Performance Of Anammox Reactor Research Articles

Effect of linear anionic surfactant (sodium dodecyl sulfate) dosage on nitrogen removal performance of an anammox reactor

AbstractThe impact of sodium dodecyl sulfate (SDS, as model linear anionic surfactant) dosage on overall nitrogen removal performance of anammox reactor alongside its microbial population and sludge properties was investigated. In this study (day 136), an anmmox sequencing batch biofilm reactor was subjected to gradual dosage of SDS from 0 to 20 mg L−1. Intriguingly, results revealed that SDS at ≥7.5 mg L−1 prompted sludge disintegration, evidenced by increased protein and polysaccharide content in the effluent. Nevertheless, reactor's average total nitrogen removal efficiency slightly improved from 83.12% (0 mg L−1) to 86.3% (20 mg L−1). The 16S rRNA gene sequencing revealed that SDS dosing significantly suppressed the unwanted and unavoidable nitrite oxidizing bacteria (NOBs) in the reactor as the abundance of genus Nitrospira declined from 40.68% (day 1) to 19.15% (day 136). The abundance of anammox genus Candidatus Kuenenia significantly improved from 1.86% (day 1) to 40.02% (day 136) as a result of NOB suppression. This study revealed that low concentration of surfactants in wastewater does not affect the anammox bacteria in a biofilm reactor. Furthermore, adding low concentrations of SDS (≥7.5 to 20 mg L−1) to wastewater may effectively suppress notorious NOBs in biofilm‐based anammox systems.

Insights into the response of Anammox sludge to the individual and combined stress of neodymium and salinity and the role of hydroxylamine regulation

Neodymium (Nd(III)) and sulfate (Na2SO4) are commonly present in neodymium mining wastewater. However, the effects of their coexistence on microorganisms responsible for removing nitrogen from wastewater have been poorly reported. In this study, the combined inhibition of Nd(III) and Na2SO4 on anaerobic ammonium oxidation (Anammox) and its recovery were investigated in terms of performance, kinetics, Nd(III) distribution characteristics and sludge morphology. The results shown that ≥ 150 mg·L−1 Nd(III) or ≥ 3 g·L−1 Na2SO4 decreased specific Anammox activity (SAA), and intracellular Nd(III) was identified as the primary factor for individual Nd(III) inhibition. Furthermore, the combined inhibition of Nd(III) and Na2SO4 on Anammox was stronger than individual inhibition, but low doses of hydroxylamine (NH2OH) could restore the Anammox. Notably, the combined effect of low doses of Na2SO4 (1 g·L−1) and Nd III (10 mg·L−1) on the long-term performance of Anammox reactor was not significant. However, when the dose of Nd(III) was kept constant and the dose of Na2SO4 was increased to 7 g·L−1, the total nitrogen removal efficiency (TNRE) decreased by 56.88%. Following the elimination of inhibitors and the addition of 5 mg·L−1 NH2OH, the TNRE of the Anammox reactor was increased from 20.83% to 29.78%. The Hill, modified Michaelis-Menten, and modified Boltzmann models were able to properly describe the inhibition effects of Nd(III) and Na2SO4 and recovery process of Anammox. In addition, scanning electron microscopy (SEM) and energy-dispersive X-ray (EDS) analysis revealed that the content of extracellular polymeric substances (EPS) and neodymium increased with increasing Na2SO4 concentration.

Promoting performance of Anammox by iron loaded sludge biochar with hydrothermal carbonization (HTC-Fe-BC) addition

Anaerobic ammonia oxidation (Anammox) treatment cannot always achieve optimal efficiency due to its sensitivity to environmental conditions. The nitrogen removal efficiency of Anammox reactors with different iron loaded sludge biochar modified by hydrothermal carbonization (HTC-Fe-BC) addition dose of 0, 2.5 and 5.0 g/L (named BC0, BC1 and BC2) were analyzed. The effects of adding HTC-Fe-BC on the performance of Anammox reactor, extracellular polymeric substances (EPS), microbial community and functional genes were investigated. The results showed that the addition of HTC-Fe-BC could reduce the environmental sensitivity of Anammox reactor, the removal efficiency of total nitrogen increased from 51.20 (BC0) to 70.83 % (BC2), and the activity of Anammox sludge improved by 49.58 %. HTC-Fe-BC increased the activity of Anammox sludge by promoting the secretion of protein, humic acids and cytochrome c in EPS and alleviated the inhibitory effect by mediating the Anammox electron transfer process. After EPS removal and enzymatic hydrolysis, the activity of Anammox sludge in BC2 decreased by 61.38% and 79.80 %, respectively, significantly higher than the reduced values of BC0. Further, the relative abundance of Candidatus_Brocadia in Anammox reactors supplemented with HTC-Fe-BC was increased by 35.56–55.56 % compared to the control group, as were the relative abundances of the key functional genes connected to N transformation. These results deepened the understanding of the potential mechanism by which HTC-Fe-BC improved the efficiency of Anammox system.

