Feasibility of nitrification/denitrification in a sequencing batch biofilm reactor with liquid circulation applied to post-treatment

An investigation was performed on the biological removal of ammonium nitrogen from synthetic wastewater by the simultaneous nitrification/denitrification (SND) process, using a sequencing batch biofilm reactor (SBBR). System behavior was analyzed as to the effects of sludge type used as inoculum (autotrophic/heterotrophic), wastewater feed strategy (batch/fed-batch) and aeration strategy (continuous/intermittent). The presence of an autotrophic aerobic sludge showed to be essential for nitrification startup, despite publications stating the existence of heterotrophic organisms capable of nitrifying organic and inorganic nitrogen compounds at low dissolved oxygen concentrations. As to feed strategy, batch operation (synthetic wastewater containing 100 mg COD/L and 50 mg N-NH(4)(+)/L) followed by fed-batch (synthetic wastewater with 100 mg COD/L) during a whole cycle seemed to be the most adequate, mainly during the denitrification phase. Regarding aeration strategy, an intermittent mode, with dissolved oxygen concentration of 2.0mg/L in the aeration phase, showed the best results. Under these optimal conditions, 97% of influent ammonium nitrogen (80% of total nitrogen) was removed at a rate of 86.5 mg N-NH(4)(+)/Ld. In the treated effluent only 0.2 mg N-NO(2)(-)/L,4.6 mg N-NO(3)(-)/L and 1.0 mg N-NH(4)(+)/L remained, demonstrating the potential viability of this process in post-treatment of wastewaters containing ammonium nitrogen.     

Multiple analysis reprogrammable titration analyser for the kinetic characterization of nitrifying and autotrophic denitrifying biomass

The system Multiple Analysis Reprogrammable TItratioN Analyser (MARTINA) based on titrimetric techniques has been used to kinetically characterize different types of sludges: nitrifying, enriched ammonia oxidizing and autotrophic denitrifying biomass. The titration system employed, combines the addition of NaOH solution and H₂O₂ solution in the mixed liquor to keep the pre-established value of pH and the dissolved oxygen concentration, respectively. Results obtained from repeated experiments performed with nitrifying sludge from municipal and industrial origin present slight differences (coefficient of variation lower than 30%) indicating that the method is highly reproducible. Besides, the kinetic parameters of the enriched ammonia oxidizing sludge obtained using the MARTINA system are comparable to those obtained using the respirometry indicating the reliability of this methodology. Changes in the procedure may be easily implemented in order to estimate half saturation constants with high values. On the other hand, experiments in anoxic conditions applied to the estimation of the kinetic parameters of the autotrophic denitrifying biomass have been successfully performed, even if this process involves a reaction characterized by slight pH changes. The titration system MARTINA is a reproducible, reliable, versatile and precise alternative to the traditional respirometric and substrate monitoring tests for the characterization of kinetics for a wide range of sludges in aerobic or anoxic conditions.     

Effect of sludge age on simultaneous nitrification and denitrification in membrane bioreactor

This study evaluated the effect of sludge age on simultaneous nitrification and denitrification in a membrane bioreactor treating black water. A membrane bioreactor with no separate anoxic volume was operated at a sludge age of 20 days under low dissolved oxygen concentration of 0.1-0.2 mg/L. Its performance was compared with the period when the sludge age was adjusted to 60 days. Floc size distribution, apparent viscosity, and nitrogen removal differed significantly, together with different biomass concentrations: nitrification was reduced to 40% while denitrification was almost complete. Modelling indicated that both nitrification and denitrification kinetics varied as a function of the sludge age. Calibrated values of half saturation coefficients were reduced when the sludge age was lowered to 20 days. Model simulation confirmed the validity of variable process kinetics for nitrogen removal, specifically set by the selected sludge age.     

