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[Display omitted] • Adding selenate enhanced the removal of total ARGs during composting. • Bacterial hosts were the primary determinant of ARGs abundance. • Selenium could affect MGEs, oxidative stress response and type IV secretion system. • Selenium-resistant genes affect the microbial abundance and altered ARGs. • Selenate was recommended for the production of selenium-rich organic fertilizers. Co-composting of selenium and livestock manure is an effective way to produce selenium-rich organic fertilizer. However, antibiotic resistance genes (ARGs), as emerging contaminants in compost, respond to selenium remains unknown. In this study, the effects of selenite and selenate on ARGs during goat manure composting were investigated. Compared to the control, the abundance of ARGs decreased by 8.39% with selenate addition, whereas increasing by 9.75% with selenite addition. ARGs degradation in selenate-added treatment was driven by a succession of potential hosts, primarily including Proteobacteria. Meanwhile, mobile genetic elements, oxidative stress response and type IV secretion system genes were down-regulated following selenate exposure, inhibiting the transmission of ARGs through horizontal gene transfer. Both selenite and selenate reduced the aminoglycoside and beta-lactam resistance genes while enriching the multidrug resistance genes in compost. In conclusion, selenate improved the removal of ARGs and was recommended for producing selenium-rich organic fertilizer. [ABSTRACT FROM AUTHOR]

[Display omitted] • The interfacial electron transfer generated by reducing agents regenerates Cu(I). • The production rate of SO 4 •− increases by 1.8 and 2.9 times with adding AA or HA. • The byproducts of reducing agents are environmentally friendly. • The quenching of •OH by AA results in less radicals for pollutant degradation. • The addition of HA developed the COD removal efficiency in effluent wastewater. Herein, hydroxylamine hydrochloride (HA) or ascorbic acid (AA) was utilized to develop the performance of CuBi 2 O 4 activating peroxymonosulfate (PMS) for degradation prometon (PMT), which was effective for the advanced treatment of pesticide wastewater, based on which the reaction mechanism of reducing agents enhanced solid-activated PMS was discussed in the points of electron transfer and the circulation of Cu+/Cu2+. The enhanced electron transfer mechanism of promoting Cu(I)/Cu(II) cycle was confirmed firstly by electrochemical characterization and X-ray photoelectron spectroscopy (XPS) analysis. Furthermore, the kinetic model results showed that the generation rate of SO 4 •− increase by 1.8 times and 2.9 times with the addition of AA or HA, respectively. AA was the quenching agent of •OH due to the stronger reactive with •OH and showed a lower enhancing efficiency. The transformation intermediates of PMT also supported the different derived reactive radicals, based on Density Functional Theory calculation. More importantly, the intermediates of HA and AA were also identified as the first report, based on which their application sense was sited. The work provided a novel and safe insight for improving PMS activation by solid catalysts using HA and AA. [ABSTRACT FROM AUTHOR]

The partial nitrification-anammox (PNA) process under intermittent aeration is feasible to treat low-strength ammonium wastewater, but the effect of chemical oxygen demand (COD) on mainstream anammox processes is not fully understood. In this study, PNA process was established for sewage treatment (average ammonium = 59.3 mg-N/L) in a sequencing batch reactor (SBR) with intermittent aeration mode. Influent organic carbon to nitrogen (C/N) ratios were gradually increased (1.1, 1.5, 2.0 and 2.5). With increasing C/N ratios, the total nitrogen (TN) removal efficiency increased steadily from 30.8% to 77.3%. When the C/N ratio increased from 1.1 to 2.0, the improvement of nitrogen removal was attributed to the increase of anammox bacteria, which exponentially increased at the C/N ratios from 1.1 to 1.5. Additionally, nitrate reduction using internal carbon was likely to combine with anammox reaction under intermittent aeration operation, which might further improve the nitrogen removal. Lastly, settleability and particle size of activated sludge were also improved with the elevated C/N ratios, which favored the enrichment of anammox bacteria and facilitated the combination of partial denitrification and anammox. When the C/N ratio was 2.5, TN removal efficiency still increased while the abundance and activity of anammox bacteria remained stable, indicating that influent organic carbon promoted denitrifying bacteria and inhibited anammox bacterial growth rate. Overall, this study demonstrates that influent COD has comprehensive effects on PNA systems and that the influent C/N ratios are suggested to adjust within optimal range to achieve long-term stability. [ABSTRACT FROM AUTHOR]

[Display omitted] • A two-stage process was developed to treat real low C/N municipal wastewater. • Biological P removal and autotrophic N removal occurred in two separate reactors. • Aerobic granulation in both reactors promoted the process efficiency and stability. • Efficient P (91%) and N removal (81%) were achieved under low C/N ratio of 5.4. • The process can recover 33% of influent organic as biogas and 68% of P as struvite. In this study, a novel two-stage aerobic granular sludge (AGS) system was developed to treat municipal wastewater. High removal efficiencies of phosphorus (91%) and nitrogen (81%) were obtained under a low influent carbon/nitrogen ratio of 5.4. The high nutrient removal was attributed to microbial segregation in the two sequencing batch reactors (SBRs). In the first reactor, the high abundance of polyphosphate-accumulating organisms (Candidatus Accumulibacter 15.3%) promoted a high rate of enhanced biological phosphorus removal (EBPR). In the second reactor, residual ammonium was autotrophically removed via partial nitritation/anammox (PN/A). Moreover, granular sludge was maintained in both SBRs with a sludge volume index of 40–80 mL/g, which reduced the settling time and improved the operational stability. Furthermore, batch tests and mass balance analysis revealed that most influent phosphorus (68%) and some organics (33%) were recovered from the waste sludge as struvite and methane, respectively. Overall, this study illustrates that the novel two-stage AGS system integrating EBPR and PN/A is promising for enhancing nutrient removal, as well as resource and bioenergy recovery from municipal wastewater. [ABSTRACT FROM AUTHOR]

Mature landfill leachate is difficult to be treated due to its complex composition, high concentration of ammonia, and low carbon/nitrogen ratio (C/N). Simultaneous partial nitrification, Anammox and denitrification (SNAD) with intermittent aeration was developed to achieve nitrogen removal from mature landfill leachate. An ammonia conversion efficiency of 99.3 ± 0.3% and total nitrogen (TN) removal efficiency of 99 ± 0.1% were obtained under the influent NH 4 + -N , SCOD and TN of 1950 ± 250 mg/L 1900 ± 200 mg/L and 2300 ± 75 mg/L, respectively. Full utilization of carbon source and high efficient Anammox were two significant factors in SNAD process. Based on the nitrogen balance, the nitrogen removal contribution was 77.1% for Anammox, and 15.6% for denitrification. Three dimensional excitation-emission matrix (EEM) fluorescence spectroscopy was used to detect dissolved organic matter (DOM) in a typical operation cycle for the first time, demonstrating that DOM increased during the anoxic phase and facilitated the reduction of excess NO 3 - -N by denitrification. Quantitative polymerase chain reaction (QPCR) analysis revealed dominant bacterial groups, aerobic ammonia-oxidizing bacteria (AOB) and anaerobic ammonia oxidizing bacteria (AnAOB), which accounted for 12.99% and 8.32% of total bacteria respectively. As a whole, in the SNAD process, nitrogen and COD are removed from the wastewater simultaneously. [ABSTRACT FROM AUTHOR]

An integrated partial nitrification, sludge fermentation and denitrification process in a sequencing batch reactor (PNSFD-SBR), was developed to enhance nitrogen removal from domestic wastewater with low C/N (i.e. SCOD/TN) between 2 to 3 and to reutilize/reduce external waste activated sludge (WAS). Average ammonium removal efficiency of 95.9%, total nitrogen removal efficiency of 93.5%, and external WAS reduction rate of 21.6% was achieved during long-term experiment at 30 ± 1 °C. Real-time pH-DO (dissolved oxygen) monitor and control played an important role in the PNSFD achievement. A batch test indicated that micro-aeration (less than 1 mg/L) sustained partial nitrification, which further facilitated subsequent sludge fermentation and denitrification processes. Moreover, Illumina MiSeq analysis demonstrated the predominant bacteria were Rhodocyclaceae , Anaerolineaceae and Saprospiraceae on family level and they were key to partial nitrification, denitrification and sludge fermentation, by which the feasibility of PNSFD process to achieve simultaneous nitrogen removal and external WAS reutilization/reduction was verified. [ABSTRACT FROM AUTHOR]

Although the limitation or deficiency of nutrients, such as nitrogen (N) and phosphorus (P), has been one of the frequently reported factors causing filamentous or non-filamentous bulking of activated sludge, the mechanisms are still unclear. In this work, the long-term effects of N and P limitation or deficiency on sludge settleability and bioflocculation characteristics were investigated in six sequencing batch reactors (SBRs) fed with wastewater with different nutrient availability. The sludge volume index (SVI), microbial community structures, intracellular poly-β-hydroxyalkanoates (PHAs) and extracellular polymeric substances (EPS) were characterised over time. Bulking was not observed in SBRs with N limitation or deficiency, in which SVI remained below 150 mL/g. In contrast, bulking was encountered in those reactors with P deficiency. The occurrence of non-filamentous bulking was associated with a higher carbohydrates fraction and a lower proteins fraction in EPS. In the case of filamentous bulking, SVI correlated negatively with the amount of PHAs. Our experimental data support the hypothesis that the occurrence and/or the type of bulking in activated sludge could be affected by the combination of kinetic selection, microbial storage, as well as the EPS composition. [ABSTRACT FROM AUTHOR]

