Advanced Nitrogen Removal Research Articles

Start-up of the combined anaerobic ammonium oxidation and solid phase denitrification process and microbial characterization analysis

To improve the nitrogen removal performance of anaerobic ammonia oxidation (anammox)-based processes, a modified anaerobic baffled reactor (ABR) equipped with a packed bed of poly-3-hydroxybutyrate-cohyroxyvelate (PHBV) was employed to start up the combined anammox and solid phase denitrification (SPD) process for the treatment of nitrogen-rich wastewater. Results showed that a stable removal of total inorganic nitrogen (TIN) of 98.5 % was achieved with a nitrogen loading rate of 0.46 kg·(m3·d)−1, decreasing the effluent TIN concentration to <2 mg·L−1. Throughout the operation period of 180 days, sludge granulation in three compartments of the ABR was promoted by a stepwise decrease in the hydraulic retention time. The anammox reaction and endogenous denitrification mainly occurred in the first two compartments with inorganic feeding and contributed >86 % of TIN removal. 16S rRNA gene amplicon sequencing showed that anammox communities, dominated by genera Candidatus Kuenenia and Candidatus Brocadiaceae, were enriched in granular sludges with symbiotic heterotrophic bacteria. Co-cultures of hydrolytic bacteria (Burkholderiales, Kapabacteriales, and Clostridium-sensu-stricto-7) and denitrifying bacteria (Comamonadaceae, Rhodocyclaceae, and Denitratisoma) were detected within the biofilm on the surface of PHBV particles. PHBV hydrolysate input effectively drove heterotrophic denitrification in the successive compartment and increased the complexity of microbial co-occurrence networks. These findings provide insight into the synergistic mechanisms between anammox and SPD and present a feasible combined process application for advanced biological nitrogen removal.

Endogenous partial denitritation as an efficient remediation to unstable partial nitritation-anammox (PNA) process: Bacteria enrichment and superior robustness

The application of partial nitritation-anammox (PNA) process suffers severe obstacles due to the instability of partial nitritation (PN) process. This study sought to evaluate the feasibility of endogenous partial denitratation (EPD) as a remediation or alternative to supply nitrite for the unstable PNA process. A novel strategy of optimal organics utilization through pre-anaerobic carbon storage and post-anoxic endogenous denitrification coupled with anammox was developed in a single-stage bioreactor treating actual municipal wastewater with low C/N (∼3.2). Specifically, the undesired NO2−/NH4+ ratio (2.4 to 0.04) and nitrate accumulation were obtained by increasing the aeration rate (0.6 to 1.8 L/min) to simulate the PN instability. Delightedly, advanced nitrogen removal efficiency (92.1%) was maintained despite a dramatic decrease in nitrite accumulation ratio from 97.6% to 2.6%. This was attributed to the significant increase in anammox contribution to total nitrogen removal from 30.2% to 80.5%. The steady nitrite flux supplied from EPD coupled with PN (EPD contribution increased from 0 to 97.0%) was assumed to be the main reason for the continually increasing abundance and bioactivity of anammox bacteria. Both the anammox bacteria (1.5%, Ca. Brocadia) and glycogen accumulating organisms (6.0%, responsible for EPD) were enriched and coexisted stably in the single reactor. Our study confirms that coupling EPD with anammox has great potential as a remediation for the unstable mainstream PNA process.

Simultaneous nitrification and denitrification in a PCL-supported constructed wetland with limited aeration.

Considerable advances have been made in the substrate design and operation strategies of constructed wetlands to facilitate nitrogen elimination. However, few studies examined the complicated interaction between solid organic substrates and limited aeration on nitrogen removal. A vertical flow constructed wetlands in gradient distribution of inorganic and solid organic substrates (polycaprolactone/PCL) (P-VFCW) and a controlled vertical flow constructed wetland without PCL (C-VFCW) were developed for the tertiary treatment of municipal tailwater. Results indicated that ammonia was nearly converted to nitrate, while the total nitrogen removal efficiencies (TNREs) in C-VFCW were negligible. In P-VFCW, however, optimal TNREs approached 95% with an aeration rate of 0.06mL·min-1 and hydraulic retention time (HRT) of 24h, and simultaneous nitrification and denitrification process (SND) in aerobic conditions was confirmed. As for the spatial microbial community structure evolution, Comamonas, which is associated with heterotrophic nitrification and anoxic/aerobic denitrification, was enriched along the vertical profiles of P-VFCW. Autotrophic nitrifier (Nitrospira), aerobic denitrifier (Bradyrhizobium and Azospira), and anoxic denitrifier (Ignavibacterium and Methyloversatilis) were dominated in different depths of P-VFCW, respectively. Besides, Canna indica biomass in P-VFCW was significantly larger than that in C-VFCW, which was attributed to the plant adaption response to diverse nitrogen. The P-VFCW in gradient distribution of inorganic and solid carbon sources under limited aeration is a promising technology for advanced nitrogen removal.

