Shortcut Nitrification-denitrification Research Articles

Simultaneous removal of ammonia nitrogen and manganese by anoxic/oxic (A/O) process from electrolytic manganese residue leachate

Ammonia nitrogen and manganese contained in the leachate of electrolytic manganese residue are causing serious damage to the ecological environment. In this study, anaerobic/oxic (A/O) process as a biological method to achieve simultaneous removal of nitrogen and manganese produced during the actual production of manganese. Results indicated that after 137 d of operation, the system achieved 96.73 ±1.25%, 98.42 ± 0.60%, 96.97 ± 0.19%, and 100% removal of Mn(II), NH4+-N, TN, and chemical oxygen demand (COD), respectively. Extracellular Polymeric Substances (EPS) secreted by microorganisms was converted to carbon source to promote denitrification. Scanning electron microscopy (SEM) showed that Mn(II) formed manganese crystals in the process of complete reflection with sludge, acting as electron donor to achieve simultaneous removal of nitrogen and manganese, and removal of Mn(II) was found by X-ray photoelectron spectroscopy (XPS) through redox and valence changes. 16S rRNA indicated that Proteobacteria, Deinococcus-Thermus, Bacteroidete, and Firmicutes were involved in the process of removal nitrogen and manganese. The presence of Limnobacter allowed a more stable accumulation of NO2--N in reactor, thus achieving shortcut nitrification-denitrification, and Flavihumibacter promoted the secretion of EPS. Collectively, the study reveals that the interaction of autotrophic denitrifying bacteria (Chryseolinea), heterotrophic denitrifying bacteria (Fusibacter, Thauera), and manganese-oxidizing bacteria (Pseudaminobacter, Bacillus, Pedomicrobium, Aeromonasr) achieved simultaneously removal of nitrogen and manganese from the reactor shortcut nitrification-denitrification. This study provides a new insight for the treatment of electrolytic manganese residue leachate produced in the process of manganese production.

Start-up of pilot-scale ANAMMOX reactor for low-carbon nitrogen removal from anaerobic digestion effluent of kitchen waste

The pilot-scale simultaneous denitrification and methanation (SDM)-partial nitrification (PN)-anaerobic ammonia oxidation (Anammox) system was designed to treat anaerobic digestion effluent of kitchen waste (ADE-KW). The SDM-PN was first started to avoid the inhibition of high-concentration pollutants. Subsequently, Anammox was coupled to realize autotrophic nitrogen removal. Shortcut nitrification–denitrification achieved by the SDM-PN. The NO2–-N accumulation (92 %) and NH4+-N conversion (60 %) were achieved by PN, and the removal of TN and COD from the SDM-PN was 70 % and 73 %, respectively. After coupling Anammox, the TN (95 %) was removed with a TN removal rate of 0.51 kg·m−3·d-1. Microbiological analyses showed a shift from dominance by Methanothermobacter to co-dominance by Methanothermobacter, Thermomonas, and Flavobacterium in SDM during the SDM-PN. While after coupling Anammox, Candidatus kuenenia was enriched in the Anammox zone, the SDM zone shifted back to being dominated by Methanothermobacter. Overall, this study provides new ideas for the treatment of ADE-KW.

Revealing the differences in metabolisms and nitrogen removal mechanisms of the full and shortcut nitrification-denitrification processes for the treatment of livestock wastewater

