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| Water Res, 2003 Mar, 37(6), 1252 - 9 Identification and quantification of nitrogen removal in a rotating biological contactor by 15N tracer techniques; Wyffels S et al.; High autotrophic nitrogen removal rates of 858mg NL(-1) day(-1) or 1.55g Nm(-2) day(-1) were obtained in a lab-scale rotating biological contactor treating an ammonium rich influent . It was postulated that ammonium was removed as dinitrogen gas by a sequence of aerobic ammonium oxidation to nitrite taking place in the outer biofilm layer and anaerobic ammonium oxidation with nitrite as electron acceptor occuring in the deeper biofilm layer . Chemical evidence for anaerobic ammonium oxidation within intact biofilm sludge from a lab-scale rotating biological contactor could be provided, without direct identification of responsible organisms catalysing this reaction . 15N tracer techniques were used for identification and quantification of nitrogen transformations . In batch tests with biofilm sludge at dissolved oxygen concentrations lower than 0.1mgL(-1), ammonium and nitrite did react in a stoichiometric ratio of 1:1.43 thereby forming dinitrogen . 15N isotope dilution calculations revealed that anaerobic ammonium oxidation was the major nitrogen transformation leading to concomitant ammonium and nitrite removal . Isotopic analysis of the produced biogas showed that both ammonium-N and nitrite-N were incorporated in N(2). J Environ Qual, 2002 Nov-Dec, 31(6), 1842 - 7 Polycyclic aromatic hydrocarbon removal from soil by surfactant solubilization and Phanerochaete chrysosporium oxidation; Zheng Z et al.; Surfactant soil washing can remove polycyclic aromatic hydrocarbons (PAHs) from contaminated soil, and the white rot fungus, Phanerochaete chrysosporium Burdsall in Burdsall & Eslyn, can oxidize PAHs . The objective of this study was to develop a novel bioremediation technology using a combination of abiological surfactant soil washing followed by PAH biological oxidation in soil washwater using P . chrysosporium in a rotating biological contactor (RBC) reactor . Soil used for experimentation was an 11-month aged contaminated soil spiked with a total of nine PAHs: acenaphthene, fluorene, phenanthrene, fluoranthene, pyrene, chrysene, benzo(a)pyrene, dibenz(a-h)anthracene, and benzo(ghi)perylene . After 11 months of aging, recovery percentages of high molecular weight PAHs {i.e., from chrysene to benzo(ghi)perylene} were greater than 86%, while those of low molecular weight PAHs (i.e., from acenaphthene to pyrene) were less than 19% . Total removal efficiency for any of the nine PAHs was greater than 90% using a combination of surfactant soil washing and P . chrysosporium oxidation of soil washwater in the RBC reactor when used in batch operation, and greater than 76% when used in continuous operation . The treatment of PAH-contaminated soil using a combination of surfactant soil washing and subsequent PAH removal from the resultant washwater in an RBC reactor, in the presence of immobilized P . chrysosporium, permits (i) a rapid abiological cleanup of soil for compliance with relevant soil quality standards and (ii) PAH biological removal in soil washwater for compliance with aqueous discharge standards. J Environ Sci Health A Tox Hazard Subst Environ Eng, 2002 Oct, 37(9), 1737 - 55 Kinetics of an anaerobic moving bed reactor system treating synthetic milk wastewater; Ramakant et al.; In the present study, anaerobic moving bed reactor called anaerobic rotating biological contactor treating synthetic milk wastewater operated at different organic loading rates and different hydraulic retention times, were evaluated to determine kinetic parameters for the substrate, biomass and biogas based on various models . The maximum substrate loading rate and half velocity constant were evaluated as 5.71 kgCOD/m3 x d and 1178 mg/L respectively by using Lineweaver-Burke plot . Maximum substrate removal efficiency and critical hydraulic retention time were compared with modified Young and McCarty model and the model is best fitted for the study . The complete removal of substrate cannot be expected due to