Anammox Upflow Anaerobic Sludge Blanket Research Articles

Stable continuous flow CANDAN process transitioning from anammox UASB reactor by facilitating indigenous nitrite-producing denitrification community

The emerging nitrogen removal process known as CANDAN (Complete Ammonium and Nitrate removal via Denitratation-Anammox over Nitrite) has been developed in Sequencing Batch Reactors (SBRs). Yet, starting up and maintaining stability in continuous-flow reactors remain challenging. This study explores the feasibility of transitioning the CANDAN process from an anammox-dominated process by introducing appropriate external organics to facilitate indigenous nitrite-producing denitrification community in an Upflow Anaerobic Sludge Blanket (UASB) reactor. 150-day operation results indicate that under feeding rates of domestic wastewater at 0.54 L/h and nitrate-containing wastewater at 1.08 L/h, excellent N removal was achieved, with effluent TN below 10.0 mg N/L. Adding external sodium acetate at a COD/NO3−-N = 2.0 triggered denitratation, ex-situ denitrification activity tests showed increased nitrite production rates, maintaining the nitrate-to-nitrite transformation ratio (NTR) above 90 %. Consequently, anammox activity was consistently maintained, dominating Total Nitrogen (TN) removal with a contribution as high as 78.3 ± 8.0 %. Anammox functional bacteria, Brocadia and Kuenenia were identified and showed no decrease throughout the operation, indicating the robustness of the anammox process. Notably, the troublesome of sludge flotation, did not occur, also contributing to sustained outstanding performance. In conclusion, this study advances our understanding of the synergistic interplay between anammox and denitrifying bacteria in the Anammox-UASB system, offering technical insights for establishing a stable continuous-flow CANDAN process for simultaneous ammonium and nitrate removal.

Enhancing anammox process at moderate temperature via employing anammox granular sludge reactor effluent addition

The anaerobic ammonium oxidation (anammox) application on mainstream wastewater treatment is limited by the ambient environment and slow growth rate of anammox bacteria. Bulk liquid in established anammox granular sludge bioreactors naturally contains active factors that could potentially boost anammox process under suboptimal conditions. In this study, effluent of a granular sludge-based anammox up-flow anaerobic sludge blanket treating ammonium-rich wastewater was harvested (the effluent is named as UAE) and continuously added into a bioreactor treating low-strength wastewater at 25 °C to study the effects and mechanisms on enhancing the anammox process. The NH4+-N removal efficiencies increased from 6.5% - 32.5% to 89.7% – 93.8%, and anammox genera accounted from 0.1% to 12.1% of microbial community in the receiving reactor with UAE addition. Coupled partial denitrification and dissimilatory nitrate reduction to ammonium (DNRA) processes with anammox were stimulated by UAE addition. Metagenomic analysis showed that the acyl-homoserine lactone-dependent quorum sensing molecules synthesis pathway was enhanced and an increased concentration of C8-HSL from 2.59 ng/L to 4.62 ng/L was observed in the UAE-receiving reactor. Selective amino acid transportation, amino acids biosynthesis and energy metabolic pathways of microbial community were upregulated with UAE addition. We demonstrate UAE as anammox biocatalyst and facilitate a deeper understanding for synergistic effect of active factors in UAE modified microhabitat for anammox metabolism in the UAE-receiving reactor.

Development of long-term dynamic BioWin® model simulation for ANAMMOX UASB micro-granular process

Three different innovative mathematical models were established to assess the volumetric nitrogen conversion rates of a lab-scale ANAMMOX upflow anaerobic sludge blanket reactor. Despite the vast technological and economical advantages of ANAMMOX, major challenges in process implementation call for mathematic simulations of the process, optimization of operating conditions, and kinetic/statistical analysis of the entire process. In this study, all developed mathematical models implemented via BioWin®, were calibrated and validated, with adequate representations of a bench-scale micro-granular ANAMMOX process, to understand the potential setbacks of ANAMMOX process start-up and stabilization. Fundamental calculations of the kinetic and stoichiometric constants were integrated in the BioWin® software, and the adjusted parameters based on experimental analysis were applied for the assessments. Based on the results from the statistical approach, one of the models (Model III) exhibited a precise prognosis of the effluent data for the entire operational phases with a mean relative error (MRE) of approximately 1.96, 4.36 and 2.54% for nitrogen removal efficiency, removal rate and loading rate, respectively. Evaluating alkalinity and pH during the operation, led to identifying an acceptable fit between the experiment and Model III results, with a MRE of −7.19 and −0.35%, correspondingly. This study confirms the reliability of ANAMMOX-based process modeling and high predictive ability with BioWin®. The presented simulation constants and modeling outline, can be further employed in full-scale applications design and development.