[Display omitted] • An ultra-low energy consumption bioprocess was firstly developed for decentralized sewage treatment. • High-efficient nitrogen removal efficiency of 93.7% with 6.7 mg/L in effluent TN was obtained. • Anammox contributed a significance nitrogen removal of 88.1% and 7.6% for denitrification. • UEFC saved 100% mechanical aeration, 100% external carbon dosage. An ultra-low energy consumption continuous flow (UECF) process was used for enhanced nitrogen removal from rural sewage. The ammonia in sewage was first oxidized to nitrite in a bio trickling filter (BTF PN) supplemented with natural oxygen. A stable nitrite accumulation ratio (NAR) of 93.2% was maintained by adding 5 mg/L NH 2 OH every seven days. BTF PN effluent was then combined with certain portion of rural sewage (1:1.2 to 1:1.5) and introduced to an upflow anaerobic sludge blanket reactor, where the nitrogen-containing pollutants were removed by Anammox process (UASB AMX). Effluent total nitrogen (TN) of 6.7 mg/L and a TN removal efficiency of 93.7% were obtained when influent chemical oxygen demand (COD), NH 4 +-N and TN were 321.9, 74.2 and 82.7 mg/L, respectively. Advanced nitrogen removal, based on the desirable cooperation between Anammox bacteria (Ca. Brocadia , 2.3%) and partial denitrification bacteria (Thauera , 4.2%), was achieved over 300 days of stable operation. Considering the nitrogen balance, 57.9% of nitrate generated in Anammox was reduced to nitrite by partial denitrification, and Anammox contributed 88.1% of nitrogen removal and 7.6% of denitrification. Compared with conventional nitrification and denitrification processes, UECF requires no mechanical aeration, no external carbon, produces 76.6% less external sludge, and reduces CO 2 emissions by 92.3%. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel PNA-PDA process was developed for high-level sidestreams treatment. • Desirable polishing treatment of PNA effluent was achieved via PDA approach. • TN removal maintained as high as 98.4% even at low temperature of 13.0 ℃. • Domestic wastewater could be simultaneously treated without aeration. Anaerobic ammonium oxidation (anammox) has been widely accepted as an energy-efficient approach for nitrogen removal from high-strength sidestreams. However, insufficient nitrogen removal due to the excessive NO 3 –-N residue represents the major challenge, especially at low temperature. In this study, highly efficient and synchronous nitrogen removal from ammonia-rich wastewater and real domestic wastewater was achieved via a novel anammox-mediated treatment by coupling with double-nitrite-shunt process in two-stage sequencing batch reactors. Stable partial nitrification/anammox (PNA) was successfully developed, while the total nitrogen (TN) removal efficiency was limited to 86.9 % due to excessive NO 3 –-N accumulation. Significantly, integration with partial denitrification (NO 3 –-N → NO 2 –-N) coupling anammox (PDA) process offered an efficient solution, which transformed the overproduced NO 3 –-N of PNA to NO 2 –-N and subsequently completely removed with NH 4 +-N via anammox pathway by mixing with real domestic wastewater (NH 4 +-N of 69.0 mg/L, COD of 203.6 mg/L). Excellent nitrogen removal performance with average TN removal efficiency of 98.4 % and high-quality effluent with average TN of 4.9 mg/L was maintained despite the temperature dropping to 13.0 ℃. 16S rRNA gene sequencing unveiled the different community of anammox bacteria cooperating stably with AOB and denitrifiers in the two systems. Compared with conventional nitrification/denitrification methods, the novel PNA-PDA process not only enabled 60% saving in aeration energy and 95.5% saving in organic carbon for ammonia-rich wastewater treatment, but also required no aeration energy for domestic wastewater treatment. Overall, this study provides a promising application with simple-control strategy for cost-effective and synchronous nitrogen removal from sidestreams and mainstreams. [ABSTRACT FROM AUTHOR]

Abstract: It has been proved that higher total nitrogen removal efficiency could be obtained in step feeding activated sludge process by adjusting the inflow rate distribution and the volume of each stage. But the optimization of the step feeding process would be complicated owing to adjustment of inflow rate and volume. To develop the auto-control and operational decision support system is an urgent and necessary work for well application of step feeding process. Although biological wastewater treatment, especially the biological nitrogen removal process, has the characteristics of complex nonlinear, it provides widespread opportunities for artificial intelligent control. In this paper a fuzzy control model of anoxic/oxic step feeding activated sludge process was developed under the condition of sufficient and insufficient influent carbon source. The detailed information on development of fuzzy model was addressed based on collecting and analyzing previous experimental data. The influent C/N ratio was selected as input variable and inflow rate and volume distribution in each stage were selected as output variables. Moreover, the calibration and application approaches of control model were also studied through pilot-scale experiments (1000 L/d) with domestic sewage. The highlight is that the method and approach of model calibration are well discussed so that it provides good opportunities on practical application. During three months experimental period enhanced total nitrogen removal efficiency of more than 95.1% was reached with the influent C/N ratio of 8.16–12.3, average of 9.78. [Copyright &y& Elsevier]

[Display omitted] • Proposed a side-stream sludge treatment method for rapid proliferation of GAOs. • Highly enriched GAOs (3.09–18.25%) facilitated ED while DOHOs decreased by 62.78%. • The abundance of PAOs was reduced but didn't deteriorate the phosphorus removal efficiency. • The TIN and PO 4 3−-P in influent and effluent were 71.26, 8.01 mg/L and 6.40, 0.30 mg/L, respectively at C/N of 3.25. Endogenous denitrification (ED) is an effective approach to achieve advanced nitrogen removal for low COD/N (C/N) municipal wastewater, in which internal carbon sources are used for denitrification. However, phosphorus-accumulating organisms (PAOs) and denitrifying ordinary heterotrophic organisms (DOHOs) outcompeting glycogen-accumulating organisms (GAOs) for carbon sources decreases total inorganic nitrogen (TIN) removal efficiency. This study proposed a novel side-stream sludge treatment strategy, i.e., through phosphorus famine, to selectively strengthen GAOs. Two sequencing batch reactors (SBR) were used, with one served as an anaerobic/aerobic/anoxic SBR (AOA-SBR) and the other as a side SBR. Side-stream phosphorus famine treatment was conducted three times during 140 days' experiment, of which 20–30% of the sludge collected from the AOA-SBR was imposed to phosphorus famine condition in the side SBR for 4 days (24 cycles). Results showed that the average TIN and phosphorus removal efficiencies were 88.76% and 95.31%, and the average TIN and phosphorus in the effluent were 8.01 and 0.30 mg/L, respectively, treating low C/N (~3.25) municipal wastewater in the AOA-SBR. The relative abundance of PAOs decreased from 3.23% to 2.15% and that of DOHOs reduced by 62.78%. In contrast, the abundance of GAOs increased from 3.09% to18.25%, which should be the key reason for the improvement of the ED efficiency. Moreover, the enrichment of GAOs promoted ED simultaneously using glycogen and poly-β-hydroxyalkanoates (PHA) as carbon sources. The strategy of side-stream treatment proved the potential of rapid proliferation of GAOs while achieving improved nitrogen removal. [ABSTRACT FROM AUTHOR]

Abstract: The step-feed anoxic/oxic biological nitrogen removal process has been proposed as an attractive alternative for the conventional biological nitrogen removal process for the purpose of enhanced nitrogen removal. For step-feed process, the biological nitrogen removal efficiency is a function of influent flow distribution. In this study, the effects of influent flow rate distribution on the performance of nitrogen removal process were investigated. The effects of influent flow rate distribution on COD, ammonia, total nitrogen removal efficiency, nitrification rate and sludge volume index value were also studied. According to the performance characteristic of the step-feed process, the concept of influent flow rate distribution ratio was firstly introduced. The maximum influent flow distribution ratios (λ max) under the condition of different influent C/N ratios were determined, respectively, by trial and error method. The experimental results showed that high total nitrogen removal efficiency, higher than 95%, could be achieved under certain influent flow rate distribution ratio without internal nitrate cycle or addition of external carbon source. It was obvious that nitrification rate of each stage under different influent flow distributions decreased along with the decreasing of sludge loading and volume loading in each stage, and the degree of reduction rise gradually with the increasing of influent flow distribution ratio. The sludge volume index value would also increase along with the increase of influent flow distribution ratio. [Copyright &y& Elsevier]

• Various unique methods for synthesizing core–shell structures have been reported. • Utilizing the features of the core–shell structure can improve battery performance. • Core-shell structures show promising applications in energy storage and other fields. In the context of the current energy crisis, it is crucial to develop efficient energy storage devices. Battery systems with core–shell structures have attracted great interest due to their unique structure. Core-shell structures allow optimization of battery performance by adjusting the composition and ratio of the core and shell to enhance stability, energy density and energy storage capacity. This review explores the differences between the various methods for synthesizing core–shell structures and the application of core–shell structured materials in various battery systems. In addition, we point out the challenges of core–shell structural materials and provide an outlook for new solutions to hotspot issues in energy and biomedicine. [ABSTRACT FROM AUTHOR]

• The NRE reached 77.8 ± 4.3% even COD/TIN ratio at 2.9 during 548 days of study. • The effect of PD/A will be enhanced after the added anammox biocarriers adapted. • Anammox bacteria abundance on biocarriers remained stable and was higher than WWTPs. • PD/A contributed about 32–47% nitrogen loss in hypoxic zones in step-feed AAO reactor. The application of partial denitrification coupling with anammox (PD/A) in municipal sewage treatment is one of the most promising research field, and it has just begun. In 548 days of experiment treating real domestic sewage, the continuous flow reactor was started up by adding biocarriers containing anammox bacteria and operated stably after acclimatization. The PD/A was successfully achieved in the step-feed AO system. Furthermore, mass balance of ammonium revealed that anammox could contribute 32–47% to nitrogen loss. Compared with no biocarriers addition phase, the nitrogen removal efficiency (NRE) increased to 77.8 ± 4.3% and the effluent total inorganic nitrogen (TIN) decreased to 11.0 ± 2.1 mg/L at the COD/TIN ratio of 2.9 from day 428 to day 548 under the condition of anammox biocarriers addition and without external carbon source. Quantitative polymerase chain reaction (qPCR) and high-throughput sequencing analysis showed that anammox bacteria on the biological carrier accounted for 3.06% of the total bacteria in the stable phase, which was much higher than the reported <0.003% in wastewater treatment plants (WWTPs). After 247 days of operation with anammox biocarriers addition, the abundance of anammox bacteria on the carriers tended to be stable at 3.36 × 1010 gene copies g−1 dry sludge. The activity of anammox decreased and maintained at 13.14 g NH 4 +-N m−3 d−1 under the biocarriers-only condition, while increased from 11.71 g NH 4 +-N m−3 d−1 to 25.65 g NH 4 +-N m−3 d−1 in the hybrid condition of biocarriers and flocs. This study indicated that PD/A is effective to strengthen nitrogen removal with low COD/TIN ratio. [ABSTRACT FROM AUTHOR]

