DEnitrifying AMmonium OXidation Research Articles

Influence of C/S ratios on nitrogen removal and microbial community on mixotrophic DEAMOX process

The effect of glucose in an inorganic and organic denitrifying ammonium oxidation (DEAMOX) reactor was assessed during short-term performance. The simultaneous effect of carbon (C) and sulfide (S) ratios on nitrogen removal and microbial community will improve our understanding of mixotrophic synergetic process. The nitrogen removal efficiencies were investigated under six different C/S ratios during DEAMOX process. Increasing C/S ratios promoted the TN removal efficiency which fluctuated widely from 53.28% to 87.39%. The most suitable C/S ratio was 1.6, which achieved a TN removal efficiency of 87.86% and provided a good coupling system. Denitrification was encouraged and accelerated nitrite accumulation with glucose addition, and anammox still played a dominant role in nitrogen removal performance. Denitrification microorganisms (Thiobacillus and Thauera) cooperated with anammox microorganism (Candidatus Kuenenia) during the DEAMOX process, and maintained a synergic relationship with nitrogen removal. Moreover, adding glucose improved the growth of the heterotrophic denitrification microorganism, and decreased the concentration of anammox bacteria. Overall, this research provides a theoretical basic for the practical application of a mixotrophic DEAMOX process.

Nitrogen removal improvement by denitrifying ammonium oxidation in anoxic/oxic-sequence batch biofilm reactor system

Denitrifying ammonium oxidation (DEAMOX) technology was applied to improve nitrogen removal from real low-carbon/nitrogen domestic wastewater in an anoxic/oxic sequencing batch biofilm reactor (A/O-SBBR) system. The system consisted of an anoxic SBBR (An-SBBR) and an oxic nitrification SBBR (N-SBBR). The system was operated in A/O mode for 240 days and anaerobic ammonium oxidation (anammox) bacteria were added into An-SBBR on day 160. Excellent nitrification performance was achieved in the N-SBBR with the NH4+-N removal efficiency of 98.01%, and nitrifiers were enriched with a proportion of 3.44%. DEAMOX was achieved in the An-SBBR with nitrite accumulation and ammonia loss. After adding anammox bacteria, the total inorganic nitrogen removal efficiency improved from 50.78% to 72.30%. Thauera and candidatus_Brocadia were detected with the proportions of 13.75% and 0.53%, respectively, which were strongly related to partial denitrification and anammox.

Hydroxylamine metabolism in mainstream denitrifying ammonium oxidation (DEAMOX) process: Achieving fast start-up and robust operation with bio-augmentation assistance under ambient temperature

Nitrogen removal from mainstream wastewater via DEnitrifying AMmonium OXidation (DEAMOX) is often challenged by undulated actual temperature and high loading rate. Here, we discovered NH2OH addition (HA) and bio-augmentation (BA) tactics on start-up and operation performance of DEAMOXs (R1 and R2) under ambient temperature (11.3–31.7 °C). Over 340-day operation suggested that R2 received 10 mg/L HA and 1:25 BA ratio (v/v, anammox/partial denitrification sludge) achieved desirable nitrogen removal efficiency (NRE) of 97.22% after 145-day, while R1 under higher BA ratio of 1:12.5 without HA obtained lower NRE (90.86%) after 184-day. Batch tests revealed that nitrate-nitrite transformation ratio reached 98.64% at low COD/NO3-–N of 2.6 with HA. Significantly, compared with R2, R1 recovered quickly with satisfactory effluent total nitrogen of 4.21 mg/L despite nitrogen loading rate greater than 0.15 kg N/m3/d and temperature decreased to 14.6 °C. The abundant narG represented high nitrate reduction potential, hzsA and hdh were extensively detected as the symbolisation of anammox metabolism. Thauera, Denitratisoma and unclassified f Comamonadaceae dominated nitrite accumulation. Ca. Brocadia as the dominant anammox bacteria, and its population maintained stable against low temperature and load shocks by NH2OH intensification. Overall, this study offers an opportunity for the wide-applications of DEAMOX treating mainstream wastewater.

