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[Display omitted] • A stable SNEDPR was achieved in AnIA-MBBR system. • 90% of TN and 74% of P was removed simultaneously with low C/N ratio. • Shorter aeration strategy led to better nutrients removal performance. • A typical DGAO Candidatus_Competibacter was enriched up to 20% in the system. • Synergy of nitrifiers/denitrifiers, PAOs/DPAOs, and GAOs/DGAOs for SNEDPR. In this study, an anaerobic/intermittently-aerated moving bed biofilm reactor (AnIA-MBBR) was proposed to realize simultaneous nitrification and endogenous denitrifying phosphorus removal (SNEDPR) in treating low carbon-to-nitrogen (C/N) ratio wastewater. The effect of different intermittent aeration modes (short and long aeration) on nutrients' removal was investigated. With the C/N ratio around 3, the removal efficiencies of total nitrogen and phosphorus were 90% and 74%, 88% and 59%, respectively, for short aeration and long aeration. The different aeration time also altered the nutrients' degradation pathway, biofilm characteristics, microbial community, and functional metabolic pathways. The results confirmed the occurrence of aerobic denitrifiers, anoxic denitrifiers, phosphorus accumulating organisms, glycogen accumulating organisms in AnIA-MBBR systems and their synergistic performance induced the SNEDPR. These results indicated that the application of AnIA in MBBR systems was an effective strategy to achieve SNEDPR, providing better simultaneous removal performance of nitrogen and phosphorus from low C/N ratio wastewater. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel immersed self-aerated biofilm reactor was used to treat rural wastewater. • 76% SND ratio was achieved in a single reactor without aeration equipment. • The system was efficient in wastewater treatment with lower energy consumption. • 70% immersion ratio and 4 r/min obtained higher removal efficiency. • nxrA , nirSK , narGHI , napABC , norBC and nosZ were highly expressed functional genes. To achieve energy-efficient treatment of the rural wastewater with satisfying performance, a novel immersed rotating self-aerated biofilm reactor (iRSABR) was proposed in this study. The iRSABR system showed better biofilm renewal performance and higher microbial activity. The effect of different regulation strategies on the iRSABR system was investigated in this study. The 70% immersion ratio and 4 r/min rotation speed (stage III) exhibited the best performance, with a total nitrogen removal efficiency of 86% and a simultaneous nitrification–denitrification (SND) rate of 76%, along with the highest electron transport system activity. The nitrogen removal pathway revealed that the SND was achieved through autotrophic/heterotrophic nitrification and aerobic/anoxic denitrification. The regulation strategy in the iRSABR system established a synergistic microbial community with main functional bacteria of nitrification (Nitrosomonas), anoxic denitrification (Flavobacterium , Pseudoxanthomonas), and aerobic denitrification (Thauera). This study highlighted the feasibility and adaptability of the iRSABR system toward energy-efficient rural wastewater treatment. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel RSABR was developed for decentralized wastewater treatment. • Achieved 62.5% SND ratio in a single reactor with no aerator. • Effluent COD, NH 4 +-N and TN were below 20, 0.4 and 15 mg/L, respectively. • The higher μ max N O 3 closely associated with denitrification efficiency. • Nitrification and denitrification were main metabolism pathways according to KEGG. Decentralized wastewater pollution in rural areas has become a serious problem for the rural environment. In this study, a novel rotating self-aerated biofilm reactor was developed for decentralized wastewater treatment without any aeration equipment. After the long-term operation of 110 days, the removal efficiency reached to 96.06 % (COD), 98.06 % (NH 4 +-N), and 62.58 % (TN) in the last phase. Under high dissolved oxygen level, the simultaneous nitrification–denitrification (SND) maintained at a stable ratio of 62.53 % and the denitrification rates reached over 28.37 mg/L/h. With the organic loading rate increased, key nitrogen functional bacterial communities such as anoxic denitrifiers (Thiothrix , Flavobacterium , Pseudoxanthomonas , Aquimonas and Azoarcus) and aerobic denitrifiers (Hydrogenophaga , Zoogloea and Terrimonas) increased obviously. Overall, microbial analysis and nitrogen metabolism pathway indicated that an integration of SND process was achieved in this single reactor by the combined action of nitrification, denitrification and comammox without any aeration equipment. [ABSTRACT FROM AUTHOR]