Effect of hydraulic retention time on effluent pH in anammox bioreactors: Characteristics of effluent pH and pH as an indicator of reactor performance

In order to assess the performance of anaerobic ammonium oxidation (anammox) bioreactors, it is necessary to study the stoichiometry of the anammox reaction and pH. This study focused on the effect of the hydraulic retention time (HRT) on the effluent pH in anammox-upflow anaerobic sludge blanket (UASB) bioreactors. Anammox-UASB bioreactors with and without a recirculation system were used to investigate the effluent pH and bioreactor performance. It was concluded that under varying HRT conditions, the decrease in effluent pH did not indicate the deterioration of nitrogen removal, but did indicate that the nitrogen removal efficiency was reduced owing to a sudden increase in the nitrogen loading rate resulting from the decrease in HRT. Moreover, the results showed that the HRT directly affected the concentration of OH−, which affected the increase/decrease in effluent pH. This study demonstrated that effluent pH is a more powerful tool than previous techniques used to assess bioreactor performance. We suggest that the effluent pH could be used for preliminary assessment.

Effects of temperature on anammox performance and community structure

A lab-scale anammox up-flow anaerobic sludge blanket (UASB) reactor was run to investigate the influence of temperature on anammox performance and community structure. The anammox system had a higher substrate tolerance at 13 °C than at 18 °C. The adverse effects caused by the use of a lower temperature (8 °C) could be restored. The nitrogen removal rate (NRR) decreased with decreasing in situ specific anammox activity (SAA). Interestingly, the ex situ SAA acclimated at 23 °C, when exposed to ex situ temperatures of 33 and 28 °C, was higher than for those acclimated at 33 and 28 °C. No shift was observed in the optimum temperature for ex situ SAA in the whole lowering process of anammox UASB. More extracellular polymeric substances were produced in response to cooler conditions (18 °C and 13 °C). Ca. Kuenenia became much more abundant (55.18% of the microbial community) and had a competitive advantage over other anammox bacteria (AnAOB) at 13 °C.

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The feasibility of an anammox (anaerobic ammonium oxidation) UASB (upflow anaerobic sludge blanket) bioreactor to treat ammonium-rich brines was investigated in batch and continuous-flow experiments. The evidence from batch tests indicated that the anammox activity was significantly inhibited under highly saline conditions while the inhibition was reversible. Saline shock loading of 30 g NaCl l−1 caused a 67.5% decrease in specific anammox activity (SAA) compared to reference biomass (not exposed to salt). However, the acclimatized biomass displayed a SAA value just 45.1% lower than that of the reference biomass. When transferred from brine to freshwater, the salt-exposed biomass resumed its activity by 43.1%. Subsequent to appropriate acclimatization, careful manipulation nitrite concentration, nitrogen loading rate (NLR), and other operational parameters for 77 days, the results of continuous-flow experiment revealed that under the salinity of 30 g NaCl l−1 the reactor performed well and the substrate removal capacity (nitrogen removal rate, NRR, of 448 ± 15 mgl−1 d−1) was comparable to the condition of freshwater (NRR of 464 ± 13 mgl−1 d−1). However, the anammox UASB bioreactor was prone to malfunction under transient operating conditions.

The inhibitory effect of fluoride on anaerobic ammonium oxidation (anammox)

AbstractBACKGROUNDAnaerobic ammonium oxidation (anammox) is a promising process for nitrogen removal, but it cannot always be used successfully in the presence of inorganic matter. The feasibility of using the anammox process for treating wastewater that contains fluoride was examined in this study. The short‐term inhibitory effect was tested at various fluoride concentrations and exposure times, and diverse pre‐exposure strategies were performed in special serum bottles. Subsequently, the long‐term effect of fluoride stress was continuously monitored and evaluated in an upflow anaerobic sludge blanket (UASB) reactor.RESULTSThe 50% inhibitory concentration (IC50) of fluoride for anammox biomass was calculated to be 767 mg L−1 in batch tests with an initial total nitrogen (TN) level of 200 mg L−1. A remarkable inhibitory effect of fluoride emerged when the substrate was supplied at >420 mg L−1 TN. The diameter and settling velocity of the granules significantly increased with the addition of 250 mg L−1 fluoride.CONCLUSIONThe performance of the anammox system and the granule properties were abnormal at a fluoride concentration of 400 mg L−1. The anammox UASB reactor was able to treat wastewater containing up to 350 mg L−1 fluoride after 183 days. © 2014 Society of Chemical Industry

