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[Display omitted] • Two-stage N-PDA was firstly used to co-treat acrylic fiber wastewater and sewage. • N-SBR achieved efficient nitrification under refractory organic stress (ARE=100 %). • PDA-UASB exhibited robust PDA by organic carbon source from domestic sewage. • NRE was up to 87 % to co-treat sewage and acrylic wastewater (66.3 and 91.7 mg/L). • The relative abundance of Candidatus Brocadia increased from 0.6 to 5.4 %. Acrylic fiber (AF) wastewater is characterized by high levels of ammonia nitrogen, refractory organic compounds, and toxic substances, making biological nutrient removal challenging. Conventional biological treatment technologies are often ineffective due to the complex composition, high toxicity, and low C/N ratios of AF wastewater. In this study, a two-stage nitrification-partial denitrification/anammox (N-PDA) process was firstly developed for the combined treatment of AF wastewater and domestic sewage, which integrated nitrification-SBR(N-SBR) and partial denitrification/anammox-UASB (PDA-UASB). The N-SBR achieved stable nitrification (ARE=100 %, HRT=4.2 h) with increasing ratios of AF wastewater, while the PDA-UASB utilized organic carbon from domestic sewage to simultaneously remove nitrate (91.7 mg/L) and ammonium (66.3 mg/L) through the PDA pathway (HRT=11.3 h). After 200 days, the relative abundance of Candidatus Brocadia increased from 0.6 to 5.4 %, ensuring robust nitrogen removal performance. The system achieved effluent ammonium and total nitrogen concentrations below 1.0 mg/L and 15.0 mg/L, respectively, with a total nitrogen removal rate of 87 %. This study demonstrates the N-PDA process as an efficient, energy-saving, and cost-effective solution for treating AF wastewater without the additional organic carbon sources, enhancing nitrogen removal efficiency and operational stability. [ABSTRACT FROM AUTHOR]

[Display omitted] • Mainstream PD/A was achieved in 300L plug-flow reactor to treat municipal sewage. • Effluent TN of 8.84 mg/L with the TNRR of 76.4 % under C/N ratio below 3. • Long anoxic HRT and introducing nitrite improve AnAOB abundance around 10 times. • The contribution of anammox to nitrogen removal gradually increased to 68.8%. • This study could achieve simultaneous nitrogen removal of side- and mainstream. Mainstream partial denitrification anammox was achieved through inoculation of side-stream mature partial nitritation anammox biofilm without domestication. The contribution of anammox to nitrogen removal was 29.4 %. Moreover, prolonging anoxic hydraulic retention time and introducing side-stream nitrite under different carbon/nitrogen ratios enriched anammox bacteria. The abundance of anammox bacteria increased by ∼ 10 times ((2.19 ± 0.17) × 1012 copies gene / g dry sludge) with a total relative abundance of 18.51 %. During 258 days of operation, the contribution of anammox to nitrogen removal gradually increased to 68.8 %. The total nitrogen in the effluent decreased to 8.84 mg/L with a total nitrogen removal efficiency of 76.4 % under a carbon/nitrogen ratio of 3. This paper proposes a novel way to rapidly achieve mainstream partial denitrification anammox via inoculation with side-stream mature partial nitritation anammox biofilm. This method achieves advanced nitrogen removal from municipal wastewater, even under low carbon/nitrogen ratios. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • The feasibility of achieving mainstream EPD-Anammox was first demonstrated. • Around 90% of nitrogen removal was achieved with a low C/N (∼2.9). • Nitrogen removal via anammox accounted for 49.8%, reducing oxygen and carbon demands. • An appropriate NO 2 −-N/NH 4 +-N (∼1.2) was achieved without complex control process. • Denitrifying GAOs (36.6%) were responsible for the high nitrite accumulation. Abstract Successful application of mainstream anammox would be favorable for energy- and resource-efficient sewage treatment. This study presents a new strategy to achieve mainstream anammox, which combined with endogenous partial denitrification (EPD) for treating sewage wastewater. In this EPD-Anammox system, nitrite was stably produced by EPD with a nitrate-to-nitrite transformation ratio of 80%. Through adjusting the volume exchange ratio of EPD-reactor after anaerobic reaction, a suitable NO 2 −-N/NH 4 +-N ratio of ∼1.20 for anammox reaction was achieved. Further, results showed a stable, high nitrogen removal efficiency (90%) with an effluent total nitrogen of 5.8 mg N/L under low C/N (∼2.9). Anammox contributed 49.8% of the overall nitrogen removal owing to the steady nitrite supply from EPD. Denitrifying glycogen-accumulating organisms (GAOs, 36.6%) having potential for endogenous denitrification and Candidatus Brocadia (34.6%) were respectively dominated in the EPD-SBR and anammox-UASB and responsible for the high nitrite accumulation and anammox reaction. [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]

First time, this study synthesized a magnetic-modified sludge biochar (MSBC) as an activator of peroxymonosulfate (PMS) to eliminate sulfamethoxazole (SMX). The removal efficiency of SMX reached 96.1% at t = 60 min by PMS/MSBC system. The larger surface area and magnetic Fe 3 O 4 of MSBC surface enhanced its activation performance for PMS. The PMS decomposition, premixing and reactive oxygen species (ROS) identification experiments combined with Raman spectra analysis demonstrated that the degradation process was dominated by surface-bound radicals. The transformed products (TPs) of SMX and the main degradation pathways were identified and proposed. The ecotoxicity of all TPs was lower than that of SMX. The magnetic performance was beneficial for its reuse and the removal efficiency of SMX was 83.3% even after five reuse cycles. Solution pH, HCO 3 − and CO 3 2− were the critical environmental factors affecting the degradation process. MSBC exhibited environmental safety for its low heavy metal leaching. PMS/MSBC system also performed excellent removal performance for SMX in real waters including drinking water (88.1%), lake water (84.3%), Yangtze River water (83.0%) and sewage effluent (70.2%). This study developed an efficient PMS activator for SMX degradation in various waters and provided a workable way to reuse and recycle municipal sludge. [Display omitted] • MSBC showed superior PMS activation performance in various waters. • Surface-bound radicals were the dominant reactive species inducing SMX removal. • The degradation pathways and toxicity of intermediates were proposed. • MSBC still presented stable catalytic performance after repetitive reuse. [ABSTRACT FROM AUTHOR]

This work demonstrates the feasibility of simultaneous nitrogen removal and external waste activated sludge (WAS) reutilization/reduction by using the synergy of sludge fermentation, denitrification and anammox processes in up-flow reactors (SFDA). Pre-treated domestic wastewater and synthetic wastewater (containing nitrite ∼20 mg/L, ammonium ∼10 mg/L in both) were fed to 1# and 2# SFDA, respectively. Long-term operation of 1# SFDA was investigated with achieving the peak ammonium removal rate of 0.021 and nitrite removal rate of 0.081 kg N/(m 3 d) as nitrogen loading rate elevated from 0.075 to 0.106 kg N/(m 3 d). Negative effect of dissolved oxygen on anammox or fermentation in the 2# SFDA was demonstrated negligible due to rapid depletion by microorganisms. Furthermore, a “net” sludge reduction of 38.8% was obtained due to sludge decay and organics consumption by denitrification. The SFDA process was expected to potentially be used for nitrogen removal and WAS reutilization/reduction in full-scale application. [ABSTRACT FROM AUTHOR]

[Display omitted] • In-situ biological phosphorus removal and recovery process greatly improved the abundance and activity of AOB. • Solved the contradiction of SRT between nitrogen and phosphorus removal. • NAR and PRR were stable above 90% in PNPR system. • Obtained more than 10 times influent PO 4 3--P supernatant with great recovery potential. • The average ratio of nitrite to ammonia nitrogen in the effluent was 1.96 with the treatment of real municipal wastewater. Achieving simultaneous semi-partial nitrification and deep phosphorus removal is a preferred process technology for Anammox pretreatment. In this study, semi-partial nitrification combined with in-situ phosphorus recovery (PNPR) was used to treat municipal wastewater. The SRT conflict between the nitrification and phosphorus removal was resolved by in-situ phosphorus recovery every 20 cycles of Anaerobic/Oxid, and a supernatant with more than 10 times the influent phosphorus concentration was obtained, thus achieving bio-enhanced phosphorus removal and recovery with satisfactory semi-partial-nitrification effluent. Interestingly, the results showed that phosphorus removal and recovery process could improve the activity of AOB. The PNPR system's nitrite accumulation rate (NAR) and phosphorus removal rate (PRR) were more than 90% each, whereas the relative abundance of AOB and PAOs increased from 0.04% to 0.74% and from 0.25% to 0.70%, respectively (P < 0.01). Furthermore, on average, the NO 2 –-N eff /NH 4 +-N eff value was 1.96, which laid the foundation for the subsequent anammox treatment. [ABSTRACT FROM AUTHOR]