The full nitrification-denitrification process (FN) and shortcut nitrification-denitrification process (SN) are both important approaches for treating livestock wastewater. However, most existing studies focus on pollutant removal performance in wastewater treatment, while the differences between the two processes in terms of bacterial communities, metabolic pathways, nitrogen removal mechanisms, and potential pathogen threats have been poorly investigated. In this study, the SN process exhibited lower oxygen demand, reduced sludge production, higher nitrogen removal rate, and lower pathogen threat for treating livestock wastewater. The bacterial communities, the primary participants of pollutant removal in wastewater treatment, were significantly different between the two processes. In the FN process, 15 genera were significantly enriched, including Saccharimonadales, Micropruina, Ferruginibacter, etc. On the other hand, the SN process showed enrichment of 10 genera, including Brachymonas, Tessaracoccus, Ottowia, etc. These enriched genera, such as Brachymonas, Tessaracoccus, and Ottowia in the SN process, were positively correlated with the denitrification genes, facilitating a higher nitrogen removal rate. Moreover, the FN process exhibited significantly higher amino acid metabolism and reproduction-related pathways, contributing to its higher alpha-diversity of the bacterial community. The significantly enriched genes involved in assimilatory nitrate reduction and nitrogen assimilation pathway suggested that nitrogen assimilation played a crucial role in ammonia nitrogen removal, but it also increased sludge production in the FN process. Additionally, the FN process had a higher number and abundance of potential pathogens, indicating a greater pathogen threat. In conclusion, this study provides valuable insights into the differences between the FN and SN processes in terms of bacterial communities, nitrogen removal mechanisms, and potential pathogen threats. It also offers theoretical guidance for adopting appropriate strategies in wastewater treatment.

Bioelectricity recovery through isolation and removal of nitrogen from wastewater by shortcut nitrification-denitrification in a coupled microbial fuel cell system

Achieving both sustainable power recovery and efficient nitrogen removal in a single microbial fuel cell (MFC) reactor is a big challenge in the selection of external resistance and choosing favorable conditions. This study introduced a coupled MFC system (N-MFC and D-MFC) with a unique approach of isolating nitrogen input from wastewater and removing it via shortcut nitrification–denitrification, achieving treatment of wastewater along with improved energy recovery. The configuration of the N-MFC facilitated it to contribute significantly to the 98 % COD removal and to the 1.27 W m−3 energy recovered of the coupled MFC system. The results highlighted that operational circumstances affected MFC performance and offered insights into power generation, ammonium isolation, and shortcut nitrification in the N-MFC. The ratio of nitrite to nitrate was maximized at 2 under the dissolved oxygen (DO) condition of 0.6 mg/L, as opposed to 1.44 under the DO condition of 1.2 mg/L, during the shortcut nitrification process in the cathode chamber of N-MFC. The total nitrogen removal efficiency of the coupled MFC system was obtained at 50.2–71.2 %, proportionate to the COD influent and nitrite-to-nitrate ratio. The nitrogen removal of the coupled MFC system was significantly aided by autotrophic denitrification in the cathode chamber of D-MFC. The finding of this study emphasized the potential for optimizing the nitrogen removal in the D-MFC to increase the performance of N-MFC in power recovery by implementing the shortcut nitrification–denitrification process. This concept can be applied in practical for meeting the goals of SDG6 (Sustainable Development Goals) and clean energy production.

Mechanisms and responses of nitrogen transformations mediated by microbial communities in constructed tailwater wetlands to salinity stress

The long-term salinity stress may affect the nitrogen transformation processes and microbial community assembly patterns in constructed wetlands treating tailwater, influencing their operational effectiveness. In this study, we employ 16S rRNA gene sequencing, combined with multivariate ecological and statistical methods, to investigate interactions between bacterial community diversity and nitrogen transformation genes in constructed tailwater wetlands under salinity stress. The results revealed that long-term salinity stress led to reduced microbial diversity and increased community heterogeneity. Additionally, salinity stress led to decreased functionality of microbial community, intensified competition, and elevated expression of functional genes. Furthermore, as predicted by PICRUSt2, long-term salinity stress resulted in overall inhibition of community nitrogen conversion functions, while short-cut nitrification-denitrification processes played a bigger part in nitrogen conversion. Moreover, the symbiotic nitrogen fixation process was promoted, while the competing dissimilatory nitrate reduction process was inhibited. Salinity can greatly explain the apparent differences in microbial communities and nitrogen transformation potential in saline constructed wetland systems compared to common wetlands. These findings provide novel insights into the mechanisms underlying nitrogen transformation processes in constructed tailwater wetlands under long-term salinity stress and important implications for redesign and renovations of constructed wetlands.