Mainstream anammox driven by micro-oxygen nitrification and partial denitrification using step-feed for advanced nitrogen removal from municipal wastewater

This study developed a novel integrated nitrification, partial denitrification (PD), and anammox (INPDA) process in micro-aerobic sequencing batch reactor using step-feed strategy treating municipal wastewater. The results showed that the INPDA could achieve a 94.5 ± 1.1% total inorganic nitrogen (TIN) removal efficiency with effluent TIN concentration as low as 2.3 mg/L. The micro-aerobic with low dissolved oxygen concentration of 0.36 ± 0.01 mg/L allowed complete ammonium oxidation to nitrate. The applied step-feed by optimizing influent distribution ratio to 5:3 provided sufficient organics for nitrate reduction to nitrite. According to mass balance analysis, anammox was the dominant nitrogen removal pathway (87.9%). Microbial analysis indicated that aerobic nitrifiers Nitrosomonas (1.2%) and Nitrospira (0.9%) ensured full nitrification, while PD bacteria Thauera (27.1%) conducted labor metabolism coordination with anammox bacteria Candidatus Brocadia (1.3%) for nitrogen removal. These findings demonstrate that the INPDA has a good prospect for energy-efficient municipal wastewater treatment.

Enhanced biofilm formation and denitrification in slow sand filters for advanced nitrogen removal by powdery solid carbon sources addition

Slow sand filter (SSF) is reliable for its economical convenience but is limited by low NO3−-N removal effect and long start-up time. In this study, the feasibilities of powdery poly butylene succinate (PBS) and polycaprolactone (PCL) as solid carbon sources for enhanced nitrogen removal in SSFs were investigated. Results suggested that the PBS with 200 mesh (PBS200) was with better carbon release capacity than PCL with 200 mesh (PCL200). During the start-up phase, SSF added PBS200 (SSFPBS) was found to achieve stable after 8-day adaptation, and 94.2 % NO3−-N and 78.9 % TN would be removed. Though a relative longer start-up time was required in SSFPBS than SSF added PCL200 (SSFPCL), the cost and the risk of secondary pollution caused by excessive COD was lower in SSFPBS. Analyses to biomass and extracellular polymeric substances (EPS) revealed that the biofilm structure in SSFPBS was more stable, which was because of higher biodiversity and biomass, as well as higher proteins and lower CO, OCO in EPS. For the study of optimizing the operating performance of SSFPBS (quartz sand/PBS200, 24:1), the results suggested that 90 % NO3−-N could be removed from municipal secondary effluent under the flow rate of 0.07 m/h. Besides, 33 % COD was further removed by two stage filter system. This study demonstrated that powdery PBS-based SSF is a promising technique to eliminate nitrate‑nitrogen pollution.

Anammox biofilter with denitrification sludge as seed in treating low nitrogen strength wastewater

Deficient seed sludge, low substrate concentrations are recognized as the major barriers for the application of anaerobic ammonia oxidation (Anammox) to treat mainstream wastewater. In this work, anammox biofilter (A-BF) was started up by inoculating denitrification sludge at low nitrogen strength at 25 °C. The total nitrogen removal efficiency (TNRE) and nitrogen removal rate (NRR) reached 74.8 ± 3.4% and 0.81 kg-N m−3 d−1 under nitrogen loading rate (NLR) of 1.20 kg-N m−3 d−1 with 7.00 mg-NH4+-N L−1 and 10.00 mg-NO2--N L−1 as influent. 1.00–2.00 mg-DO L−1 negatively impacted effluent, but the total nitrogen of effluent (TNeff) was 10.65 ± 2.76 mg L−1, in limit of the standard of Class 1A for municipal WWTP discharge (GB18918-2002). The abundance of Planctomycetes increased from 0.6% to 1.4–2.6%, in which, Candidatus_Brocadia was the dominant genera. The results establish the application feasibility of A-BFs as advanced nitrogen removal technique in treating mainstream wastewater.