[Display omitted] • Nitritation was stable with NAR always higher than 82% when temperature fluctuated. • Ca. Brocadia was enriched from 0.03% (20.4℃) to 0.24% (12.9℃) in suspended sludge. • Granulation was achieved in domestic wastewater system as temperature dropped. • Average particle size of sludge increased from 128.5 μm to 245.6 μm. • Relative abundance of Ca. Brocadia in granule was as high as 16.09% Low temperature is an important factor affecting the municipal wastewater treatment systems. The aim of this study was tracking the variations in the abundance of anammox bacteria (AnAOB) and the sludge form as the temperature decreased. Mutual boost of granulation and enrichment of AnAOB was achieved even though the temperature dropped from 20.4 °C to 12.9 °C. The average particle size of the sludge increased from 128.5 μm to 245.6 μm. With low dissolved oxygen (DO) aeration (0.2–0.5 mg/L) and short oxic hydraulic retention time (HRT) (5 h), nitritation in the anaerobic/oxic/anoxic (AOA) system was stable enough to provide NO 2 – for AnAOB. Ca. Brocadia , a type of typical AnAOB, was enriched from 0.03% to 0.24% in the suspended sludge and reached 16.09% in the granular sludge. Overall, this study presents the prospects of anammox and granule technologies when treating municipal wastewater at a low temperature. [ABSTRACT FROM AUTHOR]

• THP-AD filtrate was effectively polished by double-line anammox to TN of 8.8 mg/L. • Inhibition of complex organics can be alleviated with enrichment of Anaerolineae. • Enhanced organic degradability facilitated the external C/N decrease to 0.3 in PDA. • Increasing abundance of Ca.Brocadia and improved anammox activity was obtained. Anammox process has been widely regarded as an energy-efficient method for sludge digestion filtrate treatment. However, the complex high-strength organics in the filtrate, especially of Anaerobic Digestion after Thermal Hydrolysis Pretreatment (THP-AD), brings serious threat to anammox bacteria, and the high nitrate residue in effluent remains another significant barrier in operation. In this study, a novel double-line anammox-mediated system, integrating the Partial Nitrification/Anammox (PNA) with Partial Denitrification/Anammox (PDA) processes in separately sequencing batch reactors (SBRs), was developed to polish the THP-AD filtrate. When the real THP-AD filtrate (1946.5 mg NH 4 +-N/L, 2076.0 mg COD/L) was fed to the front PNA reactor (SBR PNA) with 5-fold dilution, effluent total nitrogen (TN) remained at 93.0 mg/L. Notably, the final effluent TN was effectively polished to as low as 8.8 mg/L by the following PDA reactor (SBR PDA), which was fed with the SBR PNA effluent and real domestic wastewater (71.0 mg NH 4 +-N/L, 209.1 mg COD/L). More severe inhibition on anammox activity was observed in SBR PNA rather than SBR PDA by refractory organics in filtrate. Fortunately, it could be alleviated with the enhanced degradability of particulate organics and aromatic protein-like compounds, attributed to the enrichment of class Anaerolineae in both SBR PNA and SBR PDA. This further stimulated the electron donor supply for PDA process with much lower external carbon source demand. 16S rRNA sequencing analysis revealed that Candidatus Brocadia as dominant anammox bacteria were efficiently enriched in both SBR PNA and SBR PDA , indicating its unexpected toughness and adaptability to the complex organic compounds in THP-AD filtrate. Overall, this study suggested that the novel double-line anammox would be a promising alternative for cost-efficient nitrogen removal from high-strength wastewater containing complex organic matter. [Display omitted]. [ABSTRACT FROM AUTHOR]

[Display omitted] • Achieving NAR (98%) of A n OAO reactor by continuously adding NH 2 OH in only 2 days. • Stable NAR (95%) maintained by decreasing NH 2 OH dosing with 1 day every 4 days. • TIN inf and TIN eff were 42.9 and 4.8 mg N/L at aerobic HRT (4.6 h) and DO (<1mg/L) • Advanced N-removal by real sewage with low C/N (2.8) without external carbon source. • AOB activity increased to 12.78 mg N/(g VSS∙h) while NOB decreased by 81% The NH 2 OH dosing strategy for nitrogen removal was investigated in a single return continuous-flow anaerobic/aerobic/anoxic/aerobic (A n OAO) reactor fed with real municipal wastewater. A high nitrite accumulation ratio of 98% was achieved in only two days by continuously adding 10 mg/L NH 2 OH. When gradually reducing dosing frequency to one day every four days, effluent total nitrogen was as low as 4.8 ± 2.2 mg N/L with removal efficiency of 88.7 ± 5.3%, under aerobic HRT of 4.6 h, DO below 1.0 mg/L, and C/N of 2.8 without external carbon sources. Batch test showed that nitrite oxidizing bacteria (NOB) activity decreased by 81% after adding NH 2 OH, while ammonia oxidizing bacteria (AOB) activity remained stable. qPCR confirmed that NOB abundance decreased, and 16S rRNA sequencing further showed that g_ Nitrospira belonging to NOB decreased significantly (P < 0.001). Overall, this study provides a novel strategy for advanced nitrogen removal from municipal wastewater in continuous flow systems. [ABSTRACT FROM AUTHOR]

[Display omitted] • Anammox contributed over 70% to N-removal with salinity of 0, 0.4, 0.7, and 1.0%. • Highest NRE of 81.2% and anammox contribution of 76.5% was achieved at 1.0%. • Salinity intensifies nitritation and denitratation processes further enhancing anammox. • Ca. Brocadia enriched on biofilms while Nitrosomonas enriched in suspended sludge. Saline wastewater present in municipal pipe networks poses challenges to biological nitrogen removal due to its inhibition on microorganisms. This study focuses on the effects of low salinity (0.0%, 0.4%, 0.7% and 1.0%) on a system featuring a combination of nitritation/anammox in oxic stage and denitratation/anammox in anoxic stage (double-anammox) in a step-feed SBR for municipal wastewater over a period of 130 days. The results showed that a maximum nitrogen removal efficiency of 81.2% was achieved at a salinity of 1.0% with anammox contribution of 76.5%. Analysis of anammox contribution and sludge activities discovered that low salinity promoted both nitritation and denitratation, further enhancing the coupling with anammox. Further, microbial analysis confirmed that Ca. Brocadia was enriched on biofilms from 0.21% to 0.51% and Nitrosomonas was enriched in flocs from 0.50% to 1.04%. Overall, the double-anammox process appears to be a promising method for the treatment of saline wastewater. [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]

A novel simultaneous partial nitrification, endogenous denitrification and phosphorus removal (SPNEDpr) system was operated for 213 days in a sequencing batch reactor to treat real domestic sewage. The nutrient removal was achieved under an operation mode of intermittent aeration at unequal intervals with low oxygen concentrations. Through optimizing intermittent aeration conditions, the removal efficiencies of total inorganic nitrogen (TIN), PO 4 3–P and chemical oxygen demand (COD) reached 78.40%, 98.13% and 84%, respectively. Low-oxygen (0.1–0.7 mg/L) and intermittent aeration effectively inhibited nitrite oxidation bacteria (NOB), maintaining stable partial nitrification with nitrite accumulation ratio of 96.45%. Notably, intermittent aeration promoted the formation of aerobic granular sludge, with the sludge particle size increasing from 217.2 ± 5.3 to 351.8 ± 4.8 μm, thereby enhancing the TIN loss efficiency (81.3%). The predominant genus was Candidatus_Competibacter (11.6%), which stored COD as intracellular carbon source and performed the endogenous denitrification. The SPNEDpr process provided a highly efficient and economical method for treating urban sewage. [Display omitted] • The operation mode of anaerobic-intermittent aeration was used to handle sewage. • TIN and P removal efficiency reached 78.40% and 98.13%, respectively. • Intermittent aeration promotes the formation of AGS. • Intermittent aeration conducive to the enrichment of AOB and detrimental to NOB. • Candidatus_Competibacter (11.6%) and Dechloromonas (1.98%) were the dominant genus. [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]