presence of metabolic refractory material produced within the reactor system from influent system . Kinetic constants for maximum specific growth rate and decay coefficient were compared with the modified Monod model . Kornegay and Andrews model were used to evaluate the area capacity constant and half velocity constant . Kinetic constants for maximum specific gas production rate and proportionality constant were evaluated using Stover model . The gas production and quality are dependent on the substrate removal and substrate loading rate . The kinetic relationships derived from lab-scale experiment provided good estimates of the performance of pilot- and full-scale anaerobic rotating biological contactor packed with fibrous nylon pads and treating synthetic milk wastewater in terms of the effluent chemical oxygen demand concentrations and specific biogas production rates. Syst Appl Microbiol, 2002 Aug, 25(2), 301 - 13 Ciliate communities of rotating biological contactor biofilms: a multivariate approach; Martin-Cereceda M et al.; Physical-chemical monitoring and characterization of ciliate communities from a full-scale rotating biological system (RBC) have been carried out for a year . RBC system operated efficiently in removing the organic matter, as the decrease of the BOD5 loading along the successive RBC units revealed . 55 species of ciliated protozoa were identified in the RBC biofilms . Differences in abundance, occurrence and type of species were found along the different units of the RBC system; the last RBC held a more stable and diverse ciliate community . The complexity of interspecific relationships among the ciliates has been outlined using multivariate methods (Cluster and Correspondence analysis) . Correlation between ciliate species and physical-chemical conditions were obtained by regression analysis . Results show that 12 species of ciliates were related to an optimal efficiency in organic matter removal, Litonotus crystallinus being the most sensitive species . The presence and abundance of Litonotus crystallinus and Acineria uncinata was associated with a decrease in the organic factor . Metopus es was the only species related to a decrease in process efficiency due to its association with an increase in organic factor . The results provide statistical evidence of the use of certain ciliate species as reliable bioindicators in full-scale RBC wastewater treatment plants. Water Sci Technol, 2002, 46(1-2), 199 - 206 An integrated approach to analyse biofilms of a full scale wastewater treatment plant; Martin-Cereceda M et al.; A rotating biological contactor (RBC) system operating in a full-scale wastewater treatment plant has been described by several approaches accounting for performance, composition and structure of biofilms in three stages through biological wastewater treatment (RBC1, RBC 2, RBC 3) . RBC biofilms were effective in removing the BOD loading from 13 g BOD5 d(-1) m(-2) in RBC 1 to 6 g BOD5 d(-1) m(-2) in RBC 3 . Analysis of biofilm composition showed: i) the volatile solids were similar in the three RBCs (0.6 g m(-2) VS per g m(-2) of TS); ii) the protozoan and metazoan biocenosis was mainly made up of ciliated protozoa, which were most abundant in RBC 2 (1.84 x 10(6) ciliates g(-1) VS) . Relationship between ciliate species and physical-chemical profile of the system by cluster analysis indicated that the species Acineria uncinata, Amphileptus punctatus, Cinetochilum margaritaceum and Holosticha mancoidea were associated with the best RBC performance; iii) the exopolymeric matrix of the three RBC biofilms was mainly constituted by proteins, although humic substances, polysaccharides, uronic acids and DNA were also found . Analysis of biofilm structure by confocal microscopy indicated changes in biofilm organisation with depth . Results have been brought together and a graphic representation of the composition and architecture of RBC biofilms is presented. Water Sci Technol, 2002, 45(10), 371 - 6 Treatment of anaerobically treated domestic wastewater using rotating biological contactor; Tawfik A et al.; A small-scale pilot plant consisting of a three-stage RBC has been investigated