Deciphering antibiotic resistome variations during nitrogen removal process transition under mixed antibiotics stress: Assembly process and driving factors

Antibiotic resistome, which encompasses all types of antibiotic resistance genes (ARGs) in a given environment, has received increasing attention in research on different wastewater treatment processes. However, the variation in antibiotic resistome during the transition from the full nitrification–denitrification to the shortcut nitrification–denitrification process remains unclear. In this study, a total of 269 targeted gene subtypes were identified, along with 108 genes were consistently present in all samples. The introduction of mixed antibioticsrapidly increased the abundance of corresponding and non-corresponding ARGs, as well as that of mobile genetic elements.The variations in of the antibiotic resistome were primarily driven by dissolved oxygen and nitrite accumulation rate. Moreover, 34 bacterial genera were identified as potential ARG hosts, with most denitrifiers considered as potential antibiotic-resistant bacteria, including Branchymonas, Rhodobacter, and Thauera. This study provides a method for controlling antibiotic resistance by regulating the changes in environmental variables and bacterial communities.

Higher impact resistance and lower antibiotic resistance genes proliferation rate in shortcut nitrification-denitrification process under long-term antibiotics selection pressure

Shortcut nitrification–denitrification (SCND) has been widely concerned due to its high nitrogen removal efficiency and low operating cost. However, little information is available on the fate of antibiotic resistance genes (ARGs) in SCND process. This study investigates the dynamics of nitrogen removal and ARGs between SCND and full nitrification–denitrification (FND) under long-term selective pressure conditions of tetracycline and sulfadiazine. The study explores the response patterns of extracellular polymers, microbial activity, and microbial community. Results show that the SCND process exhibits 9.14% higher extracellular polymers and 119.07% higher respiratory activity than FND process, resulting in better TN removal performance (67.16% vs. 49.24%) and stronger impact resistance. Compared to Phase I (0 µg/L) and Phase II (100 µg/L), the relative abundance of total ARGs experienced a sharp increase in Phase III (500 µg/L). The SCND process maintains a lower total ARGs abundance than the FND process in water phase. Specifically, in phase III, the relative abundance of intI1 and ARGs in the FND process are 0.04–2.1 logs and 0.66–1.60 logs higher than that of the SCND process in sludge and water phases, respectively. More denitrifying microbes (>40%) are enriched in the SCND process, while it changes to hydrolytic acidification bacteria (>20%) in the FND process. The Partial Least Squares Path Modeling reveals that microbial community and microbial activity play a crucial role in ARGs transmission, with microbial activity exerting greater influence. Additionally, potential pathogenic bacteria including Clostridium, Gemnobacter, Klebsiella, Enternobacter, Aeromonas, Burkholderia are identified, and SCND over FND process shows better inhibition effect on potential pathogenic bacteria proliferation (0.022% vs 0.080%). This study provides new insights into removing traditional pollutants and ARGs simultaneously from wastewater treatment system.

Comparative insight into the effects of different carbon source supplement on antibiotic resistance genes during whole-run and short-cut nitrification-denitrification processes.

Mature landfill leachate is known for nitrogen-removal challenging and meantime was considered as an important sink of antibiotic resistance genes (ARGs). The added external carbon sources, enabling the short-cut nitrification and denitrification, may facilitate the proliferation of bacteria that possibly carry ARGs. However, this speculation has yet to be studied. Here, we explored the effects of glucose, sodium acetate, and methanol supplements on ARGs during whole-run and short-cut treatment processes. The results showed that sodium acetate supplement during short-cut process efficiently reduced the abundances of total ARGs (0.84-1.99 copies/16S rRNA) and integrons (0.59-1.20 copies/16S rRNA), which were highly enhanced by methanol addition during whole-run treatment process (total ARGs: 3.60-11.01 copies/16S rRNA, integrons: 1.20-4.69 copies/16S rRNA). Indirect gradient analysis showed that the variation of ARGs was not correlated with the supplement of different external carbon source. Correlation analysis indicated that dominant intl1 (55.99 ± 17.61% of integrons) showed positively significant correlations with all detected ARGs expect for sul2 and ermB (p < 0.05), suggesting the significant role on ARGs dissemination. Redundancy analysis illustrated that the potential hosts of intl1, intl2, sul1, tetQ, tetM, mefA, and mexF were dominant Bacteroidetes and Actinobacteria. Interestingly, the numbers and significant extent of correlations under the supplement of sodium acetate during short-cut denitrification process were obviously declined, and it was in accordance with ARGs reduced by sodium acetate supplement, suggesting sodium acetate displayed the efficient ARGs reduction during short-cut process. In summary, this study provides a comparative understanding of the effects on ARGs by different carbon source supplements during nitrification-denitrification processes of leachate; sodium acetate is the optimal carbon source.