Metagenomic insights into the symbiotic relationship in anammox consortia at reduced temperature

Anammox as a promising biological nitrogen removal technology has attracted much attention. However, cold temperature would limit its wide application and little is known about the microbial interactions between anammox bacteria (AnAOB) and heterotrophic bacteria at cold temperature. Here, we observed reduced temperature (25–15 °C) promoted the secretion of EPS and thus stimulated bigger size of granular sludge in a laboratory-scale anammox reactor. We further combined co-occurrence network analysis and genome-centered metagenomics to explore the potential interactions between AnAOB and heterotrophic bacteria. Network analysis suggested 22 out of 25 positively related species were reported as definite heterotrophic bacteria in subnetwork of AnAOB. Genome-centered metagenomics analysis yielded 23 metagenomic assembly genomes (MAGs), and we found that Acidobacteriota-affiliated bacteria could biosynthesize most polysaccharides (PS) precursors and contain the most glycosyltransferases and transporters to facilitate exopolysaccharides biosynthesis, together with partial PS precursors produced by AnAOB. AMX1 as the only anammox genome could synthesize most amino acids and cross feed with some heterotrophs to affect the extracellular protein function. Additionally, Bacteroidota, Planctomycetota, Chloroflexota, and Proteobacteria could contribute folate and molybdopterin cofactor for AMX1 to benefit their activity and growth. Superphylum Patescibacteria could survive by cross-feeding with AnAOB and heterotrophic organisms about organic compounds (Glyceraldehyde-3P and lactate). These cross-feedings maintained the stability of anammox reactor performance and emphasize the importance of heterotrophs in anammox system at reduced temperature.

Start-up of Anammox systems with different biochar amendment: Process characteristics and microbial community

As the ‘go-to’ process when it comes to biological nitrogen removal from wastewaters in recent years, the Anammox process has undergone lots of investigations in order to optimize its performance. In evaluating the effect of distinct biochar types at different concentrations on the Anammox startup process, as well as analyze their corresponding influence on the microbial community structure, three additives (coconut, peach, and bamboo) at either 5%, 10%, or 15% respectively were amended in various Anammox EGSB setups. (i). The 5% coconut biochar amendment resulted in the fastest startup of 46 days with an average ammonium removal efficiency of 96% whereas the control setup took 69 days. Thus, a more robust and cost effective Anammox process could be realized on an industrial scale. (ii) The Illumina high-throughput sequencing of the collected sludge samples indicated that the amendment with distinct biochar resulted in varied prevailing microbial communities in the respective setups. (iii) Proteobacteria was the dominant microbial community. (iv) However, two Anammox bacteria species, Candidatus Brocadia and Candidatus Jettenia were identified, with relative abundances of 0–4.72% and 0–6.23% respectively. The results from this study illustrate the correlation between Anammox reactor performance (startup and nitrogen removal efficiency), type and concentration of biochar amendment employed, as well as microbial community succession.

Mainstream anammox reactor performance treating municipal wastewater and batch study of temperature, pH and organic matter concentration cross-effects

The anammox process is an energy efficient promising alternative to biologically remove the nitrogen. Thus, a 5-L anammox granular reactor was inoculated with sludge coming from a sidestream partial nitritation and anammox reactor (>200 mg TN/L and 30 °C) and it was directly subjected to 15 ± 1 °C treating mimicked municipal wastewater (50 mg TN/L). Results indicated that an acclimation period (commonly used) to progressive reach the mainstream conditions is not needed, shortening the start-up periods. The long-term anammox process stability was proved to treat synthetic wastewater with decreasing alkalinities and nitritified primary settled municipal wastewater. The low pH values (6.2 ± 0.1) of the municipal wastewater fed did not affect the process stability. Residual organic matter concentrations augmented the nitrogen removal efficiency from 80 % (with the synthetic medium) to 92 % achieving effluent concentrations below 10 mg TN/L. Finally, the effect of pH (6–8), temperature (15–30 °C) and organic matter concentration (0–75 mg TOC/L) over the specific anammox activity (SAAMX) was evaluated at short-term. pH and temperature and their interactions exerted significant influence on the SAAMX value while the TOC concentrations itself did not significantly change the SAAMX.