• Anammox (Ca.Brocadia , 0.69%) were enriched in biofilms, markedly higher than flocs. • 15N-isotope tracer tests showed partial denitrification is a prerequisite for anammox. • Anammox contributed to 68% of the nitrogen loss via anoxic biofilms in batch tests. • Nitrogen removal efficiency improved 16.9% by combining denitrification and anammox. • Mainstream partial-anammox might has great potential of engineering application. Introducing anammox technology into low-ammonia sewage treatment offers sustainable nitrogen removal, but there remain challenges to its future applications. Here, anammox bacteria were enriched by integrating into partial denitrification (NO 3 −-N to NO 2 −-N) in the anaerobic/anoxic/oxic (A2/O) reactor with low COD/N ratios (2.7 ± 0.4) sewage. This significantly enhanced nitrogen removal through partial anammox process over stable operation of 300 days. Microbial community analysis showed that the anammox bacteria were enriched in anoxic-carrier biofilms (Ca. Brocadia , 0.69%), and their abundance was significantly higher than the flocculent sludge (16 s rRNA sequencing: P < 0.001; qPCR: P < 0.001). Further activity testing via 15N-isotope tracing revealed that partial denitrification is a prerequisite for in situ occurrence of anammox reaction. Anammox contributed to 68% of the total nitrogen loss via anoxic-carrier biofilms in batch tests. Combining denitrification and anammox, the nitrogen removal efficiency of the A2/O process improved by approximately 16.9% for low COD/N ratios real sewage. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Effluent TN as low as 4.0 mg N/L was achieved via PD-Anammox process. • Anammox was stable and accounted for 78.2% on nitrogen removal. • Low nitrous oxide (N2O) was produced in PD-Anammox process. • Oxygen consumption, COD demand and sludge production would be largely reduced. • PD-Anammox process can be easily retrofitted from existing plants. Abstract High nitrate (NO 3 −-N) concentration in the effluent of wastewater treatment plants (WWTPs), cannot meet the increasing stringent discharge limits. Hence, the tertiary treatment is necessary to lower the total nitrogen concentration. In this study, an innovative partial denitrification (PD)-Anammox process was applied to remove the nitrate nitrogen (20–40 mg N/L) from secondary effluent. The nitrate wastewater were firstly fed to PD sequencing batch reactor (SBR, 10 L) to produce nitrite along with the low carbon/nitrogen ratio (C/N) municipal sewage (NH 4 + of 57.8 mg N/L, COD of 175.8 mg/L), then the effluent from SBR was pumped to the anaerobic sludge blanket (UASB, 3.2 L) performing anammox for further nitrogen removal. The integrated process was operated for 224 days with the secondary effluent to municipal sewage volume ratio of 2.9–6. The results suggested that an excellent nitrate removal efficiency of 97.9% was achieved, and the mean removal efficiency of NH 4 +-N and COD from municipal sewage were 95.2% and 81.6%, respectively, leading to the total nitrogen and COD concentration in the final effluent as low as 4.0 mg N/L and 30.1 mg/L, respectively. Anammox was the main nitrogen removal pathway with a mean proportion of 78.2%, and Candidatus_Brocadia was identified as the dominating genus. Furthermore, it was found that a minor nitrous oxide (N 2 O) was produced in the integrated process. The PD-Anammox process was verified to be economically and environmentally feasible for retrofitting of existing plants. [ABSTRACT FROM AUTHOR]

[Display omitted] • The stable anammox performance enhanced the stability of nitrogen removal. • Synergize of endogenous denitrification and anammox was critical to 87.1 % NRE. • AnAOB enriched from 4.25 × 106 and remained at 3.1 ± 0.9 × 108 copes/gSS. • Anammox activity was maintained despite temperature decreasing from 28 to 17 ℃. • The anammox contribution to nitrogen removal was above 50 % under varied C/N ratio. The anaerobic ammonium oxidation (anammox) process is a promising method for carbon reduction and energy conservation. However, the advantages of its application in municipal wastewater treatment have not been completely revealed. Stable nitrogen removal was successfully achieved in the anaerobic/aerobic/anoxic (AOA) process by directly integrating stable anammox. Over a 200 + day operating period, the abundance of anammox bacteria (3.1 ± 0.9 × 108 copies/gSS) and anammox activity (0.32 ± 0.07 mgN/(gSS·h)) remained high, despite a temperature decrease (27.8–17.2 °C) and fluctuating carbon-nitrogen (C/N) ratio (1.6–5.0). A stable nitrogen removal efficiency of 87.1 ± 2.5 % was successfully maintained, because the anammox activity compensated for the effect of low temperatures and low C/N ratios on the nitrification and denitrification. Further analysis found that anammox accounted for 52.6 %-57.5 % of N 2 production, and the rest was through nitrification–denitrification. The stable anammox reaction was mainly due to the limitation of oxygen and carbon sources and the stable supply of nitrite by endogenous denitrification. Overall, these findings confirmed that the stability and efficiency of nitrogen removal from municipal wastewater could be increased by integrating anammox under appropriate conditions. [ABSTRACT FROM AUTHOR]

A novel two-sludge system of anaerobic anoxic oxic–biological contact oxidation (A 2 /O–BCO) was developed for high-efficiency utilization of influent carbon sources treating wastewater with low carbon/nitrogen (COD/N) ratio. Unlike traditional A 2 /O process, the oxidation of ammonium (NH 4 + -N) in this system mainly took place in the BCO reactor through nitrate (NO 3 − -N) recycling to provide electron acceptors for denitrifying phosphorus removal. The results showed that the A 2 /O reactor achieved the efficient utilization of carbon sources, with 75% chemical oxygen demand (COD) in the anaerobic zone being consumed to synthesize poly-β-hydroxyalkanoates (PHA). The PHA utilization rate in the anoxic zone was more than 70% with the denitrifying phosphorus removal of 97.83%. The batch tests of phosphorus accumulating organisms (PAOs) and denitrifying PAOs (DNPAOs) activities showed that the DNPAOs accounted for 73.80% of the PAOs in the system. The A 2 /O sludge of lower extracellular polymeric substances (EPS) production exhibited a better settling ability than conventional denitrification and phosphorus removal processes. The denitrifying phosphorus removal process of higher phosphorus percentage promoted the formation of granular sludge, which was confirmed by scanning electron microscopy (SEM) and energy dispersive spectrometry (EDS). The fluorescence in situ hybridization (FISH) results showed that PAOs became dominant with low amount of nitrifiers in the A 2 /O reactor, and nitrifiers were enriched in the BCO reactor. [ABSTRACT FROM AUTHOR]

• Cu, N-CDs are synthesized by Cu, N co-doping method showing dual emission centers. • Tunable afterglow modes property of Cu, N-CDs@BA is realized by matrix-assisted method. • Afterglow enhancement and tuning mechanism of Cu, N-CDs@BA are revealed. Carbon dots (CDs) based afterglow materials have attracted much attention owing to their low toxicity, environmental protection, stable luminescence, abundant raw materials, and low cost. However, CD-based afterglow materials with both room temperature phosphorescence (RTP) and thermally activated delayed fluorescence (TADF) characteristics are rarely reported, which greatly limits their in-depth application in advanced anti-counterfeiting, intelligent sensing, and other fields. In this paper, Cu, N co-doped CDs (Cu, N-CDs) with dual emission centers were synthesized via a simple solvothermal method by heteroatom doping to enhance the spin–orbit coupling of CDs and regulate the luminescence properties of CDs. Then, boric acid (BA) was used as the matrix to synthesize Cu, N-CDs@BA composites by matrix-assisted method, and the electron transfer enhancement afterglow was realized by the inorganic electronic defects of the matrix. Cu, N-CDs@BA can realize the mutual conversion of TADF and RTP by changing the excitation wavelength or increasing the temperature. At the excitation of 285 nm, the room temperature afterglow of Cu, N-CDs@BA exhibit TADF, and the average afterglow lifetime is 94.21 ms. At the excitation of 365 nm, they exhibit RTP, and the average afterglow lifetime is 347.96 ms. Based on three different emission properties (fluorescence, RTP, and TADF), Cu, N-CDs@BA was applied in anti-counterfeiting and encryption, which shows good application potential. [ABSTRACT FROM AUTHOR]

[Display omitted] • Efficient nitrogen removal (>95 %) and a reduced organic carbon demand (50 %) was obtained. • Non-native POG cycle was energy-saving and kinetically and thermodynamically feasible. • High KHCO 3 concentration induced the most efficient natural phosphoenolpyruvate carboxylase. • Neutral pH facilitates carbon fixation products to generate energy for nitrogen removal. Sustainable development based on carbon fixation is a promising orientation for CO 2 emission reduction. Here, in an anammox-centered coupling system that involves partial denitrification and hydrolytic acidification (A-PDHA), a latent carbon-fixation pathway called phosphoenolpyruvate-oxaloacetate-glyceraldehyde (POG) cycle, was firstly awakened through high inorganic carbon injection. Correspondingly, a nitrogen removal efficiency of > 95 % and significant reduction of organic carbon demand were both achieved. To understand the nature of low-carbon and efficient nitrogen removal performance, the carbon fixation mechanism and its driving energy metabolism were elucidated using metaproteomics and metabolomics. Results revealed that the POG cycle was energy-saving, and kinetically and thermodynamically feasible. This autocatalytic route involves the reduction of HCO 3 − using the most efficient natural phosphoenolpyruvate carboxylase, followed by the phosphorylation of one molecule of glucose from starch, and then the glycolysis pathway. These guarantee the abundant production of carbon fixation products i.e., glyceraldehyde-3-phosphate and acetyl-CoA. Additionally, the neutral pH facilitates these products flowing into the tricarboxylic acid cycle, thereby generating sufficient adenosine triphosphate and reducing power, which further drives downstream multi-pathway nitrogen metabolism. These findings provide valuable insights for future research on artificial carbon emission reduction in anammox-centered coupling systems during wastewater treatment. [ABSTRACT FROM AUTHOR]