for the removal of E . coli, COD fractions and ammonia from the effluent of an UASB reactor treating domestic wastewater . The results obtained reveal that a three-stage system operated at a HRT of 3.0 h represents an effective posttreatment process . The remaining COD in the final effluent was only 51 (+/- 7) mgl(-1) . Ammonia concentration was reduced by 67 (+/- 7.6) % . The overall E . coli reduction was 1.39 log10 at an influent count of 6.5 log10 corresponding to an overall removal efficiency of 95.8 (+/- 4.7) % . However, according to prevailing standards, residual E . coli counts are still high for unrestricted reuse for irrigation purposes . When the system was operated at a HRT of 10 h, overall E . coli removal and ammonia reduction were 99.9 (+/- 0.05)% and 92 (+/- 6.5) % respectively . At a HRT of 10 h, recirculation of the 3rd stage effluent to the 1st stage reduced the residual of E . coli in the final effluent from 2 x 10(3) to 9.8 x 10(2)/100ml . Moreover, the recirculation of nitrified effluent from the 3rd stage to the 1st stage increased ammonia removal in the stage 1 from 23 to 43% . This relatively high ammonia removal likely can be attributed to the supply of nitrifiers from 3rd stage to the 1st one. Water Sci Technol, 2002, 45(10), 357 - 63 Oxygen-limited nitrogen removal in a lab-scale rotating biological contactor treating an ammonium-rich wastewater; Pynaert K et al.; A lab-scale Rotating Biological Contactor (RBC) was operated with the purpose of oxygen-limited (autotrophic) nitrification-denitrification of an ammonium-rich synthetic wastewater without Chemical Oxygen Demand (COD) . Based on the field observations that RBCs receiving anaerobic effluents come to anoxic ammonium removal, the RBC was inoculated with methanogenic sludge . Some 100 days after the addition of the anaerobic sludge to the reactor as a possible means of a rapid initiation of the nitrogen (N) removal process, a maximum ammonium removal of 1,550 mg N m(-2) d(-1) was achieved . Batch tests with 15N labeled ammonium and nitrite indicated that a large part of that N was removed via oxygen-limited oxidation of ammonium with nitrite as the electron acceptor . The other part was removed via conventional denitrification, presumably with COD released from lysis of cells . Species identification of the most abundant microorganisms revealed that Nitrosomonas spp . were the dominant ammonium-oxidizers in the sludge . Thus far, the molecular characterization of the sludge could not show the presence of Planctomycetes among the most dominant species . Overall this experiment confirms the property of the RBC system to remove ammonium to nitrogen gas without the use of heterotrophic carbon source. Environ Sci Technol, 2002 Jul 1, 36(13), 2839 - 47 Removal of fragrance materials during U.S . and European wastewater treatment; Simonich SL et al.; The concentrations and removals of 16 fragrance materials (EMs) were measured in 17 U.S . and European wastewater treatment plants between 1997 and 2000 and were compared to predicted values . The average FM profile and concentrations in U.S . and European influent were similar . The average FM profile in primary effluent was similar to the average influent profile; however, the concentration of FMs was reduced by 14.6-50.6% in primary effluent . The average FM profile in final effluent was significantly different from the primary effluent profile and was a function of the design of the wastewater treatment plant . In general, the removal of sorptive, nonbiodegradable FMs was correlated with the removal of total suspended solids in the plant, while the removal of nonsorptive, biodegradable FMs was correlated with 5-day Biological Oxidation Demand removal in the plant . The overall plant removal (primary + secondary treatment) of FMs ranged from 87.8 to 99.9% for activated sludge plants, 58.6-99.8% for carousel plants, 88.9-99.9% for oxidation ditch plants, 71.3-98.6% for trickling filter plants, 80.8-99.9% for a rotating biological contactor plant, and 96.7-99.9% for lagoons . The average concentration of FMs in final effluent ranged from the limit of quantitation (1-3 ng/L) to 8 microg/L . Measured FM removal and concentrations were compared to predicted values, which were based on industry volume, per capita water use, octanol-water partition coefficient, and biodegradability. Bioresour Technol, 2002 Sep, 84(2), 145 - 50 Degradation of 4-chlorophenol by the white rot fungus Phanerochaete chrysosporium in free and immobilized cultures; Zouari H et al.; 4-Chlorophenol (4-CP) degradation was investigated by suspended and immobilized Phanerochaete chrysosporium conducted in static and agitated cultures . The best results were achieved when experiment was carried out in a rotating biological contactor instead of an Erlenmeyer flask, for both batch degradation and repeated batch degradation . The relative contribution of lignin peroxidase (LiP) versus manganese peroxidase (MnP) to the 4-CP degradation by P . chrysosporium was investigated . 4-CP degradation slightly increased and a high level of MnP (38 nKat ml(-1)) was produced when P . chrysosporium was grown at high Mnll concentration . High LiP production in the medium had no significant effect on 4-CP degradation . 4-CP degradation occurred when P . chrysosporium was grown in a medium that repressed LiP and MnP production . This result indicates that LiP and MnP are not directly involved in 4-CP degradation by P . chrysosporium. J Biotechnol, 2002 Jul 3, 96(3), 241 - 9 Removal of surfactant solubilized polycyclic aromatic hydrocarbons by Phanerochaete chrysosporium in a rotating biological contactor reactor; Zheng Z et al.; White rot fungi can oxidize surfactant solubilized polycyclic aromatic hydrocarbons (PAH) . The objective of this study was to evaluate the performance of immobilized white rot fungus, Phanerochaete chrysosporium, to remove surfactant Tween 80 solubilized PAH i.e . phenanthrene, pyrene and benzo(alpha)pyrene in a rotating biological contactor (RBC) reactor . Results indicated that the immobilized P . chrysosporium in the RBC reactor system in continuous operation could effectively remove the three tested PAH at specific hydraulic loading rates and concentrations tested for each individual PAH . Batch operation of RBC reactor showed that the immobilized P . chrysosporium was stable and effective for the eight successive batch treatments of PAH in solution medium i.e . PAH removal was greater than 90% after 60 h, although only low levels of ligninolytic enzyme activity were detected . The removal of phenanthrene and pyrene in solution medium has been found to be a first order reaction in batch operation . A mass balance calculation indicated that biological oxidation was the main factor for removal of benzo(alpha)pyrene i.e . 95.7% in the RBC reactor . However, for phenanthrene and pyrene, both biological oxidation (i.e . 49 and 56%, respectively) and RBC disc foam adsorption (i.e . 44 and 34%, respectively) made a significant contribution to the removal of PAH. Environ Technol, 2002 Mar, 23(3), 353 - 62 Oxygen-limited nitrification and denitrification in a lab-scale rotating biological contactor; Pynaert K et al.; Rotating Biological Contactors (RBC) treating highly nitrogenous wastewaters are known to give rise to nitrogen losses, generally assumed to be due to concomitant nitrification and denitrification . In this study, a lab-scale nitrifying RBC reactor was shown to bring about losses of nitrogen of the order of 10 to 20% at ammonium loading rates of up to 2129 mg N m(-2) d(-1), when no extra carbon source was added . These higher removal values could be due to Oxygen-Limited Autotrophic Nitrification and Denitrification (OLAND), because the reactor was operated at oxygen limitation . When methanol was added as a soluble organic carbon source to further diminish oxygen transfer into the deeper parts of the biofilm, the RBC achieved 84% nitrogen removal (loading rate 2300 mg N m(-2) d(-1)) at a COD/N ratio of 3.1 . The latter also suggests that the process was occurring parallel to conventional denitrification. Appl Microbiol Biotechnol, 2002 Mar, 58(3), 416 - 20 Epub 2001 Nov 22. Bioremediation of toxic chromium from electroplating effluent by chromate-reducing Pseudomonas aeruginosa A2Chr in two bioreactors; Ganguli A