[Display omitted] • PN/A-PD/A was efficiently realized in typical UCT process to treat municipal sewage. • TIN in influent and effluent were 51.3 and 11.0 mg/L even with COD/TIN ratio of 2.9. • Anammox activity improved from 6.52 to 9.68 mg NH 4 +-N/gMLSS/d with abundance raised. • Anammox contributed 47% for NRE with two coupled ways for continuous supply of NO 2 –. Improving contribution and nitrogen removal efficiency (NRE) of partial anammox in municipal wastewater is a researching hotspot. This study developed an innovative PN/A-PD/A process with fixed biocarriers in anaerobic/anoxic chambers for actual sewage treatment in a typical step-feed reactor over 390 days. Two coupled pathways providing continuous NO 2 – (partial nitrification in oxic chambers and partial denitrification in anaerobic/anoxic chambers) for anammox were introduced to the process, achieving 47% nitrogen loss by anammox in stable phase. The influent and effluent total inorganic nitrogen (TIN) were 51.3 and 11.0 mg/L, respectively, even with chemical oxygen demand (COD)/TIN ratio of 2.9. Anammox activity improved from 6.52 to 9.68 mg NH 4 +-N/gMLSS/d and abundance on the biocarriers raised to 3.16 × 1010 gene copies/g dry sludge. Overall, this study confirmed partial anammox, spatially coupled with partial nitrification and partial denitrification via oxic/anoxic distribution with step feed mode, as an alternative for application of mainstream anammox. [ABSTRACT FROM AUTHOR]

[Display omitted] • TIN removal reached 92.06% by PN/A process and no external carbon need. • Pre-anaerobic treatment enhanced partial nitrification start-up (NAR > 90%). • The total aerobic HRT was only 5.7 h and the DO was as low as 0.5–1.0 mg/L. • Ca. Brocadia was enriched and the abundance increased from 0.02% to 0.23%. A modified two-stage partial nitrification/anammox (PN/A) process with short aerobic HRT of 5.7 h was established and realized advanced nitrogen removal from domestic wastewater. The first process was partial nitrification in the PN-SBR, the initiation and stable maintenance of partial nitrification was achieved by pre-anaerobic treatment without inoculation or addition of inhibitor, nitrite accumulation rate was over 90% and maintained over 200 days, meanwhile pre-anaerobic improved the storage of endogenous carbon sources to enhance the nitrogen removal efficiency. The second process was anammox in the AMX-SBR, which was fed with the effluent of PN-SBR, the effluent total inorganic nitrogen was below 5 mgN/L, nitrogen removal efficiency reached 92.06%. Furthermore, Candidatus-Brocadia was enriched after treating domestic sewage with low ammonia from 0.02% to 0.23%.This study demonstrated the feasibility of starting and maintaining partial nitrification by pre-anaerobic treatment and the feasibility of nitrogen removal by coupling simultaneous-nitrification–denitrification with anammox to treat actual municipal sewage. [ABSTRACT FROM AUTHOR]

As a low consumption and high efficiency process, Partial Nitrification-Anammox/denitratation (PNAD) was applied to co-treat mature landfill leachate with municipal sewage for 300 days. Specifically, ammonia (670.2 ± 63.7 mg N/L) contained in mature landfill leachate was firstly oxidized to nitrite (611.5 ± 28.1 mg N/L) in sequence batch reactor (SBR PN); meanwhile, organic matter in municipal sewage was partially removed in another reactor (SBR OMR); finally, nitrite produced (611.5 ± 28.1 mg N/L) in SBR PN and ammonia (53.1 ± 6.4 mg N/L) residing in pretreated municipal sewage were simultaneously degraded through combined Anammox-denitratation process in an up-flow anaerobic sludge bed (UASB AD). A satisfactory effluent quality of 10.3 mg/L TN was obtained after long-term operation, with Anammox and denitrification contributing to 86.2% and 5.8% nitrogen removal efficiency, respectively. Mass balance confirmed 67.2% nitrate generated from Anammox could be reduced to nitrite and in-situ reused. Anammox bacteria genes and nitrate reductase/nitrite reductase ratio were highly detected, accelerating combined Anammox-denitratation. Further, Ca. Brocadia triumph among various Anammox bacteria groups, increasing from 1.2% (day 120) to 3.6% (day 280). [Display omitted] • PNAD process was proposed to cotreat mature landfill leachate and municipal sewage. • Anammox and denitrification contributed to 86.2% and 5.8% nitrogen removal efficiency. • Candidatus. Brocadia was dominant genus (1.2-3.6%) among various Anammox bacteria groups. • PNAD process saved 25% aeration energy consumption and 100% carbon source demanding than traditional bioprocess. [ABSTRACT FROM AUTHOR]

• A continuous flow reactor for treating actual municipal wastewater was studied • Nitritation was quickly initiated in 15 d via UL-SRT during seasonal warming • Stable nitritation could be achieved by using joint UL-SRT and tapered aeration • The AOB (amoA) abundance increased approximately 50 times after nitritation Rapid achievement of nitritation of mainstream municipal wastewater in a continuous-flow process is attractive since it favors the involvement of the anammox process and reduces the operational costs. In this study, a feasible and economical strategy is proposed to rapidly achieve the nitritation of municipal wastewater. By aggressively discharging excess sludge during the seasonal warming period (temperature increasing from 18°C to 22°C), nitritation was established in 15 days with a nitrite accumulation ratio of 85.09% in a continuous-flow anaerobic/oxic (An/O) reactor. Meanwhile, qPCR results revealed that amoA abundance increased from (1.78±0.10) × 108 copies/(g VSS) to (1.05±0.11) × 1010 copies/(g VSS) while the abundance of nitrite-oxidizing bacteria decreased from (1.1±0.02) × 1010 copies/(g VSS) to (5.01±0.02) × 108 copies/(g VSS). The temperature gradually stabilized at 26°C during the following operational period and stable nitritation was maintained with a nitrite accumulation ratio above 90%, which was mainly attributed to a short sludge retention time (SRT) of 4.3 days and a low dissolved oxygen of 0.86 ± 0.5 mg/L. Falling temperature negatively impacted the stability of nitritation, but nitritation could be restarted by aggressively discharging excess sludge during another temperature increase period. Overall, this study provides a feasible strategy to start-up nitritation that has great potential applications for municipal wastewater treatment. [Display omitted] [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]

• TIN removal reached 90.36% at short HRT with low DO and no external carbon need. • Increasing AOB activity and stable nitritation was achieved at a novel AOA strategy. • Ca. Brocadia as anammox bacteria was self-enriched in suspending sludge system. • Improved anammox contributed 47.4% to the enhanced TIN removal performance. • Effluent P was below 0.5 mg/L at last with high carbon utilization efficiency. Advanced nitrogen and phosphorus removal in a single-stage suspending-sludge system was achieved by employing a novel Anaerobic/Oxic/Anoxic (AOA) strategy over 200 days. Satisfactory total inorganic nitrogen (TIN) removal efficiency of 90.4% was achieved and effluent phosphorus was below 0.5 mg/L when treating domestic wastewater with the chemical oxygen demand (COD)/TIN as low as 2.98 ± 1.26. Stable nitritation was maintained with the ammonia residual and low dissolved oxygen of 0.2–0.5 mg/L at aerobic stage following by a post anoxic stage. The much higher activity of ammonia oxidation bacteria (12.99 mgN/gVSS/h) was achieved than the nitrite oxidation bacteria (0.09 mgN/gVSS/h). Notably, improved anammox performance was obtained without initial inoculation, contributing 47.4% to TIN removal. The abundance of Nitrosomonas increased from 0.12% to 0.95% (P < 0.001) and self-enrichment of anammox bacteria Ca. Brocadia was confirmed. It provided new insight into the advanced nutrient removal with comprehensible regulation and less aeration requirement. [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]