[Display omitted] • Biological nitrate removal with municipal wastewater as co-substrate was demonstrated by CANDAN process; • High-efficient nitrogen removal with NRE and NRR of above 84 % and 0.6 Kg N/m3/d achieved; • Efficient denitratation with NTR above 84.6% always obtained despite increased municipal wastewater; • Increased municipal wastewater did not pose an adversely effect on anammox process; • Stable CANDAN process with dominated anammox sustained in treating nitrate sewage with varying concentrations. The innovative Complete Ammonium and Nitrate removal via Denitratation-Anammox over Nitrite (CANDAN) process represents a promising low-carbon technology for wastewater treatment, has been widely studied in sequential batch reactors (SBRs) treating synthetic wastewaters. This work focuses on the development of the CANDAN process within a continuous-flow Upflow Anaerobic Sludge Blanket (UASB) reactor for nitrate sewage treatment (NO 3 –-N: 100–1000 mg N/L), featuring varying proportions of real municipal wastewater as a co-substrate (61.3 mg NH 4 +-N/L, 191.5 mg COD/L). The results demonstrate consistently high N removal performance, with over 84.0 % of total nitrogen (TN) removed from the mixed wastewaters at a rate of approximately 0.6 Kg N/m3/d. As the proportion of municipal wastewater in the feed increased, the activity of denitrifying microorganisms improved. However, their growth was constrained by exacerbated endogenous respiration resulting from prolonged Hydraulic Retention Time (HRT) under a constant loading rate. The ideal nitrite production with the nitrate-to-nitrite transformation ratio (NTR) of above 84.6 % was always obtained. This sustained the dominance of the anammox pathway at around 80 % throughout the operation, underscoring its pivotal role in supporting the exceptional performance of the CANDAN process within the UASB reactor. Microbial analysis revealed an increase in species richness and diversity with higher proportions of municipal wastewater, while anammox functional bacteria exhibited slight enrichment in the later stages, further emphasizing the sustainability of the CANDAN process even with increased proportions of municipal wastewater. The outcomes of this study provide valuable insights into the successful development of a continuous-flow CANDAN process for highly efficient nitrate sewage treatment by incorporating real municipal wastewater as a co-substrate, advancing the goal of achieving carbon–neutral wastewater treatment practices. [ABSTRACT FROM AUTHOR]

Highlights: [•] A prominent ENDPR system was developed and operated with low HRT and low COD/N. [•] DPAOs could be temporarily inhibited under low aeration rate (DO=0.2mgL−1). [•] Lower poly-P accumulated in the sludge was the direct cause of the deterioration of phosphorus removal. [ABSTRACT FROM AUTHOR]

[Display omitted] • Effect of DO changes on kinetics and microbial community of PN was studied. • The V max,AOB -V max,NOB value was more crucial for PN. • Nitrospira , with a lower K O , adapted easier to DO changes than Nitrosomonas. • PN was achieved due to faster recovery of AOB after aerobic starvation. • Decreasing DO could completely destroy the PN due to Nitrospira. Partial nitrification (PN) has great significance in promoting both anaerobic ammonium oxidation (anammox) and advanced nitrogen removal. However, the kinetics of PN have not been sufficiently studied. Deterioration of PN often occurs due to nitrite-oxidizing bacteria (NOB) outgrowth, for which the dissolved oxygen (DO) is a critical factor. This study investigated the kinetic parameters of ammonia-oxidizing bacteria (AOB) and NOB by varying the DO concentration. The partial nitrification-anammox (PNA) process was operated under sequentially low (0.3–0.8 mg/L) and high (4.0–5.0 mg/L) DO. The results show that AOB could not adapt to low DO, resulting in a significant decrease in the maximum AOB activity (V max,AOB) and a slightly altered oxygen half-saturation constant of AOB (K O,AOB). Conversely, K O,NOB decreased and V max,NOB maintained, indicating that the main NOB genus, Nitrospira , was more adaptable to DO changes. Under high DO, AOB growth was weaker than NOB, leading to a low V max,AOB – V max,NOB value; K O,AOB increased and was larger than K O,NOB and PNA was eventually destroyed. The aerobic starvation was then adopted to restore PN. AOB recovered faster and dominated, with V max,AOB greatly exceeding V max,NOB. Finally, NOB were inhibited and PN was recovered. During this process, K O,NOB increased and was higher than K O,AOB. Changes in the kinetic parameters, especially the V max,AOB -V max,NOB value, have specific guiding significance for DO regulation during PNA. This work helps better understand the effect of DO variations on the nitrifying microbial community, which influences oxygen affinity and maximum activity. [ABSTRACT FROM AUTHOR]

[Display omitted] • Rising NO 2 –-N stress accelerated the growth of NPG with stable NO 2 –-N production. • EPS was stimulated with increasing size and offered supplementary electron donors. • Highly enriched functional bacteria Thauera was evenly distributed around NPG. • Enhanced electron transfer for NO 3 –-N reductase played a key role in efficient NPG. Nitrite-producing denitrification granular sludge (NPG) is emerging as a novel approach to employing anammox for cost-efficient nitrogen removal from high-strength nitrate-containing wastewater. However, the underlying impact of increasing stress of nitrite (NO 2 –-N) accumulation on microbial metabolism and cooperation of denitrifying bacteria and heterotrophs in NPG was still not clear. This study first demonstrated a high-rate NPG system with elevating nitrate (NO 3 –-N) from 52.4 mg/L to 613.2 mg/L. During this operation, a rapid increase in granular size from 322.8 µm to 1124.0 µm was observed with a relatively stable nitrate-to-nitrite transformation ratio (NTR) as high as 83.0 %, and effluent NO 2 –-N of increasing from 16.5 mg/L to 331.9 mg/L. Such an increasing NO 2 –-N stress improved the capability of the TCA cycle with rising intermediates of amino acid metabolism. This further stimulated the production of exocellular organic matter that replenished as electron donors and promoted the growth of granular size. The homogeneously spatial distribution of key bacteria (Thauera) surrounding the NPG with a calcium-dominated inorganic core inside was revealed to play a key role in enhanced substrate transfer capability. Genes nar and nap encoding NO 3 –-N reductase dominated by key species belonging to Thauera showed much higher abundance than that encoding NO 2 –-N reductase, which was the key reason for relatively stable NO 2 –-N accumulation. It illustrated the excellent persistence of NPG to high NO 2 –-N stress with special structure of functional bacteria inside granules, providing a great potential for the treatment of high-strength nitrate-containing wastewater. [ABSTRACT FROM AUTHOR]

[Display omitted] • Simultaneous anammox-denitrification is reviewed from fundamentals to implementations. • Biofilm formation are promising for retaining anammox bacteria. • Organic matter limitation plays an important role in denitrifiers' restraint. • Challenges and recent advances in three types of SAD are discussed. • Diverse future aspects of the emerging SAD process were proposed. Simultaneous anaerobic ammonium oxidation (Anammox) and Denitrification (called SAD) holds significant promise for removing nitrogen and organic matter from wastewater. Previous studies have demonstrated the ability of SAD process and its emerging extensions, such as Simultaneous Nitritation, Anammox and Denitrification (SNAD) and simultaneous Anammox, Denitrification and Sludge Fermentation (ADSF), to integrate the nitrogen cycle with the carbon cycle. This study systematically reviews three types of SAD process, in terms of their microbial groups and their relationships. Anammox bacteria and denitrifiers commonly experience a symbiotic and/or competitive relationship when treating real wastewater. Biofilm formation and organic matter limitations are considered the most critical conditions for the co-existence of anammox and denitrification. This study also provides an overview of the research and development of the state-of-the-art processes based on SAD. We conclude that, while the optimized performance of SAD process and its extensions have been largely recognized, there is a need to better understand the mechanics, particularly with respect to a kinetic and stoichiometric analysis. [ABSTRACT FROM AUTHOR]

[Display omitted] • Amino-functionalized graphene oxide aerogel (MGOA) was ingeniously synthesized. • The adsorption property of MGOA was studied by static and fix-bed adsorption. • MGOA achieves efficient adsorption towards quinoline in water. • MGOA can be easily separated from liquid phase. • Performance of MGOA was confirmed by both adsorption capacity and PC. The direct emission of quinoline in coking wastewater has great harm to human health and environmental quality. Therefore, it is urgent to develop advanced materials for efficient adsorption of quinoline in wastewater. In this study, a novel three-dimensional amino-functionalized graphene oxide aerogel (MGOA) was prepared by an acid induction strategy, which triggers the esterification and amidation of graphene oxide (GO) nanosheets and ammonium citrate. This strategy not only improves the chemical stability and mechanical strength of as-prepared MGOA, but also provides a large number of effective adsorption sites to achieve the efficient adsorption towards quinoline. MGOA has the advantages of three-dimensional interconnected hierarchical pore structure, large specific surface area, and low density. When the initial quinoline concentration is 50 mg L−1, the adsorption capacity (q e) of MGOA towards quinoline is as high as 103 mg g−1 at 298 K. More importantly, in the column adsorption system, the distribution coefficient (PC) at 10% breakthrough is 14.16 mg g−1 μM−1, which is the highest level yet reported. MGOA exhibits good reusability and outstanding solid-liquid separation advantage during eight adsorption-desorption cycles. Density functional theory and van der Waals surface electrostatic potential were used to investigated the adsorption behavior of quinoline on aerogel. The binding force between MGOA and quinoline molecule is strong, with an adsorption energy up to −78.68 kJ mol−1. Thus, MGOA is considered as a promising candidate for removing quinoline contaminants from aqueous solutions. [ABSTRACT FROM AUTHOR]