Simultaneous nitrification and denitrification using an autotrophic membrane-immobilized biofilm reactor

AIMS: To develop a laboratory-scale autotrophic membrane-immobilized biofilm reactor to remove nitrogen from drinking water. METHODS AND RESULTS: A polyvinyl alcohol (PVA) immobilized biofilm, attached to the surface of a silicone tube, was used as the basis of a bioreactor for simultaneous nitrification and denitrification of water. The bioreactor was aerated with air to supply oxygen for nitrification. Pure hydrogen was supplied to the silicone tube and diffused through the membrane wall to feed the biofilm for autotrophic denitrification. The bioreactor was effective for the simultaneous nitrification and denitrification of water after a short period of acclimation, while the biofilm exhibited good resistance to the inhibition of denitrification by dissolved oxygen; the denitrification rate decreased by only 8% as the dissolved oxygen increased from 2 mg l(-1) to saturation. CONCLUSIONS: By using PVA crosslinked with sodium nitrate to entrap nitrifying and denitrifying sludge on the surface of a silicone tube, a novel bioreactor for simultaneous nitrification and denitrification was developed. In addition to performing as an immobilizing agent to strengthen the biofilm, PVA protected the denitrifying microorganisms to reduce the inhibition by dissolved oxygen under aerobic condition. Therefore, nitrification and denitrification occurred simultaneously within the biofilm. Furthermore, the immobilization technique shortened the acclimation period of the bioreactor. SIGNIFICANCE AND IMPACT OF THE STUDY: The described space saving and simple to operate bioreactor for nitrogen removal performed autotrophic denitrification to solve the problem of residual carbon in heterotrophic denitrification, and thus is suitable for removing nitrogen from drinking water.     

N-removal in a granular sludge sequencing batch airlift reactor

The removal of N-compounds in the sequencing batch airlift reactor (SBAR) containing granular sludge was studied under conditions of decreased dissolved oxygen (DO). A simulation model was developed to describe and evaluate the effects of several process conditions in the SBAR on N-removal performance. The model described the experimental data reasonable well. It has been shown that nitrification, denitrification, and removal of chemical oxygen demand (COD) can occur simultaneously in a granular sludge SBR. It has also been shown that the exact location of the autotrophic biomass influences the net N-removal. The distribution of the autotrophic biomass is influenced by the DO in the reactor. The optimal DO value is expected to be around 40% air saturation. It was shown that storage and subsequent degradation of poly-beta-hydroxybutyrate (PHB) benefit the denitrification. In particular, PHB is stored in bacteria situated in deeper layers of the granules below where the autotrophic activity occurs, serves as a C-source for denitrification.     

Nitrifying bacterial growth inhibition in the presence of algae and cyanobacteria

Nitrifying bacteria, cyanobacteria, and algae are important microorganisms in open pond wastewater treatment systems. Nitrification involving the sequential oxidation of ammonia to nitrite and nitrate, mainly due to autotrophic nitrifying bacteria, is essential to biological nitrogen removal in wastewater and global nitrogen cycling. A continuous flow autotrophic bioreactor was initially designed for nitrifying bacterial growth only. In the presence of cyanobacteria and algae, we monitored both the microbial activity by measuring specific oxygen production rate (SOPR) for microalgae and cyanobacteria and specific oxygen uptake rate (SOUR) for nitrifying bacteria. The growth of cyanobacteria and algae inhibited the maximum nitrification rate by a factor of 4 although the ammonium nitrogen fed to the reactor was almost completely removed. Terminal restriction fragment length polymorphism (T‐RFLP) analysis indicated that the community structures of nitrifying bacteria remained unchanged, containing the dominant Nitrosospira, Nitrospira, and Nitrobacter species. PCR amplification coupled with cloning and sequencing analysis resulted in identifying Chlorella emersonii and an uncultured cyanobacterium as the dominant species in the autotrophic bioreactor. Notwithstanding their fast growth rate and their toxicity to nitrifiers, microalgae and cyanobacteria were more easily lost in effluent than nitrifying bacteria because of their poor settling characteristics. The microorganisms were able to grow together in the bioreactor with constant individual biomass fractions because of the uncoupled solids retention times for algae/cyanobacteria and nitrifiers. The results indicate that compared to conventional wastewater treatment systems, longer solids retention times (e.g., by a factor of 4) should be considered in phototrophic bioreactors for complete nitrification and nitrogen removal. Biotechnol. Bioeng. 2010;107: 1004–1011. © 2010 Wiley Periodicals, Inc.     