et al.; The chromate-reducing ability of Pseudomonas aeruginosa A2Chr was compared in batch culture, with cells entrapped in a dialysis sac, and with cells immobilized in an agarose-alginate film in conjunction with a rotating biological contactor . In all three systems, the maximum Cr(VI) reduction occurred at 10 mg Cr(VI)/l . Whereas at 50 mg Cr(VI)/l concentration, only 16% of the total Cr(VI) was reduced, five spikings with 10 mg chromate/l at 2-h intervals led to 96% reduction of the total input of 50 mg Cr(VI)/l . Thus maximum Cr(VI) reduction was achieved by avoiding Cr(VI) toxicity to the cells by respiking with lower Cr(VI) concentrations . At 10 mg Cr(VI)/l, the pattern of chromate reduction in dialysis-entrapped cells was almost similar to that of batch culture and 86% of the bacterially reduced chromium was retained inside the dialysis sac . In electroplating effluent containing 100 mg Cr(VI)/l, however, the amount of Cr(VI) reduced by the cells immobilized in agarose-alginate biofilm was twice and thrice the amount reduced by batch culture and cells entrapped in a dialysis sac, respectively. Water Res, 2002 Jan, 36(1), 147 - 55 Treatment of anaerobically pre-treated domestic sewage by a rotating biological contactor; Tawfik A et al.; The performance of a rotating biological contactor (RBC) for the post-treatment of the effluent of an up-flow anaerobic sludge blanket (UASB) was the subject of this study . Different hydraulic and organic loading rates have been investigated . The removal efficiencies of COD(total), COD(suspended), COD(colloidal) and COD(soluble) increased at a higher hydraulic retention time (HRT) and a lower influent organic loading rate . The results obtained indicated that a two-stage RBC reactor at an HRT of 10 h and an organic loading rate of 6.4g COD m(-2) d(-1) represents an effective post-treatment process . Most COD(suspended) and COD(colloidal) were removed in the first stage while nitrification proceeded in the second stage . The overall nitrification efficiency was 92% at an ammonia loading rate of 1.1 gm(-2) d(-1) . Total E . coli removal at HRTs of 10, 5 and 2.5h were 99.5%, 99.0% and 89.0% . respectively . The major part of suspended E . coli ( >4.4 microm) was removed by sedimentation or by adsorption in the biofilm of the first stage of RBC (99.66%) . However, E . coli in the colloidal fraction (<4.4 to >0.45 microm) was eliminated in the second stage of RBC (99.78%) . A comparison of the performance of a one-stage versus two-stage RBC system, operated at the same total loading rate, revealed an improvement in the effluent quality of the two-stage effluent as compared to the one-stage effluent . The two stages RBC were used to examine the effect of hydraulic shock loads on reactor performance in terms of COD, nitrification and E . coli removal. Environ Technol, 2001 Oct, 22(10), 1169 - 75 Hydraulic characteristics of an anoxic rotating biological contactor: influence of biofilm; Teixeira P et al.; The hydraulic characteristics of an anoxic rotating biological contactor were studied under different flow rates . The experiments were carried out with the reactor clean (without biomass) and containing denitrifying biofilm (Alcaligenes denitrificans) covering the disks . Residence Time Distribution (RTD) experiments were performed by the stimulus-response technique using lithium chloride as tracer . Experiments without biomass revealed the existence of hydraulic dead volumes (around 40% for hydraulic residence time of 0.94 and 2 hours) that occur in corners, where stagnant eddies form . When in normal operation, with the disks covered by biofilm and with biogas production, these values decreased significantly . For hydraulic residence time (HRT) of 2 hours a minimum dead volume was observed, being appropriate to run the reactor under this condition, from the hydraulic viewpoint . The Dispersion number decreased with increasing HRT from 0.94 h on, for both types of experiment, without, and in the presence of biomass . For this HRT the dispersion number was maximal in both situations . A considerable diffusion of tracer into the biofilm was detected, being faster in the more