Effect of zero-valent iron on the start-up performance of anaerobic ammonium oxidation (anammox) process.

The long start-up time of anaerobic ammonium oxidation (anammox) process hinders the widespread application of anammox technology in practical wastewater treatment when anammox seed sludge is not available. Meanwhile, the production of nitrate cannot meet the increasingly more strict discharge standards. To combine the chemical nitrate reduction to ammonium with biological nitrogen removal, two anammox upflow anaerobic sludge blanket reactors packed with different types of zero-valent iron (ZVI), microscale ZVI (mZVI) and nanoscale ZVI (nZVI), were developed to accelerate the start-up of anammox process. The results revealed that anammox start-up time shortened from 126 to 105 and 84 days with the addition of mZVI and nZVI. The nitrogen removal performance was also improved remarkably by adding ZVI, especially in the start-up stage. The value of dissolved oxygen showed that ZVI could be regarded as a useful deoxidant to create anaerobic condition for the proliferation of anammox bacteria. ZVI was favorable for the secretion of EPS, which would represent the activity of anammox bacteria. The result of real-time quantitative PCR (qPCR) further confirmed that the proliferation of anammox bacteria was enhanced by ZVI.

Comparison of sulfate-reducing and conventional Anammox upflow anaerobic sludge blanket reactors

Autotrophic NH4(+) removal has been extensively researched, but few studies have investigated alternative electron acceptors (for example, SO4(2-)) in NH4(+) oxidation. In this study, sulfate-reducing anaerobic ammonium oxidation (SRAO) and conventional Anammox were started up in upflow anaerobic sludge blanket reactors (UASBRs) at 36 (±0.5)°C and 20 (±0.5)°C respectively, using reject water as a source of NH4(+). SO4(2-) or NO2(-), respectively, were applied as electron acceptors. It was assumed that higher temperature could promote the SRAO, partly compensating its thermodynamic disadvantage comparing with the conventional Anammox to achieve comparable total nitrogen (TN) removal rate. Average volumetric NH4(+)-N removal rate in the sulfate-reducing UASBR1 was however 5-6 times less (0.03kg-N/(m(3) day)) than in the UASBR2 performing conventional nitrite-dependent autotrophic nitrogen removal (0.17kg-N/(m(3) day)). However, the stoichiometric ratio of NH4(+) removal in UASBR1 was significantly higher than could be expected from the extent of SO4(2-) reduction, possibly due to interactions between the N- and S-compounds and organic matter of the reject water. Injections of N2H4 and NH2OH accelerated the SRAO. Similar effect was observed in batch tests with anthraquinone-2,6-disulfonate (AQDS). For detection of key microorganisms PCR-DGGE was used. From both UASBRs, uncultured bacterium clone ATB-KS-1929 belonging to the order Verrucomicrobiales, Anammox bacteria (uncultured Planctomycete clone Pla_PO55-9) and aerobic ammonium-oxidizing bacteria (uncultured sludge bacterium clone ASB08 "Nitrosomonas") were detected. Nevertheless the SRAO process was shown to be less effective for the treatment of reject water, compared to the conventional Anammox.

Performance of an Anammox UASB reactor at high load and low ambient temperature

The performance of high-loaded anaerobic ammonium oxidation (Anammox) upflow anaerobic sludge blanket (UASB) reactors (R1, R2 and R3) was investigated at low ambient temperatures (28.3–8.5°C), and measurements of sequential biomass addition (SBA) (R2) and glycine betaine (GB) addition (R3) were carried out as countermeasures for operation under psychrophilic temperature conditions (8.5–13.5°C). By adding 10mL highly active Anammox sludge every 2days, the nitrogen removal rate (NRR) at 9.1°C increased to 6.6kgm−3d−1, almost 20% higher than that of R1 (acclimation). The effect of GB addition on Anammox was varied. Operation using either strategy changed the sludge characteristics. Low biomasses of 12.90 and 9.74gVSSL−1 were detected in R1 and R2, respectively, after whole investigation, whereas R3 had a biomass of 22.36gVSSL−1. Adapted sludge had a higher Anammox activity at 15°C than its non-adapted counterpart. The amount and composition of extracellular polymeric substance (EPS) shifted with different control strategies.