High-rate nitrification at low pH in suspended- and attached-biomass reactors

This article reports on high-rate nitrification at low pH in biofilm and suspended-biomass reactors by known chemolithotrophic bacteria. In the biofilm reactor, at low pH (4.3 +/- 0.1) and low bulk ammonium concentrations (9.3 +/- 3.3 mg.liter(-1)), a very high nitrification rate of 5.6 g of N oxidized.liter(-1).day(-1) was achieved. The specific nitrification rate (0.55 g of N.g of biomass(-1).day(-1)) was similar to values reported for nitrifying reactors at optimal pH. In the suspended-biomass reactor, the average pH was significantly lower than that in the biofilm reactor (pH 3.8 +/- 0.3), and values as low as pH 3.2 were found. In addition, measurements in the suspended-biomass reactor, using isotope-labeled ammonium (15N), showed that in spite of the very low pH, biomass growth occurred with a yield of 0.1 g of biomass.g of N oxidized(-1). Fluorescence in situ hybridization using existing rRNA-targeted oligonucleotide probes showed that the nitrifying bacteria were from the monophyletic genus Nitrosomonas, suggesting that autotrophic nitrification at low pH is more widespread than previously thought. The results presented in this paper clearly show that autotrophic nitrifying bacteria have the ability to nitrify at a high rate at low pH and in the presence of only a negligible free ammonia concentration, suggesting the presence of an efficient ammonium uptake system and the means to cope with low pH.     

Novel mathematical modeling on pilot-scale of plug-flow aerated submerged biofilm reactor for dissolved organic matter and nitrogen removal

The investigation aimed to present mathematical models for describing the dynamic behavior of the dissolved organic matter removal and nitrification in the Aerated Submerged Bio-Film (ASBF) for a plug-flow reactor. Based on the experimental data from the batch system of the ASBF pilot plant, mathematical models for the plug-flow reactor were developed to predict dissolved organic matter and ammonia nitrogen removal rates as a function of heterotrophic and autotrophic bacteria populations, dissolved organic matter concentrations, ammonia nitrogen concentrations, dissolved oxygen concentrations, and temperature. The mathematical models for dissolved organic matter and ammonia nitrogen removal in ASBF include two differential equations reflecting heterotrophic and autotrophic bacteria populations, and a number of kinetic parameters. Consequently, the results present a better insight into the dynamics behavior of heterotrophic and autotrophic biofilm growth and their practical application to wastewater for dissolved organic matter and ammonia nitrogen removal process. The mathematical model for ammonia nitrogen and dissolved organic matter removals present good results for the plug-flow reactor.     

Effect of carbon dioxide on nitrification rates

Lab-scale ideal mixed, aerated reactors were employed to test the influence of carbon dioxide (CO(2)) on the growth rate of a nitrifier community. The buffer medium used did not contain any carbon sources. Reactors were inoculated alternatively with sludge from a nitrifying membrane assisted bioreactor, reflecting autotrophic material, or with sludge from a plant having denitrification and nitrification steps, which reflects mixed heterotrophic and autotrophic material. CO(2) was added as a gas with the intake air supply. Nitrification rates were related to the CO(2) in the intake air as well as to the total inorganic carbon in the medium. The batch experiments show a relationship between CO(2) concentration and growth rate. The optimum growth rate occurred at 5 mg CO(2)/L, corresponding to 0.4% (V/V) CO(2) in the inlet air. Different CO(2) optima for autotrophic and mixed sludges were found. In the case of the autotrophic sludge, the observed optimum growth rate was about 0.47/d and the optimum for the mixed sludge was about 0.75/d. Higher CO(2) concentrations lead to a decreasing growth rate. The first part of the kinetic graph can be described by Monod kinetics. Overall, the resulting graph can be described by Haldane kinetics.     

Modelling and dynamic simulation of a moving bed bioreactor using respirometry for the estimation of kinetic parameters

Respirometry was used for the characterization of active autotrophic and heterotrophic biomass in a pilot scale moving bed bioreactor (MBBR). For this purpose biofilm samples attached to the carrier elements of the MBBR were transferred to a static gas/static liquid type respirometer with intermittent aeration. Known amounts of ammonia nitrogen and acetate were added to the respirometer. The dissolved oxygen (DO) decrease during the non-aeration phase was measured and used to calculate the oxygen uptake rate (OUR) of the active biomass. The resulting respirograms featured the typical endogenous and exogenous respiration phases and the shape of the respirogram was as expected from analogous respirometry with activated sludge. The OUR response was modelled with the activated sludge model ASM1 and the relevant kinetic parameter values for autotrophic and heterotrophic growth were adjusted. The adjusted parameter set and data originating from a 4-day long intensive measurement campaign were used for modelling and simulation of the pilot scale MBBR. The parameter estimation resulted in a good dynamic simulation of ammonia and nitrate variations in the effluent of the MBBR. Important MBBR properties including biofilm age, biofilm composition, and both attachment and detachment rate were extracted from the model.     