Advanced nitrogen removal from mature landfill leachate based on novel step-draining partial nitrification-denitrification and Anammox process: Significance of low volume exchange ratio

To save external carbon source dosage and simplify NH4+ to NO2− ratio control strategy, this study established a novel step-draining based partial nitrification-denitrification and Anammox (PND-AMX) system for advanced nitrogen removal from mature landfill leachate. Separation of partial nitrification and denitrification was realized based on step-draining, achieving 74.8 % nitrogen removal. 25 % was the optimal volume exchange ratio for synergistic removal of organics and nitrogen, allowing full use of carbon source. NH4+ to NO2− ratio was easily controlled by varying the volume ratio of the first and second effluent of PND reactor. Brocadia, Kuenenia and Jettenia collectively accounted for 13.61 % in AMX reactor, contributing 21.0 % of nitrogen removal. Nitrogen removal efficiency and nitrogen removal rate reached 98.3 ± 1.2 % and 3.07 ± 0.09 kgN/(m3∙d), respectively. Partial Anammox process based on step-draining was easier to realize and of practical significance for application in treatment of landfill leachate.

Development and characterizations of hydrogenotrophic denitrification granular process: Nitrogen removal capacity and adaptability

Hydrogenotrophic denitrification (HD) is a promising autotrophic biological process for advanced nitrogen removal, while sludge granulation was seldom reported. This study aimed to cultivate granular sludge to improve capacity and stability of HD process. The resulting HD granular sludge performed high nitrogen removal rate (NRR) of 0.42 ± 0.0.4 kgN/(m3·d) with low accumulation of nitrite and nitrous oxide emission. HD granular sludge reactor performed over 3 times higher NRR compared to that in HD fixed-bed biofilm reactor (0.13 ± 0.01 kgN/(m3·d). Besides, granular sludge reactor could treat groundwater well even at the low temperature of 15 °C. The dominant genera were Hydrogenophaga and Comamonas in granular sludge, and Dechloromonas in biofilm. Noticeably, sulfate in the groundwater stimulated the growth of sulfur converting microbes with increasing abundances of sulfite reductase gene and sulfate-reducing bacteria Desulfovibrio. This study highlights the potential implementation of HD process in granular sludge reactor for advance nitrogen removal from impaired groundwater.

Effects of External Carbon Sources on Ultimate Nitrogen Removal Performance and Microbial Community in Secondary Effluent Treating Process

Adding external carbon sources is an important method for advanced nitrogen removal of secondary effluent in wastewater treatment plants (WWTPs). In order to compare the denitrification performance and economy of different carbon sources sufficiently, as well as the effect of long-term addition of carbon sources on the microbial population structure, four single carbon sources (methanol, ethanol, glucose, and sodium acetate) and four types of composite carbon sources were prepared by mixing sodium acetate and ethanol with a higher reaction rate and cheap glucose. The results showed that the effluent ρ(NOx--N) concentration of all systems was less than 1.0 mg·L-1 during the experiment. For single-carbon source systems, ethanol had the fastest denitrification rate, followed by sodium acetate and methanol; that of the glucose was the slowest. In the composite carbon source systems, the sodium acetate/glucose (1:1) with COD/ρ(N) was 6, which was equivalent to the results of sodium acetate/glucose (1:3), ethanol/glucose(1:1), and ethanol/glucose (1:3) with COD/ρ(N) of 9, 10, and 10, respectively. The sodium acetate/glucose (1:1) system had the fastest reaction rate and the best economy. High-throughput sequencing results showed that after more than 70 days of operation, the structure of the microbial community had changed completely. In the glucose-related system, the abundance of Candidatus Saccharibacteria, which is not popular in typical nitrogen removal systems, increased from 1.16% of seed sludge to 47.37%, and Saccharibacteria_genera_incertae_sedis correspondingly became the dominant community. This study not only provides a more comprehensive comparison for the selection of carbon sources in WWTPs with ultimate nitrogen removal but also provides basic data for the role of carbon sources in the domestication of microbial communities.

