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1.
Organics and nitrogen removal and sludge stability in aerobic granular sludge membrane bioreactor 总被引:3,自引:0,他引:3
Novel aerobic granular sludge membrane bioreactor (GMBR) was established by combining aerobic granular sludge technology with membrane bioreactor (MBR). GMBR showed good organics removal and simultaneous nitrification and denitrification (SND) performances for synthesized wastewater. When influent total organic carbon (TOC) was 56.8-132.6 mg/L, the TOC removal of GMBR was 84.7-91.9%. When influent ammonia nitrogen was 28.1-38.4 mg/L, the ammonia nitrogen removal was 85.4-99.7%, and the total nitrogen removal was 41.7-78.4%. Moreover, batch experiments of sludge with different particle size demonstrated that: (1) flocculent sludge under aerobic condition almost have no denitrification capacity, (2) SND capacity was caused by the granular sludge, and (3) the denitrification rate and total nitrogen removal efficiency were enhanced with the increased particle size. In addition, study on the sludge morphology stability in GMBR showed that, although some granular sludge larger than 0.9 mm disaggregated at the beginning of operation, the granular sludge was able to maintain the stability of its granular morphology, and at the end of operation, the amount of granular sludge (larger than 0.18 mm) stabilized in GMBR was more than 56-62% of the total sludge concentration. The partial disaggregation of large granules is closely associated with the change of operating mode from sequencing batch reactor (SBR) system to MBR system. 相似文献
2.
Rainer Gross Karsten Lang Katja Bühler Andreas Schmid 《Biotechnology and bioengineering》2010,105(4):705-717
Biofilms are known to be robust biocatalysts. Conventionally, they have been mainly applied for wastewater treatment, however recent reports about their employment for chemical synthesis are increasingly attracting attention. Engineered Pseudomonas sp. strain VLB120ΔC biofilm growing in a tubular membrane reactor was utilized for the continuous production of (S)‐styrene oxide. A biofilm specific morphotype appeared in the effluent during cultivation, accounting for 60–80% of the total biofilm irrespective of inoculation conditions but with similar specific activities as the original morphotype. Mass transfer of the substrate styrene and the product styrene oxide was found to be dependent on the flow rate but was not limiting the epoxidation rate. Oxygen was identified as one of the main parameters influencing the biotransformation rate. Productivity was linearly dependent on the specific membrane area and on the tube wall thickness. On average volumetric productivities of 24 g L day?1 with a maximum of 70 g L day?1 and biomass concentrations of 45 gBDW L have been achieved over long continuous process periods (≥50 days) without reactor downtimes. Biotechnol. Bioeng. 2010. 105: 705–717. © 2009 Wiley Periodicals, Inc. 相似文献
3.
Comparison of biological removal via nitrite with real-time control using aerobic granular sludge and flocculent activated sludge 总被引:2,自引:0,他引:2
The process of nitrification–denitrification via nitrite for nitrogen removal under real-time control mode was tested in two
laboratory-scale sequencing batch reactors (SBRs) with flocculent activated sludge (R1) and aerobic granular sludge (R2) to
compare operational performance and real-time control strategies. The results showed that the average ammonia nitrogen, total
inorganic nitrogen (TIN), and chemical oxygen demand (COD) removal during aeration phase were 97.6%, 57.0%, and 90.1% in R2
compared with 98.6%, 48.7%, and 88.1% in R1. The TIN removed in both SBRs was partially due to the presence of simultaneous
nitrification–denitrification via nitrite, especially in R2. The specific nitrification and denitrification rates in R2 were
0.0416 mgNH4+–N/gSS-min and 0.1889 mgNOX−–N/gSS-min, which were 1.48 times and 1.35 times that of R1. The higher rates for COD removal, nitrification, and denitrification
were achieved in R2 than R1 with similar influent quality. Dissolved oxygen (DO), pH, and oxidization reduction potential,
corresponding to nutrient variations, were used as diagnostic parameters to control the organic carbon degradation and nitrification–denitrification
via nitrite processes in both SBRs. The online control strategy of granular SBR was similar to that of the SBR with flocculent
activated sludge. However, a unique U-type pattern on the DO curve in granular SBR was different from SBR with flocculent
activated sludge in aerobic phase. 相似文献
4.