Performance of anammox UASB reactor treating low strength wastewater under moderate and low temperatures

An integrated approach to enhance and maintain high anammox activity and abundance in an upflow anaerobic sludge blanket (UASB) treating low strength wastewater under moderate and low temperatures was developed. A quantitative PCR assay showed the abandance of anammox bacteria to be 1.68±0.08×109copies/ml in mixed liquor when the temperature was 30°C and was maintained at the level of 1.93±0.41×109copies/ml in mixed liquor at 16°C. A nitrogen removal rate (NRR) of up to 5.72kgN/m3/d was achieved with a hydraulic retention time (HRT) of 0.12h at 30°C, while nitrite and ammonium removal efficiencies were 94.35% and 92.81%, respectively. NRR decreased with a decrease in temperature and was maintained at 2.28kgN/m3/d with an HRT of 0.28h when at 16°C, while nitrite and ammonium removal efficiencies were 92.31% and 78.45%, respectively. The emission rate of the greenhouse gas N2O was below 0.006% of the NRR in the anammox UASB reactor treating low strength wastewater.

Anammox in a UASB reactor treating saline wastewater

The feasibility of an anammox (anaerobic ammonium oxidation) UASB (upflow anaerobic sludge blanket) bioreactor to treat ammonium-rich brines was investigated in batch and continuous-flow experiments. The evidence from batch tests indicated that the anammox activity was significantly inhibited under highly saline conditions while the inhibition was reversible. Saline shock loading of 30 g NaCl l −1 caused a 67.5% decrease in specific anammox activity (SAA) compared to reference biomass (not exposed to salt). However, the acclimatized biomass displayed a SAA value just 45.1% lower than that of the reference biomass. When transferred from brine to freshwater, the salt-exposed biomass resumed its activity by 43.1%. Subsequent to appropriate acclimatization, careful manipulation nitrite concentration, nitrogen loading rate (NLR), and other operational parameters for 77 days, the results of continuous-flow experiment revealed that under the salinity of 30 g NaCl l −1 the reactor performed well and the substrate removal capacity (nitrogen removal rate, NRR, of 448 ± 15 mgl −1 d −1) was comparable to the condition of freshwater (NRR of 464 ± 13 mgl −1 d −1). However, the anammox UASB bioreactor was prone to malfunction under transient operating conditions.

Influence of substrates on nitrogen removal performance and microbiology of anaerobic ammonium oxidation by operating two UASB reactors fed with different substrate levels

Both ammonium and nitrite act as substrates as well as potential inhibitors of anoxic ammonium-oxidizing (Anammox) bacteria. To satisfy demand of substrates for Anammox bacteria and to prevent substrate inhibition simultaneously; two strategies, namely high or low substrate concentration, were carefully compared in the operation of two Anammox upflow anaerobic sludge blanket (UASB) reactors fed with different substrate concentrations. The reactor working at relatively low influent substrate concentration (NO 2 −-N, 240 mg-N L −1) was shown to avoid the inhibition caused by nitrite and free ammonia. Using the strategy of low substrate concentration, a record super high volumetric nitrogen removal rate of 45.24 kg-N m −3 day −1 was noted after the operation of 230 days. To our knowledge, such a high value has not been reported previously. The evidence from transmission electron microscopy (TEM) showed that the morphology and ultrastructure of the Anammox cells in both the reactor enrichments was different.

Suppression of anaerobic ammonium oxidizers under high organic content in high-rate Anammox UASB reactor

The effect of organic matter on the nitrogen removal performance of anaerobic ammonium oxidation (Anammox) process was investigated in an upflow anaerobic sludge blanket (UASB) reactor fed with nitrogen loading rate of 13.92 kg N m −3 day −1 at an HRT of 0.83 h. Mass balance showed that the heterotrophic denitrification prevailed in the UASB reactor, and became the dominant reactions when high influent COD/ NO 2 - –N ratios of 2.92 were applied. The Anammox bacterial growth was significantly suppressed by denitrifying communities under high organic matter content due to the weaker competition for nitrite (electron acceptor) and living space. Long-term operation of the Anammox UASB reactor under relatively high organic content resulted in weak recovery performance.

