Shortcut Biological Nitrogen Removal Research Articles

Comammox and unknown ammonia oxidizers contribute to nitrite accumulation in an integrated A-B stage process that incorporates side-stream EBPR (S2EBPR)

A novel integrated pilot-scale A-stage high rate activated sludge, B-stage short-cut biological nitrogen removal and side-stream enhanced biological phosphorus removal (A/B-shortcut N-S2EBPR) process for treating municipal wastewater was demonstrated with the aim to achieve simultaneous and carbon- and energy-efficient N and P removal. In this studied period, an average of 7.62 ± 2.17 mg-N/L nitrite accumulation was achieved through atypical partial nitrification without canonical known NOB out-selection. Network analysis confirms the central hub of microbial community as Nitrospira, which was one to two orders of magnitude higher than canonical aerobic oxidizing bacteria (AOB) in a B-stage nitrification tank. The contribution of comammox Nitrospira as AOB was evidenced by the increased amoB/nxr ratio and higher ammonia oxidation activity. Furthermore, oligotyping analysis of Nitrospira revealed two dominant sub-clusters (microdiveristy) within the Nitrospira. The relative abundance of oligotype II, which is phylogenetically close to Nitrospira_midas_s_31566, exhibited a positive correlation with nitrite accumulation in the same operational period, suggesting its role as comammox Nitrospira. Additionally, the phylogenetic investigation suggested that heterotrophic organisms from the family Comamonadacea and the order Rhodocyclaceae embedding ammonia monooxygenase and hydroxylamine oxidase may function as heterotrophic nitrifiers. This is the first study that elucidated the impact of integrating the S2EBPR on nitrifying populations with implications on short-cut N removal. The unique conditions in the side-stream reactor, such as low ORP, favorable VFA concentrations and composition, seemed to exert different selective forces on nitrifying populations from those in conventional biological nutrient removal processes. The results provide new insights for integrating EBPR with short-cut N removal process for mainstream wastewater treatment.

Nitrite accumulation in activated sludge through cyclic anaerobic exposure with acetate

Achieving nitrite accumulation still remains challenging for efficient short-cut biological nitrogen removal in municipal wastewater treatment. To tackle the problem of insufficient carbon in incoming wastewater for biological nutrient removal, a return activated sludge (RAS) fermentation method has been proposed and demonstrated to enable producing supplemental volatile fatty acids (VFAs) and enhance biological phosphorus removal via sludge cycling between mainstream and a sidestream anaerobic reactor. However, the impacts of long anaerobic exposure with acetate on nitrifying bacteria, known as the aerobic chemoautotrophic microorganisms, remains unexplored. In this study, the activated sludge underwent a cyclic anaerobic treatment with the addition of acetate (Ac), the effects on nitrification rate, abundance and microdiversity of nitrifying communities were comprehensively assessed. Firstly, batch activity tests proved the direct addition of high acetate (above 1000 mg/L) could cause inhibition on the nitrification rate, moreover, the inhibitory effect was stronger on nitrite-oxidizing bacteria (NOB) activity than that of ammonia-oxidizing bacteria (AOB). Then, a sequencing batch reactor (SBR) was applied to test the nitrogen conversion performance for low-strength ammonium wastewater. Nitrite accumulation could be achieved via the cyclic anaerobic exposure with 1000–5000 mg Ac/L. The maximum effluent concentration of nitrite was 40.8 ± 3.5 mg N/L with nitrite accumulation ratio (NAR) of 67.6 ± 3.5%. The decrease in NOB activity (72.7%) was greater than AOB of 42.4%, promoting nitrite accumulation via nitritation process. Furthermore, the cyclic anaerobic exposure with acetate can largely reshape the nitrifying communities. As the dominant AOB and NOB, the abundance of Nitrosomonas and Nitrospira were both decreased with species-level microdiversity in the nitrifying communities. However, the heterotrophic microorganism, Thauera, were found to be highly enriched (from 0 to 17.3%), which may act as the potential nitrite producer as proved by the increased nitrate reduction gene abundance. This study can provide new insights into achieving mainstream nitrite accumulation by involving sidestream RAS fermentation towards efficient wastewater treatment management.

