Simultaneous Partial Nitrification, Anammox And Denitrification Process Research Articles

Weak magnetic field stimulated nitrite oxidizing bacteria and destroyed the SNAD process

Simultaneous partial nitrification, anammox and denitrification (SNAD) process was successfully constructed in a fixed bed reactor. The ammonium and TN removal efficiencies exceeded 90% under the collaboration of ammonium oxidizing bacteria (AOB), anammox and denitrifying bacteria (DNB). However, the well cooperation was interrupted after introducing the weak MF of 3.5 mT, which was reflected directly by the increased nitrite oxidizing bacteria (NOB) activity and decreased AOB, anammox and DNB activities calculated via mass balance. Moreover, drastic microbial community structure changes induced by weak MF were observed. The dominant phylum changed from Proteobacteria (25.6%) to Deferribacteres (35.2%). The weak MF suppressed the growth of AOB (genus Nitrosomanas), anammox (genus Candidatus Brocadia and clone Anammox) and DNB (genus Denitratisoma) while promoted the enrichment of NOB (genus Nitrospira). Moreover, the weakened NH3-NH2OH, NO-N2O and N2O-N2 pathways might explain the deterioration of SNAD process caused by weak MF.

Optimization of nitrogen and carbon removal with simultaneous partial nitrification, anammox and denitrification in membrane bioreactor.

In this study, a membrane bioreactor (MBR) was used to achieve both nitrogen and carbon removal by a simultaneous partial nitrification, anammox and denitrification (SNAD) process. During the entire experiment, the intermittent aeration (non-aerobic time : aeration time, min min−1) cycle was controlled by a time-controlled switch, and the aeration rate was controlled by a gas flowmeter, and the optimal operating parameters as determined by response surface methodology (RSM) were a C/N value of 1.16, a DO value of 0.84 mg l−1 and an aerobic time (Tae) of 15.75 min. Under these conditions, the SNAD process achieved efficient and stable nitrogen and carbon removal; the total inorganic nitrogen removal efficiency and chemical oxygen demand removal efficiency were 92.31% and 95.67%, respectively. With the formation of granular sludge, the membrane fouling rate decreased significantly from 35.0 Pa h−1 at SNAD start-up to 19.9 Pa h−1 during stable operation. Fluorescence in situ hybrid analyses confirmed the structural characteristics and the relative ratio of aerobic ammonia-oxidizing bacteria, anaerobic ammonia-oxidizing bacteria and denitrifying bacteria in the SNAD system.

Start-up Characteristics of SNAD Process and Functional Abundance Succession of Volcanic Rock Biological Aerated Filter

A SNAD(simultaneous partial nitrification,ANAMMOX,and denitrification) process initiated in a submerged biological aerated filter (SBAF) was started up by seeding nitrification sludge and an ANAMMOX filter to investigate the operating characteristics and the succession of functional bacteria. The results showed that when the autotrophic nitrogen removal and denitrification were operated stably for 67 days at an initial COD concentration of 60 mg·L-1, the maximum nitrogen removal efficiency, the COD removal rate, and the nitrogen removal rate were 92.0%, 82.9%, and 2.3 kg·(m3·d)-1, respectively. Moreover, the total nitrogen removal rate of the SNAD process in this study was 12.6% higher than that of CANON process. The results of quantitative PCR showed that the abundance of AOB slightly increased, while the abundance of ANAMMOX was one order higher than that before the start-up of SNAD. In comparison, the abundances of denitrifiers and NOB remained at a relatively low level (107 copies·g-1). Taken together, these results suggested that the SBAF process with volcanic filter was beneficial for the accumulation of ANAMMOX and AOB.

An improved start-up strategy for mainstream anammox process through inoculating ordinary nitrification sludge and a small amount of anammox sludge