[Display omitted] • A two-stage PN/A system for integrated MLL and KWDL treatment had been developed. • The process achieved NRE of 98.1 ± 1.3 % with effluent TIN of 15.2 ± 1.8 mg/L. • Aerobic HRT accounted for just 36.4 % of the whole process with DO < 0.3 mg/L. • The PDA-driving ability of KWDL was comparable to sodium acetate. • Adding KWDL in the later phase of each cycle in A-SBR promoted achieving high NRE. The advanced nitrogen removal of mature landfill leachate (MLL) with low carbon to nitrogen ratio (C/N) is a topic worthy of further research. A two-stage partial nitrification/anammox (PN/A) system for integrated MLL and kitchen waste digestion liquid (KWDL) treatment was established in this study. The nitrogen removal efficiency (NRE) of this process was 98.1 ± 1.3 %, with an effluent TIN concentration of 15.2 ± 1.8 mg/L. In the partial nitrification-sequencing batch reactor (PN-SBR), aerobic hydraulic retention time (HRT) accounted for just 36.4 % of the whole process with dissolved oxygen (DO) < 0.3 mg/L, which significantly reduced energy consumption. Furthermore, the introduction of KWDL heightened anoxic denitrification and aerobic simultaneous nitrification and denitrification (SND) processes, contributing to 74.2 ± 4.3 % and 25.8 ± 4.3 % of the total NRE, respectively. This greatly strengthened the nitrogen removal capacity of PN-SBR. Batch tests indicated that the capacity of KWDL as a carbon source to drive the process of partial denitrification coupled with anammox (PDA) was equal to that of sodium acetate. Adding KWDL in the later phase of each cycle in the anammox-sequencing batch reactor (A-SBR) facilitated achieving stable PDA and advanced nitrogen removal. The nitrate accumulation problem in the traditional two-stage PN/A process has been resolved without the addition of carbon sources. Nitrosomonas (3.7 %→7.9 %), Thauera (0.04 %→40.7 %) and a salt-tolerant AnAOB microbe, unclassified_f_Brocadiaceae (0 %→5.3 %) were dominant in the combined system. This study revealed a pioneering avenue for efficient high-strength wastewater treatment. [ABSTRACT FROM AUTHOR]

[Display omitted] • PD/A granules achieved high-rate and enhanced N removal with continuous feeding. • Dynamic migration of anammox bacteria to outer edge of granules was found in CSTR. • Stratified structure benefited for cross-feeding between anammox and denitrifiers. • Versatile metabolism of anammox bacteria for reducing NO 3 −-N was assumed in PD/A process. • Anammox bacteria could be efficiently enriched at cost of decreased PD bacteria. Anammox coupling with denitrification has attracted increasing attention in low-strength wastewater treatment. However, its wide application in continuous-flow process is seriously restricted by insufficient anammox capacity due to the failed biomass retention. The functional capacities of communities inhabiting the fluctuating habitat has been little understood. This study developed a novel granular sludge-based partial denitrification coupling with anammox (PD/A) process with the feeding strategy shifting from sequencing to continuous flow in a Continuous Stirred Tank Reactor (CSTR), treating low-strength wastewater containing ammonia (NH 4 +-N) of 46.1 mg/L and nitrate (NO 3 −-N) of 60.7 mg/L. Significantly enhanced specific anammox activity was demonstrated, attributed to the robust nitrite (NO 2 −-N) generation with NO 3 −-N to NO 2 −-N transformation ratio (NTR) averaged 84.1 %. Remarkable total nitrogen (TN) removal of 95.4 % was thus achieved with anammox pathway contribution as high as 88.3 %. Interestingly, a dynamic and stratified microbial structure was obtained in CSTR, in which anammox migrated to outer layer together with Thauera capable of partial denitrification (PD) in big granules, resulting in more efficient cross-feeding and strengthening the cooperation between anammox and heterotrophic PD bacteria in CSTR. Metagenomic-based metabolic inferences provide first insight into the versatile microbial metabolic potential of anammox bacteria for reducing NO 3 −-N with acetate as electron donor in PD/A process. They were successfully enriched and retained with the relative abundance of 8.4 %, being attributed to the enhanced mass transfer efficiency. On the contrary, dominant denitrifier Thauera decreased sharply to 4.2 %. This study provides a new alternative of anammox coupling with heterotrophics granular sludge for efficient low-strength wastewater treatment under continuous feeding, and open up new perspectives for selecting distinctive communities that stand out by expansive metabolic versatility and excellent microbial collaboration. [ABSTRACT FROM AUTHOR]

[Display omitted] • PN/A-SPDN/A was firstly developed at seasonal temperature of 25.3–13.2℃. • Remarkable 98.8% NRE was obtained with high-efficient effluent quality. • Anammox downregulate genes expression for survival towards temperature plunge. • NO 2 – provision is more determinant factor for Anammox rather than temperature. Anammox, an energy-efficient bioprocess, is gaining growing attention. However, its widespread adoption confronts challenges due to residual nitrate and unstable nitrite supply, especially during seasonal temperature fluctuations. To address this, we developed an innovative Anammox-mediate biotechnology, incorporating a double nitrite autotrophic shunt: partial nitrification (PN/A) and sulfur-driven partial denitrification (SPDN/A). Remarkably, a nitrogen removal efficiency was realized over 183 days, encompassing a significant seasonal temperature decrease (from 25.3℃ to 13.2℃). Functional gene analysis revealed Anammox spontaneously downregulated functional gene expression to allocate core metabolic energy for essential cellular processes towards temperature plunge condition. Interestingly, as seasonal temperature decreased, nitrogen removal contribution of Anammox in SPDN/A exhibited a noticeable upward tendency from 66.4 % to 86.7 %. Enriched Thiobacillus and decreased NO 2 − reductase gene expression in SPDN/A ensured sustainable nitrite supply for Anammox process, promoting superiority of Candidatus Kuenenia to 7.3 %. However, Anammox groups decreased significantly in PN/A. Divergence in responses towards temperature fluctuation credibly concluded Anammox's correlation with temperature is not necessarily positive or parallel. Instead, stable provision of NO 2 − is primary determinant. Comprehensive analysis, integrating functional gene transcription, microbiota synergetic interactions, and kinetics underscores PN/A–SPDN/A's potential for reliable nitrogen removal, offering a sustainable solution subject to seasonal temperature fluctuation. [ABSTRACT FROM AUTHOR]

[Display omitted] • Molecular-level insight of DOM and DON were investigated in PN/A and A2O. • Transformation of DOM and DON were coupled in PN/A, while they were desynchronized in A2O. • PN/A's metabolism for bio-available and aromatic compounds was higher than A2O. • Autotrophs and heterotrophs produced DON with distinct molecular characteristics. There is limited knowledge regarding the differences and relationships in molecular composition between dissolved organic matters (DOM) and dissolved organic nitrogen (DON) in autotrophic and heterotrophic nitrogen removal processes. In this study, the composition of DOM and DON during two full-scale wastewater treatment plants (WWTPs), an autotrophic nitrogen removal with partial nitrification-anammox process (PN/A) and a heterotrophic nitrogen removal with anaerobic/anoxic/oxic process (A2O), were systematically investigated by using ultraviolet–visible spectroscopy, Excitation-Emission Matrix (EEM) and Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). The results indicated that both PN/A and A2O resulted a decrease in molecular diversity and bio-availability of DOM. However, there were distinct variations in DON between the two processes. In PN/A, transformation of DOM and DON was found to be coupled, while there was a lack of correlation observed between DOM and DON in A2O. Pearson correlation analysis revealed that transformation of DOM and DON in WWTPs was associated with microbial roles. During biotreatment, PN/A exhibited a higher metabolic capacity for degrading high bio-available and high aromatic compounds compared to A2O. The autotrophic nitrogen removal unit in PN/A resulted in an increase in molecular weight (MW) of DON, as well as a decrease in bio-availability and unsaturation degree of DON. Therefore, autotrophic nitrogen removal unit may have a positive influence on control of eutrophication and disinfection by-products (DBPs) formation. This study improved the understanding of molecular composition and relationship between DOM and DON, as well as microbial roles on DON transformation within autotrophic and heterotrophic nitrogen removal processes. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel DPR-PDA process was initiated with fully ordinary suspended sludge. • The deep removal of N and P without aeration was achieved under COD/TN of 1.8. • Candidatus_ Brocadia was enriched from 0.01% to 1.86% by prolonging anoxic stage. • The effluent TN and TP were 0.9 and 0.2 mg/L with influent of 106.0 and 1.4 mg/L. Partial Denitrification coupled with Anammox (PDA) process was used as for nitrogen removal from wastewater. However, the phosphate removal still relies on chemical methods in wastewater treatment plants. Denitrifying Phosphorus Removal (DPR) process allows phosphorus uptake under anoxic conditions using nitrate (NO 3 −) as electron acceptor. In this study, the PDA and DPR processes were successfully coupled into a novel integration (DPR-PDA) for co-treatment of simulated domestic wastewater and NO 3 − wastewater to achieve simultaneous nitrogen and phosphorus removal. The effluent TN and TP were 0.9 and 0.2 mg/L during phase Ⅵ (day450-513) under influent COD/TN of 1.8, respectively. Anammox bacteria was self-enriched in this fully suspended sludge system, with abundances increasing from undetected at day19 to 2.0 × 1010 copies/g dry sludge at day468. Anammox bacteria was effectively retained and was responsible for the main nitrogen removal, accompanied by increasing activity up to 3.1 mg N/g VSS/h. Batch tests demonstrated that denitrifying polyphosphate accumulating organisms exhibited DPR capacity immediately after the introduction of NO 3 −, but not after the introduction of nitrite (NO 2 −) only. Candidatus_Competibacter with endogenous denitrification ability was enriched from 13.30 % to 35.42 %, which coexisted with anammox bacteria stably. The novel DPR-PDA process is a promising technology for simultaneous removal of nitrogen and phosphorus with low carbon demand and without aeration. [ABSTRACT FROM AUTHOR]