Advanced nitrogen removal from municipal sewage via partial nitrification-anammox process under two typical operation modes and seasonal ambient temperatures

A novel two-stage partial nitrification-anammox (PN-A) process was developed, achieving nitrogen removal from low carbon/nitrogen ratio municipal sewage under two typical operational modes and seasonal ambient temperatures. When complete nitritation-anammox was performed at temperatures greater than 19.4 °C, the effluent concentration of total inorganic nitrogen (TIN) was 4.1 mg/L, corresponding to a nitrogen removal efficiency (NRE) of 94.3 %. In contrast, when partial nitritation-anammox was performed at temperatures below 19.4 °C, the effluent TIN was 12.3 mg/L, corresponding to a NRE of 83.6 %. The relative abundance of Nitrosomonas and Nitrosomonadaceae increased from 0.02 % to 0.28 %, while Ca. Brocadia decreased from 1.85 % to 1.30 %, with the contribution of anammox to nitrogen removal being highest under low temperatures (19.4℃ to 13.8℃), at 59.0 %. This novel two-stage PN-A process provides a new approach for the stable operation of wastewater treatment plants (WWTPs) under low ambient temperatures.

Modified integrated fixed-film activated sludge process: Advanced nitrogen removal for low-C/N domestic wastewater

Actual low-C/N domestic wastewater was treated using the high-concentration powder carrier bio-fluidized bed (HPB) process comparing diatomite and Fe–C as the carriers. The total nitrogen removal efficiencies were increased from 50.08% to 65.40% and 78.58%, respectively. The diatomite HPB process increased the relative abundance of autotrophic N-cycle bacteria to more than twofold and the sludge size. Therefore, the contributions for nitrogen removal by anammox and simultaneous nitrification–denitrification were increased. The Fe–C HPB process improved the nitrogen removal efficiency mainly by increasing the biodegradability and activities of electron transfer system and key enzymes. The key device (hydrocyclone separator) of the HPB process significantly improved the recovery efficiency of the carriers. It also improved the capacity of microbial aggregations for adsorbing pollutants. Furthermore, it reduced the relative abundance of filamentous bacteria. This study demonstrated the feasibility and mechanism of the HPB process for improving the nitrogen removal efficiency for low-C/N wastewater.

Establishment and optimization of partial nitrification/anammox/partial nitrification/anammox (PN/A/PN/A) process based on multi-stage ammonia oxidation: Using response surface method as a tool

The presence of nitrite-oxidizing bacteria (NOB) when treating low-strength ammonia wastewater was a challenge in the application of the PN/A process. The partial nitrification/ANAMMOX/partial nitrification/ANAMMOX (PN/A/PN/A) process based on multiple oxidations of ammonia was proposed to solve this problem. The influence of independent variables such as nitrite concentration was analyzed based on the response surface method (RSM). The model showed that nitrite concentration has an adverse impact on ammonia removal efficiency and nitrite accumulation rate. The model provided optimal parameters for the PN/A/PN/A process: the dissolved oxygen concentration was 0.60 mg/L, and the cycle duration was 90 min. Advanced nitrogen removal was achieved by maintaining the nitrite concentration below 10.0 mg/L. The nitrogen removal efficiency was 81.44 ± 4.15 %, and the nitrogen removal rate was 0.18 ± 0.02 kg N/(m3⋅d). Potential functions of microorganisms were analyzed by functional annotation of prokaryotic taxa (FAPROTAX) and the correlation network analysis was performed.

Study on Advanced Nitrogen Removal and Microbial Community Structure of Traditional Chinese Medicine Wastewater by a Novel System Coupling Anaerobic Sequencing Batch Reactor and Modified Sequencing Batch Biofilm Reactor

To improve the efficiency of nitrogen removal from pharmaceutical wastewater, wastewater from traditional Chinese medicine was treated in an anaerobic sequencing batch reactor (ASBR) combined with a modified sequencing batch biofilm reactor (SBBR). The chemical oxygen demand (COD) and total nitrogen (TN) contents were 3,750 ± 50 mg/L and 210 ± 10 mg/L, respectively. After 99 days of start-up and domestication, the COD, NH4+-N, and TN contents in the effluent were 230 ± 10 mg/L, 1 ± 0.5 mg/L, and 5 ± 3 mg/L, respectively, and the removal efficiencies reached more than 93.5, 99, and 96%, respectively. Among these results, the COD removal efficiency in traditional Chinese medicine wastewater with an ASBR reached more than 85%, and the effluent and raw water were mixed to adjust the C/N ratio in the SBBR influent. The initial operation mode of the improved SBBR was anaerobic–aerobic–anoxic. When the C/N ratio in the influent was adjusted to 5, the simultaneous nitrification and denitrification (SND) in the aerobic section was gradually enhanced, and the endogenous denitrification (ED) in the anoxic section gradually decreased. In conclusion, deep denitrification of the system was achieved only through SND, and the running time of the cycle was shortened from the initial 24 to 4.6 h. High-throughput sequencing analysis showed that the relative abundances of Bacteroidetes and Proteobacteria in the system were 39.69 and 37.34%, respectively. The content of Firmicutes with denitrification in the system was also high, accounting for 5.17%. At the genus level, the bacteria with denitrification functions in the system were mainly Thauera and unidentified_Sphingobacteriales, accounting for 5.67 and 1.66% of the system, respectively. In addition, there was heterotrophic nitrification–aerobic denitrification (HN-AD) activated in the system, including Denitratisoma, Paracoccus, and Pseudomonas. The total relative abundance of these bacteria was 0.612%. Their existence may be one of the reasons for the good effect of SND in this system.