Development of a Novel Hydrodynamic Sequencing Batch Reactor for Landfill Leachate Treatment by Shortcut Biological Nitrogen Removal

This study introduced an alternative shortcut biological nitrogen removal (SBNR) process for landfill leachate treatment by developing a novel hydrodynamic sequencing batch reactor (H-SBR). The reactor could enhance the oxygen transfer rate (OTR) and nitrite accumulation ratio (NAR) by modifying internal hydrodynamic turbulence intensity. The average chemical oxygen demand (COD) and total nitrogen (TN) concentrations introduced into the reactor were 660 and 250 mg L−1, respectively, and the average removal efficiencies were 93% (COD) and 96% (TN). The effect of geometric parameters on oxygen transfer was estimated by performing a hydrodynamic model and a nonlinear least square analysis. After correcting the constants (α and β) of mass transfer coefficients (KLa) to values of 0.7361 and 1.2639, the model data fit the experiment well with an R-squared value of 0.99. The OTR improved by up to 30%, and hence, increased the NAR by up to 20% with a reduction of about 0.5 kg N kW−1 for power efficiency. The H-SBR development is innovative because the oxygen transfer efficiency was improved by the hydrodynamic modification of internal turbulence intensity, although not by mechanical equipment or chemical supplements. For the SBNR process, the modification of the reactor configuration for OTR enhancement could significantly improve nitrogen removal efficiency with successful nitrite accumulation. In addition to landfill leachate treatment, the H-SBR process can be employed in the treatment of low C/N ratio wastewaters.

Achieving robust mainstream nitritation by implementing light irradiation: long-term performance and microbial dynamics

The effective inhibition of nitrite-oxidizing bacteria (NOB) is widely acknowledged to be a critical issue for mainstream short-cut biological nitrogen removal. This study demonstrated a stable mainstream nitritation by implementing light irradiation. A sequencing batch reactor with ultraviolet-A (UVA) irradiation was operated for 250 days, and a high nitrite accumulation ratio was achieved and stabilized at about 90 %. UVA irradiation also positively impacts denitrification activity, with total nitrogen removal up to 63 %. Microbial community analysis confirmed that the UVA effectively and stably decreased the abundance of Nitrospira (the only detected NOB) from 6.0 % to 0.1 %, while it showed no effect on Nitrosomonas. The enriched genus Rhodocyclaceae was the major contributor to the increase in denitrification activity in the light-induced nitritation system. The proposed UVA irradiation strategy has the potential to be integrated with an anoxic/aerobic (A/O) or integrated fixed-film activated sludge (IFAS) process for achieving mainstream short-cut biological nitrogen removal.

Whole process analysis on the efficiency of RBC+SBNR+[Fenton+BAF]<sup>2</sup> full-scale facilities for mature landfill leachate treatment

<p indent="0mm">Although the “biological treatment + advanced oxidation technology” method can avoid the concentration difficulties generated by the widely used “membrane biological reactor + membrane separation” process, a complete full-scale assessment of this type of combined process is lacking. The study used three parallel treatment facilities as the research object, evaluating the transformation efficiency and contribution rate of pollutants in each treatment unit using “rotating biological contactor (RBC) + shortcut biological nitrogen removal (SBNR) + two stages of [Fenton + biological aerated filter (BAF)]” process. The results show that RBC does not contribute to nitrogen removal, and the entire process relies on multistage tandem aeration tanks to remove nitrogen in the mature landfill leachate via SBNR. The SBNR unit in two of the three facilities contributed more than 100% to the removal of dissolved nitrogen (DN). The backend BAF unit is primarily responsible for controlling dissolved organic nitrogen and ammonia. An abundant combination of biological treatment can keep DN and ammonia in the effluent below 40 and <sc>25 mg/L,</sc> respectively. Meanwhile, SBNR removes the majority of organic matter, with a contribution to dissolved organic carbon of 48.7%–75.3% and RBC, 9.49%–48.1%. However, the effluent of “RBC + SBNR” is more fragrant. Nevertheless, the first level Fenton can remove the dissolved organic matter formed from “RBC + SBNR” as well as the high aromatic humus compounds in raw leachate, thereby boosting biodegradability and assuring that BAF is in low toxicity and low organic loading operating state. The second level BAF, in contrast, did not show a stable operation impact for eliminating organic materials. The type of external carbon supply and its mixing mechanism in RBC can be optimized in the future to improve nitrogen elimination. The process can be simplified by reducing terminal nitrogen removal units (e.g., the second level BAF) while ensuring that nitrogen in the effluent is up to standard.

