance obviously differed under the stresses of different NiO NPs concentrations. After the withdrawal of NiO NPs, the nitrogen removal performance of the anammox reactor returned to nearly that of the initial phase within 35 days. Compared with 0 mg L−1 NiO NPs, the specific anammox activity first increased and then decreased to the minimum value of 116.8 ± 13.8 mg TN g−1 VSS d−1 at 60 mg L−1 NiO NPs. The variations in the heme c contents and extracellular polymeric substance amounts were similar to the variations in the specific anammox activity throughout the whole experiment. Additionally, the relative abundance of the dominant bacteria (Candidatus kuenenia) increased from 20.44% at 60 mg L−1 NiO NPs to 23.14% at the end of the last phase. Thus, the potential effects of NiO NPs on anammox systems should be a cause for great concern. Graphical abstract Unlabelled Image Highlights • Long-term effects of NiO NPs on the anammox system were firstly investigated. • The anammox performance was enhanced below 10 mg L−1 NiO NPs and suppressed by 10–60 mg L−1 NiO NPs. • The stability of the reactor operation could be controlled by the (F/M)/SAA ratio. • "Ca. kuenenia " dominated the community in the presence of 1–60 mg L−1 NiO NPs. • The performance of the anammox reactor could recover after withdrawing the NiO NPs. [ABSTRACT FROM AUTHOR]

The long-term impacts of MnO 2 on performance, sludge characteristics and microbial community of biogranule-based anaerobic ammonium oxidation (anammox) process were evaluated in an up-flow anaerobic sludge blanket reactor. It was found that the total nitrogen removal efficiency of reactor was fluctuated between 90%–93% at 1–200 mg L −1 MnO 2 . Notably, the specific anammox activity was increased to maximum value of 657.3 ± 10.6 mg TN g −1 VSS d −1 at 50 mg L −1 MnO 2 and then slightly decreased, but still higher than that achieved at 0–15 mg L −1 MnO 2 , which had similar variation trends to the content of heme c and extracellular polymeric substances in anammox granules. High throughput sequencing indicated that MnO 2 could improve the microbial richness and diversity of anammox granules and Candidatus Kuenenia was always the dominant species, and its abundance continued to increase to 21.3% at the end of operational experiment. Therefore, MnO 2 could be applied to enhance the anammox process and the optimal influent MnO 2 concentration was lower than 50 mg L −1 in view of the reactor performance and cost issues. [ABSTRACT FROM AUTHOR]

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]

• Long-term effects of Fe 3 O 4 NPs on anammox UASB reactor were firstly investigated. • The anammox performance was not obviously influenced under exposure of 2−200 mg L−1 Fe 3 O 4 NPs. • The sludge characteristics were increased with Fe 3 O 4 NPs concentration elevated. • The Fe 3 O 4 NPs could enhance the relative abundance of Candidatus Kuenenia. The performance of anaerobic ammonium oxidation (anammox) granules were studied under long-term exposure to Fe 3 O 4 NPs. The Fe 3 O 4 NPs had no negative impacts on nitrogen removal performance with the addition of 2−200 mg L−1. The specific anammox activity (SAA) slightly decreased from 287.0 ± 13.2 to –253.0 ± 9.2 mg TN g-1VSS d-1 with the increase in Fe 3 O 4 NPs level from 2 to 60 mg L-1, and then significantly enhanced to 381.8 ± 15.7 mg TN g-1VSS d-1 at 200 mg L-1 Fe 3 O 4 NPs. And the change trends of the heme c content, extracellular polymeric substance amount and settling velocity were consistent with that of SAA. The Candidatus_Kuenenia was the dominant species during the entire experiment and its relative abundance was up to 33.4 % at the end the experiment. The results provide some useful information for comprehending the impact of Fe 3 O 4 NPs on the performance of wastewater biological treatment systems. [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]

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]

Magnetic nanoparticles (NPs) have been widely applied in environmental remediation, biomass immobilization and wastewater treatment, but their potential impact on anaerobic ammonium oxidation (anammox) biomass remains unknown. In this study, the short-term and long-term impacts of maghemite NPs (MHNPs) on the flocculent sludge wasted from a high-rate anammox reactor were investigated. Batch assays showed that the presence of MHNPs up to 200 mg L −1 did not affect anammox activity, reactive oxygen species production, or cell membrane integrity. Moreover, long-term addition of 1–200 mg L −1 MHNPs had no adverse effects on reactor performance. Notably, the specific anammox activity, the abundance of hydrazine synthase structural genes and the content of extracellular polymeric substance were increased with elevated MHNP concentrations. Meanwhile, the community structure was shifted to higher abundance of Candidatus Kuenenia indicated by high-throughput sequencing. Therefore, MHNPs could be applied to enhance anammox flocculent sludge due to their favorable biocompatibility. [ABSTRACT FROM AUTHOR]

The effect of oxytetracycline (OTC) on anaerobic ammonium oxidation (anammox) performance and the evolution of anammox consortia under OTC stress were analyzed in this study. Meanwhile, the level of resistance genes under OTC stress was monitored for the first time in the anammox system. The nitrogen removal capacity of anammox reactor was almost deprived within three weeks under the stress of 2 mg L −1 OTC, accompanied by a significant reduction of specific anammox activity of 81.3% and heme c content of 50.1%. However, the abundance of hydrazine synthase gene was adversely affected, with a loss of 29.7%. The efflux pump antibiotic resistance genes tetA , tetB , and tetC and the enzymatic modification gene tetX were first detected in anammox mixed culture. The abundance of tetA was increased from 1.03 to 2.51%. The ratios of tetB and tetC doubled, while there was no obvious change in the ratios of tetX . Therefore, it can be inferred that anammox microorganisms resisted the biotoxicity of OTC via efflux pumping mechanism. After the withdrawal of OTC from the influent, the nitrogen removal capacity of anammox reactor recovered, and the abundance of resistance genes declined gradually. [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]