Formation and long-term stability of nitrifying granules in a sequencing batch reactor

The formation and long-term stability of nitrifying granules in a sequencing batch reactor was investigated in this study. The results showed that nitrifying granules with a size of 240 microm and SVI of 40 ml g(-1) were formed on day 21 at a settling time of 10 min. Maintaining settling time at 15 min from day 57 to 183 did not affect the physical characteristics of sludge and the fraction of suspended floc in the sludge. In addition, nitrifying granules could tolerate the fluctuations of nitrogen loading rate from 0.72 to 1.8 g l(-1)d(-1) during 2 months without the change of physical characteristics. However, it was observed that complete nitrification to nitrate and partial nitrification to nitrite by sludge converted each other corresponding to the change of the influent NH4+-N concentration. Thus, an appropriate method is needed to maintain a stable complete nitrification or partial nitrification under the conditions with changing influent NH4+-N concentrations and nitrogen loading rates.     

Simultaneous estimation of sludge biological activity and influent nitrogen load using ORP and DO dynamics

This paper proposes a new optimization strategy to estimate nitrifiable nitrogen concentration in wastewater, nitrification rate, denitrification rate and/or COD available for denitrification of an activated sludge process submitted to intermittent aeration. The approach uses the oxydo-reduction potential and dissolved oxygen measurements only. The parameter identification is based on a Simplex optimization of a cost function related to the error between an experimental cycle (an aerobic period followed by an anoxic one) and a simulation of a reduced model derived from ASM1. Results show very good prediction of experimental oxygen, ammonium and nitrate profiles. The estimation of nitrifiable nitrogen and removal rates has been validated both on simulated data obtained from COST action 624 benchmark and on experimental data.     

Use of microbial electrodes for observation of microbiological nitrogen elimination process

Microbial electrodes for the determination of ammonia and the estimation of biochemical oxygen demand (BOD) were applied to the nitrogen elimination process. The dimensions of the nitrification and the denitrification vessels were 170 and 70 L, respectively. The wastewater used for the experiment was obtained from a fermentation factory and adjusted to 470-530 mg/L of total Kjeldahl nitrogen and 1700-3000 mg/L of BOD. The ammonia electrode was assembled with a membrane containing nitrifying bacteria and an oxygen probe. The BOD electrode was similarly constructed, except it used a membrane containing the yeast, Trichosporon cutaneum. A flow system was employed for the automatic measurement of samples every 30 min. The nitrification and denitrification rates of the activated sludge were measured to investigate the optimum conditions and evaluate the capacity of the plant. The various data obtained by the microbial electrodes allowed us to inspect the situation of the plant and estimate control paramerers such as nitrogen and BOD loadings. The average removals of ammonia nitrogen and total Kjeldahl nitrogen were 96% and 89%, respectively, during the experiment for period of 2 weeks.     

Rapid startup and high rate nitrogen removal from anaerobic sludge digester liquor using a SNAP process

In this study, a single-stage autotrophic nitrogen removal reactor, packed with a novel acrylic fiber biomass carrier material (Biofix), was applied for nitrogen removal from sludge digester liquor. For rapid start-up, conventional activated sludge was added to the reactor soon after the attachment of anammox biomass on the Biofix carriers, which allowed conventional activated sludge to form a protective layer of biofilm around the anammox biomass. The Nitrogen removal efficiency reached 75% within 1 week at a nitrogen loading rate of 0.46 kg-N/m³/day for synthetic wastewater treatment. By the end of the synthetic wastewater treatment period, the maximum nitrogen removal rate had increased to 0.92 kg-N/m³/day at a nitrogen loading rate of 1.0 kg-N/m³/day. High nitrogen removal rate was also achieved during the actual raw digester liquor treatment with the highest nitrogen removal rate being 0.83 kg-N/m³/day at a nitrogen loading rate of 0.93 kg-N/m³/day. The thick biofilm on Biofix carriers allowed anammox bacteria to survive under high DO concentration of 5–6 mg/l resulting in stable and high nitrogen removal performance. FISH and CLSM analysis demonstrated that anammox bacteria coexisted and surrounded by ammonium oxidizing bacteria.     