Application of natural biodegradable fiber as biofilm medium and carbon source in DEnitrifying AMmonium OXidation (DEAMOX) process for nitrogen removal from wastewater

Nitrite (NO2−) accumulation and retaining of anammox bacteria are two decisive factors for stable operation of partial denitrification coupled with the anammox process. Denitrifying ammonium oxidation (DEAMOX) process has been regarded as a promising method for nitrogen removal from wastewater containing both ammonium (NH4+) and nitrate (NO3−) pollutants simultaneously. However, performance and efficiency of DEAMOX process in biofilm reactors are still not fully understood. This study successfully implements biodegradable Luffa Cylindrica fiber as both carbon source and biofilm carrier in the DEAMOX system. 87% nitrate-to-nitrite transformation was achieved through the partial denitrification process. An average total nitrogen (TN) removal efficiency of ~98% was obtained with influent NH4+-N and NO3−-N concentration of 100 mg L−1 in an up-flow packed bed biofilm reactor. The Field Emission-Scanning Electron Microscopy (FE-SEM) analysis indicated that for the proposed conditions, the DEAMOX packed bed reactor favor biofilm granulation developed on L. cylindrica. The results imply that solid phase partial denitrification and granulation of anammox bacteria were achieved using L. cylindrica as a carbon source and biofilm carrier, respectively. Complete NO3− removal observed in this study supports the hypothesis that solid carbon source can support denitrification of NO3− produced through the anammox process.

Simultaneous removal of ammonia and nitrate by coupled S0-driven autotrophic denitrification and Anammox process in fluorine-containing semiconductor wastewater

To achieve the simultaneous removal of NH4+-N and NO3−-N in F−-containing semiconductor wastewater by coupled S0-driven autotrophic denitrification and Anammox process, the effect of variable F− concentration on the Anammox process was investigated by batch experiments. The denitrifying ammonium oxidation (Deamox) reactor was then started-up to explore the feasibility of the coupling of Anammox and sulfur autotrophic denitrification (SADN) for the treatment of semiconductor wastewater. Short-term variation of F− concentration has an obviously effect on the activity of Anammox sludge, but didn't affect the nitrogen conversion rate. The activity of Anammox obviously decreased after long-term operation of the Deamox reactor when influent F− concentrations reached 552 mg/L. The sensitivity of Anammox bacteria to F− concentration is stronger than that of SADN bacteria. Total nitrogen removal efficiency of 98% and total nitrogen removal rate of 4.11 kg/(m3·d) were achieved in the Deamox reactor, when the F− was pre-treated by calcium ions. Moreover, the high-throughput 16S rRNA gene sequence analysis indicated that variation in F− concentrations could influence the structure and functional of microbial communities in the Deamox process. Candidatus Kuenenia, Thiobacillus and Sulfurimonas were main functional bacteria that achieved symbiotic.

Step-feeding organic carbon enhances high-strength nitrate and ammonia removal via DEAMOX process

The innovative DEnitrifying AMmonium OXidation (DEAMOX) process, coupling partial-denitrification (PD) with anammox, was designed for treating high-strength nitrate (NO3−-N) and ammonia (NH4+-N) wastewater for the first time. With influent total nitrogen (TN) up to 1600 mg L−1 (NO3−-N/NH4+-N of 1.0), DEAMOX process proved to be relatively stable for simultaneously removing NO3−-N and NH4+-N. The step-feeding organic carbon (OC) demonstrated as an efficient strategy for avoiding NO2−-N consumption by denitrification, facilitating the increased of NO3−-N to NO2−-N transformation ratio (NTR) to 99% at COD/NO3−-N of 1.77. The TN removal was significantly enhanced to 96.7% with the considerably high anammox contribution of 88.9%. Also, the inhibitory effect of high NO2−-N accumulation on denitrifying bacteria could be mitigated. High-throughput sequencing revealed a relatively stable cooperation of functional groups in DEAMOX system. Genus Thauera possibly capable of NO2−-N accumulation remained dominant (39.81% to 44.09%), while Candidatus Brocadia responsible for anammox was detected with much lower percentage (2.01% to 1.81%). Results of qPCR confirmed the evident growth of anammox bacteria under increasing nitrogen and organic loading. The DEAMOX process offers a significantly stable and efficient method in treating high-strength NO3−-N and NH4+-N wastewater.