Rapidly recovering and maintaining simultaneous partial nitrification, denitrification and anammox process through hydroxylamine addition to advance nitrogen removal from domestic sewage

The collapse of simultaneous partial nitrification, denitrification and anammox (SPNDA) system, caused by the destruction of partial nitrification (PN), is the most likely phenomenon to occur. Therefore, recovering the process quickly and maintaining efficient nitrogen removal is a valuable topic for research. In the anaerobic/aerobic/anoxic operation mode, SPNDA process was used to treat domestic sewage in a sequencing batch biofilm reactor. After the deterioration of PN effect, with the addition of hydroxylamine, the activity of ammonia-oxidizing bacteria in the nitrobacteria increased (61.0–91.3 %), whereas the accumulation of nitrite quickly recovered to 90.4 % within 5 days. Meanwhile, the nitrogen removal efficiency improved (61.8–95.6 %) and the effluent TN was 2.1 mg/L. Furthermore, Candidatus Brocadia was enriched (0.50–1.82 %) in the system. The results indicated that the addition of hydroxylamine was an effective strategy to recover and economically maintain the SPNDA process for advanced nitrogen removal from domestic sewage.

Study on the advanced nitrogen removal under low temperature by biofilm on weak magnetic carriers

The advanced nitrogen removal under low temperature is inhibited because of reduction of the microbial activity. Packed bed reactors filled with different magnetic carriers (0, 0.3, 0.6, 0.9 mT) were constructed to enhance advanced denitrification under low temperature (5 ℃). Results showed that 0.3 and 0.9 mT carriers significantly improved denitrification, indicating the “window” effect. Total nitrogen removals were increased by 6.96% and 8.25%, and NO2– accumulation decreased by 25.70% and 13.90% in 0.3 and 0.9 mT reactors, respectively. Analysis of enzyme activity and electron transport chain showed that 0.3 mT carrier mainly increased NIR activity by improving compound III and cytC abundance while 0.9 mT carrier mainly increased NAR activity by improving compound I and NADH abundance, indicating different pathways. Similar microbial community in 0.3 and 0.9 mT reactors were revealed. Overall, weak magnetic carriers can be used to enhance advanced nitrogen removal under low temperature.

Deciphering the concurrence of comammox, partial denitrification and anammox in a single low-oxygen mainstream nitrogen removal reactor

One-stage anammox-based autotrophic nitrogen removal technology has attracted increasing interest to sustainable biological nitrogen removal for future wastewater treatment. However, its application in mainstream municipal wastewater treatment is still challenging due to low nitrogen and high organics of raw wastewater. Herein, a novel Simultaneous Carbon Oxidation, partial Comammox, Denitratation and Anammox (SCOCDA) was firstly developed in a single sequencing batch biofilm reactor operated at a dissolved oxygen concentration of ∼0.5 mg/L for treating synthetic municipal wastewater (50 mg/L NH4+-N and 100–250 mg/L COD). The long-term operation showed that almost complete COD and nitrogen removal performance could be achieved at a carbon/nitrogen ratio (COD/NH4+-N) of 3–5 with the corresponding effluent total nitrogen (TN)＜5 mg/L. Microbial community and amoA-targeting amplicon sequencing analysis further verified that comammox Nitrospira spp., denitrifier Thauera and other aerobic/facultative heterotrophs could work synergistically with anammox bacteria, Candidatus Kuenenia. Moreover, nitrogen metabolic and inorganic carbon fixation pathways through the interaction between comammox and anammox were also revealed with the aid of Kyoto Encyclopedia of Genes and Genomes (KEGG). Lastly, potential application of proposed SCOCDA process was illustrated. This research sheds new light on advanced nitrogen removal towards limit of technology via the synergy of comammox and anammox.

