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| Water Res, 2004 Dec, 38(20), 4297 - 304 Model for oxygen transfer in rotating biological contactor; Kubsad V et al.; Rotating biological contactor is being widely used for wastewater treatment but there is an apparent lack of knowledge about the rate at which oxygen transfer occurs, in physical and biological system . In this study the transfer of oxygen from air to water by a rotating disc air-liquid contactor in physical system is investigated . The oxygen transfer model suggested by Kim and Molof, Water Sci . Technol . 14 (1982) 569, was modified and the developed model is termed as modified Kim and Molof model . The model was calibrated by using available data in literature and validated by experiments conducted in this study . The effect of significant physical parameters was integrated into a single term and is termed as volume renewal number . The modified Kim and Molof model was compared with the other available models . The coefficient of determination (R(2)) for the modified Kim and Molof model obtained is 0.95 which is much higher than in the other available models . Thereby the model is expected to estimate oxygen transfer more accurately . Further, a simplified linear model between K(L)a and the volume renewal number is proposed . Both modified Kim and Molof and linear model estimate the overall oxygen transfer coefficient (K(L)a) accurately. Water Sci Technol, 2004, 49(11-12), 69 - 76 Improved nitrogen removal in upflow anaerobic sludge blanket (UASB) reactors by incorporation of Anammox bacteria into the granular sludge; Schmidt JE et al.; 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. Commun Agric Appl Biol Sci, 2003, 68(2 Pt A), 67 - 75 Performance of a submerged aerated filter and a rotating biological contactor under dynamic loading conditions; Philips N et al.; Two types of small wastewater treatment systems were studied for their performance under normal conditions, including the hydraulic peak flows associated with small systems connected to just one house . Furthermore, the systems were subjected to a 7-day starvation period to simulate the effect of a holiday from home . The systems studied are (1) a combined submerged aerated filter-activated sludge system and (2) a rotating biological contactor system . Both the organic removal and the nitrification process were closely monitored . During normal operation, very good treatment results were achieved . The combined SAF-AS system realized 95% BOD removal, 88% COD removal and 94% NH4-N removal . The RBC system removed 92% of the BOD, 89% of the COD and 99% of the ammonium nitrogen . Both systems do not experience severe problems dealing with the lack of influent for a duration of seven days . The effluent concentrations did not change much, except for a small peak of nitrite which was present in all tests . However, both the ammonium oxidizing and the nitrite oxidizing bacterial populations were still active, as evidenced by the continued removal of ammonium and formation of nitrate. Water Res, 2004 May, 38(10), 2571 - 8 Dynamics of nematodes in a high organic loading rotating biological contactors; Salvado H et al.; Nematode diversity and dynamics of a full-scale rotating biological contactor plant (RBC) has been studied . Analysis of biofilm composition showed a well-established zoning of microfauna among the three RBC sections analysed . Nematodes appeared to be the dominant group within the larger microfauna populations with average abundances between 200 and 300ind/mg or 8000 and 17000ind/cm(2) . The most abundant nematode species were Diplogasteritus nudicapitatus and Paroigolaimella coprophages and, to a lesser extent, Paroigolaimella bernensis and Steinernema intermedia . The relationship between nematodes and filamentous bacteria (specifically the genus Beggiatoa) was the most significant biotic relationship found, and to a lesser extent, nematodes with ciliates . The relationship between the abundance of nematode species and the physical-chemical variables suggests that nematodes may be good indicators of low pollutant load levels in the entry of the RBC system . Finally, the results indicate that nematodes may have a relevant role for a good biofilm development. Environ Technol, 2004 Feb, 25(2), 165 - 71 Full scale comparison of heterotrophic and nitrifying RBC biofilms; Meng QE et al.; Heterotrophic and nitrifying biofilms, from the secondary and tertiary full-scale Rotating Biological Contactor (RBC) wastewater treatment plants (WWTP) were investigated . Physical properties and structural features, such as, water content, organic portion (VS/TS), density, thickness, porosity, and fractal characteristics, including boundary/surface roughness, and Sierpinski and internal pore boundary fractals were examined . The results indicated that the heterotrophic biofilms were thicker and had higher porosity, larger internal voids, and