[Display omitted] • Double Anammox was developed on multiple-autotrophic NO 2 − supply. • Instability NO 2 − supply and excessive nitrate residue are comprehensively addressed. • High-efficient nitrogen removal efficiency of 97.8% was obtained with Anammox contributing up to 72.4%. • PN/A-SPDN/A exhibit significant economic and environmental benefits. Anammox holds significant promise as a next-generation technology for achieving energy-positive wastewater treatment. However, its application remains challenging due to unstable nitrite supply and excessive nitrate residue. To address this, a groundbreaking Anammox bioprocess incorporating a double nitrite autotrophic shunt was developed within single system to realize energy-efficient nitrogen removal from wastewater. Partial nitrification/Anammox converted a portion of ammonia in leachate to nitrogen gas in oxic stage. Significantly, sulfur-driven partial denitrification utilizing sulfide as electron donor, efficiently reduced generated nitrate to nitrite in subsequent anoxic stage, facilitating nitrite reutilization via Anammox and removing residual ammonia. Over 200-day monitoring, bioprocess demonstrated desirable effluent quality with 9.0 mg/L NH 4 +-N, 0.6 mg/L NO 2 −-N, and 6.2 mg/L NO 3 −-N. Delightedly, efficient nitrogen removal efficiency of 97.8 % was achieved even under fluctuation conditions. Priority position held by Anammox consortium (Candidatus Kuenenia 11.2 %) mainly derives from similar growth rate of autotrophic bacteria within their shared ecological niche and stable nitrite supply, enabling Anammox to contribute impressive 72.4 % of nitrogen removal. By combing electron flow preference kinetic, stability toward fluctuation, core microbial community, the ecological niche of Candidatus Kuenenia and self consistent logic governing functional microorganisms were revealed. The cost-effective system exhibited significant advantages over conventional bioprocess, reducing organic matter demand by 100 %, aeration energy consumption by 61.7 %, and biomass production by 82.9 %. [ABSTRACT FROM AUTHOR]

[Display omitted] • Seawater shock impacts anaerobic P release less than aerobic P uptake in EBPR. • Seawater shock reduced glycogen metabolism of PAOs by excluding intracellular Mg2+. • Butyrate optimized the adaptability of Accumulibacter to seawater conditions. • Seawater shock restricted protein synthesis and esterase metabolism. • Anaerobic PHH synthesis enhanced aerobic stability of clade IIF under seawater shock. In enhanced biological phosphorus removal (EBPR) systems, seawater intrusion may introduce uncertainty into the metabolism of Polyphosphate Accumulating Organisms (PAOs), especially when volatile fatty acid (VFA) profiles derived from fermentation liquids serves as the carbon source. This study investigated the impacts of varying sea salt salinity levels on the metabolism of Accumulibacter with different VFA as carbon sources. As sea salt salinity increased from 0.5 % to 3.5 %, catabolism (phosphorus release, glycogen and PHA biodegradation) was inhibited to a much lower degree compared to anabolism (phosphorus uptake, glycogen and PHA synthesis). Under seawater conditions, the intracellular free Mg2+ was partially excreted, leading to a subsequent reduction in glycogen metabolism and PHA synthesis. The decrease in PHA synthesis resulted in the diminished aerobic metabolic activity and polyphosphatase (PPX) enzyme activity, collectively causing decreased phosphorus uptake. Moreover, additional energy consumption was used to alleviate osmotic stress, which limited the energy used for esterase activity, translation activity, and phosphorus and glycogen metabolism, resulting in a decrease in growth activity. When using butyrate as a carbon source, Accumulibacter exhibited the highest metabolic activity (49.8 %), making it more adaptable to seawater conditions. The clade IIF was the dominant Accumulibacter in seawater conditions and could synthesize more PHA with butyrate, isobutyrate and valerate as a carbon source, respectively, stabilizing aerobic metabolism. Therefore, fermentation liquid containing high concentrations of butyrate and the activated sludge dominated by clade IIF have the potential to enhance the stabilization of EBPR systems in wastewater treatment plants infiltrated by seawater. [ABSTRACT FROM AUTHOR]

[Display omitted] • Excellent N and P removal were achieved at the nitrite concentration of 20 mgN/L. • Tet2-892 clade was main DPR bacteria with nitrite as electron acceptor. • Threonine and phenylalanine were the main intracellular metabolites for DPR. • Intracellular metabolism and bioactivity were inhibited by FNA at 12.8 µgHNO 2 -N/L. • Tet2-892 clade was more tolerant to FNA compared to Accumulibacter and GAOs. Tetrasphaera has been identified as the main polyphosphate-accumulating organism (PAOs) in enhanced biological phosphate removal (EBPR), but the ability of Tetrasphaera to use nitrite as electron acceptor for denitrifying phosphorus removal (DPR) is still unclear. This study investigated the DPR performance and mechanism, microbial structures, and FNA inhibition of Tetrasphaera -dominated culture in the long-term acclimatization at different nitrite concentrations (10, 20, 40 and 50 mgN/L). The results showed that the most optimal influent nitrite concentration was 20 mgN/L (C/N = 6), and the removal efficiency of nitrite and phosphorus reached above 90 % and 95 %, respectively. Fluorescence In Situ Hybridization-Flow Cytometry (FISH-FCM) showed that the population abundance of Tetrasphaera was 80.95 %, in which Tet2-892 clade was the most abundant and mainly responsible for DPR with nitrite as electron acceptor. When the nitrite concentration reached 50 mgN/L (FNA = 12.80 µgHNO 2 -N/L, pH = 7.0 ± 0.1), electron supply deficiency and FNA inhibition resulted in only 43.0 % and 68.4 % of nitrite and phosphorus removal efficiency, respectively. The intracellular amino acid and glycogen metabolism were inhibited by FNA under this condition. A significant accumulation of N 2 O was observed, resulting from a combination of the insufficient electron supply, absence of nos-Z gene, and long-term FNA inhibition. DPR dominated by Tetrasphaera with appropriate nitrite as electron acceptor provides a new way to achieve nitrogen and phosphorus simultaneous removal. In addition, this study found that Tet2-892 clade of Tetrasphaera was more tolerant to FNA compared to Accumulibacter and GAOs, which provides a strategy for inhibiting GAOs activity to maintain the stability of the EBPR system. [ABSTRACT FROM AUTHOR]

[Display omitted] • Co-fermentation liquid provided abundant VFAs as carbon source. • Co-fermentation liquid promoted the NAR to 99.07% to notably save energy. • The NRE of the PNED system reached 98.53% by enhancing endogenous denitrification. • The co-fermentation reactor could achieve a sludge reduction ratio of 21.72%. • The cooperative mechanism of HNADB, DGAOs and AOB in the oxic stage was revealed. In mature landfill leachate with high ammonia nitrogen and extremely low biodegradable organic matter, it is difficult to achieve advanced nitrogen removal through traditional nitrification–denitrification processes. In this study, a low- carbon/nitrogen mature landfill leachate treatment process with an anaerobic/oxic/anoxic strategy was constructed by inputting co-fermentation liquid of corn straw and excess sludge. Under the effect of the co-fermentation liquid, partial nitrification was enhanced. Meanwhile, with the cooperation of the heterotrophic nitrification-aerobic denitrification process, the nitrite accumulation ratio and simultaneous nitrification and denitrification ratio reached 99.07 ± 0.52% and 23.26 ± 1.02%, respectively. The carbon source from the co-fermentation liquid was efficiently converted into polyhydroxyalkanoates, which could drive endogenous denitrification to achieve advanced nitrogen removal. The nitrogen removal efficiency in this system reached 98.53 ± 1.21%. In addition to effectively supplying carbon sources, the co-fermentation reactor also achieved a sludge reduction ratio of 24.78 ± 1.68%. Through metagenomic analysis, the cooperative mechanism by which denitrifying glycogen-accumulating organisms, heterotrophic nitrifying-aerobic denitrifying bacteria and ammonia-oxidizing bacteria achieve nitrogen removal and nitrite accumulation in oxic stage was revealed. This study provides a new and efficient treatment process for mature landfill leachate and sludge reduction. [ABSTRACT FROM AUTHOR]

[Display omitted] • Efficient nitrite production with high PD activity was achieved even at an influent nitrate of 800 mg N/L. • P removal initially increased with influent nitrate, but decreased with further increments beyond 400 mg N/L. • High Ca had minor effect on nitrite production, but facilitated P removal with maximum efficiency of 96.9% achieved. • PD-HAP granules tended to disintegrate at nitrate >400 mg N/L, while good settleability still obtained. • Controlling pH levels is expected to enable high-efficiency nitrite production and P removal from high-nitrate wastewater. This study introduces a novel PD-hydroxyapatite (HAP) coupled granular sludge process that efficiently produces nitrite while also addressing the issue of phosphorus (P) removal. Three laboratory-scale sequencing batch reactors (SBRs) were operated with varying calcium (Ca) concentrations, the performance of nitrite production, P removal, and the characteristics of PD-HAP granules under increasing nitrate concentrations (200–800 mg N/L) were investigated. Results demonstrated an increase in nitrite production with influent nitrate, with high PD activity maintained even in the presence of elevated nitrite levels. P removal improved as influent nitrate increased to 400 mg N/L but declined thereafter, likely due to the elevated pH promoting carbonate formation, which competed with phosphate for Ca2+. Supplying a higher Ca2+ concentration improved P removal, with R3 achieving a maximum removal efficiency of 96.9% at an influent nitrate of 400 mg N/L, surpassing R2 (85.7%) and R1 (70.0%). Additionally, it was observed that PD-HAP granules increased in size with higher nitrate concentrations but turned to be disintegrated with small granules formed when nitrate exceeded 400 mg N/L. However, despite this, the granules still maintained good settleability, with only a slight increase in sludge volume index (SVI 5) from 14.8 to 25.9 ml/g MLSS. This study demonstrated the tremendous potential of PD-HAP granular sludge process for treating high-nitrate wastewater in combination with anammox. [ABSTRACT FROM AUTHOR]