What's the variation in anammox reactor performance after single and joint temperature based shocks?

A laboratory-scale up-flow anaerobic sludge blanket reactor was used to investigate the effects of temperature-based (single and combined with loading) shocks on the performance of anaerobic ammonium oxidation (anammox) reactor. The reactor was tolerant to 15 °C and 25 °C shocks; however, temperature shock of 55 °C led to severe accumulation of effluent NO2−-N (>100 mg L−1), which induced substrate inhibition. Although the shock experiments achieved a maximum effluent NO2−-N concentration of 205.4 mg L−1 after a hydraulic retention time-substrate concentration shock at 25 °C, the inhibition was still reversible. During the experiments, the content of extracellular polymeric substances (EPS) increased significantly after each shock to protect the anammox bacteria, and the value decreased correspondingly at the end of the recovery phase. The specific anammox activity showed the opposite tendency compared with that of the EPS. The performance of anammox reactor under a series of short-term temperature shocks was investigated, and the results can provide new ideas for future research.

Effect of organic matters on anammox coupled denitrification system: when nitrite was sufficient.

Anaerobic ammonia oxidation (anammox) and denitrification can work together to weaken the influence of organic matter on anaerobic ammonia oxidation bacteria (AAOB) and improve nitrogen removal performance. As the common substrate of anammox and denitrification, nitrite will also affect nitrogen removal performance when it is insufficient, which is not conducive to reflect the endurance of anammox reactor to organic matter. The UASB continuous flow experiment was carried out to investigate the effect of the concentration of glucose and sodium acetate on nitrogen removal performance of anammox reactor under the condition of sufficient nitrite. With glucose as the organic matter, when the chemical oxygen demand (COD) concentration increased to 200 mg l−1, nitrogen removal performance of the system began to deteriorate significantly, and the anammox activity was significantly inhibited. With sodium acetate as the organic substance, the anammox activity was affected when the COD was 20 mg l−1. Adequate nitrite could relieve the inhibition of the coupling system by a low concentration (COD < 200 mg l−1) of glucose organic matter. However, it could not relieve the inhibitory effect of sodium acetate. With the increase of organic concentration, the biological density of AAOB in granular sludge gradually decreased, while the biological density of denitrifying bacteria increased gradually.

Relationship of heme c, nitrogen loading capacity and temperature in anammox reactor

The characteristic carmine red color due to heme proteins is always observed in enriched anammox biomass. Heme c is a very important co-factor participating the main metabolic reactions with catalytic and electron-transfer potential in the anammox bacteria, and is possible for use as an indicator to evaluate anammox performance. Knowledge of the relationship between the heme c concentration and the anammox reactor performance is, however, very limited available information is constrained at an operation temperature of 35 °C. In this study, we report the heme c concentration change along with nitrogen removal rate (NRR) in three anammox expanded granular sludge bed reactors operated at different temperatures (15, 25, 35 °C). The response of specific anammox activity (SAA) to temperature was revealed for biomass originating from three reactors. The results indicate a strong relationship between heme c concentration and NRR at different culture temperatures. The possibility of evaluating the anammox performance by combining heme c quantification and the temperature is revealed.

The performance of anammox reactor during start-up: Enzymes tell the story

Abstract Start-up is the first and essential step in the operation of anammox (anaerobic ammonia oxidation) reactor. It is helpful to know the progress of start-up for the real-time optimization of reactor performance. In this work, a start-up mode was successfully established, by which the anammox reactor was smoothly put into use, with NLR (Nitrogen Loading Rate) and NRR (Nitrogen Removal Rate) of 11.0 and 10.1 kg-N /(m3 d), respectively. During the start-up, the dehydrogenase, alkaline phosphatase, hydrazine oxidase and heme of the anammox granular sludge were investigated and their activity/content was correlated with the reactor performance. The activity of dehydrogenase and alkaline phosphatase was found to decrease with the elevation of NLR. On the contrary, the hydrazine oxidase activity and heme content were observed to increase with the elevation of NLR. Based on the relative enzyme level, an enzyme indicator system was created to monitor the start-up progress of anammox reactor.