• The Fe(II)-dependent DNRA-anammox process was first developed in an anammox reactor. • Candidatus Kuenenia was the dominant microbe in nitrate wastewater treatment system. • Visual MINTEQ analysis was conducted to estimate the predominant speciation. • Kinetic simulation was applied to describe the EDTA inhibition and pH dependency. • A TNRR of 0.23 ± 0.01 kg-N/m3/d was maintained for 60 days. A long-term experiment in an anaerobic ammonium oxidation (anammox) reactor showed that anammox consortia could perform a stable and efficient Fe(II)-dependent dissimilatory nitrate reduction to ammonium (DNRA) coupled to the anammox (DNRA-anammox) process by controlling the EDTA-2Na/Fe(II) ratio and pH, with a total nitrogen removal rate (TNRR) of 0.23 ± 0.01 kg-N/m3/d. Anammox bacteria (Candidatus Kuenenia) were the dominant and functional microbes in such a nitrate wastewater treatment system. Visual MINTEQ analysis showed that the EDTA-2Na/Fe(II) molar ratio affected the influent composition of Fe and EDTA species and hence nitrate removal, while pH influenced both nitrate removal and the coupling degree of the Fe(II)-dependent DNRA-anammox process due to its own physiology. The kinetic simulation results showed that excess EDTA-2Na imposed a competitive inhibition on the Fe(II)-dependent DNRA-anammox process, and the Bell-shaped (A), (B), (C) and Ratkowsky models could be used to explore the pH dependency of the Fe(II)-dependent DNRA-anammox process. [ABSTRACT FROM AUTHOR]

• Novel two-stage process to treat low C/N domestic wastewater. • Successful out-selection of NOB by step-wise DO reduction to 0.1 mg/L. • Stable and high-rate partial nitritation with low-DO conditions (0.1 mg/L). • High activity and abundance of anammox with low influent substrate (<38 mg-N/L). • High TIN removal efficiency of 88.24% with short aerobic HRT of 6.7 h. Simultaneous partial nitritation and denitritation (SPND) coupled with anammox was established in this study to treat domestic wastewater. Two lab-scale bioreactors, namely SPND-SBR and ANA-UASB, were used in the two-stage system. In SPND-SBR, stable nitrogen removal efficiency of 51.1% was achieved with a high ammonia oxidation rate of 0.117 kg N/(m3·d). Besides, successful out-selection of nitrite-oxidizing bacteria (NOB) under low-DO of 0.1 mg/L during the steady period, resulting in an average effluent NO 2 −-N/NH 4 +-N ratio of 1.04. In ANA-UASB, the abundance of Candidatus Brocadia and Candidatus Kuenenia increased from 8.21% and 4.01% to 21.33% and 6.41% with low influent substrate contents of only 38 mg N/L. The effluent total inorganic nitrogen (TIN) was only 8.4 ± 1.1 mg N/L and the nitrogen removal efficiency reached 88.24%. Overall, the study demonstrated that the novel low-DO two-stage process for nitrogen removal is a promising technique for wastewater of low C/N ratio. [ABSTRACT FROM AUTHOR]

Mainstream anammox still faces the challenges of non-ideal NO 2 −/NH 4 + ratios and excess nitrate resulted from the instability of partial nitrification (PN) in municipal wastewater. To address these problems, in this study, we developed a novel two-sludge process that combined PN with synchronous anammox and endogenous partial denitrification (SAEPD); the process was tested with pre-treated domestic sewage at ambient temperatures for 205 d. High nitrogen removal efficiency of 91.2% was achieved with an influent C/N ratio of 1.7 at 15.4 °C; the success was attributed to the fact that EPD replenished the deficient nitrite by reducing nitrate and the excess nitrite was further reduced to nitrogen gas. With a non-ideal NO 2 −/NH 4 + ratio of 0.89, the contribution of the SAEPD-sequencing batch reactor (SBR) during the anoxic stage reached 98.2% and the proportional contributions of the anammox and denitrification pathways were 77.2% and 22.8%, respectively. Although the low nitrite accumulation (66.1%) caused 10.8 mg N/L of nitrate to be transported into the SAEPD-SBR and the anammox reaction also converted 20% of nitrite to nitrate, only 1.1 mg N/L of nitrate remained in the effluent. High-throughput sequencing analysis revealed that although NH 2 OH was added, some genera of nitrite-oxidizing bacteria (0.73%) remained in the PN-SBR and potentially resulted in the oxidation of nitrite to nitrate. In the SAEPD-SBR, anammox and endogenous denitrifying bacteria co-existed and synergistically achieved the removal of ammonium, nitrite, and nitrate. Overall, the PN-SAEPD process has great potential for achieving cost-effective and energy-efficient municipal wastewater treatment. Image 10859164 • EPD enhanced the robustness of mainstream anammox to cope with different NO 2 −/NH 4 + ratios. • High TIN removal efficiency (91.2%) was achieved with a C/N ratio of 1.7 at 15.4 °C. • PN-SAEPD process has a unique advantage over the traditional PN/A process for treating nitrate. • Anammox and endogenous denitrifying bacteria synergistically achieved nitrogen removal. • PN-SAEPD process is an energy-efficient municipal wastewater treatment process. [ABSTRACT FROM AUTHOR]

• NAR was stabilized at above 95% by low DO combine with aeration time control. • Synergistic nitrogen removal achieved by introducing municipal wastewater. • Partial denitrification was another way to supply nitrite in the SAD system. • The TIN removal efficiency reached 97.1% with a short HRT of 6 h. A modified two-stage anammox process was constructed and achieved advanced nitrogen removal from municipal wastewater. The first stage was Partial Nitrification (PN), in which nitrite accumulation rate was over 95% by controlling dissolved oxygen concentration (<1 mg/L) and aeration time (90–120 min). The second stage was simultaneous anammox and denitrification (SAD), in which the reactor was fed with the effluent of the first stage and a part of raw wastewater. The effluent total inorganic nitrogen (NH 4 +-N, NO 2 −-N and NO 3 −-N) was only 1.6 ± 0.8 mg N/L and the nitrogen removal efficiency reached 97.1%. The proportion of anammox in nitrogen removal was up to 73–82% and Candidatus Brocadia was the main anammox genus accounted for 8.0–2.2%. And partial denitrification occurred with the appearance of Thauera (0–1.0%). The PN-SAD process is an energy-saving treatment for municipal wastewater with a total hydraulic retention time of 6 h. [ABSTRACT FROM AUTHOR]

For achieving energy-efficient wastewater treatment, a novel simultaneous nitrogen and phosphorus removal (SNPR) process, which integrated anammox, endogenous partial-denitrification and denitrifying dephosphatation in a sequencing batch reactor with granular sludge was developed to treat mainstream wastewater. After 200 days of operation, a simultaneous high-level nitrogen and phosphorus removal of 93.9% and 94.2%, respectively was achieved with an average influent C/N ratio of 2.9. Anammox pathway contributed 82.9% of the overall nitrogen removal because of the stable nitrite production from nitrate via endogenous partial-denitrification. In addition, phosphorus was mainly removed via denitrifying dephosphatation utilizing nitrate as the electron acceptor, resulting in a significant saving of carbon sources and oxygen demands. Further, adsorption/precipitation of phosphorus occurred in this novel SNPR process, which displaced the energy source to the metabolism of glycogen accumulating organisms (GAOs) for nitrite production and alleviated competition between phosphorus accumulating organisms (PAOs) and anammox for electron acceptor. Using 16S rRNA gene amplicon sequencing analysis, the study found that anammox bacteria (8.4%), GAOs (1.5%) and PAOs (1.1%) co-existed in this system, potentially resulting in simultaneous endogenous partial-denitrification, anammox and denitrifying dephosphatation. The above results demonstrated that the novel SNPR process is a promising technique for energy-efficient wastewater treatment. Image 1 • Anammox can co-exist with GAOs and PAOs, ensuring the effective SNPR performance. • High-level nitrogen and phosphorus removal (93.9% and 94.2%, respectively) was achieved. • Nitrogen removal via anammox accounted for 82.9%, reducing energy and carbon demands. • Adsorption/precipitation of P were involved and facilitated stable SNPR performance. • The novel SNPR process is promising in energy-efficient wastewater treatment. [ABSTRACT FROM AUTHOR]