faster growth and sloughing rates than the nitrifying biofilms . The nitrifying biofilms had much higher density(TS) and VS/TS ratio than the heterotrophic biofilms . In contrast to earlier results from laboratory scale studies, full-scale biofilms had structures and properties (porosity, density, and fractal dimensions) of more irregular spatial distribution. Environ Pollut, 1992, 76(1), 61 - 70 Performance of RBC coupled to a polyurethane foam to biodegrade petroleum refinery wastewater; Tyagi RD et al.; Biological treatment of petroleum refinery wastewater was studied in a rotating biological contactor (RBC) coupled to a polyurethane foam (PUF) as a porous biomass support . The PUF was attached on both sides of biodisks . The biodegradation studies were carried out at varying hydraulic and organic loadings . COD removal efficiency of up to 87% was achieved . The results obtained in terms of biodegradation of COD, NH(3)?N, phenol, hydrocarbons and suspended solids in this study were compared with those in the literature . The RBC-PUF bioreactor was found to have a better performance than a conventional RBC for the biodegradation of the above mentioned parameters . A higher concentration of active biomass (77 g TVS/m(2)) was observed in the RBC-PUF as compared to other treatment systems . A linear relationship between COD applied and COD removed was observed for the combined four stage system as well as for the individual stages. Environ Sci Technol, 2004 Feb 15, 38(4), 1228 - 35 Start-up of autotrophic nitrogen removal reactors via sequential biocatalyst addition; Pynaert K et al.; A procedure for start-up of oxygen-limited autotrophic nitrification-denitrification (OLAND) in a lab-scale rotating biological contactor (RBC) is presented . In this one-step process, NH4+ is directly converted to N2 without the need for an organic carbon source . The approach is based on a sequential addition of two types of easily available biocatalyst to the reactor during start-up: aerobic nitrifying and anaerobic, granular methanogenic sludge . The first is added as a source of aerobic ammonia-oxidizing bacteria (AAOB), the second as a possible source of planctomycetes including anaerobic ammonia-oxidizing bacteria (AnAOB) . The initial nitrifying biofilm serves as a matrix for anaerobic cell incorporation . By subsequently imposing oxygen limitation, one can create an optimal environment for autotrophic N removal . In this way, N removal of about 250 mg of N L(-1) d(-1) was achieved after 100 d treating a synthetic NH4+-rich wastewater . By gradually imposing higher loads on the reactor, the N elimination could be increased to about 1.8 g of N L(-1) d(-1) at 250 d . The resulting microbial community was compared with that of the inocula using general bacterial and AAOB- and planctomycete-specific PCR primers . Subsequently, the RBC reactor was shown to treat a sludge digestor effluent under suboptimal and strongly varying conditions . The RBC biocatalyst was also submitted to complete absence of oxygen in a fixed-film bioreactor (FFBR) and proved able to remove NH4+ with NO2- as electron acceptor (maximal 434 mg of NH4+-N (g of VSS)(-1) d(-1) on day 136) . DGGE and real-time PCR analysis demonstrated that the RBC biofilm was dominated by members of the genus Nitrosomonas and close relatives of Kuenenia stuttgartiensis, a known AnAOB . The latter was enriched during FFBR operation, but AAOB were still present and the ratio planctomycetes/AAOB rRNA gene copies was about 4.3 after 136 d of reactor operation . Whether this relates to an active role of AAOB in the anoxic N removal process remains to be solved. Bioresour Technol, 2004 May, 93(1), 91 - 8 Organic and nitrogen removal in a two-stage rotating biological contactor treating municipal wastewater; Hiras DN et al.; A laboratory scale rotating biological contactor (RBC) predenitrification system incorporating anoxic and aerobic units was evaluated for the treatment of settled high-strength municipal wastewater . The system was operated under four recycle ratios (1, 2, 3 and 4) and loading rates of 38-182 gCOD/m(2)d and 0.22-14 gOxid-N/m(2)d on the anoxic unit and 3.4-18 gCOD/m(2)d and 0.24-1.8 gNH(4)-N/m(2)d on the aerobic . The average removal efficiency in terms of chemical oxygen demand (COD), biochemical oxygen demand (BOD(5)), total suspended solids (TSS) and total nitrogen (Total-N) was 82%, 86%, 63% and 54%; settling of the RBC effluent increased COD and TSS removal to 94% and 97% . An increase in hydraulic loading resulting from higher recirculation, had limited negative effect on organic removal but improved nitrogen removal, and in terms of Total-N removal efficiency increased up to a ratio of 3 and then decreased. Water Res, 2004 Mar, 38(5), 1081 - 8 Physico-chemical factors affecting the E . coli removal in a rotating biological contactor (RBC) treating UASB effluent; Tawfik A et al.; The removal mechanism of E . coli