Development of a Novel Hydrodynamic Sequencing Batch Reactor for Landfill Leachate Treatment by Shortcut Biological Nitrogen Removal

Development of a Novel Hydrodynamic Sequencing Batch Reactor for Landfill Leachate Treatment by Shortcut Biological Nitrogen Removal

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.

Comparison of an integrated short-cut biological nitrogen removal process with magnetic coagulation treating swine wastewater and food waste digestate

An integration of two processes, magnetic coagulation (MC) and short-cut biological nitrogen removal (SBNR), coupled with a sequencing batch membrane bioreactor (SMBR) controlled by an automatic real-time control strategy (RTC), was developed to treat different characteristics of high strength wastewater. The treatment efficiency and microbial community-diversity of the proposed method was evaluated and investigated using swine wastewater and food waste (FW) digestate. The MC showed high removal of TSS (89.1 ± 1.5%, 92.21 ± 1.8%), turbidity (90.58 ± 2.1%, 95.1 ± 2.1%), TP (88.5 ± 1.9%, 92.1 ± 1.5%), phosphate (87.76 ± 1.6%, 91.22 ± 1.5%), and SMBR achieved stable and excellent removal of COD (96.05 ± 0.2%, 97.39 ± 0.2%), TN (97.30 ± 0.3%, 97.44 ± 0.3%) andNH4+-N (99.07 ± 0.2%, 98.54 ± 0.2%) for swine wastewater and FW digestate, respectively. The effluent COD andNH4+-N concentrations were found to meet their discharge standards. The microbial community comparison showed similar diversity and richness, and genus Diaphorobacter and Thaurea were dominant in denitritation, and Nitrosomonas was dominant in nitritation treating both swine wastewater and FW digestate.

Full-scale semi-centralized wastewater treatment facilities for resource recovery: operation, problems and resolutions.

The first full-scale semi-centralized wastewater treatment and resource recovery system based on source separation was implemented from 2014. To assess the operation performance, operating costs and resolve the problems faced in this system, the latest operation data from April 2017 to September 2018 was investigated. The results show that greywater and blackwater modules exhibited good removal performance for organics and nutrients, although misconnection between pipelines existed and influent loading rates fluctuated. The effluent could meet reuse standards. The biogas production rates of raw sludge could reach 7.27-10.9 m3 gas·per cubic raw sludge. The specific cost of treated water was higher than in a conventional treatment system. Power consumption made a major contribution to the total cost with a proportion of 55.3-94.2%. After optimizing and considering the comprehensive efficiencies, the costs would be affordable. The dewatered sludge of the anaerobic digestion module has been applied to agricultural and landscaping soil. It is suggested that organics in blackwater could be recovered as volatile fatty acids with high-efficiency anaerobic fermentation and used as an external carbon source for short-cut biological nitrogen removal. In conclusion, the semi-centralized system will be a feasible and sustainable alternative for conventional treatment systems in future.

Operational Evaluation of Pilot-Scale Side-Line Treatment Based on Microbial Population and Activity

AbstractA pilot-scale study conducted in a municipal wastewater treatment plant (WWTP) for short-cut biological nitrogen removal (SBNR) from anaerobic reject water (ARW) was evaluated based on the ...