• Novel two–sludge DNPR system of A/A/O–N mode was developed for low C/N ratio. • Advanced nutrient removal was attained, solved the ammonia bottle–neck problem. • Nitrosomonas (1.29%) and Nitrospira (9.31%) were enriched in the biofilm system. • Dechloromonas and Accumulibacter were believed as the main DPAOs and enriched. A two-sludge system with separated phosphorus removal unit and nitrification unit was used to treat the actual municipal sewage deficient in organic carbon sources, with the carbon/nitrogen (C/N) ratio of 4.39. The system was first operated as anaerobic/oxic–nitrification (A/O–N) mode for 60 days (phase I), and then transformed into anaerobic/anoxic/oxic-nitrification (A/A/O–N) mode for the next following 80 days (phase II). Noteworthy, oxygen and nitrate acted as electronic acceptors for phosphorus removal in chronological order. Results indicated that deep phosphorus removal and complete nitrification were achieved at both phase I and phase II, and the system exhibited a higher microbial diversity. Microbial community abundance on genus level analysis indicated that Dechloromonas and Accumulibacter were respectively accumulated with 11.6 and 2.42% abundance (A/A/O sludge); and 9.31 and 1.29% Nitrospira and Nitrosomonas occupied the biofilm, and they performed denitrifying phosphorus removal (DNPR) and nitrification, respectively. [ABSTRACT FROM AUTHOR]

Anaerobic ammonium oxidation (anammox) has been extensively investigated for cost-efficient nitrogen removal from wastewater. However, the major issues of nitrate (NO 3 −-N) residue and instability in the current combination of nitritation and anammox process necessitates being addressed efficiently. The recently proposed partial-denitrification (PD), terminating NO 3 −-N reduction to nitrite (NO 2 −-N), has been regarded as a promising alternative of NO 2 −-N supplying for anammox bacteria. Given the engineering practices, the steadily high NO 2 −-N production, alleviating organic inhibition, and reducing greenhouse gas of PD process offers a viable and efficient approach for anammox implementation. Moreover, it allows for the extending applications of anammox process due to the NO 3 −-N removal availability. Here we comprehensively review the important new outcomes and discuss the emerging applications of PD-based anammox including the process development, mechanism understanding, and future trends. Significant greater stability and enhanced nitrogen removal efficiency have been demonstrated in the novel integrations of PD and anammox process, indicating a broad perspective in dealing with the mainstream municipal sewage, ammonia-rich streams, and industrial NO 3 −-N contained wastewater. Furthermore, researches are still needed for the predictable and controllable strategies, along with the detailed microbiological information in future study. Overall, the achievement of PD process provides unique opportunity catalyzing the engineering applications of energy-efficient and environmental-friendly wastewater treatment via anammox technology. • Partial-Denitrification provides a stable and efficient alternative for nitrite supply. • PD process offers extending application of anammox treating nitrate wastewater. • PD/A holds potential in improved efficiency for mainstreams and sidestreams treatment. • Emerging opportunities are given for wastewater treatment engineering by PD/A. • Predictable controlling strategies and penetrating microbial mechanism are needed. [ABSTRACT FROM AUTHOR]

• PD using carbon sources in domestic wastewater was achieved with pH, time control. • NO 2 −-N production reached 25.2 mg/L at an influent NO 3 −-N of about 30 mg/L. • PD performance remained effective without pH control after start-up. • NO 2 −-N production was related to consumed Ss with optimal Ss/NO 3 −-N of about 3.5. • Three genera were enriched and may be responsible for high NO 2 −-N production. Partial denitrification (PD, nitrate → nitrite) using carbon sources in domestic wastewater with waste-activated sludge as inoculum was firstly achieved in this study. Through controlling influent pH at about 9.0 and anoxic reaction time of 1 h in the start-up, the nitrite (NO 2 −-N) production reached as high as 25.2 mg/L, with influent nitrate (NO 3 −-N) of about 30 mg/L and chemical oxygen demand (COD) to NO 3 −-N ratio of 5.9. Furthermore, PD performance remained stable without pH control during subsequent operations. Efficient NO 2 −-N production was closely related to the consumed amount of readily biodegradable COD (Ss) fraction, with optimal Ss/NO 3 −-N ratio of about 3.5. Thauera (19.1%), norank_f__Xanthomonadaceae (5.2%), and Thiobacillus (5.0%) were enriched during the 208-day operation, which may be responsible for high NO 2 −-N production. These findings provided a novel strategy for promoting mainstream PD/Anammox application, without additional nitrite-accumulating denitrifying sludge and external carbon sources. [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]

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]

[Display omitted] • Initial application of novel AAnO process achieved N-removal under real wastewater. • Anammox enriched in-situ in novel AAnO process at ambient temperature. • Anammox abundance reached 1.56% driven by partial denitrification on day 75. • Anammox contributed to 55.8 ± 19.2 % of total nitrogen removal in anoxic zone. • Anammox bacteria genus was closely related to Candidatus Brocadia fulgida. Anaerobic ammonia oxidation (Anammox) exhibits promise for wastewater treatment, but the enrichment of anammox bacteria (AnAOB) in municipal wastewater treatment plants is a significant challenge. This study constructed a novel A noxic- An aerobic- O xic (AAnO) process with a pure biofilm anoxic zone fed with actual fluctuating municipal wastewater and operated for six months to enrich AnAOB at ambient temperature. High-throughput sequencing (HTS), qPCR, and fluorescence in situ hybridization showed that AnAOB were successfully enriched in the anoxic biofilms, reaching 1.56 % relative abundance on day 75 detected by HTS. During the period from day 130 to day 186, the anammox process contributed to 55.8 ± 19.2 % of the nitrogen removal in the anoxic zone. Phylogenetic analysis revealed this AnAOB species was closely related to Candidatus Brocadia fulgida. This study provides technical support for the application of anammox in mainstream wastewater. [ABSTRACT FROM AUTHOR]

[Display omitted] • PD/A-A2O process was started up rapidly by inoculating PD/A biofilm in 30 days. • NRE improved by 23.8% contrasted to traditional A2O process. • The contribution of anammox to TN loss was maintained at 37.9 %∼55.7 %. • Reducing HRT would simultaneously improve denitrification and anammox activity. • Cooperation of DNB, GAO and AnAOB resulted in enhanced nitrogen removal. This study investigated the rapid start-up of mainstream partial denitrification coupled with anammox (PD/A) and nitrogen removal performance by inoculating precultured PD/A biofilm. The results showed mainstream PD/A in the anaerobic-anoxic-aerobic (A2O) process was rapidly established within 30 days. Nitrogen removal efficiency (NRE) improved by 23.8 % contrasted to the traditional A2O process. The mass balance showed that anammox contribution to total nitrogen (TN) removal were maintained at 37.9 %∼55.7 %, and reducing hydraulic retention time (HRT) strengthened simultaneously denitrification and anammox activity. The microbial community showed that the dominant bacteria such as denitrifying bacteria (DNBs) and glycogen accumulating organisms (GAOs) both in biofilm and flocculent sludge (floc), integrating with anammox bacteria (AnAOB) in biofilm might lead to enhanced nitrogen removal. Overall, this study offered a fast start-up strategy of mainstream PD/A with enhanced nitrogen removal, which are valuable for upgradation and renovation of existed municipal wastewater treatment plants (WWTPs). [ABSTRACT FROM AUTHOR]