Performance of anammox process treating nitrogen-rich saline wastewater: Kinetics and nitrite inhibition

A sequencing batch reactor (SBR) was operated more than 200 d to treat nitrogen-rich saline wastewater by anammox process. The temperature was controlled at 35 ± 0.5 °C and the mixed liquor suspended solids (MLSS) was around 4000 mg TSS/L. Anammox reactor could gradually acclimate to 100% seawater. However, the long-term effects of 50% seawater not only affected nitrogen removal performance, resulting in a decrease of nitrogen removal rate (NRR) to 0.114 kg N/(m3·d), but also weakened sludge settling ability. The effect resulting from 50% seawater was reversible and the NRR gradually increased to 0.419 kg N/(m3·d) by adding sponge carriers. Analysis of variance (ANOVA) test shown that △NO3−-N/△NH4+-N ratio was significantly different (p < 0.05) under different seawater content. After inhibition resulting from 100% seawater, the response process of anammox could be divided into three periods. At 100% seawater, nitrogen removal performance of anammox reactor was affected when influent nitrite was higher than 150 mg N/L (NO2−-Ninf/NH4+-Ninf = 1.37 ± 0.02). Luong model was suitable to analyze inhibitory effect resulting from nitrite under saline surroundings.

Using low frequency and intensity ultrasound to enhance start-up and operation performance of Anammox process inoculated with the conventional sludge

A lab-scale ultrasound enhancing Anammox reactor (R1) was established and irradiated once a week by ultrasound with the optimal parameter (frequency of 25 kHz, intensity of 0.2 W cm−2 and exposure time of 3 min) obtained by batch experiments. R1 and the controlled Anammox reactor (R2) without exposure to the ultrasound were operated in parallel. The start-up period of Anammox process (53 days) in R1 was shorter than that (61 days) in R2. The nitrogen loading-enhancing period (day 53-day 135) in R1 was also shorter than that (day 61-day 151) in R2. At the end of the nitrogen loading-enhancing period, NLR (0.76 kg N m−3 d−1) and NRR (0.68 kg N m−3 d−1) of R1 were both higher than NLR (0.66 kg N m−3 d−1) and NRR (0.56 kg N m−3 d−1) of R2. Moreover, The stability of Anammox process in R1 was better than that in R2. The results demonstrated that the periodical irradiation of ultrasound enhanced the start-up and operational performance of Anammox reactor. Microbial community analysis indicated that the ultrasound accelerated the microbial succession from some other bacteria to Anammox bacteria so that shorten the start-up period of Anammox process from the conventional activated sludge. It also indicated that the ultrasound strengthened the competitive advantage of Candidatus Kuenenia stuttgartiensis in Anammox bacteria of the mature sludge so as to enhance the nitrogen removal performance of the Anammox reactor under the operation condition of high nitrogen loading.

Characterization of a Microbial Community in an Anammox Process Using Stored Anammox Sludge

This study investigated a rapid start-up anaerobic ammonium oxidation (Anammox) process by inoculation with stored Anammox sludge and characterized the associated microbial communities. The Anammox process took only 43 days to start. A high nitrogen removal rate of 1.13 kg N m−3 d−1 and a nitrogen loading rate of 1.28 kg N m−3 d−1 were achieved. The ratio of ammonium removal to nitrite removal to nitrate production (1:1:0.2) was slightly lower than the theoretical value, which indicated nitrogen removal by denitrification in the reactor. Illumina high-throughput sequencing of sludge samples confirmed the co-existence of Anammox bacteria and denitrifying bacteria in the reactor and demonstrated that denitrifying bacteria play a role in nitrogen removal during the Anammox process. The dominant microbes in the reactor were Proteobacteria, Chlorobi, Chloroflexi, and Planctomycetes. However, only one species of Anammox bacteria, Candidatus jettenia, was identified and had an abundance of 4.92%. Our results illustrate the relationship between Anammox reactor performance and microbial community succession.

Recovery Performance of ANAMMOX Process after Inhibition Resulting from Seawater

An anaerobic sequencing batch reactor (ASBR) was operated to investigate the recovery performance of ANAMMOX reactor after the inhibition of 100% seawater concentration. The results showed that the nitrogen removal performance of ANAMMOX reactor suffered inhibition of high salinity concentration. However, it could enter a period of stable nitrogen removal efficiency again after an interim stable period and a recovery period. The nitrogen removal rate (NRR) could reach 0.52 kg·(m3·d)-1, which was similar to the control group, containing 10% seawater and having a NRR of 0.462 kg·(m3·d)-1. The modified Logistic model and modified Gompertz model were revised and their application field was broadened. The re-modified Logistic model was suggested to be used to simulate the NRR recovery process of ANAMMOX reactor that suffered inhibition of 100% seawater concentration. The doubling time of NRR was calculated to be 11.359 d using the prediction formula established for the recovery time of NRR.