Achieving completely anaerobic ammonium removal over nitrite (CAARON) in one single UASB reactor: Synchronous and asynchronous feeding regimes of organic carbon make a difference

At least 11% of total nitrogen (TN) remains in the anammox effluent, making it difficult to meet increasingly stringent discharge standards. To overcome this bottleneck, an innovative process to achieve completely anaerobic ammonium removal over nitrite (CAARON) in one single up-flow anaerobic sludge blanket reactor was proposed in this study. The synchronous feeding of acetate at a C/N (nitrite) ratio of 0.6 significantly reduced the nitrogen removal capacity of anammox reactor by limiting the abundance and metabolism of anammox bacteria. In contrast, the asynchronous feeding of acetate optimized the partition of the reactor column into two specific compartments: the lower half favoring anammox and the upper half dominated by DEAMOX (DEnitrifying AMmonium Oxidation). A high TN removal efficiency of 96.2±0.4% and a low effluent TN concentration of 9.3±0.9mgL−1 were obtained under a high TN loading rate of 9.0kgNm−3d−1. The dominant functional microbes in the CAARON process were identified as Candidatus Kuenenia and Thauera, which were responsible for the anammox and denitratation reactions, respectively. Overall, the results in this study provide valuable insight into the coupling of anammox with denitratation, which is a cost-efficient approach for treating ammonium-rich wastewaters.

Mechanisms and characteristics of biofilm formation via novel DEAMOX system based on sequencing biofilm batch reactor

A denitrifying ammonium oxidation (DEAMOX) process has been regarded as an innovative process to simultaneously treat ammonia and nitrate containing wastewaters, whereas very limited research has focused on its application in biofilm system. In this research, a novel DEAMOX process was established with fixed sponge carriers in a sequencing biofilm batch reactor (SBBR). To investigate biofilm formation process and characteristics can encourage further research on DEAMOX system optimization, deteriorated performance recovery strategies and application with actual wastewater. Total nitrogen removal efficiency was maintained at 93.0 % after 240 days of operation. With biofilm growth, the protein-like extracellular polymeric substances (EPS) and tightly-bound EPS (TB-EPS) of biofilms increased from 65.6 to 46.1, to 179.6 and 142.0mg gVSS-1, respectively, revealing that protein-like substances and TB-EPS promote biofilm formation. The mechanism of biofilm formation was discussed by analyzing the morphological development and functional bacterial activities of biofilms. Furthermore, high anammox activity was obtained in biofilms with specific NH4+N removal rates over 4.29 mgN gVSS-1h-1, which were significantly higher than in suspended sludge (2.56 mgN gVSS-1h-1). Quantitative polymerase chain reaction results showed that the abundance of anammox bacteria in biofilms increased from 1.87 % to 11.48 % with biofilm growth. These results imply that mature biofilms formed on carriers and the anammox bacteria were sufficient enriched in DEAMOX-SBBR system.