Advanced nitrogen removal from real municipal wastewater by multiple coupling nitritation, denitritation and endogenous denitritation with anammox in a single suspended sludge bioreactor

Achieving advanced nitrogen removal based on anammox for treating mainstream municipal wastewater in a single suspended sludge bioreactor is a challenging research topic. In this study, multiple coupling nitritation, denitritation and endogenous denitritation with anammox (PNA-(E)PDA) was simultaneously achieved in a 10 L step-feed bioreactor, which enhanced stable nitrogen removal. After 223 days of operation, the total nitrogen concentrations of the influent and effluent were 70.7 ± 6.1 and 4.3 ± 1.8 mg/L, respectively, when treating municipal wastewater even at C/N ratio of 2.24 with only 5 h of aerobic time (DO: 0.5–0.8 mg/L). After the evolution of nitritation/anammox to PNA-(E)PDA, the contribution of anammox to nitrogen removal increased to 78.6% and the anammox activity increased from 4.3 ± 0.2 to 15.2 ± 0.7 mg NH4+-N/gVSS/d. qPCR results showed that the abundance of anammox bacteria increased from 4.1 × 109 to 4.5 × 1010 copies/ (g VSS). High-throughput sequencing further revealed that the relative abundance of Candidatus Brocadia, the dominant anammox genus, increased from 0.09 to 0.46%. Based on the strong competitiveness of anammox on nitrite, this novel PNA-(E)PDA process provides a potential strategy for enriching anammox bacteria in municipal wastewater treatment plants.

Study on enhanced nitrogen removal of caprolactam production wastewater

Caprolactam (CPL) is widely used in polymer material and engineering plastics synthesis. The CPL production wastewater is difficult to treat due to high chemical oxygen demand (COD) and ammonia nitrogen (NH3-N), complex components and poor biodegradebility. The common treatment method for this wastewater is biochemical treatment combined with physicochemical pretreatment. Though the NH3-N of effluent can decrease to 1 mg/L, total nitrogen (TN) usually is above 100 mg/L. Herein, the enhanced nitrogen removal way was studied. The results showed TN was mainly composed of nitrate nitrogen which the concentration was approximately 90 mg/L via traditional A/O process. A simulated A/O/A process with methanol addition was investigated and TN of the effluent was below 20 mg/L, indicating this process with carbon source is efficient for advanced nitrogen removal.

Integrated moving bed biofilm reactor with partial denitrification-anammox for promoted nitrogen removal: Layered biofilm structure formation and symbiotic functional microbes

Partial denitrification/anaerobic ammonia oxidation (anammox) (PD/A) is currently an advanced nitrogen removal process. This study developed a PD/A system in a moving bed biofilm reactor. Results showed that the nitrogen removal efficiency reached 76.60% with a COD/NO3-N of 2.0, and the contribution of anammox was 88.01%. Further analysis showed that the biocarriers could form layered pH and dissolved oxygen structures to promote the aggregation of different functional bacteria at various depths, thus stabilizing the coupled process. Microbial structure analysis showed that the abundance of Saccharimonadales, responsible for denitrification, increased from 0% to 36.27% between day 0 and day 120, while the abundance of Candidatus Jettenia, responsible for anammox, decreased from 10.41% to 2.20%. The synergistic effect of Saccharimonadales and Candidatus Jettenia enabled stable and efficient removal of nitrogen. This study proposed a novel configuration of the PD/A process and provided a theoretical basis for its promotion and application.

Synergistic simultaneous endogenous partial denitrification/anammox (EPDA) and denitrifying dephosphatation for advanced nitrogen and phosphorus removal in a complete biofilm system

To achieve simultaneous biological nitrogen and phosphorus removal from municipal wastewater, the endogenous partial denitrification/anammox (EPDA) was combined with denitrifying dephosphatation in a complete biofilm reactor. Advanced nitrogen and phosphorus removal were achieved with effluent total nitrogen (TN) and PO43−-P concentrations of 7.77 ± 0.33 mg/L and 0.35 ± 0.10 mg/L, respectively. Anammox took a major role in the system, accounting for 76 ± 7% of nitrogen removal. 16S rRNA high-throughput sequencing results showed that the anammox bacteria co-existed with the denitrifying glycogen accumulating organisms (DGAOs) and the denitrifying phosphorus accumulating organisms (DPAOs). Anammox bacteria were mainly distributed in the inner layer, while DGAOs and DPAOs existed in the outer layer of EPDA biofilms. Furthermore, based on the EPDA biofilm system, a promising advanced nitrogen and phosphorus removal process was suggested to achieve lower requirements for energy and reagent consumption.