Unravelling and enhancing the power recovery and nitrogen removal mechanism from wastewater by isolating input nitrogen in a coupled microbial fuel cell system

Poor recovery energy of microbial fuel cells (MFCs) persists and is considerably lower when dealing with nitrogen, a substantial challenge of this technology. This study investigated power generation from treating different COD/N ratio wastewater by isolating the input nitrogen using the coupled MFC system, including nitrification-MFC (N-MFC) and denitrification-MFC (D-MFC). Energy from wastewater was predominantly recovered in the N-MFC due to the system's configuration, which allowed for the oxidation of over 75% of organic matter input while simultaneously isolating nitrogen input. The nitrogen isolation was affected by the electricity generation of the N-MFC. The complete nitrification was done in the first mode under dissolved oxygen (DO) of 4 mg L−1 in the cathode chamber of the N-MFC. When the DO was decreased to 0.6 mg L−1 in the second mode, over 95% of the ammonium was oxidized to nitrite and nitrate in a 2:1 ratio. The N-MFC's power density of 6.16–6.3 W m−3 was achieved in the first mode, while a power generation of 0.82 W m−3 was obtained in the second mode. The principal mechanism for nitrogen removal at the D-MFC was autotrophic denitrification. The first mode nitrogen removal efficiency was 56.9%, 72.7%, and 80.2% for COD/N input of 5.5, 7.1, and 10.3, respectively. The second mode utilized the short-cut nitrification-denitrification process, superior to the first mode with regards to energy efficiency and nitrogen removal. However, the usage of CEM as separator and aeration requirement makes this technology expensive. Results indicated that nitrogen removal and effective utilization of organic matter for energy recovery could be achieved with a proper configuration for a coupled MFC and in future the cost can be reduced.

Optimizing SCND with carbon-rich hydrolysates from typical organic wastes: Material composition, augmentation performance, microbiome response, and life cycle impact

The rapid growth of production and consumption has led to severe environmental pollution, creating a major challenge to achieving the United Nations' sustainable development goals (SDGs). To address it, recycling of organic wastes into value-added products is a possible solution. In this work, four typical organic wastes including sewage sludge (SS), chicken manure (CM), food waste (FW), and corn straw (CS) were employed to produce hydrolysates augmenting shortcut nitrification-denitrification (SCND) for nitrogen depletion in wastewater. The hydrolysates were carbon-rich, with total COD (TCOD), soluble COD (SCOD), and volatile fatty acids (VFA) concentrations ranging from 32.5 to 102.7, 5.7 to 48.4, and 2.0–16.5 mg/L, respectively. The most effective nitrogen depletion was obtained in units supplemented with CM and FW hydrolysates, which had reduced average NH3–N concentrations and near-zero TN removal failure rates under legal requirements. The microbial community analysis demonstrated that various functional bacteria from phylum to genus level were detected in all scenarios, which was corroborated by abundant genetic functions involved in nitrogen metabolism. Further, life cycle assessment revealed negative environmental impact on all categories, with an exception of eutrophication potential (EP) with negative values (∼−0.04 kg Phosphate eq.), allowing positive net environmental benefit (NEB). Operational cost analysis revealed that CM and FW are more effective but costlier than SS and CS. Together, these results indicate that, after hydrolysis, organic wastes can be efficient stimulant augmenting SCND performance for nitrogen depletion in wastewater, benefiting the overall environmental impact.

Simultaneous removal of nitrogen and arsenite by heterotrophic nitrification and aerobic denitrification bacterium Hydrogenophaga sp. H7.