Simultaneous domestic wastewater and nitrate sewage treatment by DEnitrifying AMmonium OXidation (DEAMOX) in sequencing batch reactor

A novel DEAMOX system was developed for nitrogen removal from domestic wastewater and nitrate (NO3−-N) sewage in sequencing batch reactor (SBR). High nitrite (NO2−-N) was produced from NO3−-N reduction in partial-denitrification process, which served as electron acceptor for anammox and was removed with ammonia (NH4+-N) in domestic wastewater simultaneously. A 500-days operation demonstrated that the efficient and stable nitrogen removal performance could be achieved by DEAMOX. The total nitrogen (TN) removal efficiency was as high as 95.8% with influent NH4+-N of 63.58 mg L−1 and NO3−-N of 69.24 mg L−1. The maximum NH4+-N removal efficiency reached up to 94.7%, corresponding to the NO3−-N removal efficiency of 97.8%. The biomass of partial-denitrification and anammox bacteria was observed to be wall-growth. The deteriorated nitrogen removal performance occurred due to excess denitrifying microbial growth in the outer layer of sludge consortium, which prevented the substrate transfer for anammox inside. However, an excellent nitrogen removal could be guaranteed by scrapping the superficial denitrifying biomass at regular intervals. Furthermore, the high-throughput sequencing analysis revealed that the Thauera genera (26.33%) was possibly responsible for the high NO2−-N accumulation in partial-denitrification and Candidatus Brocadia (1.7%) was the major anammox species.

Performance and microbial community analysis of a novel DEAMOX based on partial-denitrification and anammox treating ammonia and nitrate wastewaters

In this study, a novel DEAMOX (DEnitrifying AMmonium OXidation) process coupling anammox with partial-denitrification generated nitrite (NO2−-N) from nitrate (NO3−-N) was developed for simultaneously treating ammonia (NH4+-N) and NO3−-N containing wastewaters. The performance was evaluated in sequencing batch reactors (SBRs) with different carbon sources for partial-denitrification: acetate (R1) and ethanol (R2). Long-term operation (180 days) suggested that desirable nitrogen removal was achieved in both reactors. The performance maintained stably in R1 despite the seasonal decrease of temperature (29.2 °C–12.7 °C), and high nitrogen removal efficiency (NRE) of 93.6% on average was obtained with influent NO3−-N to NH4+-N ratio (NO3−-N/NH4+-N) of 1.0. The anammox process contributed above 95% to total nitrogen (TN) removal in R1 with the nitrate-to-nitrite transformation ratio (NTR) of 95.8% in partial-denitrification. A little lower NRE was observed in R2 with temperature dropped from 90.0% at 22.7 °C to 85.2% at 16.6 °C due to the reduced NTR (87.0%–67.0%).High-throughput sequencing analysis revealed that Thauera genera were dominant in both SBRs (accounted for 61.53% in R1 and 45.17% in R2) and possibly played a key role for partial-denitrification with high NO2−-N accumulation. The Denitratisoma capable of complete denitrification (NO3−-N→N2) was found in R2 that might lead to lower NTR. Furthermore, different anammox species was detected with Candidatus Brocadia and Candidatus Kuenenia in R1, and only Candidatus Kuenenia in R2.

Feasibility of enhancing the DEnitrifying AMmonium OXidation (DEAMOX) process for nitrogen removal by seeding partial denitrification sludge

The recently proposed DEnitrifying AMmonium OXidation (DEAMOX) process combined anaerobic ammonia oxidation (ANAMMOX) with denitrification to convert nitrate to nitrite, which was a promising way for treating wastewater containing nitrate and ammonia. This study investigated the feasibility of establishing DEAMOX process by seeding partial denitrification sludge (NO3− → NO2−) using sodium acetate as an electron donor in a sequencing batch reactor. Results showed that the DEAMOX process was established successfully and operated stably in 114-days operation. The average effluent total nitrogen concentration was below 5 mg L−1 and TN removal efficiency reached up to 97% at COD/NO3− ratio of 3.0 under initial NH4+ concentration of 25 mg L−1 and NO3− of 30 mg L−1. It suggested that the presence of NO2− in the system supplied for ANAMMOX and the relatively long sludge retention time (SRT) for denitrifiers were attributed to commendable coexistence of ANAMMOX and denitrifying bacteria.