Nitrification-denitrification via nitrite accumulation for nitrogen removal from wastewaters

The biological nitrification-denitrification process is used extensively for removal of ammonia nitrogen from wastewaters. Saves in aeration, organic matter (for denitrification) and surplus sludge are achievable if nitrite accumulation is possible in the nitrification step. In this paper, operational parameters were studied for each process for maximum nitrite accumulation in the nitrification step and nitrite adaptation in the denitrification step. Nitrite accumulation during nitrification can be controlled by the dissolved oxygen (DO) concentration, presenting a maximum of 65% at around 0.7 mg DO/L. Denitrification can be adapted to nitrite and the process is stable if nitrite in the reactor is keep low. The performance of a continuous stirred tank reactor (CSTR) and an up flow sludge blanket reactor (USB) were compared. Once the operational parameters were established, a CSTR for nitrification and an USB reactor for denitrification were operated in series for 25 days. The process was stable and a steady state was maintained for 20 days, and 93.5% of overall nitrogen removal was achieved in the nitrification-denitrification via the nitrite process.     

厌氧氨氧化工艺的应用现状和问题

厌氧氨氧化(Anaerobic ammonium oxidation,ANAMMOX)工艺因其高效低耗的优势,在废水生物脱氮领域具有广阔的应用前景。在过去的20年中,许多基于ANAMMOX反应的工艺得以不断研究和应用。预计到2014年末,全球范围内的ANAMMOX工程将会超过100座。综述了各种形式的ANAMMOX工艺,包括短程硝化-厌氧氨氧化、全程自养脱氮、限氧自养硝化反硝化、反硝化氨氧化、好氧反氨化、同步短程硝化-厌氧氨氧化-反硝化耦合、单级厌氧氨氧化短程硝化脱氮工艺。对一体式和分体式工艺运行条件进行了比较,结合ANAMMOX工艺工程(主要包括移动床生物膜,颗粒污泥和序批式反应器系统)应用现状,总结了工程化应用过程中遇到的问题及其解决对策,在此基础上对今后的研究和应用方向进行了展望。今后的研究重点应集中于运行条件的优化和水质障碍因子的解决,尤其是工艺自动化控制系统的开发和特殊废水对工艺性能影响的研究。     

Accelerating effect of hydroxylamine and hydrazine on nitrogen removal rate in moving bed biofilm reactor

In biological nitrogen removal, application of the autotrophic anammox process is gaining ground worldwide. Although this field has been widely researched in last years, some aspects as the accelerating effect of putative intermediates (mainly N?H? and NH?OH) need more specific investigation. In the current study, experiments in a moving bed biofilm reactor (MBBR) and batch tests were performed to evaluate the optimum concentrations of anammox process intermediates that accelerate the autotrophic nitrogen removal and mitigate a decrease in the anammox bacteria activity using anammox (anaerobic ammonium oxidation) biomass enriched on ring-shaped biofilm carriers. Anammox biomass was previously grown on blank biofilm carriers for 450 days at moderate temperature 26.0 (±0.5) °C by using sludge reject water as seeding material. FISH analysis revealed that anammox microorganisms were located in clusters in the biofilm. With addition of 1.27 and 1.31 mg N L?1 of each NH?OH and N?H?, respectively, into the MBBR total nitrogen (TN) removal efficiency was rapidly restored after inhibitions by NO??. Various combinations of N?H?, NH?OH, NH??, and NO?? were used as batch substrates. The highest total nitrogen (TN) removal rate with the optimum N?H? concentration (4.38 mg N L?1) present in these batches was 5.43 mg N g?1 TSS h?1, whereas equimolar concentrations of N?H? and NH?OH added together showed lower TN removal rates. Intermediates could be applied in practice to contribute to the recovery of inhibition-damaged wastewater treatment facilities using anammox technology.     