from UASB effluent using a Rotating Biological Contractor (RBC) has been investigated . Preliminary batch experiments in a RBC indicate a first-order removal kinetics . Variation in the dissolved oxygen concentration and E . coli counts over the depth of the RBC has been recorded and indicates that the RBC is not a completely mixed reactor . Therefore batch experiments were carried out in a beaker where the different operating conditions can be controlled . Factors affecting the removal of E . coli via a biofilm system as stirring, dissolved oxygen concentration, pH, and addition of cationic polymer were investigated . The results obtained indicated that the most important removal mechanism of E . coli in the biofilm is the adsorption process, followed by sedimentation . Die-off is a relatively minor removal mechanism in an RBC system . Higher removal rate of E . coli was observed in an aerobic compared to an anaerobic biofilm system . Variation of dissolved oxygen concentration (3.3-8.7 mgl(-1)) and pH-values between 6.5 and 9.3 did not exert any significant effect on the removal rate of the E . coli by the heterotrophic biofilm . A rapid adsorption of E . coli to the biofilm occurred during the first days after adding the cationic polymer, after which the adsorption slowed down. Bioprocess Biosyst Eng, 2003 Dec, 26(2), 83 - 92 Epub 2003 Oct 22. Film analysis of activated sludge microbial discs by the Taguchi method and grey relational analysis; Chen MY et al.; A biofilm model with substrate inhibition is proposed for the activated sludge growing discs of rotating biological contactor (RBC); this model is different from the steady-state biofilm model based on the Monod assumption . Both deep and shallow types of biofilms are examined and discussed . The biofilm models based on both Monod and substrate inhibition (Haldane) assumptions are compared . In addition, the relationships between substrate utilization rate, biofilm thickness, and liquid phase substrate concentration are discussed . The influence order of the factors that affect the biofilm thickness is studied and discussed by combining the Taguchi method and grey relational analysis . In this work, a Taguchi orthogonal table is used to construct the series that is needed for grey relational analysis to determine the influence priority of the four parameters S(B), kX(f), K(s), and K(i). Bioprocess Biosyst Eng, 2003 Nov, 26(1), 69 - 74 Epub 2003 Oct 16. Biological waste gas treatment with a modified rotating biological contactor . Iota . Control of biofilm growth and long-term performance; Vinage I et al.; In this work, we introduce a modified rotating biological contactor (RBC) system and demonstrate its feasibility by applying the newly devised process to the biological treatment of artificial waste gas . In the proposed system, the waste gas is introduced to the bioreactor in the spacings between the rotating discs through a hollow shaft, thus allowing for intimate gas-liquid contact . A 91-l modified RBC containing 20 biofilm support discs 40 cm in diameter was used in the experiments . Toluene was used as the model pollutant, and the system was operated under standard operating conditions for more than one year in order to investigate its long-term performance and assess its ability to control the growth of the biofilm . It was demonstrated that the proposed system allows to efficiently control the growth of the biofilm, thus overcoming the clogging problem inherent in most conventional methods for the biological treatment of waste gas . Moreover, the system was shown to exhibit stationary long-term performance for a period of more than one year, hence indicating its feasibility for industrial application. Biotechnol Adv, 1984, 2(2), 301 - 8 A continuous biological process to decolorize bleach plant effluents; Joyce TW et al.; Although almost every U.S . pulp mill has a biological wastewater treatment system, these systems based on bacteria, are largely ineffective in the removal of color . For this reason, we have attempted to utilize Phanerochaete chrysosporium, a fungus known to degrade lignin, as the primary organism in a novel waste treatment scheme named the MyCoR Process . Color from bleached Kraft mills originates principally from the first extraction stage of the bleach plant . It is this waste stream which is sent to the MyCoR Process reactor, a rotating biological contactor, for decolorization.We have found that under optimal conditions up to 2,000 color units/L/day can be removed from the waste stream . There is also a concomitant removal of COD and BOD . In addition, chlorolignins originating from the bleaching process were found to be dechlorinated; this is of interest to those concerned with the impact of bleach plant effluents on the environment . The process uses conventional wastewater treatment equipment . However, the use of a pure culture of fungus in a secondary metabolic state has not