For low carbon-to-nitrogen ratio municipal wastewater, full utilization of carbon sources is positive in reducing carbon emissions and carbon source addition. This study evaluated and proposed appropriate anaerobic duration control to improve nitrogen and phosphorus removal performance in Denitrifying Phosphorus Removal and Partial Denitrification coupled with Anammox (DPR-PDA) system. Excessive anaerobic duration resulted in wasted carbon source, anaerobic stage should be stopped after carbon source had been utilized. Hydraulic Retention Time-Anaerobic (HRT-An) of R1 was shortened from 5h to 0.56h, while R2 was maintained at 5h. The removal efficiency of nitrate (NO 3 −) were 91.7% in R1 and 71.5% in R2. Peak of NO 2 − accumulation (Peak-NO 2 --N) during denitrification in R1 was 4.5 times than in R2. Candidatus_Brocadia as anammox bacteria was self-enriched, the abundance in R1 was 4.67 times than in R2. This provided a practical guide for optimization of wastewater treatment processes and application of anammox technology. [Display omitted] • The effect of HRT-An on N and P removal was examined in two DPR-PDA systems. • Re-NO 3 --N of R1 (HRT-An: 5. → 0.56h) and R2 (HRT-An: 5h) were 91.7% and 71.5%. • Peak-NO 2 --N during denitrification process in R1 was 4.5 times higher than in R2. • Candidatus_Brocadia was self-enriched, abundance in R1 was 4.67 times than in R2. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel granulation approach with Thiothrix -hydroxyapatite coupled particles was established. • Mixotrophic denitrification and anammox were integrated in single particle for nitrogen removal. • Coupled particles could effectively cope with low temperatures and organic loading shocks. • Thiothrix produced elemental sulfur as secondary electron donor and energy source. • Coupled particles provided suitable ecological niches for functional microorganisms. Sulfur-driven autotrophic denitrification coupled with anammox (SPDA) is a promising process for autotrophic nitrogen removal, but autotrophic microorganisms are challenging to retain in wastewater treatment units. In this study, a single-stage mixotrophic denitrification coupled with anammox (MDA) process was established in an up-flow anaerobic sludge bed reactor with Thiothrix -hydroxyapatite coupled particles. The advancement of the sludge granulation process effectively strengthened the resistance of the MDA system to environmental stresses, and the SPDA-dominated nitrogen removal process achieved a total nitrogen removal efficiency of 88.6 %, a nitrogen removal rate of 0.432 KgN/m3/d at temperatures as low as 12.8 °C and an organic loading rate of 0.63 KgCOD/m3/d. Interestingly, the ecological niche integration of sulfur oxidizing bacteria (SOB), anammox bacteria and heterotrophic denitrifying bacteria in the granular sludge was observed during long-term operation. The FISH-CLSM results revealed the spatial distribution of functional microorganisms in the granular sludge and the potential pollutant transformation mechanism. The aggressive growth of SOB dominated by Thiothrix constructed a biological wall at the periphery of the granules, which ensured their priority for nitrate acquisition, supplied nitrite to the internal anammox bacteria, and acted as an important barrier against the shock of organic loads. Overall, this study presents a novel granulation approach for the biological treatment of sulfur-containing wastewater, highlighting the efficacy of functional integration within Thiothrix -hydroxyapatite coupled particles as an effective strategy to resist environmental stress. [ABSTRACT FROM AUTHOR]

[Display omitted] • Ultrafast mainstream PN rate of more than 1 kg N m−3 d−1 was first obtained. • Ultrarapid PN start-up was achieved in 8 days at 10-day SRT under saturated DO. • Ultrastable PN with a NAR of 98.5 % maintained over 250 days under fluctuations. • NOB groups and activity decreased by 99.9 % and high-rate AOB species was enriched. • PN reproducibility and robustness were validated under real-world conditions. Achieving stable and high-rate partial nitrification (PN) remains a worldwide technical conundrum in low-strength mainstream conditions. This study successfully achieved ultrarapid mainstream PN within 8 days under a saturated dissolved oxygen (DO) supply strategy, reaching a record-breaking PN rate of over 1.0 kg N m−3 d−1 treating municipal wastewater. Stable PN was maintained for over 200 days with an ultrahigh nitrite accumulation ratio of 98.5 ± 0.9 %, resilient to seasonal fluctuations in temperature (16.0–25.6 °C) and load (NH 4 +-N, 40–80 mg N/L). Kinetics revealed a remarkable 159.1-fold increase in the maximum activity ratio of ammonia-oxidizing bacteria (AOB) to nitrite-oxidizing bacteria (NOB). The faster response of AOB to saturated DO stimulated its highest activity difference with NOB, contributing to the AOB (Nitrosomonas oligotropha) boom and the elimination of NOB groups (−99.9 %). Our results highlight the importance of promoting AOB rather than solely focusing on NOB suppression for initiating and stabilizing high-rate mainstream PN. [ABSTRACT FROM AUTHOR]

[Display omitted] • 2 mg/L NH 2 OH dosing once every 6 h could achieve NAR of 91.6 % and TNRE of 92.6 %. • NH 2 OH dosing would promote the SND and END while inhibit EXD. • Suppression for SNOR, Nitrospira and Nxr led to the stable partial nitrification. • Advanced N removal was owing to the synergistic effect of multiple denitrifiers. • NH 2 OH dosage was related to NAR, SND and END, which were beneficial for TNRE. Intermittent hydroxylamine (NH 2 OH) dosing strategy was applied to enhance the stability of partial nitrification and total nitrogen (N) removal efficiency (TNRE) in a continuous-flow process. The results showed 2 mg/L of NH 2 OH dosing (once every 6 h) could maintain stably partial nitrification with nitrite accumulation rate (NAR) of 91.6 % and TNRE of 92.6 %. The typical cycle suggested NH 2 OH dosing could promote simultaneous nitrification–denitrification (SND) and endogenous denitrification (END) while inhibit exogenous denitrification (EXD). Nitrification characteristics indicated the NH 2 OH dosing enhanced stability of partial nitrification by suppressing specific nitrite oxidation rate (SNOR), Nitrospira and nitrite oxidoreductase enzyme (Nxr). The microbial community suggested the aerobic denitrfiers, denitrifying glycogen accumulating organisms (DGAOs) and traditional denitrfiers were the potential contributor for advanced N removal. Moreover, NH 2 OH dosage was positively associated with NAR, SND and END. Overall, this study offers a feasible strategy to maintain sustainably partial nitrification that has great application potential. [ABSTRACT FROM AUTHOR]

• Sludge alkaline fermentation enhanced partial nitrification and anammox. • The abundance of NOB was reduced by 8.4 times. • The abundance of anammox bacteria has increased by 80.5 times. • NAR reached 60.40% and the contribution rate of anammox was as high as 47.17%. • No external carbon source dosing and short HRT oxic (5.3 h) could save energy. A continuous-flow anaerobic/aerobic/anoxic reactor with complete suspended activated sludge using sludge alkaline fermentation products as carbon source was utilized to strengthen nitrogen removal performance for low C/N ratio (<4) wastewater. Long-time performance indicated that the nitrite accumulation rate reached 60.40%, which strengthened the contribution of anammox. The average total inorganic nitrogen removal efficiency improved 19.40%. The abundance of ammonia oxidizing bacteria has not changed, but the abundance of nitrite oxidizing bacteria reduced from 5.79% to 0.69%. Quantitative PCR results demonstrated that the abundance of anammox bacteria has raised by 80.5 times. These results indicated that side-stream sludge alkaline fermentation promoted the mainstream partial nitrification, consequently accelerating the in-situ enrichment of anammox bacteria. No external carbon source dosing and short oxic hydraulic retention time (5.3 h) save energy and reduce consumption significantly in this system. [ABSTRACT FROM AUTHOR]