Nitrogen and arsenic contaminants often coexist in groundwater, and microbes show the potential for simultaneous removal of nitrogen and arsenic. Here, we reported that Hydrogenophaga sp. H7 was heterotrophic nitrification and aerobic denitrification (HNAD) and arsenite [As(III)] oxidation bacterium. The appearance of nitrogen removal and As(III) oxidation of Hydrogenophaga sp. H7 in liquid culture medium was studied. The effect of carbon source, C/N ratio, temperature, pH values, and shaking speeds were analyzed. The impact of strains H7 treatment with FeCl3 on nitrogen and As(III) in wastewater was assessed. The key pathways that participate in simultaneous nitrogen removal and As(III) oxidation was analyzed by genome and proteomic analysis. Strain H7 presented efficient capacities for simultaneous NH4 +-N, NO3 --N, or NO2 --N removal with As(III) oxidation during aerobic cultivation. Strikingly, the bacterial ability to remove nitrogen and oxidize As(III) has remained high across a wide range of pH values, and shaking speeds, exceeding that of the most commonly reported HNAD bacteria. Additionally, the previous HNAD strains exhibited a high denitrification efficiency, but a suboptimal concentration of nitrogen remained in the wastewater. Here, strain H7 combined with FeCl3 efficiently removed 96.14% of NH4 +-N, 99.08% of NO3 --N, and 94.68% of total nitrogen (TN), and it oxidized 100% of As(III), even at a low nitrogen concentration (35 mg/L). The residues in the wastewater still met the V of Surface Water Environmental Quality Standard of China after five continuous wastewater treatment cycles. Furthermore, genome and proteomic analyses led us to propose that the shortcut nitrification-denitrification pathway and As(III) oxidase AioBA are the key pathways that participate in simultaneous nitrogen removal and As(III) oxidation.

Evaluation of the stability of shortcut nitrification-denitrification process based on online specific oxygen uptake rate monitoring

Shortcut nitrification-denitrification (SCND) is widely concerned because of its low energy consumption and high nitrogen removal efficiency. However, the current difficulty lies in the stable maintenance of SCND performance, which leads to the challenge of large-scale application of this new denitrification technology. In this study, the nitrogen removal pathway from complete nitrification-denitrification (CND) to SCND was rapidly realized under high free ammonia (FA), high pH and low dissolved oxygen (DO) conditions. The variations of specific oxygen uptake rate (SOUR) of activated sludge in both processes were investigated by an online SOUR monitoring device. Different curves of SOUR from CND to SCND process were observed, and the ammonia peak obtained based on SOUR monitoring could be used to control aeration time accurately in SCND process. Accordingly, the SOUR ratio of ammonia oxidizing bacteria (AOB) to nitrite oxidizing bacteria (NOB) (SOURAOB/SOURNOB) was increased from 1.40 to 2.93. 16S rRNA Miseq high throughput sequencing revealed the dynamics of AOB and NOB, and the ratio of relative abundance (AOB/NOB) was increased from 1.03 to 3.12. Besides, SOURAOB/SOURNOB displayed significant correlations to ammonia removal rate (P < 0.05), ammonia oxidation rate / nitrite oxidation rate (P < 0.05), nitrite accumulation rate (P < 0.05) and the relative abundance of AOB/NOB (P < 0.05). Thus, a strategy for evaluation the SCND process stability based on online SOUR monitoring is proposed, which provides a theoretical basis for optimizing the SCND performance.

Microbial mechanisms of refractory organics degradation in old landfill leachate by a combined process of UASB-A/O-USSB

A combined process of anaerobic digestion (UASB), shortcut nitrification-denitrification (A/O), and semi-anoxic co-metabolism (operated by an up-flow semi-anoxic sludge bed; USSB) was constructed for the treatment of old landfill leachate (>10 years). The performance and mechanism of refractory organics degradation by the combined process (UASB-A/O-USSB) were investigated. The results showed that the semi-anoxic co-metabolism contributes 57 % of the totally degraded refractory organics. Specific microorganisms and their corresponding metabolic functions drive the degradation of refractory organics in each unit of the UASB-A/O-USSB process. In detail, organics with simple molecular structures were preferentially degraded by anaerobic digestion and shortcut denitrification, whereas those with complex structures were subsequently degraded in the oxic tanks and USSB reactor by shortcut nitrification and semi-anoxic co-metabolism. The structural equation model showed that the combined process of shortcut nitrification and semi-anoxic co-metabolism had a better effect on the degradation of recalcitrant organics than the single process. These findings provide information on how refractory organics are metabolically degraded in a combined process.