been attempted previously in a waste treatment scheme . Minor equipment modification and close operator attention may therefore be required . A preliminary economic analysis shows that the MyCoR Process, in its present state, would cost about US$30/metric ton of bleached Kraft pulp produced . This cost will decrease as improved or new strains of fungi are developed for the process. Bioprocess Biosyst Eng, 2003 Nov, 26(1), 75 - 82 Epub 2003 Sep 19. Biological waste gas treatment with a modified rotating biological contactor . II . Effect of operating parameters on process performance and mathematical modeling; Vinage I et al.; In the first part of this paper, we introduced a modified rotating biological contactor (RBC) for the biological treatment of waste gas, and demonstrated its feasibility by applying the process to the biodegradation of toluene in a 91-liter reactor containing 20 biofilm support discs with a diameter of 40 cm {1} . We showed that the proposed system allows the unlimited growth of the biofilm to be suppressed, hence eliminating the risk of clogging associated with other biological waste gas treatment systems . Furthermore, we observed stationary long-term performance for more than one year under typical standard operating conditions . In this part of our work, we investigate experimentally the influence of the main process parameters, i.e., gas flow rate, inlet gas concentration, and rotational speed of the biofilm supports on process performance for the same system . Experimental results indicate that the modified RBC system is mass transfer limited for toluene loadings below 150 g/m(3)h, whereas at higher inlet concentrations of the pollutant, it becomes limited by the biodegradation reaction inside the biofilm . Surprisingly, the disc rotational speed is found to have no major effect on process performance for the system under investigation . A time-independent mathematical model of the process is also presented, and predictions are compared with experimental degradation data . In the range of the investigation process parameters, good agreement between the experimental data and simulation results is obtained. Water Res, 2003 Oct, 37(17), 4125 - 34 Microbiology of a biological contactor for winery wastewater treatment; Malandra L et al.; Winery wastewaters are characterised by large seasonal fluctuations in volume and composition and are often discarded with little or no treatment . A rotating biological contactor (RBC) was used to investigate microorganisms associated with the biological treatment of winery wastewater . Extensive biofilms developed on the RBC discs and contained a number of yeast and bacterial species that displayed a dynamic population shift during the evaluation period . This suggested that the naturally occurring microorganisms were able to form a stable biofilm and also reduce the chemical oxygen demand (COD) of winery wastewater (on average 43% with a retention time of 1h) . One of the yeast isolates, MEA 5, was able to reduce the COD of synthetic wastewater by 95% and 46% within 24h under aerated and non-aerated conditions, respectively . The yeast isolates could therefore play an important role in the degradation of organic compounds under aerobic conditions, such as those associated with an RBC. Water Sci Technol, 2003, 48(1), 131 - 8 Treatment of domestic sewage in a combined UASB/RBC system . Process optimization for irrigation purposes; Tawfik A et al.; A Rotating Biological Contactor (RBC) was fed with raw domestic wastewater or anaerobic effluents . The experiments were conducted at increasing operational temperatures viz . 11, 20 and 30 degrees C to assess the potential increase in removal efficiencies for the different COD fractions (COD(total), COD(suspended), COD(colloidal) and COD(soluble)), E . coli and in the nitrification rate . The results clearly show that, the RBC at HRT of 2.5 h and OLR of 47 g COD/m2 x d provided a very high residual COD(total) value of 228 mg/l when treating domestic wastewater . This was not the case as compared to the results obtained for the system when operated at the same HRT but at lower OLR's of 27, 20 and 14.5 g COD/m2 x d with a UASB effluent at operational temperatures of 11, 20 and 30 degrees C respectively . The residual COD(total) values amounted to 100, 85 and 72 mg/l in the final effluents . Moreover, a high removal of ammonia and low residual values of E . coli was found for the RBC when treating a UASB effluent at operational temperature of 30 degrees C as compared to the situation for treatment of domestic wastewater and UASB effluent at lower temperatures of 11 and 20 degrees C . It can be concluded that an efficient pre-treatment of sewage implies a substantial reduction of OLR applied to the RBC and consequently improves the residual of COD(total) ammonia and E . coli in the final effluent . Therefore, this study supports using a combined system UASB/RBC for