Autotrophic Ammonia-Oxidizing Bacteria Contribute Minimally to Nitrification in a Nitrogen-Impacted Forested Ecosystem

Deposition rates of atmospheric nitrogenous pollutants to forests in the San Bernardino Mountains range east of Los Angeles, California, are the highest reported in North America. Acidic soils from the west end of the range are N-saturated and have elevated rates of N-mineralization, nitrification, and nitrate leaching. We assessed the impact of this heavy nitrogen load on autotrophic ammonia-oxidizing communities by investigating their composition, abundance, and activity. Analysis of 177 cloned β-Proteobacteria ammonia oxidizer 16S rRNA genes from highly to moderately N-impacted soils revealed similar levels of species composition; all of the soils supported the previously characterized Nitrosospira clusters 2, 3, and 4. Ammonia oxidizer abundance measured by quantitative PCR was also similar among the soils. However, rates of potential nitrification activity were greater for N-saturated soils than for soils collected from a less impacted site, but autotrophic (i.e., acetylene-sensitive) activity was low in all soils examined. N-saturated soils incubated for 30 days with ammonium accumulated additional soluble ammonium, whereas less-N-impacted soils had a net loss of ammonium. Lastly, nitrite production by cultivated Nitrosospira multiformis, an autotrophic ammonia-oxidizing bacterium adapted to relatively high ammonium concentrations, was significantly inhibited in pH-controlled slurries of sterilized soils amended with ammonium despite the maintenance of optimal ammonia-oxidizing conditions. Together, these results showed that factors other than autotrophic ammonia oxidizers contributed to high nitrification rates in these N-impacted forest soils and, unlike many other environments, differences in nitrogen content and soil pH did not favor particular autotrophic ammonia oxidizer groups.     

Autotrophic ammonia-oxidizing bacteria contribute minimally to nitrification in a nitrogen-impacted forested ecosystem

Deposition rates of atmospheric nitrogenous pollutants to forests in the San Bernardino Mountains range east of Los Angeles, California, are the highest reported in North America. Acidic soils from the west end of the range are N-saturated and have elevated rates of N-mineralization, nitrification, and nitrate leaching. We assessed the impact of this heavy nitrogen load on autotrophic ammonia-oxidizing communities by investigating their composition, abundance, and activity. Analysis of 177 cloned beta-Proteobacteria ammonia oxidizer 16S rRNA genes from highly to moderately N-impacted soils revealed similar levels of species composition; all of the soils supported the previously characterized Nitrosospira clusters 2, 3, and 4. Ammonia oxidizer abundance measured by quantitative PCR was also similar among the soils. However, rates of potential nitrification activity were greater for N-saturated soils than for soils collected from a less impacted site, but autotrophic (i.e., acetylene-sensitive) activity was low in all soils examined. N-saturated soils incubated for 30 days with ammonium accumulated additional soluble ammonium, whereas less-N-impacted soils had a net loss of ammonium. Lastly, nitrite production by cultivated Nitrosospira multiformis, an autotrophic ammonia-oxidizing bacterium adapted to relatively high ammonium concentrations, was significantly inhibited in pH-controlled slurries of sterilized soils amended with ammonium despite the maintenance of optimal ammonia-oxidizing conditions. Together, these results showed that factors other than autotrophic ammonia oxidizers contributed to high nitrification rates in these N-impacted forest soils and, unlike many other environments, differences in nitrogen content and soil pH did not favor particular autotrophic ammonia oxidizer groups.     

限氧自养硝化-反硝化生物脱氮新技术

限氧自养硝化—反硝化是部分硝化与厌氧氨氧化相耦联的生物脱氮反应过程,通过严格控制溶解氧在0．1～0．3mg·L^-1,实现硝化反应控制在亚硝酸阶段,然后以硝化阶段剩余的NH4^+作为电子供体,在厌氧条件下实现反硝化,该反应过程是完全的自养硝化—反硝化过程,具有能耗低、脱氮效率高、反应系统占地面积小等优点,适用于处理COD／NH4^+—N低的废水,是一种非常有应用前景的生物脱氮技术,文中详细介绍了限氧自养硝化—反硝化生物脱氮反应过程的研究进展,讨论了其微生物学机理及应用前景。