The difficulties in enriching anammox bacteria and maintaining stable partial nitrification during start-up phase limit the application of mainstream anammox process. In this study, the feasibility of starting up simultaneous partial nitrification, anammox and denitrification (SNAD) reactor treating municipal wastewater by inoculating ordinary nitrification sludge (96.2%) and a small amount of anammox sludge (3.8%) was investigated. A sequencing batch reactor with intermittent aeration was used for the SNAD process. The SNAD reactor was started up in 75 days with a nitrogen removal efficiency of 85.4% at ambient temperature. The nitrogen removal performance maintained stable despite the fluctuating inflow. Anammox bacterial activity exponentially increased although nitrite oxidizing bacteria (NOB) activity in seeding sludge was high. The enhanced ammonium oxidizing bacterial activity and partial denitrification provided sufficient nitrite for anammox bacteria. Moreover, NOB was inhibited by intermittent aeration, anammox bacteria had competitive advantage on nitrite. The improved particle size and settleability of activated sludge also favored the anammox bacterial enrichment. This study provided an improved and easily-implemented start-up strategy for mainstream anammox. The seeding sludge was easily obtained and the operation strategy was simple. These findings were meaningful to the engineering application of mainstream anammox.

[Biological Nitrogen Removal Process in a Microbubble-aerated Biofilm Reactor Treating Low C/N Wastewater].

The microbubble-aerated biofilm reactor as a new treatment process combines microbubble aeration technology with aerobic biological treatment. A microbubble aerated biofilm reactor was used in this study to treat low C/N ratio wastewater at a low air/water ratio. The process and performance of biological nitrogen removal were investigated, and the functional bacterial populations for nitrogen removal in the biofilm were analyzed. The results showed that the biological nitrogen removal process was converted from simultaneous nitrification-denitrification to simultaneous partial nitrification, ANAMMOX and denitrification (SNAD) processes when DO concentration was controlled by an air/water ratio of lower than 1:2 and the influent C/N ratio was reduced. As a result, the efficient biological nitrogen removal performance was achieved when treating low C/N ratio wastewater. When the DO concentration was lower than 1.0 mg·L-1 and the influent C/N ratio was 1:2.8, the SNAD process became dominant for biological nitrogen removal. In this case, the average total nitrogen (TN) removal efficiency was 76.3%, and the average TN loading rate removed was 1.42 kg·(m3·d)-1. In addition, it was estimated that 86.0% of TN removal was attributed to the ANAMMOX process. The relative abundances of ammonia-oxidizing bacteria populations and ANAMMOX bacteria populations in the biofilm increased gradually, while the relative abundances of nitrite-oxidizing bacteria populations and denitrifying bacteria populations decreased gradually, with a decrease in influent C/N ratio. The variation of functional bacterial populations for nitrogen removal was consistent with the conversion of nitrogen removal process to SNAD process.

Evaluation of mainstream nitrogen removal by simultaneous partial nitrification, anammox and denitrification (SNAD) process in a granule-based reactor

The mainstream anaerobic ammonium oxidation (anammox) has attracted extensive attention recently, particularly due to its potential of transforming current wastewater treatment plants from energy consuming to energy neutral or positive. However, the presence of biodegradable chemical oxygen demanding (COD, 20–80mgCODL−1) in the mainstream anammox reactor stimulates the growth of heterotrophic bacteria, which would compete for oxygen with ammonia-oxidizing bacteria (AOB) and for nitrite with anammox bacteria, thus interfering with the autotrophic nitrogen removal process. In the present work, with consideration of granule size distribution, a one-dimensional model describing the mainstream simultaneous partial nitrification, anammox and denitrification (SNAD) in a granule-based reactor was established, calibrated and validated, based on the long-term experimental results. Through applying the verified model, simulation studies were conducted and the results showed that the effluent total nitrogen concentration of <5mgNL−1 could be achieved at C/N ratio of 0.2–0.6, DO concentration of 0.2–0.4mgL−1 and granule radius of 300–600μm. The combined effects indicated that the SNAD process with TN removal efficiency >90% was obtained at C/N ratio and DO concentration of 0.2–1.0 and 0.2–0.4mgO2L−1 respectively. Finally, the various granule size distribution patterns were simulated, which confirmed that the size distribution needed to be incorporated in the model to accurately describe the granular anammox system, considering a model based on a uniform granule size does not reflect the real situations. These results provide guides to optimize the operation of mainstream granular autotrophic nitrogen removal process.