Elemental sulfur formation and nitrogen removal from wastewaters by autotrophic denitrifiers and anammox bacteria

Elemental sulfur (S0) formation from and nitrogen removal on sulfide, nitrate and ammonium-laden wastewaters were achieved by denitrifying ammonium oxidation (DEAMOX) reactor with autotrophic denitrifiers and anaerobic ammonium oxidation (anammox) bacteria. The sulfide to nitrate ratio is a key process parameter for excess accumulation of S0 and a ratio of 1.31:1 is a proposed optimum. The Alishewanella, Thauera and Candidatus Anammoximicrobium present respectively the autotrophic denitrifiers and anammox bacteria for the reactor. DEAMOX is demonstrated promising biological process for treating organics-deficient (S+N) wastewaters with excess S0 production.

Sustainable nitrogen removal by denitrifying anammox applied for anaerobic pre-treated potato wastewater

The feasibility of sustainable nitrogen removal was investigated in a two stage biofilm configuration consisting of a MBBR (Moving Bed Biofilm Reactor) and a Deamox reactor (Biobed-EGSB). The MBBR is used for nitrification and the denitrifying ammonium oxidation (Deamox) is aimed at a nitrogen removal process in which part of the required nitrite for the typical anammox reaction originated from nitrate. Anaerobic pre-treated potato wastewater was supplied to a MBBR and Deamox reactor operated in series with a bypass flow of 30%. The MBBR showed stable nitrite production at ammonium-loading rates of 0.9-1.0 kg NH₄-N/m³ d with ammonium conversion rates of 0.80-0.85 kg NH₄-N/m³ d. The nitrogen-loading rate and conversion rate of the Deamox reactor were 1.6-1.8 and 1.6 kg N/m³ d. The maximum ammonium removal capacity in the Deamox reactor was 0.6 kg NH₄-N/m³ d. The removal efficiency of soluble total nitrogen reached 90%. The Deamox process performance was found to be negatively affected during decline of the operating temperature from 33 to 22 °C and by organic loading rates with a chemical oxygen demand (COD)/NO₂-N ratio >1.

DEAMOX – New microbiological process of nitrogen removal from strong nitrogenous wastewater

This paper summarises the results obtained on a laboratory scale under development and optimisation of a new nitrogen removal process called DEAMOX (DEnitrifying AMmonium OXidation) for treatment of strong nitrogenous wastewater. The concept of this process combines the recently discovered anammox (anaerobic ammonium oxidation) reaction with denitrifying conditions for generation of nitrite from nitrate. Both the autotrophic (sulphide-driven) and heterotrophic (organics-driven) modifications of the DEAMOX process are reviewed with regard to process performance as well as outcome of competition for nitrite between anammox and denitritation. Some microbiological characteristics of the unique DEAMOX sludges formed during long-term runs are also discussed.

Development and optimisation of VFA driven DEAMOX process for treatment of strong nitrogenous anaerobic effluents

The recently proposed DEAMOX (DEnitrifying AMmonium OXidation) process combines the anammox reaction with autotrophic denitrifying conditions using sulphide as an electron donor for the production of nitrite from nitrate within an anaerobic biofilm. This paper firstly presents a feasibility study of the DEAMOX process using synthetic (ammonia + nitrate) wastewater where sulphide is replaced by volatile fatty acids (VFA) as a more widespread electron donor for partial denitrification. Under the influent N-NH+4/N-NO3(-) and COD/N-NO3(-) ratios of 1 and 2.3, respectively, the typical efficiencies of ammonia removal were around 40% (no matter whether a VFA mixture or only acetate were used) for nitrogen loading rates (NLR) up to 1236 mg N/l/d. This parameter increased to 80% by increasing the influent COD/N-NO3(-) ratio to 3.48 and decreasing the influent N-NH4 +/N-NO3(-) ratio to 0.29. As a result, the total nitrogen removal increased to 95%. The proposed process was further tested with typical strong nitrogenous effluent such as reject water (total N, 530-566 mg N/l; total COD, 1530-1780 mg/l) after thermophilic sludge anaerobic digestion. For this, the raw wastewater was split and partially ( approximately 50%) fed to a nitrifying reactor (to generate nitrate) and the remaining part ( approximately 50%) was directed to the DEAMOX reactor where this stream was mixed with the nitrified effluent. Stable process performance up to NLR of 1,243 mg N/l/d in the DEAMOX reactor was achieved resulting in 40, 100, and 66% removal of ammonia, NOx(-), and total nitrogen, respectively.