hydrated biofilm, and Justifying the long tails observed in the RTD experimental curves. Environ Technol, 2001 Aug, 22(8), 951 - 9 Characterization of extracellular polymeric substances in rotating biological contractors and activated sludge flocs; Martin-Cereceda M et al.; Extracellular polymeric substances (EPS) from biofilms of a rotating biological contactor (RBC) system and from activated sludge flocs were extracted using ultrasound and a cation exchange resin . In both wastewater treatment systems, the EPS matrix was mainly constituted of proteins, humic-like substances and polysaccharides, although other components--DNA and uronic-like substances--were also present . The composition of the biofilm EPS was different in the succesive RBC wastewater treatment stages: protein had its highest concentration in the first RBC unit, while humic substances and polysaccharides in the third RBC . Significant differences between biofilm and sludge floc EPS were also reported . The amount of proteins was 3.5 times higher for RBC biofilms than for sludge flocs, and quantities of humic substances and polysaccharides extracted from biofilms were twice as high than in sludges . Moreover, biofilm exopolymers were two times more hydrophobic than those of sludge flocs . Implications of wastewater chemistry and microbial growth strategies into EPS composition and properties are suggested. Water Res, 2001 Oct, 35(15), 3715 - 23 Bioremediation of heavy metals in a synthetic wastewater using a rotating biological contactor; Costley SC et al.; Immobilised microorganisms provide a potential system for the treatment of metal-contaminated waters . This study investigates the efficiency of a rotating biological contactor (RBC) in the treatment of waters contaminated with cadmium, copper and zinc in multiple sorption-desorption cycles . Each sorption cycle extended over a period of 12 weeks at an HRT of 24h to determine the efficiency of the system over a protracted period of time . The removal pattern observed in the initial cycle, namely Cu >> Zn > Cd, was repeated in both subsequent cycles . After completion of each cycle metals were successfully desorbed by means of an acid wash . The sorption ability of the biofilm was not adversely affected by the desorption process as evidenced by the similar metal removal rates obtained in each of the three sorption cycles . These results suggest that RBCs can be used successfully in the treatment of high-strength metal-contaminated wastewaters. J Appl Microbiol, 2001 Jul, 91(1), 93 - 103 A study of the effect of isothiazolones on the performance and characteristics of a laboratory-scale rotating biological contactor; Laopaiboon L et al.; AIMS: To study the effect of the isothiazolone biocide (Kathon WT) on the performance of laboratory-scale rotating biological contactors (RBCs) and their component biofilms . METHODS AND RESULTS: Biofilms were established on the RBCs and then exposed to 0.7-15 p.p.m . isothiazolones . Young, 1-week-old, biofilms were found to attain treatment efficiency equal to that of mature, 2-month-old, biofilms . Isothiazolone concentrations at 3 p.p.m . and above caused a progressive decline in treatment efficiency and 15 p.p.m . isothiazolones inhibited all microbial activity and resulted in the death of the biofilms . Bio-oxidation and the biodegradation of isothiazolones within the biofilms ontinued unhindered at concentrations which caused the total inhibition of planktonic bacteria . CONCLUSION: There was at least a 10-fold difference in susceptibility of planktonic and biofilm bacteria to isothiazolones . The chemical oxygen demand (COD) test was shown to be a reliable tool for investigating the efficiency of wastewater treatment units when the influent contains isothiazolones, while the biochemical oxygen demand (BOD) was unreliable due to the inhibition of bio-oxidation by the biocide . SIGNIFICANCE AND IMPACT OF THE STUDY: The results show that RBCs can be used to treat effluents containing isothiazolones at concentrations up to 1.5 p.p.m. Arch Microbiol, 2001 Mar, 175(3), 198 - 207 Enrichment and characterization of an anammox bacterium from a rotating biological