Novel shortcut biological nitrogen removal method using an algae-bacterial consortium in a photo-sequencing batch reactor: Process optimization and kinetic modelling

This study evaluated a novel shortcut nitrogen removal method using a mixed consortium of microalgae, enriched ammonia oxidizing bacteria (AOB) and methanol utilizing denitrifier (MUD) in a photo-sequencing batch reactor (PSBR) for treating ammonium rich wastewater (ARWW). Alternating light and dark periods were followed to obtain complete biological nitrogen removal (BNR) without any external aeration and with the addition of methanol as the sole carbon source, respectively. The results showed that influent NH4+ was oxidized to NO2− by AOB during the light periods at a rate of 8.09 mg NH4+-N L−1h−1. Subsequently, NO2− was completely reduced during the dark period due to the action of MUD in presence of methanol. The high activities of ammonia monooxygenase (AMO) and nitrite reductase (NIR) enzymes revealed the strong role of AOB and MUD for achieving shortcut nitrogen removal from the wastewater. The reduced activities of nitrate reductase (NR) and nitrite oxidoreductase (NOR) at a high concentration of DO, NH4+ and NO2−in the system further confirmed the nitrogen removal pathway involved in the process. The biomass produced from these experiments showed good settling properties with a maximum sedimentation rate of 0.7–1.8 m h−1, a maximum sludge volume index (SVI) of 193 ml g−1- 256 ml g−1and floc size of 0.2–1.2 mm. In order to describe the growth and interaction among the algae, AOB and MUD for nitrogen removal in the system, the experimental results were fitted to four metabolic models, which revealed best fit of the experimental data due to the models based on algae-AOB and algae-AOB-MUD activities than with the other two models.

Effect of Cu2+ on Denitrification Using NO2- as an Electron Acceptor

The short-cut biological nitrogen removal process has been widely used in industrial wastewater treatment, and denitrification is a crucial step for removing nitrogen on which the effect of Cu2+, a common heavy metal ion in wastewater, has not been studied. In this study, sludge with good short-range biological nitrogen removal characteristics in an A/O reactor was selected to investigate the short-term and long-term effects of Cu2+ on denitrification using NO2- as an electron acceptor. The results showed that Cu2+ had a significant inhibitory effect on denitrification process using NO2- as an electron acceptor, and the semi-inhibitory concentration EC50 of sludge activity was 4.79 mg·L-1. In the long-term experiment, the concentration of Cu2+ was gradually increased. When the concentration of Cu2+ was 0.5 mg·L-1and 1 mg·L-1, the denitrification activity of the sludge could be restored to the original level after acclimation. When the concentration of Cu2+ was increased to 3 mg·L-1, the denitrification performance was destroyed and difficult to recover, at which point the NO2--N removal rate was reduced to less than 10% and the denitrification system was severely inhibited. However, there was some recovery of sludge denitrification capacity after the addition of Cu2+ had been stopped for 14 days. At the same time, during the long-term effect of Cu2+, the EPS content increased, which played an important role in protecting the microorganism against Cu2+ toxicity, and increased the sludge particle size and, as a result, sludge sedimentation.

Evaluation of predominant factor for shortcut biological nitrogen removal in sequencing batch reactor at ambient temperature.

The shortcut biological nitrogen removal (SBNR) process requires less aeration and external carbon due to the oxidization of ammonia into nitrite and its direct denitrification to nitrogen gas during the biological nitrogen removal process. However, this process produces a poor effluent containing NH4+, since the system has to maintain a high free ammonia (FA, NH3) concentration. To overcome this drawback, in this study, the solid retention time (SRT) and the dissolved oxygen (DO) concentration were controlled to achieve both a high ammonia removal rate and nitrite accumulation in the sequencing batch reactor (SBR) process, which can remove nitrogen from wastewater to the desired concentration and provide high free ammonia inhibition and continuous shock loading. When sufficient DO was supplied, nitrite did not accumulate with a 20-day SRT, but the wash-out of nitrite oxidizers in a shorter SRT resulted in a high nitrite accumulation. When DO acted as a limitation, nitrite accumulated at all SRTs. This indicates that nitrite accumulation is more highly influenced by SRT and DO concentration than by FA inhibition. Also, as nitrite accumulated over a 10-day SRT regardless of DO concentration, the accumulation was more highly influenced by SRT than by DO concentration.