Feasibility of nitrification/denitrification in a sequencing batch biofilm reactor with liquid circulation applied to post-treatment 总被引:1,自引:0,他引:1
Andrade do Canto CS Rodrigues JA Ratusznei SM Zaiat M Foresti E 《Bioresource technology》2008,99(3):644-654
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. 相似文献
5.
Linting Zhao Zonglian She Chunji Jin Shiying Yang Liang Guo Yangguo Zhao Mengchun Gao 《Bioprocess and biosystems engineering》2016,39(9):1375-1389
The composition and distribution of extracellular polymeric substance (EPS) both from suspended sludge and attached biofilm were investigated in a simultaneous nitrification and denitrification (SND) system with the increase of the salinity from 1.0 to 3.0 %. Fourier-transform infrared (FTIR) spectroscopy and three-dimensional excitation-emission matrix (3D-EEM) fluorescence spectroscopy were used to examine proteins (PN), polysaccharides (PS) and humic substances (HS) present in EPS. High total nitrogen removal (above 83.9 %) via SND was obtained in the salinity range of 1.0–2.5 %. Total EPS in the sludge increased from 150.2 to 200.6 mg/gVSS with the increase of salinity from 1.0 to 3.0 %, whereas the corresponding values in the biofilm achieved the maximum of 288.6 mg/g VSS at 2.0 % salinity. Dominant composition of EPS was detected as HS in both sludge and biofilm, having the percentages of 50.6–68.6 and 41.1–69.9 % in total EPS, respectively. Both PN and PS contents in soluble EPS (S-EPS), loosely bound EPS (LB-EPS) and tightly bound EPS (TB-EPS) of sludge and biofilm increased with the increased salinity. The FTIR spectrum and 3D-EEM fluorescence spectroscopy of S-EPS, LB-EPS and TB-EPS in the sludge and biofilm showed the changes of functional groups and conformations of the compositions in EPS with the increase of salinity. The results demonstrated that the characteristics of EPS varied from sludge to biofilm. The obtained results could provide a better understanding of the salinity effect on the EPS characteristics in a SND system. 相似文献
6.
Effect of oxygen concentration on nitrification and denitrification in single activated sludge flocs 总被引:10,自引:0,他引:10
Simultaneous nitrification and denitrification (SND) was investigated in the single aeration tank of a municipal wastewater treatment plant. Microelectrode measurements and batch experiments were performed to test for the presence of SND. Microelectrodes recorded the presence of O(2) concentration gradients in individual activated sludge flocs. When the O(2) concentration in the bulk liquid was <45 microM, anoxic zones were detected within flocs with a larger diameter (approximately 3000 microm). The O(2) penetration depth in the floc was found to be dependent on the O(2) concentration in the bulk liquid. Nitrification was restricted to the oxic zones, whereas denitrification occurred mainly in the anoxic zones. The nitrification rate of the activated sludge increased with increasing O(2) concentration in the bulk liquid, up to 40 microM, and remained constant thereafter. SND was observed in the aerated activated sludge when O(2) concentration was in the range of 10 to 35 microM. 相似文献
7.