COD/TN ratios shift the microbial community assembly of a pilot-scale shortcut nitrification-denitrification process for biogas slurry treatment.

In this study, effects of carbon to nitrogen (COD/TN) ratios of biogas slurry on shortcut nitrification-denitrification in a pilot-scale integrated fixed film activated sludge (IFAS) system were investigated. Lowering the COD/TN ratio from 11.7 to 6.2 exerted a negative impact on shortcut nitrification-denitrification performance. Accordingly, the NH3-N and TN removal rates decreased from 94.4 to 91.2% and 92.3 to 85.9%, respectively. The dynamics of microbial assembly was analyzed by MiSeq sequencing, and the denitrifying functional genes were quantified by qPCR. The results showed that ammonia oxidizing bacteria and amoA gene were more abundant on the biofilm of oxic tank, indicating they play a key role in NH3-N removal. Autotrophic, endogenous, and fast heterotrophic kinetics denitrifiers were coexisted and enriched in the IFAS system with a decreasing of COD/TN ratio. TN removal was mainly affected by denitrifiers (including Arenimonas, Acidovorax, and Thaurea) harboring narG and nirS genes. Canonical correspondence analysis proved that COD/TN ratio was the most critical factor driving the succession of microbial community. Dissolved oxygen (DO) and pH were found positively correlated with denitrifiers at low COD/TN ratio conditions. As a result, NH3-N and TN removal were effectively enhanced when the DO level in the oxic tank of IFAS system was increased to 1.0-3.0 mg/L.

Dynamics of antibiotic resistance genes and microbial community in shortcut nitrification-denitrification process under antibiotic stresses.

In this study, the performance of shortcut nitrification-denitrification (SCND) at different TC and SD stress conditions (0μg/L, 1-97days; 100μg/L, 98-138days; 500μg/L, 139-175days) was investigated. Higher level antibiotic stress (500μg/L) led to the serious deterioration of nitrogen removal, and denitrification was more sensitive to antibiotic stress than nitrification. The dynamics of antibiotic resistance genes (ARGs) and microbial community were revealed by quantitative real-time PCR and 16S rDNA high-throughput sequencing, respectively. Tet-genes (tetA, tetQ, tetW), sul-genes (sulI, sulII), and mobile genetic element (intI1) in activated sludge increased by 1.2 ~ 2.5 logs with long-term exposure of antibiotic stress, and sulI, tetA, tetQ, and tetW were significantly positively correlated with intI1. Long-term antibiotics stress caused the decrease of most denitrifiers, and five genera were identified as the potential host of ARGs. The key impact factors of SCND drove the dynamics of ARGs and microbial community. Except for sulII gene, DO and FA were significantly positively correlated with ARGs, while FNA, NAR, and NO2--N showed opposite effects to ARGs. Overall, maintaining relative lower DO, higher FNA, NAR, and NO2--N conditions are not only benefit to the stable operation of SCND, but may also conducive to the control of ARG dissemination. This study provides theoretical basis on the control of ARGs in the SCND process.

Research on Biological Fluidized Bed System Treatment Performance and Nitrogen Removal Process for Seafood Processing Wastewater with Different Operation Conditions

In this study, the biological fluidized bed system was used to treat seafood processing wastewater. The sludge was collected from the secondary sedimentation tank of a municipal wastewater treatment plant and acclimated for 200 days before the experiment. The treatment efficiencies of simulated seafood processing wastewater by biological fluidized bed system with different sludge concentrations, different hydraulic retention times (HRTs) and different bio-carriers were studied. The results showed that the removal efficiency of nitrogen and phosphorus increased with the increasing sludge concentration and by extending hydraulic retention time, and the higher removal efficiency of nitrogen and phosphorus could be obtained with the higher specific surface area of the bio-carrier. The nitrogen removal process analysis showed that the nitrification and denitrification activity of sludge could be changed with different operation conditions resulting in different nitrogen removal efficiency in the biological fluidized bed system. This was mainly because the change tendency of the ammonia nitrogen oxidizing process, nitrite oxidizing process, nitrite reduction process and nitrate reduction process was different with different operation conditions in a high salinity environment. Theoretically, the difference of the inhibitory effect of a high-salt environment on different nitrification and denitrification processes could be used to realize shortcut nitrification denitrification by controlling a certain operation condition.