Start-up and performance of partial nitritation process using short-term starvation

Partial nitritation is a key step toward cost-effective shortcut biological nitrogen removal and anammox process. The current study presents a novel method for achieving partial nitritation at influent ammonium nitrogen concentration of 100 mgNL−1 using short-term starvation and low air flow rate. Mixed activated sludge was introduced into sequencing batch reactor (SBR) under aerobic/anaerobic condition. Variations in the reactor performance, nitrifying bacteria activities, and bacterial community structures were investigated. The results showed that partial nitritation was rapidly achieved, and an average nitrite accumulation rate (NAR) of 878 gNm−3d−1 was observed. The short-term starvation stress on nitrite oxidation bacteria (NOB) activity was relatively higher than that on aerobic ammonium oxidation bacteria (AerAOB) activity. The dominant species of general AerAOB were Nitrosomonas and Nitrosomonadaceae_uncultured, which had better self-adaption to short-term starvation. The moderate starvation could be utilized to achieve nitrite accumulation and nitritation.

Shortcut Biological Nitrogen Removal from Coal Gasification Wastewater in Three-Stage MBBRs.

A lab-scale aerobic-anoxic-aerobic (AE1-AN-AE2) MBBR system was tested for the removal of COD, <inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="01977-ilm01.gif"/>, SCN-, phenols, and nitrogen from coal gasification wastewater, using a shortcut biological nitrogen removal process. Dissolved oxygen concentration in AE1 was maintained at 1.0 to 2.0 mg/L to ensure stable <inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="01977-ilm12.gif"/> accumulation. Adding methanol wastewater to AN guaranteed denitrification efficiency. AE2 ensured high removal rates of <inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="01977-ilm23.gif"/>, SCN-, and phenols. The effects of influent pollutant concentration and hydraulic retention time (HRT) on nitrogen removal were studied. Improving the dissolved oxygen concentration in AE1 eliminated the negative effect of increased organic loading on nitrification, but it affected the stability of nitrosation. Shortening the HRT had negative effects on the performance of the system and performance recovered after it was extended. The average total nitrogen removal rate was 82.6% with a CODmethanol/<inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="01977-ilm34.gif"/> ratio of 3.5. Biomass and activity of ammonia-oxidizing bacteria and nitrite-oxidizing bacteria were measured to understand the evolution of nitrification.

Shortcut Biological Nitrogen Removal (SBNR) in an MFC Anode Chamber under Microaerobic Conditions: The Effect of C/N Ratio and Kinetic Study

In this work, the feasibility of the Shortcut Biological Nitrogen Removal (SBNR) in the anodic chamber of a Microbial Fuel Cell (MFC) was investigated. Thirty day experiments were carried out using synthetic wastewaters with a Total Organic Carbon vs. nitrogen ratio (TOC/N) ranging from 0.1 to 1. Ammonium, nitrite, nitrate, pH, and TOC were daily monitored. Results showed that microaerobic conditions in the anodic chamber favored the development of nitritation reaction, due to oxygen transfer from the cathodic chamber through the membrane. Nitritation was found to depend on TOC/N ratio: at TOC/N equal to 0.1 an ammonium removal efficiency of up to 76% was observed. Once the oxygen supply to the cathodic chamber was stopped, denitritation occurred, favored by an increase of the TOC/N ratio: a nitrite removal of 80.3% was achieved at TOC/N equal to 0.75. The presence of nitrogen species strongly affected the potential of the electrochemical system: in the nitritation step, the Open Circuit Voltage (OCV) decreased from 180 mV to 21 mV with the decrease of the TOC/N ratio in the investigated range. Lower OCV values were observed in the denitritation steps since the organic carbon acted as the energy source for the conversion of nitrite to nitrogen gas. A kinetic analysis was also performed. Monod and Blackman models described the ammonium and the organic carbon removal processes well during the nitritation step, respectively, while Blackman-Blackman fitted experimental results of the denitritation step better.