Comparison of quasisteady‐state performance of the DEAMOX process under intermittent and continuous feeding and different nitrogen loading rates

The recently developed denitrifying ammonium oxidation (DEAMOX) process combines the anammox reaction with autotrophic denitrifying conditions using sulfide as an electron donor for the production of nitrite from nitrate within an anaerobic biofilm. This paper compares a quasisteady-state performance of this process for treatment of baker's yeast wastewater under intermittent and continuous feeding and increasing nitrogen loading rate (NLR) from 300 till 858 mg N/L/d. The average total nitrogen removal slightly decreased on increasing the NLR: from 86 to 79% (intermittent feeding) and from 87 to 84% (continuous feeding). The better performance under continuous feeding was due to a more complete nitrate removal in the former case whereas the ammonia removal was similar for both feeding regimes under the comparable NLR. A possible explanation can be that, during continuous feeding (simultaneous supply of nitrate and sulfide), there were less mass transfer limitations for sulfide oxidizing denitrifiers presumably located in the outer layer of sludge aggregates. On the contrary, the ammonia oxidisers presumably located inside the aggregates apparently suffered from nitrite mass transfer limitations under both the feedings. The paper further describes some characteristics of the DEAMOX sludge.

New anaerobic process of nitrogen removal

This paper reports on successful laboratory testing of a new nitrogen removal process called DEAMOX (DEnitrifying AMmonium OXidation) for the treatment of strong nitrogenous wastewater such as baker's yeast effluent. The concept of this process combines the recently discovered ANAMMOX (ANaerobic AMMonium OXidation) reaction with autotrophic denitrifying conditions using sulfide as an electron donor for the production of nitrite within an anaerobic biofilm. The achieved results with a nitrogen loading rate of higher than 1,000 mg/L/d and nitrogen removal of around 90% look very promising because they exceed (by 9-18 times) the corresponding nitrogen removal rates of conventional activated sludge systems. The paper describes also some characteristics of DEAMOX sludge, as well as the preliminary results of its microbiological characterization.

DEAMOX—New biological nitrogen removal process based on anaerobic ammonia oxidation coupled to sulphide-driven conversion of nitrate into nitrite

This paper reports about the successful laboratory testing of a new nitrogen removal process called DEAMOX (DEnitrifying AMmonium OXidation) for treatment of typical strong nitrogenous wastewater such as baker's yeast effluent. The concept of this process combines the recently discovered anammox ( anaerobic ammonium oxidation) reaction with autotrophic denitrifying conditions using sulphide as an electron donor for the production of nitrite from nitrate within an anaerobic biofilm. To generate sulphide and ammonia, a Upflow Anaerobic Sludge Bed (UASB) reactor was used as a pre-treatment step. The UASB effluent was split and partially fed to a nitrifying reactor (to generate nitrate) and the remaining part was directly fed to the DEAMOX reactor where this stream was mixed with the nitrified effluent. Stable process performance and volumetric nitrogen loading rates of the DEAMOX reactor well above 1000 mg N/l/d with total nitrogen removal efficiencies of around 90% were obtained after long-term (410 days) optimisation of the process. Important prerequisites for this performance are appropriate influent ratios of the key species fed to the DEAMOX reactor, namely influent N-NO x /N-NH 4 ratios >1.2 (stoichiometry of the anammox reaction) and influent S-H 2S/N-NO 3 ratios >0.57 mg S/mg N (stoichiometry of the sulphide-driven denitrification of nitrate to nitrite). The paper further describes some characteristics of the DEAMOX sludge as well as the preliminary results of its microbiological characterisation.