[Display omitted] • The BTF achieved a selectivity of S–S0 of 89.5% with high O 2 /H 2 S of 1.8–2.1. • A S0-producing bacterium– Mycobacterium (79.2%) was enriched under pH < 1.0. • Myobacterium possesses S0–synthesis gene but lacks S0–oxidation genes, resulting in S0 accumulation. • The pathways of sulfur metabolism under different pH conditions were revealed. In the gas biodesulfurization process, converting sulfides into elemental sulfur (S0) for reuse holds significant environmental, economic, resource, and social values. While the influence of pH on microbial community structure and enzyme activity is recognized, its effect on S0 yield has been underestimated. This study delves into how pH fluctuations affect the S0 yield in a biodesulfurization system. Under extremely acidic condition (pH < 1), the selectivity of S0 reached 90% even at high O 2 /H 2 S supply ratio of 1.8–2.1. Metagenomic analyses showed that as the pH decreased from neutral–alkaline to extremely acidic range, the dominant bacterium gradually shifted from Acidithiobacillus (37.0%), Acidiphilium (1.5%) and Thiomonas (1.2%), which possess complete sulfur metabolism (from sulfide to sulfate) genes, to Mycobacterium (79.2%) possessing the S0–synthesis gene (sqr) without the S0–oxidizing genes (ETHE1 , sor , hdr , dsr and the Sox and S 4 I complex genes), resulting in a robust S0 yield in extremely acidic period. Various pathways for respiratory sulfur oxidation were present in different pH periods. The extremely acidic condition facilitated the selection of specific microorganisms by creating a highly selective environment, promoting the growth of acidophilic or acid-tolerant microorganisms with unique traits and altering the sulfur–metabolic pathways. These finding filled a knowledge gap regarding the impact of pH on sulfur–metabolic pathways and offered a new strategy for gaining S0. [ABSTRACT FROM AUTHOR]

• Completely 3D perovskite films without 2D phase were fabricated. • The BDACl 2 -based PSCs achieves a maximum PCE from 22.47% to 24.12%. • The BDACl 2 -based PSCs retained over 80% initial PCE after 1500 h of operation. Bulk alkyl ammonium salt additives can significantly improve the stability of perovskite solar cells (PSCs) by forming 2D perovskite structures. However, these ammonium salts form organic interlayers impairing device efficiency. We doped the perovskite precursor with 1,4-butanediamine dihydrochloride (BDACl 2) with a concentration that is low enough (BDACl 2 :FAI ≤ 1.0 mol %) not to form 2D perovskite. It is found that BDACl 2 doping promotes grain growth and reduces the defect density, thus improving the crystalline quality of the perovskite films, resulting in an increase in PSCs device efficiency from 22.47% to 24.12%. More importantly, BDACl 2 can effectively inhibit the transition from α-phase to δ-phase of FAPbI 3 under operation. Therefore, PSCs retained more than 80% of their initial PCE after nearly 1500 h of operation with maximum power point tracking under simulated white light illumination in a nitrogen glove box, whereas the control cell without BDACl 2 modification showed PCE decay of over 58% after aging for the same time. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • DEAMOX maintained stable performance for high-strength NO 3 −-N and NH 4 +-N removal. • TN removal efficiency achieved 96.7% with both NO 3 −-N and NH 4 +-N over 800 mg L−1. • Step-feed of organic carbon significantly improved NO 2 −-N production in PD process. • Anammox bacteria was more tolerant to NO 2 −-N in DEAMOX system than single anammox. • Functional groups cooperated stably with anammox responsible for 88.9% TN removal. Abstract The innovative DEnitrifying AMmonium OXidation (DEAMOX) process, coupling partial-denitrification (PD) with anammox, was designed for treating high-strength nitrate (NO 3 −-N) and ammonia (NH 4 +-N) wastewater for the first time. With influent total nitrogen (TN) up to 1600 mg L−1 (NO 3 −-N/NH 4 +-N of 1.0), DEAMOX process proved to be relatively stable for simultaneously removing NO 3 −-N and NH 4 +-N. The step-feeding organic carbon (OC) demonstrated as an efficient strategy for avoiding NO 2 −-N consumption by denitrification, facilitating the increased of NO 3 −-N to NO 2 −-N transformation ratio (NTR) to 99% at COD/NO 3 −-N of 1.77. The TN removal was significantly enhanced to 96.7% with the considerably high anammox contribution of 88.9%. Also, the inhibitory effect of high NO 2 −-N accumulation on denitrifying bacteria could be mitigated. High-throughput sequencing revealed a relatively stable cooperation of functional groups in DEAMOX system. Genus Thauera possibly capable of NO 2 −-N accumulation remained dominant (39.81% to 44.09%), while Candidatus Brocadia responsible for anammox was detected with much lower percentage (2.01% to 1.81%). Results of qPCR confirmed the evident growth of anammox bacteria under increasing nitrogen and organic loading. The DEAMOX process offers a significantly stable and efficient method in treating high-strength NO 3 −-N and NH 4 +-N wastewater. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • A novel process combined SPNA with modified DPR in two SBRs was established for treating ammonia and domestic wastewaters. • Under low DO condition, SPNA contributed to ∼90% NH 4 +-N removal from ammonia sewage (70–200 mg·L−1). • DPR achieved ∼70% PO 4 3−-P removal from domestic wastewater using the generated NO 3 –-N by SPNA. • Post SNEDPR further reduced ∼30% PO 4 3−-P and ∼70% NH 4 +-N contained in domestic wastewater. • The average final effluent TN and PO 4 3−-P concentrations were 5.0 and 0.2 mg·L−1, respectively. Abstract A novel process combined simultaneous partial nitrification-anammox (SPNA) with modified denitrifying phosphorus removal (DPR) in two sequencing batch reactors (terms as SPNA-SBR and mDPR-SBR) was proposed for treating ammonia (NH 4 +-N) and domestic wastewaters. Firstly, NH 4 +-N contained wastewater was fed into SPNA-SBR for autotrophic nitrogen removal. Meanwhile, domestic wastewater was introduced to mDPR-SBR for anaerobic phosphorus release and intracellular carbon storage. Then, nitrate (NO 3 –-N) produced in SPNA-SBR was discharged to mDPR-SBR, where NO 3 –-N was reduced to dinitrogen gas (N2) via anoxic denitrifying phosphorus removal. Finally, the residual NH 4 +-N and PO 4 3−-P in mDPR-SBR were removed via aerobic simultaneous nitrification, endogenous denitrification and phosphorus removal (SNEDPR). The long-term operation (235-day) suggested that a desirable nutrient removal performance was achieved in the SPNA-mDPR process, and the final effluent NH 4 +-N, total nitrogen and PO 4 3−-P concentrations were 1.5, 5.0 and 0.2 mg·L−1, respectively. In the SPNA-SBR, SPNA contributed to ∼90% of NH 4 +-N removal at low aeration intensity (dissolved oxygen (DO): 0.1 mg·L−1); in the mDPR-SBR, ∼70% of PO 4 3−-P and ∼100% of NO 3 –-N were simultaneously removed via anoxic DPR, and post-aerobic SNEDPR further reduced ∼30% of PO 4 3−-P and ∼70% of NH 4 +-N. Stoichiometry-based microbial activity analysis demonstrated that, in the mDPR-SBR, high activity of denitrifying phosphorus accumulating organisms (DPAOs) over denitrifying glycogen accumulating organisms (DGAOs) in anoxic NO 3 –-N removal (71.1% > 28.9%) facilitated DPR, and high percentage of SNEDPR via nitrite (89.6%) over nitrate saved 52% intracellular carbon demand to realize the deep-level nutrient removal without external carbon addition. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Partial nitrification-anammox process was started up without adding anammox sludge. • Anammox reaction could be the primary nitrogen removal pathway in the reactor. • Reactor could efficiently treat low-strength and low C/N ratio domestic sewage. • Sequencing batch biofilm reactor was stable even at low temperatures (<15 °C). Abstract In this study, enhanced removal of nitrogen from real domestic wastewater with low organic carbon to nitrogen ratio of 2.1–3.6 was achieved in a sequencing batch biofilm reactor (SBBR) with enriching anammox bacteria in situ. The SBBR was inoculated with ordinary nitrification sludge and operated under alternative anaerobic, aerobic and anoxic patterns. During the start-up period, influent nitrogen and carbon loading rate gradually increased. According to the quantitative microbial analysis, the growth of ammonium oxidizing bacteria and anammox bacteria were promoted, resulting in an increase from 6.56 × 104 to 1.51 × 107 and from 1.11 × 104 to 1.69 × 106 gene copies·mL−1, respectively. During the steady period (Day 102–205), nitrogen removal efficiency of 88.2% was achieved with an effluent total nitrogen of 6.3 mg N·L−1 for average influent ammonium of 53.9 ± 4.0 mg·L−1. Nitrogen removal was steady when temperature decreased from 27.0 to 12.8 °C. Variations in nitrogen compounds suggested that anammox reaction could be the main pathway for nitrogen removal, according to the results of activity batch and continuous tests. For the high nitrogen removal performance, biofilm and post-anoxic unit could play important roles. Overall, this study provided an alternative method to improve the removal of nitrogen from sewage by directly enriching anammox bacteria. [ABSTRACT FROM AUTHOR]

[Display omitted] • Anammox coupled with partial denitrification enhanced to nitrogen removal above 55%. • Ultra-high abundance of Ca. Brocadia (5.5, 6.5%, 5.8%) in connected anoxic biofilms. • Ca. Brocadia sapporoensis is acetate-resistant, explaining its high enrichment in biofilms. • Anammox activity increased with decreasing denitrifying activity along anoxic zones. For municipal wastewater treatment via partial-denitrification/anammox (PD/A) in the anoxic zone, the primary challenge is effective enrichment of anaerobic ammonium oxidation (anammox) bacteria with a stable autotrophic nitrogen removal performance. This long-term study investigated a pure-biofilm anoxic/oxic reactor using real municipal wastewater with an ammonia concentration of 49.1 ± 3.6 mg N/L, achieving a total inorganic nitrogen concentration of 11.2 ± 3.5 mg N/L in the effluent, resulting in a removal efficiency of 77.4 ± 7.2%. Driven by partial denitrification, the anammox contribution to total nitrogen removal represented an ultra-high level over 55%, and was considerable in the first anoxic zone. Candidatus Brocadia, the only anammox genus detected by 16S rRNA gene sequencing, reached robust abundances of 5.46, 6.49 and 5.79% in the three sequentially connected anoxic zones. Metagenomic sequencing further identified that the main species was Ca. Brocadia sapporoensis, which is inhibited by nitrite but not by acetate, supporting its high-level enrichment under acetate conditions in the anoxic zone. Batch tests indicate that heterotrophic denitrification activity decreased while anammox activity increased along the anoxic zones, and that excessive heterotrophic denitrifying activity was not conducive to increasing the anammox contribution. This study achieved robust anammox bacterial abundance using a pure-biofilm system, shedding fresh light on the application of mainstream anammox in municipal wastewater treatment. [ABSTRACT FROM AUTHOR]