Tertiary nitrogen removal using simultaneous partial nitrification, anammox and denitrification (SNAD) process in packed bed reactor

The study aimed to polish wastewater effluent from an activated treatment system for nitrogen removal by a packed bed bioreactor (PBR). The nitrogen removal via simultaneous partial nitrification, anammox and denitrification (SNAD) process was investigated with different hydraulic retention times (HRTs). The results show that both effluent ammonia- and nitrate-nitrogen concentrations approached to 0 mg/L at the HRT as low as 3 h. The total nitrogen removal efficiency decreased from an average of 84% at both 18- and 24-h HRTs to 38% at 3-h HRT. This low nitrogen removal efficiency was due to the presence of incomplete degradation of organic nitrogen at shorter HRTs. The analysis using quantitative real-time polymerase chain reaction resolves that the ratio of ammonia-oxidizing bacteria (AOB) to the domain Eubacteria changed limited in the range between 2.8 and 4.0% during the continuous operation. Meanwhile, the nitrite-oxidizing bacteria (NOB) increased from 0.0 to 2.9% when the HRT was gradually reduced to 3 h. The anammox bacteria accounting for 30.5% of microbial consortia dominated the AOB and the NOB at the 3-h HRT. In sum, inorganic form of nitrogen in a typical wastewater plant effluent could be efficiently polished via SNAD process in the PBR.

A novel simultaneous partial nitrification Anammox and denitrification (SNAD) with intermittent aeration for cost-effective nitrogen removal from mature landfill leachate

Mature landfill leachate is difficult to be treated due to its complex composition, high concentration of ammonia, and low carbon/nitrogen ratio (C/N). Simultaneous partial nitrification, Anammox and denitrification (SNAD) with intermittent aeration was developed to achieve nitrogen removal from mature landfill leachate. An ammonia conversion efficiency of 99.3±0.3% and total nitrogen (TN) removal efficiency of 99±0.1% were obtained under the influent NH4+-N, SCOD and TN of 1950±250mg/L 1900±200mg/L and 2300±75mg/L, respectively. Full utilization of carbon source and high efficient Anammox were two significant factors in SNAD process. Based on the nitrogen balance, the nitrogen removal contribution was 77.1% for Anammox, and 15.6% for denitrification. Three dimensional excitation-emission matrix (EEM) fluorescence spectroscopy was used to detect dissolved organic matter (DOM) in a typical operation cycle for the first time, demonstrating that DOM increased during the anoxic phase and facilitated the reduction of excess NO3--N by denitrification. Quantitative polymerase chain reaction (QPCR) analysis revealed dominant bacterial groups, aerobic ammonia-oxidizing bacteria (AOB) and anaerobic ammonia oxidizing bacteria (AnAOB), which accounted for 12.99% and 8.32% of total bacteria respectively. As a whole, in the SNAD process, nitrogen and COD are removed from the wastewater simultaneously.

Development of simultaneous partial nitrification, anammox and denitrification (SNAD) in a non-aerated SBR

The objective of this work was to develop simultaneous partial nitrification, anammox and denitrification (SNAD) process in a twenty liter non-aerated sequencing batch reactor (SBR). Flocculent type activated sludge sourced from a tannery common effluent treatment plant was used as seed biomass. The SBR was operated for 161 days in 23 cycles with initial feed concentrations of NH4-N and COD as 250 ± 14.9 mg l−1 and 250 ± 4.6 mg l−1, respectively. The process was developed in a non-mixing condition in a dark room with no temperature control, but the temperature in SBR varied between 30 °C and 36 °C. The average HRT was 10.5 d with SBR cycle time of 7 d. The last three cycles gave the best average removals of NH4-N (94%), COD (92%) and TN (82%). The conversion ratio Y(NO2-N+ NO3-N)/(NH4-N) during the last 10 cycles remained below 0.11, confirming a stable SNAD process. Maximum specific substrate (NH4-N, COD and TN) utilization rates of SNAD biomass were determined as 185 mg NH4-N g−1 MLVSS d−1, 153 mg COD g−1 MLVSS d−1 and 172 mg N g−1 MLVSS d−1. These results contribute towards the application of SNAD process in shallow anoxic ponds/tanks/ditches in the absence of sunlight.