Rapid start-up of a nitritation granular reactor using activated sludge as inoculum at the influent organics/ammonium mass ratio of 2/1

Partial oxidation of ammonium to nitrite is a pre- and crucial step to achieve shortcut biological nitrogen removal from ammonium-rich wastewater. In the present study, a nitritation granular reactor using activated sludge as inoculum was started up in a sequencing batch reactor (SBR) at a fixed influent C/N ratio of 2:1. Variations in the reactor performance, functional bacteria activities, sludge morphology and bacterial community structure were investigated. Results showed the formation of compact granules was achieved in 55 days, and a stable nitrite accumulation rate of 0.68 kg N·m−3·d−1 was maintained in the following period. With a rapid growth of granular size, the total nitrogen removal by simultaneous nitritation/denitritation was progressively increased to 50%. In sludge granulation, the significant enrichment of r-strategist ammonium oxidizing bacteria (Nitrosomonas) was identified. Additionally, both high free ammonia concentration and extra nitrite competition by heterotrophic denitrifiers were critical to suppress nitrite oxidizing bacteria effectively.

Operational strategies and environmental conditions inducing aerobic denitritation in short-cut biological nitrogen removal at side-line treatment

ABSTRACTFactors promoting aerobic denitritation in a pilot-scale short-cut biological nitrogen removal (SBNR) process were investigated. The study implemented optimization of nitrogen removal in the anaerobic reject water (ARW) having a low organic C:N ratio ARW was produced in a large-scale municipal wastewater treatment plant (WWTP). Aerobic denitritation occurred consistently during study of a specific period of sequential batch reactor (SBR) where nitrite removal under fully aerobic conditions was obtained with a switch from oxygen to nitrite respiration, creating an aerobic (high oxidation–reduction potential) condition. Specific factors inducing aerobic denitritation were found related to several parameters as ammonium concentration, temperature, feeding mode, duration of the oxic stage and substrate availability due to beta-oxidation of lipid matter. Microbial analyses indicated a higher increase in nitrite reducing than ammonium oxidizing activity, as an evidence for nitrifying denitrifier bacterial dominance in the biomass. The reaction induced a reduction in the inhibitory products of the process as volatile fatty acids (VFAs) and free nitrous oxide (FNA), produced bicarbonate and increased removal efficiency of ammonium and nitrite, thus, total nitrogen. The outcome presents potential ways for further saving on aeration and chemical need via operational means, while taking advantage of the slowly degrading organic matter on SBNR performance.

Development of partial nitrification as a first step of nitrite shunt process in a Sequential Batch Reactor (SBR) using Ammonium Oxidizing Bacteria (AOB) controlled by mixing regime

Shortcut biological nitrogen removal is a non-conventional way of removing nitrogen from wastewater using two processes either nitrite shunt or deammonification. In the nitrite shunt process, the ammonia oxidation step stops at the nitrite stage, which is known as partial nitrification, then nitrite is directly reduced to nitrogen gas. Effective partial nitrification could be achieved by accumulating Ammonia Oxidizing Bacteria (AOB) and inhibiting Nitrite Oxidizing Bacteria (NOB). In this research, a novel control strategy has been developed to control the DO using the variable mixing regime in a suspended growth system using a Sequential Batch Reactor (SBR) in order to achieve a stable ammonia removal efficiency (ARE) and nitrite accumulation rate (NAR) at a high nitrogen loading rate (NLR). The new controlled SBR system has been successfully running at NLR up to 1.2kg/(m3.day) and achieved an ARE of 98.6±2.8% and NAR of 93.0±0.7%.

Settling and Dewatering Characteristics of an A-stage Activated Sludge Process Proceeded by Shortcut Biological Nitrogen Removal

Settling and Dewatering Characteristics of an A-stage Activated Sludge Process Proceeded by Shortcut Biological Nitrogen Removal