[Display omitted] • The UDLA system based on the PNAPD process was set up to treat landfill leachate. • TINRE was 92.9 ± 1.5% and isotope tests showed 88.2–93.9% of TIN removed by anammox. • The share of medium granules with the highest PNAPD activity increased to 24.9%. • Brocadia (15.7–16.0 %), Kuenenia (2.0–4.8 %), and Jettenia (0.2–0.8 %) were highly enriched. • Up-flow effluent and produced gas dual-loop strategy favored anammox granules formation. Achieving the effective retention and rapid enrichment of anammox bacteria (AnAOB) remains a challenge in landfill leachate treatment systems. The application of the anammox process is also restricted by an inadequate supply of nitrite and poor resistance to adverse environments. To overcome these obstacles, an up-flow dual-loop anammox (UDLA) system treating mature landfill leachate was established, based on partial nitrification, anammox, and partial denitrification (PNAPD) technology. The nitrogen removal efficiency and nitrogen loading rate reached 92.9 ± 1.5% and 0.4 kg N/m3/d, and isotope tracing tests demonstrated that 88.2 ± 6.5%-93.9 ± 3.9% of the nitrogen loss contributed by anammox pathway. Under the up-flow dual-loop strategy, anammox granules were successfully cultivated when flux ratios of effluent/influent and produced gas/influent were maintained at 1640.0%, and 250.0%, respectively. The proportion of medium granules (500–1000 μm) with the highest PNAPD activity increased from 0 to 24.9%, whereas the percentage of floc (0–200 μm) reduced from 98.4% to 23.3%. The mechanism of anammox granules formation in the UDLA system was revealed by multidimensional analysis. Candidatus_Brocadia_sapporoensis (13.3%-13.5%), Candidatus_Kuenenia_stuttgartiensis (2.0%-4.8%), and Candidatus_Brocadia_sp. (0.9%-1.1%) were the predominant anammox species, enriched in medium and macro granules. Metagenomic sequencing confirmed the functional divergence of nitrogen and carbon metabolism among the size-fractioned granules, possible functions of specific species, and gene distribution in the nitrogen metabolism pathway. The abundant GlnA, GltB(D), GdhA, GudB (GDH2), and GLUD1_2 genes might promote the synthesis of adhesive proteins and further facilitate microbial aggregation. This study enhanced the comprehension of anammox granules formation and showed important implications for leachate treatment in engineering. [ABSTRACT FROM AUTHOR]

[Display omitted] • Domestic sewage & PNA-treated reject water are polished to 4.5 mg/L by anoxic PDA. • External COD supply is finally canceled profiting by enhanced sewage utilization. • Clustered anammox bacteria in compact granule strengthen performance and robustness. • Uronic acid and special protein in EPS promote granulation and pollutant adsorption. • Orderly activated Thauera , Brocadia , Competibacter in PDA cycle coordinate N removal. Partial denitrification/anammox (PD/A) has been recently applied to co-treat domestic wastewater and nitrate-containing anammox effluent. However, studies regarding its performance without external organic supplement, spatial characteristics within sludge aggregates, and chronological changes of active microorganisms along PD/A cycle have rarely been reported. Herein, one-stage PD/A unit extremely and simultaneously polished anammox-pretreated reject water (NH 4 +-N: 65.4 ± 5.7 mg/L, COD: 199.7 ± 23.2 mg/L) and domestic wastewater (NO 3 −-N: 81.6 ± 7.8 mg/L, TN: 85.8 ± 8.9 mg/L, COD: 338.2 ± 29.0 mg/L) to 4.5 ± 2.1 mg/L without external organic carbon supply. Protective "granules-in-granule" aggregates with densely clustered anammox bacteria embedded in homogeneous denitrifying Thauera prevailed in PD/A system, surviving disadvantages from complex wastewater. Uronic acids and β-sheet proteins in outer extracellular matrix facilitated granulation and pollutants adsorption, while tryptophan- and aromatic-like proteins with tighter secondary structure in inner extracellular matrix maintained granular robustness. Importantly, succession of active microorganisms along the PD/A cycle was revealed by transcript-level analysis for the first time. In PD-period, stimulated Thauera contributed to rapid nitrite accumulation. In subsequent anammox-period, Ca.Brocadia was activated to conduct advanced nitrogen removal, which accompanied the timely nitrate-to-nitrite reduction by Thauera and Ca.Competibacter. Elusimicrobia was active throughout the PD/A cycle, which is conducive to eliminate the dependence of PD process on external carbon source by decomposing complex organics in actual wastewater. Protective granular structure, orderly activation and harmonious cooperation of functional consortia facilitated practical nitrogen removal rate of 0.6 ± 0.1 kg-N/m3/d under anoxic condition, which sheds light on engineering application of anammox technology. [ABSTRACT FROM AUTHOR]

[Display omitted] • Complete nitrogen removal was achieved treating actual low C/N (2.8) sewage. • The double nitrite shunt from PN and EPD guaranteed the thorough anammox reaction. • ED and DPR pathways jointly contributed 37% to TIN removal via nitrate respiration. • Coexistence of enriched AnAOB, GAOs and DPAOs favored co-metabolism stability. • Directional transfer of electrons and substrates radically supported superior performance. Autotrophic nitrogen removal processes based on anammox are facing huge challenges of high effluent quality in wastewater treatment. In this study, a novel hybrid system of anammox coupled with heterotrophic endogenous metabolisms was developed in a single-stage bioreactor to treat real domestic wastewater. Complete nitrogen removal was achieved at a low carbon to nitrogen (C/N) ratio of 2.8 and more than 95.2% nitrogen removal was maintained under an extremely low C/N ratio of 1.9. The nitrite shunt supplied by dual partial pathways (partial nitritation and endogenous partial denitratation) guaranteed the anammox activity with a high contribution to nitrogen removal above 60%. While endogenous denitrification (ED) and denitrifying phosphorus removal (DPR) both participated in nitrate respiration, contributing more than 28% and 9% to nitrogen removal, respectively. The coexistence and enrichment of anammox bacteria (Ca. Brocadia, 0.9%), glycogen accumulating organisms (Ca. Competibacter, 6.4%) and phosphorus accumulating organisms (Dechloromonas , 3.9% and Ca. Accumulibacter, 0.7%) contributed to the co-metabolism of carbon, nitrogen and phosphorus. The functional genes encoding the above metabolism were highly correlated with the dominant strains, indicating that the multiple pathways of carbon and nitrogen metabolism supported the continuous supply of electrons required for nitrogen removal. This study puts forward a novel complete nitrogen removal process by successfully coupling autotrophic and endogenous heterotrophic metabolism. [ABSTRACT FROM AUTHOR]

• A favorable preparation strategy toward FeP/Fe 2 P heterostructure is proposed by regulating the calcination temperature of phosphating process. • Deciphering the role of energy gap between cation 3d and anion 2p band in regulating the adsorption and catalysis of polysulfides. • The charge migration and an internal electric field of FeP and Fe 2 P are induced after reaching a thermodynamic equilibrium state. Exploring advanced electrocatalysts and understanding their mechanism in regulating polysulfides-transformation is of great importance but a challenging task for lithium-sulfur batteries (LSBs). Herein, FeP/Fe 2 P heterostructure nanoparticles with an internal electric field, prepared by a temperature-controlled phosphating process, can effectively improve the electrocatalytic activities of the bidirectional Li 2 S deposition/dissolution. This improvement can be attributed to the modulating absorptivity of lithium polysulfides (LiPSs) and propelling charge transfer. The reduced d-p band center between bonding and antibonding orbitals of the Fe 3d and P 2p band in the heterostructure enables bonding with LiPSs to achieve a higher electronic concentration at the Fermi level. This regulates the adsorption-diffusion-conversion process, reduces the activation energy, and improves the Li+ diffusion. Benefiting from the boosted kinetics of the FeP/Fe 2 P heterostructure, the cells exhibit a high reversible capacity of 1412 mAh g−1 at 0.1 C and outstanding energy efficiency of ∼ 90% from 0.1 C to 2 C. Furthermore, the cell with high sulfur loading of 4 mg cm−2 demonstrates a high capacity of 786 mAh g−1 after 100 cycles at 0.5 C. This work presents an effective method and favorable guidance for developing advanced heterostructures in LSBs. [ABSTRACT FROM AUTHOR]

Bottleneck issues such as difficult biofilm culturing, time-consuming granular formation and excessive nitrate production, always limited the application of anammox processes. By using the common but meaningful suspended activated sludge instead of biofilm or granule activated sludge, a combined anammox process, simultaneous partial nitrification, anammox and denitrification (SNAD), was established in a sequencing batch reactor (SBR) in this study to treat real domestic sewage and was operated for 300 days. Results indicated that a high ammonia removal rate and nitrogen removal rate (1.1 and 1.03 (kgN/(m 3 ·d)), respectively) were achieved during the baseline phase treating high ammonia wastewater (350–550 mg/L). During the experimental phase treating domestic sewage with a C/N of 3–3.5, 86.1% of total nitrogen removal efficiency was achieved and only 1.02 mg/L of nitrate concentration was detected in the effluent with an averagely 64.6 mg/L of ammonium in the influent. Nitrogen mass balance analysis demonstrated that about 89% of total nitrogen (TN) was removed by anammox and the remaining 11% of TN was removed by denitrification. Bacterial abundance of Candidatus Brocadia and Thauera increased from 0.02% to 0.5% and 0.39% to 2.24% (from baseline phase to experimental phase), respectively, which made an essential contribution to the nitrogen removal. The advanced nitrogen removal performance reached in the SNAD process showed the possibility of using suspended sludge as a substitute of biofilm and granule sludge concerning anammox, and the process could treat real domestic sewage with a C/N of 3–3.5 without pretreatment of chemical oxygen demand (COD). [ABSTRACT FROM AUTHOR]