Jianhua Guo Yongzhen Peng Shuying Wang Yanan Zheng Huijun Huang Zhongwei Wang 《Bioresource technology》2009,100(11):2796-2802
In this study, the performance of partial nitrification via nitrite and microbial community structure were investigated and compared in two sequencing batch reactors (SBR) with different dissolved oxygen (DO) levels. Both reactors achieved stable partial nitrification with nitrite accumulation ratio of above 95% by using real-time aeration duration control. Compared with high DO (above 3 mg/l on average) SBR, simultaneous nitrification and denitrification (SND) via nitrite was carried out in low DO (0.4–0.8 mg/l) SBR. The average efficiencies of SND in high DO and low DO reactor were 7.7% and 44.9%, and the specific SND rates were 0.20 and 0.83 mg N/(mg MLSS h), respectively. Low DO did not produce sludge with poorer settling properties but attained lower turbidities of the effluent than high DO. Fluorescence in situ hybridization (FISH) analysis in both the reactors showed that ammonia-oxidizing bacteria (AOB) were the dominant nitrifying bacteria and nitrite-oxidizing bacteria (NOB) did not be recovered in spite of exposing nitrifying sludge to high DO. The morphology of the sludge from both two reactors according to scanning electron microscope indicated that small rod-shaped and spherical clusters were dominant, although filamentous bacteria and few long rod-shaped coexisted in the low DO reactor. By selecting properly DO level and adopting process control method is not only of benefit to the achievement of novel biological nitrogen removal technology, but also favorable to sludge population optimization. 相似文献
8.
Wenjie Sun Reyes Sierra‐Alvarez Ivann Hsu Pieter Rowlette Jim A. Field 《Biotechnology and bioengineering》2010,105(5):909-917
In this study, the anoxic oxidation of arsenite (As(III)) linked to chemolithotrophic denitrification was shown to be feasible in continuous bioreactors. Biological oxidation of As(III) was stable over prolonged periods of operation ranging up to 3 years in continuous denitrifying bioreactors with granular biofilms. As(III) was removed with a high conversion efficiency (>92%) to arsenate (As(V)) in periods with high volumetric loadings (e.g., 3.5–5.1 mmol As L day?1). The maximum specific activity of sampled granular sludge from the bioreactors was 0.98 ± 0.04 mmol As(V) formed g?1 VSS day?1 when determined at an initial concentration of 0.5 mM As(III). The microbial population adapted to high influent concentrations of As(III) up to 5.2 mM. However, the As(III) oxidation process was severely inhibited when 7.6–8.1 mM As(III) was fed. Activity was restored upon lowering the As(III) concentration to 3.8 mM. Several experimental strategies were utilized to demonstrate a dependence of the nitrate removal on As(III) oxidation as well as a dependence of the As(III) removal on nitrate reduction. The molar stoichiometric ratio of As(V) formed to nitrate removed (corrected for endogenous denitrification) in the bioreactors approximated 2.5, indicating complete denitrification was occurring. As(III) oxidation was also shown to be linked to the complete denitrification of NO to N2 gas by demonstrating a significantly enhanced production of N2 beyond the background endogenous production in a batch bioassay spiked with 3.5 mM As(III). The N2 production also corresponded closely to the expected stoichiometry of 2.5 mol As(III) mol?1 N2–N for complete denitrification. Biotechnol. Bioeng. 2010;105: 909–917. © 2009 Wiley Periodicals, Inc. 相似文献
9.
Byung-Hyun Moon Jong-Soo Heo Hyoung-Sub Choi 《Biotechnology and Bioprocess Engineering》1997,2(2):136-140
Direct membrane separation using nonwoven fabric was applied to saline wastewater treatment by an activated sludge process.
A nonwoven fabric module was immersed in an aeration tank. The part of treated was filtered through the module by suction
and the rest of that was separated by a settlingtank. Various F/M ratios and salt concentrations were applied to investigate
stable flux as well as pollutant removal. The pollutant removal efficiencies of nonwoven fabric separation was not affected
by F/M ratios and salt concentrations and was higher than that of settling tank separation. The decline in flux was seemed
to be caused by the biofilm on nonwoven fabricsurface 相似文献
10.