Novel shortcut biological nitrogen removal using activated sludge-biofilm coupled with symbiotic algae

This study evaluated a novel shortcut biological nitrogen removal (BNR) method using activated sludge-biofilm coupled with microalgae in a photo-sequencing batch biofilm reactor (PSBBR) for treating high ammonia nitrogen (NH4+-N) wastewater. Results showed that the symbiotic microalgae supplied oxygen and an additional organic carbon source for bacteria. The consortium achieved high nitrogen removal efficiency (> 90%) and had the potential to lower the operating cost when used for treating biogas slurry (BS). It saved more than 50% of the external carbon source and reduced about 78% of oxygen demand compared with the conventional BNR process. Nitrogen was removed mainly through shortcut nitrification-denitrification (SCND) (> 80%) and biological assimilation (6.8%) in the PSBBR. The algal-bacterial symbiosis improved the species richness but reduced the microbial diversity of the biofilm. Nitrosomonas with an abundance of 19.81% was the dominant ammonia-oxidizing bacteria (AOB) in the biofilm, while Thauera with an abundance of 45.03% played a leading role in denitrification. This study concurrently indicated that algae and activated sludge coupling increased the nitrous oxide (N2O) emission in the shortcut nitrogen removal process.

Shortcut nitrification-denitrification and biological phosphorus removal in acetate- and ethanol-fed moving bed biofilm reactors under microaerobic/aerobic conditions

This study investigated the feasibility of coupling simultaneous partial nitrification and denitrification (SPND) to biological phosphorus removal in continuous-flow intermittently-aerated moving bed biofilm reactors (MBBRs) fed with different carbon sources, i.e. ethanol and acetate. Bacterial cultivation at pH 8.2 (±0.2), 26–28 °C and SRT of 4 day and microaerobic/aerobic MBBR operation allowed to achieve average dissolved organic carbon (DOC), total inorganic nitrogen (TIN) and P-PO43− removal efficiencies (REs) of 100%, 81–88% and 83–86% at HRT of 1 day, dissolved oxygen (DO) range of 0.2–3 mg L−1 and feed C/N and C/P ratios of 3.6 and 11, respectively. Acetate supplementation favored a diversified microbial community, while overgrowth of heterotrophs was observed when increasing feed C/N ratio in ethanol-fed MBBR. Illumina sequencing displayed the presence of putative phosphorus accumulating organisms (PAOs) such as Hydrogenophaga and Pseudomonas in MBBR biofilm and suspended biomass, whereas no typical NOB was identified during the study.

Shortcut nitrification-denitrification achieved by hydroxylamine addition in constructed rapid infiltration system

Shortcut nitrification-denitrification achieved by hydroxylamine addition in constructed rapid infiltration system

Sludge fermentation liquid addition attained advanced nitrogen removal in low C/N ratio municipal wastewater through short-cut nitrification-denitrification and partial anammox

Biological nitrogen removal of wastewater with low COD/N ratio could be enhanced by the addition of wasted sludge fermentation liquid (SFL), but the performance is usually limited by the introducing ammonium. In this study, the process of using SFL was successfully improved by involving anammox process. Real municipal wastewater with a low C/N ratio of 2.8–3.4 was treated in a sequencing batch reactor (SBR). The SBR was operated under anaerobic-aerobic-anoxic (AOA) mode and excess SFL was added into the anoxic phase. Stable short-cut nitrification was achieved after 46d and then anammox sludge was inoculated. In the stable period, effluent total inorganic nitrogen (TIN) was less than 4.3 mg/L with removal efficiency of 92.3%. Further analysis suggests that anammox bacteria, mainly affiliated with Candidatus_Kuenenia, successfully reduced the external ammonia from the SFL and contributed approximately 28%–43% to TIN removal. Overall, this study suggests anammox could be combined with SFL addition, resulting in a stable enhanced nitrogen biological removal.