Distribution of anammox bacteria in domestic WWTPs and their enrichments evaluated by real-time quantitative PCR

Enrichment of anaerobic ammonium oxidation (anammox) bacteria using five activated sludges in three domestic wastewater treatment plants (WWTPs) were processed in a short term of 70 days and evaluated by real-time quantitative PCR (RTQ-PCR). Before the enrichment, building phylogenetic trees of Planctomycetes phylum in four reactors of sequencing batch reactor (SBR), anoxic and oxic reactors of anaerobic–anoxic–oxic (A2O) process, and rotating biological contactor (RBC) revealed six groups of distantly relative genera of Planctomyces, Pirellula, Gemmata, Isophaera, Candidatus and putative anammox bacteria. All clones of Candidatus sp. were affiliated with anammox bacteria and the majority of anammox clones were related to Planctomycete KSU-1 (AB057453). The discovery of anammox bacteria in raw activated sludges provided a partial rationale for the utilization of activated sludge as a seeding source of the anammox process. To verify the activity of anammox bacteria in the activated sludges, enrichment cultivations were conducted using SBRs. The enrichment of anammox bacteria resulted in the significant anammox activity of three samples. Quantification of 16S rRNA gene of anammox bacteria using RTQ-PCR showed the highest concentration of anammox bacteria of 2.48 ± 0.22 × 109 copies of 16S rRNA gene/mg-volatile suspended solids (VSS), which was the same order of magnitude as that of the referential granular anammox sludge, 6.23 ± 0.59 × 109 copies of 16S rRNA gene/mg-VSS, taken from an anammox upflow anaerobic sludge blanket (UASB) reactor. The doubling time of anammox bacteria enriched in this study was 1.18 days. The growth yield of anammox bacteria enriched in this study was 4.75 ± 0.57 × 106 copies of 16S rRNA gene/mg of ammonium- and nitrite-nitrogen, which was similar to 4.50 ± 0.61 × 106 copies of 16S rRNA gene/mg of ammonium- and nitrite-nitrogen for the referential anammox sludge. Substrate uptake rates of three successful enrichments at the end of the enrichment were comparable to those of granular and suspended anammox sludges. Rapid enrichment of anammox bacteria using activated sludge could offer an alternative method for obtaining a large volume of seeding anammox sludge.

Improved nitrogen removal in upflow anaerobic sludge blanket (UASB) reactors by incorporation of Anammox bacteria into the granular sludge

Upflow anaerobic sludge blanket reactors may offer a number of advantages over conventional mixed-tank, SBR, and biofilm reactors, including high space-loading, low footprint, and resistance to shocks and toxins. In this study, we assessed the use of upflow anaerobic sludge blanket (UASB) reactor technology as applied to anaerobic ammonia removal, or Anammox. Four 200 ml UASB reactors were inoculated with 50% (by volume) anaerobic granular sludge and 50% flocular sludge from different sources (all with the potential for containing Anammox organisms). Tools used to assess the reactors included basic analyses, fluorescent in-situ hybridisation, and mathematical modelling, with statistical non-linear parameter estimation. Two of the reactors showed statistically identical Anammox activity (i.e., identical kinetic parameters), with good ammonia and nitrite removal (0.14 kgNHx m(-3) reactor day(-1), with 99% ammonia removal). The third reactor also demonstrated significant Anammox activity, but with poor identifiability of parameters. The fourth reactor had no statistical Anammox activity. Modelling indicated that poor identifiability and performance in the third and fourth reactors were related to an excess of reduced carbon, probably originating in the inoculum. Accumulation of Anammox organisms was confirmed both by a volume loading much lower than the growth rate, and response to a probe specific for organisms previously reported to mediate Anammox processes. Overall, the UASB reactors were effective as Anammox systems, and identifiability of the systems was good, and repeatable (even compared to a previous study in a rotating biological contactor). This indicates that operation, design, and analysis of Anammox UASB reactors specifically, and Anammox systems in general, are reliable and portable, and that UASB systems are an appropriate technology for this process.