Bing‐Jie Ni Zhiguo Yuan Kartik Chandran Peter A. Vanrolleghem Sudhir Murthy 《Biotechnology and bioengineering》2013,110(1):153-163
There is increasing evidence showing that ammonia‐oxidizing bacteria (AOB) are major contributors to N2O emissions from wastewater treatment plants (WWTPs). Although the fundamental metabolic pathways for N2O production by AOB are now coming to light, the mechanisms responsible for N2O production by AOB in WWTP are not fully understood. Mathematical modeling provides a means for testing hypotheses related to mechanisms and triggers for N2O emissions in WWTP, and can then also become a tool to support the development of mitigation strategies. This study examined the ability of four mathematical model structures to describe two distinct mechanisms of N2O production by AOB. The production mechanisms evaluated are (1) N2O as the final product of nitrifier denitrification with NO as the terminal electron acceptor and (2) N2O as a byproduct of incomplete oxidation of hydroxylamine (NH2OH) to NO. The four models were compared based on their ability to predict N2O dynamics observed in three mixed culture studies. Short‐term batch experimental data were employed to examine model assumptions related to the effects of (1) NH concentration variations, (2) dissolved oxygen (DO) variations, (3) NO accumulations and (4) NH2OH as an externally provided substrate. The modeling results demonstrate that all these models can generally describe the NH, NO, and NO data. However, none of these models were able to reproduce all measured N2O data. The results suggest that both the denitrification and NH2OH pathways may be involved in N2O production and could be kinetically linked by a competition for intracellular reducing equivalents. A unified model capturing both mechanisms and their potential interactions needs to be developed with consideration of physiological complexity. Biotechnol. Bioeng. 2013; 110: 153–163. © 2012 Wiley Periodicals, Inc. 相似文献
11.
Control of carbon and ammonium ratio for simultaneous nitrification and denitrification in a sequencing batch bioreactor 总被引:1,自引:0,他引:1
《International biodeterioration & biodegradation》2007,59(1):1-7
This study shows how the carbon and nitrogen (C/N) ratio controls the simultaneous occurrence of nitrification and denitrification in a sequencing batch reactor (SBR). Data demonstrated that a low C/N ratio resulted in a rapid carbon deficit, causing an unbalanced simultaneous nitrification–denitrification (SND) process in SBR. When the initial COD/NH4+-N ratio was adjusted to 11.1, the SND-based SBR achieved complete removal of NH4-N and COD without leaving any NO2−-N in the effluent. The nitrogen removal efficiency decreases gradually with increasing ammonium-loading rate to the SND–SBR system. Altogether, data showed that appropriate controls of carbon and nitrogen input are required to achieve an efficient SND–SBR. An established SND technology can save operation time and energy, and might replace the traditional two-stage biological nitrification and denitrification process. 相似文献
12.
Xinfeng Li Tong Liu Yongqiang Wu Guoping Zhao Zhihua Zhou 《Biotechnology and bioengineering》2010,106(4):564-572
Purple non‐sulfur (PNS) bacteria produce hydrogen by photofermentation of organic acids in wastewater. However, NH in wastewater may inhibit hydrogen synthesis by repressing the expression and activity of nitrogenase, the enzyme catalyzing hydrogen production in PNS bacteria. In this study, the Rhodobacter sphaeroides 6016 glnA gene encoding glutamine synthetase (GS) was knocked out by homologous recombination, and the effects on hydrogen production and nitrogenase activity were examined. Using 3 mM glutamine as the nitrogen source, hydrogen production (1,245–1,588 mL hydrogen/L culture) and nitrogenase activity were detected in the mutant in the presence of relatively high NH concentrations (15–40 mM), whereas neither was detected in the wild‐type strain under the same conditions. Further analysis indicated that high NH concentrations greatly inhibited the expression of nifA and nitrogenase gene in the wild‐type strain but not in the glnA1? mutant. These observations suggest that GS is essential to NH repression of nitrogenase and that deletion of glnA1 results in the complete derepression of nitrogenase by preventing NH assimilation in vivo, thus relieving the inhibition of nifA and nitrogenase gene expression. Knocking out glnA1 therefore provides an efficient approach to removing the inhibitory effects of ammonium ions in R. sphaeroides and possibly in other hydrogen‐producing PNS bacteria. Biotechnol. Bioeng. 2010;106: 564–572. © 2010 Wiley Periodicals, Inc. 相似文献
13.