Study of simultaneous partial nitrification, ANAMMOX and denitrification (SNAD) process in an intermittent aeration membrane bioreactor

Simultaneous partial nitrification, ANAMMOX and denitrification (SNAD) process was applied to remove ammonium and COD from wastewater in an intermittent aeration membrane bioreactor (MBR). The operating parameters (influent carbon to nitrogen ratio (C/N), alternating aerobic/anaerobic (Tae/Tan) period and air flow) were optimized through response surface methodology (RSM). The optimal operating parameters were: a C/N of 0.42–0.55, a Tae/Tan of 1min/(2.5–3.1) min and an air flow of 0.48–0.51Lmin−1. Under these conditions, the mean N2O and NO (biogas) emissions were 2.0% and 0.17% of the total incoming nitrogen, respectively. For the SNAD process, stoichiometric modeling results indicated that total nitrogen (TN) removal by ANAMMOX was 76.1%, and that heterotrophic denitrification was responsible for 19.0% of TN removal and 95.0% of COD removal. Photo of SNAD granules, scanning electron microscopy (SEM) and fluorescence in situ hybridizations (FISH) analysis proved the co-existence of AOB, ANAMMOX and denitrifying bacteria in the reactor, and showed that the biomass in the outer part of the SNAD granule was mostly AOB, while ANAMMOX and denitrifiers were in the inner anoxic part. These results provide useful information for the application of the SNAD process.

Development of enhanced SNAD process in a down-flow packed bed reactor for removal of higher concentrations of NH4–N and COD

Enhanced simultaneous partial nitrification, anammox and denitrification (SNAD) process was developed using a 2.4L down-flow packed bed reactor for removing higher concentrations of ammonia and chemical oxygen demand (COD) (at COD/NH4–N ratio=1.0) in low dissolved oxygen concentrations (≤0.35mg/L). SNAD was developed using flocculent type activated sludge sourced from a tannery common effluent treatment plant and the reactor was operated continuously for 122d at various loading rates with hydraulic retention time (HRT) varied between 12h and 3h. The reactor was operated in room temperature and the liquid temperature varied between 28 and 32°C. The performance of the reactor at 3h HRT showed enhanced removal rates of NH4–N (2.8g/Ld), total nitrogen (2.5g/Ld) and COD (4.9g/Ld) at ammonia and COD loading rates of 5.4g/Ld. The nitrogen removal was due to the competitive involvement of anammox (∼50%) and denitrification (∼50%) and these processes were confirmed by conducting separate batch experiments. There was no external addition of alkalinity at higher loading rates corresponding to the requirement of oxidation of NH4–N. This study demonstrates SNAD for enhanced rate of removals of NH4–N and COD at high concentrations compared to the reported results in literature and indicates a potential application.

Start-up of simultaneous partial nitrification, anammox and denitrification (SNAD) process in sequencing batch biofilm reactor using novel biomass carriers

Simultaneous partial nitrification, anammox and denitrification (SNAD) process was started-up in a 2.5L sequencing batch biofilm reactor (SBBR) using novel biomass carriers. The SNAD process took only 51d for start-up at nitrogen loading rate (NLR) and organic loading rate (OLR) of 120 and 60g/m3-d, respectively. Long-term stable operation of SNAD process was observed at NLR and OLR of 360 and 180g/m3-d with average total nitrogen and COD removal efficiencies of >88% and >90%, respectively. The values of conversion ratio Y(NO2-+NO3-)/NH4+ remained below 0.11 after the start-up period, which further confirmed the long-term stability of SNAD process. Results of polymerase chain reaction (PCR), qualitative PCR, and scanning electron microscopic (SEM) analysis of sludge samples confirmed the co-existence and enrichment of AOB, anammox bacteria and denitrifying bacteria in the reactor and biofilm formation on to the carriers.

Microbial characteristics and nitrogen removal of simultaneous partial nitrification, anammox and denitrification (SNAD) process treating low C/N ratio sewage

Simultaneous partial nitrification, anammox and denitrification (SNAD) process was successfully realized for treating low C/N ratio sewage, nitrogen and COD removal achieved to 3.26kgm−3d−1, 81%, respectively. The nitrogen removal performance, microbial community and distribution of the functional microorganisms were investigated. Results suggested that the presence of COD performed activity inhibition on both aerobic ammonia-oxidizing bacteria (AerAOB) and anaerobic ammonia-oxidizing bacteria (AnAOB), and led to the number decreasing of both AerAOB and AnAOB. Even though COD presence resulted in the biodiversity increasing of AerAOB and decreasing of AnAOB, the dominant species were always Nitrosomonas and Candidatus brocadia during the whole experiment. Clone-sequencing of 16S rRNA results suggested the emergence of five different denitrifying species, which then led to a higher nitrogen removal. Results in this study demonstrated that the applied start-up strategy was feasible for SNAD process treating low C/N ratio sewage.