treatment of domestic wastewater for reuse in irrigation. Biotechnol Prog, 2003 Jul-Aug, 19(4), 1372 - 6 Bioremediation of textile azo dyes by an aerobic bacterial consortium using a rotating biological contactor; Abraham TE et al.; The degradation of an azo dye mixture by an aerobic bacterial consortium was studied in a rotating biological reactor . Laterite pebbles of particle size 850 microm to 1.44 mm were fixed on gramophone records using an epoxy resin on which the developed consortium was immobilized . Rate of degradation, BOD, biomass determination, enzymes involved, and fish bioassay were studied . The RBC has a high efficiency for dye degradation even at high dye concentrations (100 microg/mL) and high flow rate (36 L/h) at alkaline pH and salinity conditions normally encountered in the textile effluents . Bioassays (LD-50) using Thilapia fish in treated effluent showed that the percentage mortality was zero over a period of 96 h, whereas the mortality was 100% in untreated dye water within 26 h . Fish bioassay confirms that the effluent from RBC can be discharged safely to the environment. Water Environ Res, 2003 May-Jun, 75(3), 232 - 7 Posttreatment of upflow anaerobic sludge blanket-treated industrial wastewater by a rotating biological contactor; Torkian A et al.; The performance of a rotating biological contactor (RBC) for posttreatment of the slaughterhouse effluent from an upflow anaerobic sludge blanket (UASB) reactor was investigated in this study . The 280-L, six-stage RBC pilot plant was operated at different organic loading rates (OLRs) and biodisk speeds . The overall removal efficiencies for soluble biochemical oxygen demand (SBOD), total biochemical oxygen demand (TBOD), and total chemical oxygen demand (TCOD) decreased with increasing OLRs . Disk rotational speed did not have a significant effect on performance in the range studied . The results showed that satisfactory posttreatment to meet regulatory requirements for agricultural purposes (effluent biochemical oxygen demand of 100 mg/L) can be achieved at an OLR of 5.3 +/- 2.9 g SBOD x m(-2) x d(-1), with an SBOD removal efficiency of 85 +/- 3% . Most of the organics were removed in the first three stages, with minimal contribution from the remaining stages of the RBC reactor . There was a decrease in SBOD removal efficiency to 74 +/- 3% at an OLR value of 17.8 +/- 2.1 g SBOD x m(-2) x d(-1) . The results for elimination capacity indicated a linear relationship with first-stage OLRs without any signs of limitation at the range of loading rates investigated in this study . However, average first-stage elimination capacity rates of 4.8 and 3.8 g x m(-2) x d(-1) at OLR values of 17.8 and 11 g SBOD x m(-2) x d(-1) were relatively lower than previous studies of RBC performance using domestic or industrial wastewater without anaerobic pretreatment . It was suggested that the lower elimination capacity rates were due to the fact that a smaller fraction of UASB effluent was biodegradable as reflected in TBOD/TCOD ratios of 0.47 +/- 0.04. Appl Environ Microbiol, 2003 Jun, 69(6), 3626 - 35 Characterization of an autotrophic nitrogen-removing biofilm from a highly loaded lab-scale rotating biological contactor; Pynaert K et al.; In this study, a lab-scale rotating biological contactor (RBC) treating a synthetic NH(4)(+) wastewater devoid of organic carbon and showing high N losses was examined for several important physiological and microbial characteristics . The RBC biofilm removed 89% +/- 5% of the influent N at the highest surface load of approximately 8.3 g of N m(-2) day(-1), with N(2) as the main end product . In batch tests, the RBC biomass showed good aerobic and anoxic ammonium oxidation (147.8 +/- 7.6 and 76.5 +/- 6.4 mg of NH(4)(+)-N g of volatile suspended solids {VSS}(-1) day(-1), respectively) and almost no nitrite oxidation (< 1 mg of N g of VSS(-1) day(-1)) . The diversity of aerobic ammonia-oxidizing bacteria (AAOB) and planctomycetes in the biofilm was characterized by cloning and sequencing of PCR-amplified partial 16S rRNA genes . Phylogenetic analysis of the clones revealed that the AAOB community was fairly homogeneous and was dominated by Nitrosomonas-like species . Close relatives of the known anaerobic ammonia-oxidizing bacterium (AnAOB) Kuenenia stuttgartiensis dominated the planctomycete community and were most probably responsible for anoxic ammonium oxidation in the RBC . Use of a less specific planctomycete primer set, not amplifying the AnAOB, showed a high diversity among other planctomycetes, with representatives of all known groups present in the biofilm . The spatial organization of the biofilm was characterized using fluorescence in situ hybridization (FISH) with confocal scanning laser microscopy (CSLM) . The latter showed that AAOB occurred side by side with putative AnAOB (cells hybridizing with probe PLA46 and AMX820/KST1275) throughout the biofilm, while other