A new solid support membrane aerated biofilm reactor was designed for the synthesis of enantiopure (S)‐styrene oxide utilizing Pseudomonas sp. strain VLB120ΔC growing in a biofilm as biocatalyst. In analogy to traditional packed bed systems, maximizing the volumetric oxygen mass transfer capability (kLa) was identified as the most critical issue enabling a consistent productivity, as this parameter was shown to directly influence biofilm growth and biotransformation performance. A microporous ceramic unit was identified as an ideal microenvironment for biofilm growth and for efficient oxygen transfer. A uniform and dense biofilm developed on this matrix. Due to this dual function, the reactor configuration could be significantly simplified by eliminating additional packing materials, as used in traditional packed bed reactors. Up to now, a maximum productivity of 28 g L day?1 was achieved by integrating an in situ substrate feed and an in situ product recovery technique based on a silicone membrane. The system was stable for more than 30 days before it was actively terminated. Biotechnol. Bioeng. 2010;106: 516–527. © 2010 Wiley Periodicals, Inc. 相似文献
14.
Air-lift internal loop biofilm reactor for realized simultaneous nitrification and denitrification 总被引:2,自引:0,他引:2
Cuiyi Zhang Lu Wang Ning Yan Yongming Zhang Rui Liu 《Bioprocess and biosystems engineering》2013,36(5):597-602
Simultaneous nitrification and denitrification (SND) was realized by means of a novel air-lift internal loop biofilm reactor, in which aeration was set in middle of the reactor. During operation, the aeration was adjusted to get appropriate dissolve oxygen (DO) in bulk solution and let aerobic and anoxic zone coexist in one reactor. When aeration was at 0.6 and 0.2 L/min, corresponding to DO of 5.8 and 2.5 mg/L in bulk solution, ammonia nitrogen removal percentage reached about 80 and 90 %, but total nitrogen removal percentage was lower than 25 %. While the aeration was reduced to 0.1 L/min, aerobic and anoxic zones existed simultaneously in one reactor to get 75 % of ammonia nitrogen and 50 % of total nitrogen removal percentage. Biofilms were, respectively, taken from aerobic and anoxic zone to verify their function of nitrification and denitrification in two flasks, in which ammonia nitrogen was transferred into nitrate completely by aerobic biofilm, and nitrate was removed more than 80 % by anoxic biofilm. Microelectrode was used to measure the DO distribution inside biofilms in anoxic zone corresponding to different aerations. When aeration was at 0.6 and 0.2 L/min, DO inside biofilm was more than 1.5 mg/L, but the DO inside biofilm decreased to anoxic status with depth of biofilm increasing corresponding to aeration of 0.1 L/min. The experimental results indicated that SND could be realized because of simultaneous existence of aerobic and anoxic biofilms in one reactor. 相似文献
15.
Sjef Cornelissen Mattijs K. Julsing Jan Volmer Ole Riechert Andreas Schmid Bruno Bühler 《Biotechnology and bioengineering》2013,110(5):1282-1292
Living microbial cells are considered to be the catalyst of choice for selective terpene functionalization. However, such processes often suffer from side product formation and poor substrate mass transfer into cells. For the hydroxylation of (S)‐limonene to (S)‐perillyl alcohol by Pseudomonas putida KT2440 (pGEc47ΔB)(pCom8‐PFR1500), containing the cytochrome P450 monooxygenase CYP153A6, the side products perillyl aldehyde and perillic acid constituted up to 26% of the total amount of oxidized terpenes. In this study, it is shown that the reaction rate is substrate‐limited in the two‐liquid phase system used and that host intrinsic dehydrogenases and not CYP153A6 are responsible for the formation of the undesired side products. In contrast to P. putida KT2440, E. coli W3110 was found to catalyze perillyl aldehyde reduction to the alcohol and no oxidation to the acid. Furthermore, E. coli W3110 harboring CYP153A6 showed high limonene hydroxylation activities (7.1 U g). The outer membrane protein AlkL was found to enhance hydroxylation activities of E. coli twofold in aqueous single‐phase and fivefold in two‐liquid phase biotransformations. In the latter system, E. coli harboring CYP153A6 and AlkL produced up to 39.2 mmol (S)‐perillyl alcohol L within 26 h, whereas no perillic acid and minor amounts of perillyl aldehyde (8% of the total products) were formed. In conclusion, undesired perillyl alcohol oxidation was reduced by choosing E. coli's enzymatic background as a reaction environment and co‐expression of the alkL gene in E. coli represents a promising strategy to enhance terpene bioconversion rates. Biotechnol. Bioeng. 2013; 110: 1282–1292. © 2012 Wiley Periodicals, Inc. 相似文献
16.