[Display omitted] • NAR maintained at above 95% under the normal operation even temperature <15℃. • Ca. Brocadia was enriched in anoxic-carrier biofilms (6.67%) without inoculation. • High NRE of 95.1% was obtained from low COD/TIN (3.4) municipal wastewater. • Spontaneous anammox occurred in anoxic zone contributed to 13.5%±5.8% TIN removal. A continuous plug-flow reactor with anaerobic/front-aerobic/anoxic/post-aerobic zones, where partial nitrification occurred in the front-aerobic zone, followed by simultaneous anammox and endogenous denitrification in the anoxic zone (PN-SAED), was built up to treat municipal wastewater. Alternating anoxic/aerobic conditions and longer anoxic duration facilitated stable partial nitrification. The nitrite accumulation ratio (NAR) was maintained at 97.4 ± 1.2%, with temperatures between 13.3℃ to 19.8℃. Candidatus Brocadia were naturally enriched in-situ from the anoxic zone with relative abundances of 31.93% and 6.67% on the agitator blade and carriers, respectively. High removal efficiencies of total inorganic nitrogen (TIN) (95.1 ± 1.9%) and effluent TIN (2.6 ± 1.1 mg N/L) were acquired from low COD/TIN (3.4 ± 0.4) municipal wastewater with anammox contribution of 13.5%±5.8% to TIN removal. The PN-SAED process is a promising mainstream nitrogen removal method. [ABSTRACT FROM AUTHOR]

[Display omitted] • SPDAF system showed adaptability to gradual cooling at 19.6–16.5 ℃. • SPDAF system was robust to sudden cooling and drastic temperature fluctuations. • Hydrolysis and acidogenesis bacteria promoted the use of complex organics. • In-situ fermentation supplemented electron donors for NO 3 –-N reduction. A synergistic partial denitrification, anaerobic ammonium oxidation (Anammox), and in-situ fermentation (SPDAF) system was established to solve problems of wastewater treatment plants (WWTPs) in combined treatment of domestic sewage, and nitrate wastewater discharged from industrial areas. The SPDAF system was started up at decreasing temperatures (26.8–18.9 ℃), and remained robust at abrupt temperature drop and drastic temperature fluctuations (20.7–14.1 ℃). The influent and effluent total inorganic nitrogen (TIN) were 97.0 ± 3.7 mg/L and 10.3 ± 4.0 mg/L, respectively. In-situ fermentation supplemented electron donors for NO 3 –-N reduction. A high TIN removal efficiency, of 89.5 ± 3.9% was obtained. Specifically, Anammox contributed 90.9 ± 5.2% to TIN removal. Furthermore, the abundances of hydrolysis and acidogenesis bacteria were 14.02% and 29.47% in the low and high zones, respectively, which promoted fermentation and the use of complex organics. This study provided novel insights for actual operation of WWTPs. [ABSTRACT FROM AUTHOR]

The deep removal of quinoline from coking wastewater is a prerequisite for reducing its potential threat to environmental safety. Therefore, it is urgent to develop advanced materials for efficient removal of quinoline in wastewater. In this work, a nitrogen-doped hollow carbon nanosphere/graphene composite aerogel (HCNS/NGA) was prepared by in-situ reduction self-assembly strategy, in which HCNS prevents the agglomeration of graphene oxide (GO) nanosheets, and a special sphere-sheet mutual support structure is formed to ensure the structural stability. As-prepared HCNS/NGA exhibits large specific surface area, hierarchical pore structure, and excellent conductivity. Large cavity inside and hierarchically porous structure that primarily consists of micropores, resulting in high quinoline adsorption performance (138.37 ± 2.58 mg g-1 at 298 K). Furthermore, in a fixed-bed column adsorption system, the partition coefficient at 10% breakthrough reaches up to 35.19 mg g-1 μM-1. More importantly, HCNS/NGA, as a conductive monolithic sorbent, can realize easy solid-liquid separation, as well as efficient regeneration in situ by electrochemically assisted regeneration. After ten regeneration cycles, the adsorption capacity retention is 91.54%. In short, as an efficient adsorbent, HCNS/NGA has an enormous application potential in wastewater treatment. [Display omitted] • Hollow carbon nanospheres/graphene composite aerogel (HCNS/NGA) was synthesized. • The adsorption property of HCNS/NGA was studied by static and fix-bed adsorption. • HCNS/NGA achieves efficient adsorption towards quinoline in water. • HCNS/NGA could be easily separated from liquid phase. • HCNS/NGA could be regenerated in situ by electrochemical assisted device. [ABSTRACT FROM AUTHOR]

• Sludge fermentation liquid enhanced partial-denitrification in domestic wastewater. • The capability of NO 3 –-N reduction was enhanced while that of NO 2 –-N was weakened. • Effluent ratio of NH 4 +-N/NO 2 –-N is 1:1 which is suitable to couple with anammox. • Anammox bacteria was enriched and Ca. Brocadia (0.13%) was detected in phase IV. Partial-denitrification (PD; NO 3 –→NO 2 –) has recently been proposed to be a feasible choice of NO 2 –-N supply for anammox bacteria. In this study, an aerobic/anoxic process for treating domestic wastewater was operated for 176 days to evaluate the feasibility of using sludge fermentation liquid for partial denitrification of the wastewater. Results show that, with the ratio of C/N (COD/ NO 3 –-N) increased at anoxic stage, the average NO 2 –-N concentration in the effluent and nitrate-to-nitrite transformation ratio (NTR) at anoxic stage showed relative growth. High-throughput sequencing analysis demonstrated that the enhancement of PD can be explained by the increases of Thauera , Paracoccus and Enterobacteriaceae. Moreover, Candidatus_Brocadia (0.13%) was detected as the predominant anammox bacteria. Ex-situ isotopic tracing technique analysis assessed that the ratio of anammox role (ra%) was 7.29%. This study has a great potential for being coupled with the anammox bacteria for advanced nitrogen removal. [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]

· The S0PDA process implementing granular sludge was successfully established. · The S0PDA process exhibited rapid startup and robust operation. · NRR and NRE reached up to 1.75 ± 0.07 kg-N/(m3·d) and 88.5 ± 2.0 %, respectively. · Anammox contributed 82.3 ± 5.6 % of N removal under an ultra-short HRT of 2.0 h. · The synergy of SOB on S0 particles and AnAOB in granular sludge promoted the S0PDA. This study proposed a novel strategy that integrates S0 particles (diameter: 2–3 mm) and granular sludge to establish S0-driven partial denitrification coupled with anammox (S0PDA) process for autotrophic nitrogen removal from NH 4 +- and NO 3 −-containing wastewaters. This process was evaluated using an up-flow anoxic sludge bed bioreactor, operating continuously for 240 days. The influent concentrations of NH 4 + and NO 3 − were 29.9 ± 2.7 and 50.2 ± 2.7 mg-N/L, respectively. Throughout the operation, the hydraulic retention time was shortened from 4.0 h to 2.0 h, while the effluent concentrations of NH 4 + and NO 3 − were maintained at a desirable level of 1.45–1.51 mg-N/L and 4.46–6.52 mg-N/L, respectively. Despite an autotrophic process, the nitrogen removal efficiency and rate reached up to 88.5 ± 2.0 % and 1.75 ± 0.07 kg-N/(m3·d), respectively, indicating the remarkable robustness of the S0PDA process. Autotrophic anammox and sulfur-oxidizing bacteria (Candidatus Brocadia and Thiobacillus) were the predominant bacterial genera involved in the S0PDA process. Candidatus Brocadia was primarily enriched in the granular sludge, with a relative abundance of 6.70 %. Thiobacillus occupied a unique niche on the S0 particles, with a relative abundance as high as 57.6 %, of which Thiobacillus thioparus with partial denitrification function (reducing NO 3 − to NO 2 − without further reduction to N 2) accounted for 78.0 %. These findings challenge the stereotype of low efficiency in autotrophic nitrogen removal from wastewater, shedding fresh light on the applications of autotrophic processes. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • 30 m3 anaerobic/aerobic/anoxic pilot-scale SBR system was first set up with sewage. • Total nitrogen and phosphate in effluent were 10.9 and 0.1 mg/L at 15.7℃. • The relative abundance of Competibacter and Tetrasphaera rose to 1.25% and 1.52%. • The contribution rate by endogenous denitrification was more than 43.3%. • Sludge reduction (17.1 %) and short aerobic time (6.0 h) helped to save energy. Removing nitrogen and phosphorus from low ratio of chemical oxygen demand to total nitrogen and temperature municipal wastewater stays a challenge. In this study, a pilot-scale anaerobic/aerobic/anoxic sequencing batch reactor (A/O/A-SBR) system first treated 15 m3/d actual municipal wastewater at 8.1–26.4 °C for 224 days. At the temperature of 15.7 °C, total nitrogen in influent and effluent were 45.5 and 10.9 mg/L, and phosphorus in influent and effluent were 3.9 and 0.1 mg/L. 16 s RNA sequencing results showed the relative abundance of Competibacter and Tetrasphaera raised to 1.25 % and 1.52 %. The strategy of excessive, no and normal sludge discharge enriched and balanced the functional bacteria, achieving an endogenous denitrification ratio more than 43.3 %. Sludge reduction and short aerobic time were beneficial to energy saving contrast with a Beijing municipal wastewater treatment. This study has significant implications for the practical application of the AOA-SBR process. [ABSTRACT FROM AUTHOR]