planctomycetes hybridizing with probe PLA886 (not detecting the known AnAOB) were present as very conspicuous spherical structures . This study reveals that long-term operation of a lab-scale RBC on a synthetic NH(4)(+) wastewater devoid of organic carbon yields a stable biofilm in which two bacterial groups, thought to be jointly responsible for the high autotrophic N removal, occur side by side throughout the biofilm. Water Res, 2003 May, 37(10), 2281 - 90 Nitrification efficiency and nitrifying bacteria abundance in combined AS-RBC and A2O systems; You SJ et al.; This study makes a comparison between the nitrification performance of TNCU-I (a combined activated sludge-rotating biological contactor process) and A2O systems by the use of a pilot plant and batch experiments . The nitrifier abundance in both systems was determined, using cloning-denaturing gradient gel electrophoresis (DGGE) and fluorescent in-situ hybridization (FISH), to investigate the role of rotating biological contactor in the TNCU-I process . The stability of the nitrification performance and the specific nitrification rate were found to be greater in TNCU-I system than in the A2O system . RBC biofilm promoted nitrifying activity that contributed to the nitrification performance, especially at a low SRT . By using the cloning-DGGE method, the genera Nitrosospira and Nitrospira were found to be present in all the samples, while the genus Nitrosomonas was observed only in the TNCU-I RBC biofilm . In addition, the proportions of ammonia oxidizer in the TNCU-I RBC biofilm, the TNCU-I activated sludge and the A2O activated sludge were 11.4%, 13.2%, and 4.1%, respectively, higher than the nitrite oxidizer fractions of 3.3%, 5.7% and 2.1%, respectively, according to the cloning-DGGE method . On the other hand, the proportions of ammonia oxidizers in the afore-mention materials were 10.3%, 13.7%, and 5.2%, higher than the nitrite oxidizer fractions of 2.5%, 3.6% and 2.3%, according to the FISH experiments . This implies that the proportion of ammonia oxidizer in the TNCU-I process was 3.2 and 2.6 times that in the A2O process, determined by the cloning-DGGE and FISH methods, respectively . These amounts are also close to the ammonia oxidization rate of 2.9 times . All the data show that RBC added to the aerobic zone of TNCU-I process would increase the nitrifier abundance and enhance the nitrification performance of the system. Microb Ecol, 2003 May, 45(4), 419 - 32 Epub 2003 Apr 22. Microbial composition and structure of a rotating biological contactor biofilm treating ammonium-rich wastewater without organic carbon; Egli K et al.; High nitrogen losses were observed in a rotating biological contactor (RBC) treating ammonium-rich (up to 500 mg NH4(+)-N/L) but organic-carbon-poor leachate from a hazardous waste landfill in Kolliken, Switzerland . The composition and spatial structure of the microbial community in the biofilm on the RBC was analyzed with specific attention for the presence of aerobic ammonium and nitrite oxidizing bacteria and anaerobic ammonium oxidizers . Anaerobic ammonium oxidation (anammox) involves the oxidation of ammonium with nitrite to N2 . First the diversity of the biofilm community was determined from sequencing cloned PCR-amplified 16S rDNA fragments . This revealed the presence of a number of very unusual 16S rDNA sequences, but very few sequences related to known ammonium or nitrite oxidizing bacteria . From analysis of biofilm samples by fluorescence in situ hybridization with known phylogenetic probes and by dot-blot hybridization of the same probes to total RNA purified from biofilm samples, the main groups of microorganisms constituting the biofilm were found to be ammonium-oxidizing bacteria from the Nitrosomonas europaea/eutropha group, anaerobic ammonium-oxidizing bacteria of the "Candidatus Kuenenia stuttgartiensis" type, filamentous bacteria from the phylum Bacteroidetes, and nitrite-oxidizing bacteria from the genus Nitrospira . Aerobic and anaerobic ammonium-oxidizing bacteria were present in similar amounts of around 20 to 30% of the biomass, whereas members of the CFB phylum were present at around 7% . Nitrite oxidizing bacteria were only present in relatively low amounts (less than 5% determined with fluorescence in situ hybridization) . Data from 16S rRNA dot-blot and in situ hybridization were not in all cases congruent . FISH analysis of thin-sliced and fixed biofilm samples clearly showed that the aerobic nitrifiers were located at the top of the biofilm in an extremely high density and in alternating clusters . Anammox bacteria were exclusively present in the lower half of the biofilm, whereas CFB-type filamentous bacteria were present throughout the biofilm . The structure and composition of these biofilms correlated very nicely with the proposed physiological functional separations in ammonium conversion.
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