Biofilm stratification during simultaneous nitrification and denitrification (SND) at a biocathode 总被引:3,自引:0,他引:3
Bernardino VirdisSuzanne T. Read Korneel RabaeyRené A. Rozendal Zhiguo YuanJürg Keller 《Bioresource technology》2011,102(1):334-341
The aeration of the cathode compartment of bioelectrochemical systems (BESs) was recently shown to promote simultaneous nitrification and denitrification (SND). This study investigates the cathodic metabolism under different operating conditions as well as the structural organization of the cathodic biofilm during SND. Results show that a maximal nitrogen removal efficiency of 86.9 ± 0.5%, and a removal rate of 3.39 ± 0.08 mg N L−1 h−1 could be achieved at a dissolved oxygen (DO) level of 5.73 ± 0.03 mg L−1 in the catholyte. The DO levels used in this study are higher than the thresholds previously reported as detrimental for denitrification. Analysis of the cathodic half-cell potential during batch tests suggested the existence of an oxygen gradient within the biofilm while performing SND. FISH analysis corroborated this finding revealing that the structure of the biofilm included an outer layer occupied by putative nitrifying organisms, and an inner layer where putative denitrifying organisms were most dominant. To our best knowledge this is the first time that nitrifying and denitrifying microorganisms are simultaneously observed in a cathodic biofilm. 相似文献
17.
Dong Wei Xiaodong Xue Shuwei Chen Yongfang Zhang Liangguo Yan Qin Wei Bin Du 《Applied microbiology and biotechnology》2013,97(20):9235-9243
The aim of this study was to evaluate the impact of zeolite powders on feasibility of rapid aerobic granulation in the column-type sequencing batch reactors. After 90 days' operation, aerobic granular sludge was formed in both reactors by altering influent chemical oxygen demand/nitrogen (COD/N) ratios. R1 with zeolite powders had better removal capabilities of COD and total nitrogen than R2, which was without zeolite powders. Mixed liquor volatile suspended solid concentrations of the two reactors were 7.36 and 5.45 g/L, while sludge volume index (SVI30) values were 34.9 and 47.9 mg/L, respectively. The mean diameters of aerobic granular sludge in the above two reactors were 2.5 and 1.5 mm, respectively. Both reactors achieved the largest simultaneous nitrification and denitrification (SND) efficiency at an influent COD/N ratio of 8; however, R1 exhibited more excellent SND efficiency than R2. The obtained results could provide a novel technique for rapid aerobic granulation and N removal simultaneously, especially when treating nitrogen-rich industrial wastewater. 相似文献
18.
Toluene was anaerobically degraded by an enriched mixed culture under methanogenic conditions. The mixed culture was originally developed from cow-dung and sludge from a laboratory reactor, in which benzene was anerobically degraded by sulphate-reducing bacteria. First the mixed culture was enriched on toluene over a year with and without the use of sulphate in the medium. For the evaluation of growth-kinetic and maintenance parameters, namely μmax, Ks, kd and Y, the anaerobic degradation of toluene was carried out in batch as well as in continous reactors systems. The gas volume and the methane content in the produced gas was somewhat lover than the theoretical value expected, indicating an incomplete degradation of some of the complex intermediates of the toluene degradation pathway. However, the mixed culture was able to transform 41.3% of the toluene carbon into methane. 相似文献
19.
20.
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. 相似文献