Mathematical modeling of high-rate Anammox UASB reactor based on granular packing patterns

A novel mathematical model was developed to estimate the volumetric nitrogen conversion rates of a high-rate Anammox UASB reactor based on the packing patterns of granular sludge. A series of relationships among granular packing density, sludge concentration, hydraulic retention time and volumetric conversion rate were constructed to correlate Anammox reactor performance with granular packing patterns. It was suggested that the Anammox granules packed as the equivalent simple cubic pattern in high-rate UASB reactor with packing density of 50–55%, which not only accommodated a high concentration of sludge inside the reactor, but also provided large pore volume, thus prolonging the actual substrate conversion time. Results also indicated that it was necessary to improve Anammox reactor performance by enhancing substrate loading when sludge concentration was higher than 37.8gVSS/L. The established model was carefully calibrated and verified, and it well simulated the performance of granule-based high-rate Anammox UASB reactor.

Development of anammox reactor equipped with a degassing membrane to improve biomass retention

In up-flow anammox reactors, one of the contributing factors to biomass wash-out is the adherence of nitrogen gas produced by the anammox reaction to biomass. In this study, we operated an up-flow anammox reactor equipped with a degassing membrane to minimize the biomass wash-out from the reactor by separating the produced gas from the biomass. In addition, both the effect of degassing on the anammox reactor performance and the durability of the membrane submerged in the anammox reactor were investigated. The results show that the use of the degassing membrane in the anammox reactor could (1) improve the biomass retention ability (by separating the produced gas from the biomass), and (2) increase the component ratio of anammox bacteria in the reactor. In addition, degassing could reduce the N(2)O emission produced in the reactor (for the gas selectivity of the degassing membrane). No membrane fouling was observed even after 2 months of operation without washing, indicating an advantage to the use of the degassing membrane.

Linking Community Profiles, Gene Expression and N-Removal in Anammox Bioreactors Treating Municipal Anaerobic Digestion Reject Water

Anaerobic ammonium oxidation (anammox) requires 60% less oxygen and no external organic carbon compared to conventional biological nitrogen removal (BNR). Nevertheless, full-scale installations of anammox are uncommon, primarily owing to the lack of well-established process monitoring and control strategies that result in stable anammox reactor performance. The overarching goal of this study was to develop and apply molecular biomarkers that link microbial community structure and activity to anammox process performance in a bioreactor fed with actual anaerobic digestion centrate from a full-scale operational wastewater treatment facility. Over long-term operation, Candidatus "Brocadia sp. 40" emerged as the dominant anammox population present in the reactor. There was good correspondence between reactor nitrogen removal performance and anammox bacterial concentrations. During the period of reactor operation, there was also a marked shift in biomass morphology from discrete cells to granular aggregates, which was paralleled by a shift also to more stable nitrogen removal and the succession and establishment of bacteria related to the Chlorobi/Bacteroidetes superfamily. Based on batch assays, hydrazine oxidoreductase (hzo) expression and concentrations of the 16S-23S rRNA intergenic spacer region (ISR) were good quantitative biomarkers of oxygen- and nitrite-mediated inhibition. When applied to a continuous anammox reactor, both molecular biomarkers show promise as monitoring tools for "predicting" reactor performance.

The effect of urban landfill leachate characteristics on the coexistence of anammox bacteria and heterotrophic denitrifiers

Heterotrophic denitrification coexists with the anammox process contributing to N removal owing to the biodegradable organic matter supply from urban landfill leachate and the decay of microorganisms. Both biomasses consumed nitrite increasing the nitrite requirements of the system. The aim of this paper is the study of the causes which induce the system to decrease nitrogen removal efficiency. In this study, urban landfill leachate has been treated in an anammox Sequencing Batch Reactor (SBR) for 360 days. The anammox reactor treated on average 0.24 kgN m(-3) d(-1) obtaining nitrogen removal efficiencies up to 89%. The results demonstrated that i) a suitable influent nitrite to ammonium molar ratio is a crucial factor to avoid troubles in the anammox reactor performance; ii) an excess of nitrite implied nitrite accumulation in the reactor; iii) a lower nitrite supply than the necessary for the system could force a loss of specific anammox activity due to nitrite competition with denitrifiers. These results pointed out the importance of the previous partial-nitritation process control in order to obtain a correct influent nitrite to ammonium molar ratio for the anammox reactor. In addition, sudden variation of the leachate characteristics must be avoided.