Effect of zinc on anammox activity and performance of simultaneous partial nitrification, anammox and denitrification (SNAD) process.

In the present study, short-term effects of zinc on anammox activities and long-term effect of zinc on the performance of simultaneous partial nitrification, anammox and denitrification (SNAD) process were evaluated. The anammox activity decreased with increasing zinc concentration and exposure time in short-term tests. The IC50 value of zinc was found to be 6.9mg/L. However, the presence of zinc (<10mg/L) in wastewater stimulated the microbial activities and nitrogen removal performance of SNAD process in sequencing batch biofilm reactor (SBBR). At first, inhibition of SNAD process was observed when influent zinc concentration increased to 20mg/L. The system recovered immediately, suggesting the acclimatization of microbial communities of SNAD process. The results showed that SBBR was well acclimatized under high zinc concentration (50-100mg/L) achieving 98% NH4(+)-N, 96% TN and 87% COD removal efficiencies.

Landfill-leachate treatment by simultaneous partial nitrification, anammox and denitrification (SNAD) process

Simultaneous partial nitrification, anammox and denitrification (SNAD) process was developed in a sequential batch reactor (SBR), and the application of SNAD process for landfill-leachate treatment was investigated. The SNAD process was developed from the biomass of a full-scale landfill-leachate treatment plant. After the adaptation of biomass, the SBR was operated in four stages (I–IV) with varying nitrogen loading rates (NLRs), i.e. 118–280 mg-N/L/d, and organic loading rates (OLRs), i.e. 100–200 mg/L/d. The increase in the NLR has proportionately reduced the NH4 +-N removal. However, the NO2 –-N concentration was close to zero and the NO3 –-N concentration was less than 36 mg/L in all the stages. A consistent chemical oxygen demand (COD) removal was observed in stages I to IV, which indicate that the SBR was not affected by the increase or decrease of the OLR. The total nitrogen removal in the SBR was mainly achieved by partial nitrification and anammox (69–88%) that was evaluated by a stoichiometric model. Moreover, the influence of NLR and OLR on the SNAD process was determined based on sensitivity index (SI). The SI values indicate that the SNAD process was highly affected by the influent NH4 +-N compared to COD.

Development of simultaneous partial nitrification, anammox and denitrification (SNAD) process in a sequential batch reactor

Simultaneous partial nitrification, anammox and denitrification (SNAD) process was developed in a sequential batch reactor (SBR) and the influence of hydraulic retention time (HRT) on the SNAD process was investigated. Around 96% NH 4 + –N removal and 87% COD removal were observed at 9 d HRT. Marginal decreases in the removal efficiencies were observed when the HRT was reduced to 3 d or the loading rate was increased by three times. On the other hand, a drastic decrease in NH 4 + –N and COD removals were observed when the DO, pH and temperature were dropped shockingly. The response of the SNAD system towards the shock in substrate loading and operating conditions was evaluated by sensitivity index. Finally, the extent of total nitrogen (TN) removal by partial nitrification with anammox and denitrification was modeled using stoichiometric relationship. Modeling results indicated a TN removal of 85–87% by anammox with partial nitrification and 7–9% by denitrification.

Environmental biotechnology.

Simultaneous partial nitrification, anammox and denitrification (SNAD) process was started-up in a 2.5 L sequencing batch biofilm reactor (SBBR) using novel biomass carriers. The SNAD process took only 51 d for start-up at nitrogen loading rate (NLR) and organic loading rate (OLR) of 120 and 60 g/m3-d, respectively. Long-term stable operation of SNAD process was observed at NLR and OLR of 360 and 180 g/m3-d with average total nitrogen and COD removal efficiencies of >88% and >90%, respectively. The values of conversion ratio Y(NO2-+NO3-)/NH4+ remained below 0.11 after the start-up period, which further confirmed the long-term stability of SNAD process. Results of polymerase chain reaction (PCR), qualitative PCR, and scanning electron microscopic (SEM) analysis of sludge samples confirmed the co-existence and enrichment of AOB, anammox bacteria and denitrifying bacteria in the reactor and biofilm formation on to the carriers.