[Display omitted] • An intermittently-aerated MBBR assessed for treating low C/N rural wastewater. • Less resistance of mass transfer to oxygen was found under microaerobic condition. • The proportion of active autotrophic biomass increased with low C/N and DO level. • SND progress in intermittently-aerated MBBR was observed with low oxygen. An intermittently-aerated moving bed biofilm reactor (MBBR) was proposed for nitrogen and carbon removal from low C/N synthetic rural wastewater. In purposes of low energy consumption and costs, the intermittent aeration modes were changed and the dissolved oxygen was reduced gradually during the operation. The results showed that effluent concentrations of ammonia nitrogen and chemical oxygen demand were lower than 15 and 50 mg/L, respectively, even under microaerobic condition (0.1–1.0 mg/L). Meanwhile, the simultaneous nitrification–denitrification was achieved by intermittent aeration. The activity of functional bacteria was still high and the proportion of autotrophic biomass increased significantly under intermittent micro-aeration mode, which improved the nitrification performance. Aerobic denitrifier Hydrogenophaga , anoxic denitrifier Thiothrix , and heterotrophic nitrifier such as Rhodobacter were enriched in the intermittently micro-aerated MBBR, which will provide an applicable solution for rural wastewater treatment under low C/N and costs. [ABSTRACT FROM AUTHOR]

Iron-assisted wastewater treatment has garnered significant attentions due to its promising potential for nitrogen removal under low carbon/nitrogen (C/N) ratios. However, the continuous addition of iron would result in unacceptably high operational cost. Herein, the iron mental-organic frame (MIL-88A(Fe)) modified sponge (MS) was developed as a source of continuous reactive iron sites and integrated in an intermittently-aerated moving bed biofilm reactor (MBBR) to enhance nitrogen removal efficiency under low (C/N) ratios. The results demonstrated that the MS-assisted system achieved stable total nitrogen removal of 76.2 ± 6.0% without adding additional iron and carbon sources when the C/N was 3.5 ± 0.3. After MS addition, the electron transport system activity increased from 8.2 ± 0.9 μgO 2 /g/h to 12.7 ± 2.6 μgO 2 /g/h, and the scanning electron microscope images revealed that the MS were covered with biofilm. Meanwhile, iron autotrophic bacteria (Thermomonas , Dechloromonas) and heterotrophic denitrifying bacteria (Candidatus_Competibacter) were enriched in the MS-assisted system, confirming the successful inducing of iron autotrophic denitrification process inside the reactor. This study revealed the effect of MS addition on microbial community succession and their pollutants removal characteristics, offering a feasible strategy for low C/N wastewater treatment. [Display omitted] • A ferric iron-mediated MBBR has been developed to improve the nitrogen removal. • Achieved 76.2 ± 6.0% of TN removal when C/N was 3.5 ± 0.3, DO was 1.8 ± 0.3 mg/L. • The valence state transition of Fe (Ⅲ) to promote the continuous nitrogen removal. • The ETSA increased by 54.9% after adding MS. • The addition of MS facilitated the enrichment of IRB and Fe-ADB. [ABSTRACT FROM AUTHOR]

[Display omitted] • Confinement of nano Mg-oxide in biochar was achieved via sequential doping of N and Mg. • More porous structure in biochar with smaller pore size was created by N pre-doping. • Nanosized MgO successfully induced the enhanced phosphate adsorption capacity. Advanced metal-doped biochar with superior phosphate (P) adsorption capacity plays a crucial role in combating eutrophication, depending on the rational design of the biochar structure for uniform and nanoscale dispersion of metal oxides. Herein, the nanoconfinement of magnesium oxide (MgO) was successfully attained in nitrogen pre-doped biochar (Mg/N-BC). The well-dispersed MgO was confined within nanoscale structure of Mg/N-BC, delivering P adsorption capacity of 108.41 mg g−1 and adsorption rate of 18.01 mg g-1h−1. More importantly, its adsorption performance at equilibrium 0.5 mg P/L was 17.70 times higher. Results suggested the decrease in pore size was positively correlated with the increase of N, confirming the role of N pre-doping in structure shaping and MgO confinement. The enhanced P adsorption was attributed to the well-dispersed MgO nanoparticles within the biochar. This study introduced a facile synthesis approach for biochar-incorporated nanoscale MgO, offering a new strategy for enhanced P removal. [ABSTRACT FROM AUTHOR]