• A pilot-scale plant of A2O-BCO was established and operated continuously for 385 days. • PDPRA was proposed and applied by leveraging DPAOs as NO 2 - suppliers for anammox. • PDPRA enabled a mainstream anammox activity as high as 6.14 μmol-N/(L·h). • PDPRA facilitated a high-level enrichment of AnAOB (Ca. Brocadia, 2.46 ± 0.52 %). • CRE, ARE, NRE, and PRE achieved up to 83.5 %, 99.8 %, 77.1 %, and 99.3 %, respectively. Applying anaerobic ammonium oxidation (anammox) in municipal wastewater treatment plants (MWWTPs) can unlock significant energy and resource savings. However, its practical implementation encounters significant challenges, particularly due to its limited compatibility with carbon and phosphorus removal processes. This study established a pilot-scale plant featuring a modified anaerobic-anoxic-oxic (A2O) process and operated continuously for 385 days, treating municipal wastewater of 50 m3/d. For the first time, we propose a novel concept of partial denitrifying phosphorus removal coupling with anammox (PDPRA), leveraging denitrifying phosphorus-accumulating organisms (DPAOs) as NO 2 − suppliers for anammox. 15N stable isotope tracing revealed that the PDPRA enabled an anammox reaction rate of 6.14 ± 0.18 μmol-N/(L·h), contributing 57.4 % to total inorganic nitrogen (TIN) removal. Metagenomic sequencing and 16S rRNA amplicon sequencing unveiled the co-existence and co-prosperity of anammox bacteria and DPAOs, with Candidatus Brocadia being highly enriched in the anoxic biofilms at a relative abundance of 2.46 ± 0.52 %. Finally, the PDPRA facilitated the synergistic conversion and removal of carbon, nitrogen, and phosphorus nutrients, achieving remarkable removal efficiencies of chemical oxygen demand (COD, 83.5 ± 5.3 %), NH 4 + (99.8 ± 0.7 %), TIN (77.1 ± 3.6 %), and PO 4 3− (99.3 ± 1.6 %), even under challenging operational conditions such as low temperature of 11.7 °C. The PDPRA offers a promising solution for reconciling the mainstream anammox and the carbon and phosphorus removal, shedding fresh light on the paradigm shift of MWWTPs in the near future. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • Denitrifying phosphorus removal was validly established using AOA operation mode. • Appropriate C/P is beneficial for inhibiting the excessive growth of GAOs. • The abundance of Dechloromonas significantly increased as typical DPAOs. • PAOs-GAOs balance was obtained under low DO concentration with aeration for 10 min. Realizing the quick enrichment and development of denitrifying phosphorus accumulating organisms (DPAOs) in actual household wastewater and industrial nitrate wastewater has significant research significance. In this study, a novel operation mode of anaerobic-oxic-anoxic (AOA) was adopted to successfully realize the enrichment and cultivation of DPAOs in urban domestic wastewater. Adjusting influent COD to PO 4 3−-P ratio, shortening the aerobic time and decreasing the aeration volume were conducive to select DPAOs in microbial populations. The system was operated for 180 days and the DPAOs were well enriched during the stable operation with the percentage of Dechloromonas increased to 5.1 %. Accordingly, the effluent PO 4 3−-P was < 0.3 mg P/L, the removal efficiency of phosphorus was 96.9 % and the removal efficiency of nitrate was 92.5 %. Above all, DPR can be successfully applied to AOA systems with good phosphorus removal performance. [ABSTRACT FROM AUTHOR]

[Display omitted] • Novel anammox granules were cultivated from conventional activated sludge. • Ultra-low floc SRT of 8d eliminated nitrifiers and achieved partial nitrification. • Ultra-low floc SRT realized highly bacteria-enriched anammox granules retention. • In-situ enrichment of Ca. Brocadia (0.0 → 3.0 %) treating actual municipal wastewater. The direct integration of anammox process into municipal wastewater treatment has caused widespread concern, but the lack of anammox seeds limited its real application. This study successfully cultivated anammox granules (322.0 μm) from conventional activated sludge treating municipal wastewater. Through ultra-low floc sludge retention times of 8d, nitrifiers on flocs were eliminated and partial nitrification was realized. Furthermore, highly bacteria-enriched granules were initially formed, with Nitrosomonas and Ca. Competibacter 4-fold higher than that of flocs. Specific staining results revealed the microbial interaction with Ca. Brocadia , considering that Ca. Competibacter and Nitrosomonas correspondingly identified in the inner and outer layers of granules. The percentage of Ca. Brocadia present on the granules increased substantially from 0.0 % to 3.0 %, accompanied by a nitrogen removal rate of 0.3 kg·m−3·d−1. Our findings revealed a valuable reference for the anammox bacteria in-situ enrichment under mainstream conditions, which provides theoretical guidance for anammox-based processes practical application. [ABSTRACT FROM AUTHOR]

• SBR achieved up to 93 % above partial nitrification of municipal wastewater. • SBR effluent and mature landfill leachate in UASB had an 89.4 % anammox contribution. • UASB achieved simultaneous anammox and partial denitrification with an HRT of 3.8 h. • The PN-SAPD process achieved an Eff.TIN of 3.4 mg/L and a removal efficiency of 95 %. • Ca. Brocadia had the highest abundance and was the only AnAOB for nitrogen removal. Anaerobic ammonia oxidation (anammox) of municipal wastewater is a research focus, especially the combined treatment with mature landfill leachate is a current research hotspot. In this study, municipal wastewater was treated by partial nitrification via sequencing batch reactor (SBR), and its effluent and mature landfill leachate were then mixed into an up-flow anaerobic sludge blanket (UASB) for simultaneous anammox and partial denitrification reaction. Through partial nitrification, a high nitrite accumulation rate (93.0 ± 3.8 %) was achieved by low dissolved oxygen (0.5–1.6 mg/L) and controlled aerobic time (3.5 h) in SBR. The UASB system was responsible for 78.8 ± 2.1 % nitrogen removal of the entire system with a hydraulic reaction time (HRT) of 3.8 h, accompanied by the anammox contribution up to 89.4 ± 6.0 %. The overall partial nitrification-simultaneous anammox and partial denitrification (PN-SAPD) system was controlled at a total COD/TIN of 2.8 ± 0.3 and a total HRT of only 10.2 h, achieving the nitrogen removal efficiency and effluent TIN were 95.2 ± 2.2 % and 3.4 ± 1.5 mg/L, respectively. The qPCR results showed functional genes (hzsA(B), hdh) associated with anaerobic ammonia-oxidizing bacteria (AnAOB), whose high gene copy abundance and transcription expression ensured the removal of major nitrogen from municipal wastewater and mature landfill leachate. 16S amplicon sequencing showed that the Ca. Brocadia (9.72–12.6 %) was further enrichment after sodium acetate was added, and the transcription expression of Thauera (0.5–7.0 %) caused nitrate to nitrite. The high abundance of related enzymes (hao, hzs, hdh, narGHI) involved in anammox and partial denitrification processes were found in the macrogenomic sequencing, and only Ca. Brocadia was involved in multi-pathway nitrogen metabolism in AnAOB. Based on the efficient nitrogen removal by AnAOB and denitrifying bacteria, this modified PN-SAPD process provides a new option for the co-treatment of mature landfill leachate in municipal wastewater treatment plants. [Display omitted] [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]