contactor treating ammonium-rich leachate; Egli K et al.; Anaerobic ammonium oxidation with nitrite to N2 (anammox) is a recently discovered microbial reaction with interesting potential for nitrogen removal from wastewater . We enriched an anammox culture from a rotating disk contactor (near Kolliken, Switzerland) that was used to treat ammonium-rich leachate with low organic carbon content . This enrichment led to a relative population size of 88% anammox bacteria . The microorganism carrying out the anammox reaction was identified by analysis of the 16S rDNA sequence and by fluorescence in situ hybridization (FISH) with 16S-rRNA-targeting probes . The percentage sequence identity between the 16S rDNA sequences of the Kolliken anammox organism and the archetype anammox strain Candidatus Brocadia anammoxidans was 90.9%, but between 98.5 and 98.9% with Candidatus Kuenenia stuttgartiensis, an organism identified in biofilms by molecular methods . The Kolliken culture catalyzed the anaerobic oxidation of ammonium with nitrite in a manner seemingly identical to that of Candidatus B . anammoxidans, but exhibited higher tolerance to phosphate (up to 20 mM) and to nitrite (up to 13 mM) and was active at lower cell densities . Anammox activity was observed only between pH 6.5 and 9, with an optimum at pH 8 and a temperature optimum at 37 degrees C . Hydroxylamine and hydrazine, which are intermediates of the anammox reaction of Candidatus B . anammoxidans, were utilized by the Kolliken organisms, and approximately 15% of the nitrite utilized during autotrophic growth was converted to nitrate . Electron microscopy showed a protein-rich region in the center of the cells surrounded by a doughnut-shaped region containing ribosomes and DNA . This doughnut-shape region was observed with FISH as having a higher fluorescence intensity . Similar to Candidatus B . anammoxidans, the Kolliken anammox organism typically formed homogenous clusters containing up to several hundred cells within an extracellular matrix. Water Res, 2001 May, 35(7), 1714 - 22 Simultaneous carbon and nitrogen removal from high strength domestic wastewater in an aerobic RBC biofilm; Gupta AB et al.; High strength domestic wastewater discharges after no/partial treatment through sewage treatment plants or septic tank seepage field systems have resulted in a large build-up of groundwater nitrates in Rajasthan, India . The groundwater table is very deep and nitrate concentrations of 500-750 mg/l (113-169 as NO3(-)-N) are commonly found . A novel biofilm in a 3-stage lab-scale rotating biological contactor (RBC) was developed by the incorporation of a sulphur oxidising bacterium Thiosphaera pantotropha which exhibited high simultaneous removal of carbon and nitrogen in fully aerobic conditions . T . pantotropha has been shown to be capable of simultaneous heterotrophic nitrification and aerobic denitrification thereby helping the steps of carbon oxidation, nitrification and denitrification to be carried out concurrently . The first stage having T . pantotropha dominated biofilm showed high carbon and NH4(+)-N removal rates of 8.7-25.9 g COD/m2 d and 0.81-1.85 g N/m2 d for the corresponding loadings of 10.0-32.0 g COD/m2 d and 1.0-3.35 g N/m2 d . The ratio of carbon removed to nitrogen removed was close to 12.0 . The nitrification rate increased from 0.81 to 1.8 g N/m2 d with the increasing nitrogen loading rates despite a high simultaneous organic loading rate . However, it fell to 1.53 g N/m2 d at a high load of 3.35 g N/m2 d and 32 g COD/m2 d showing a possible inhibition of the process . A simultaneous 44-63% removal of nitrogen was also achieved without any significant NO2(-)-N or NO3(-)-N build-up . The second and third stages, almost devoid of any organic carbon, acted only as autotrophic nitrification units, converting the NH4(+)-N from stage 1 to nitrite and nitrate . Such a system would not need a separate carbon oxidation step to increase nitrification rates and no external carbon source for denitrification . The alkalinity compensation during denitrification for that destroyed in nitrification may also result in a high economy. Lett Appl Microbiol, 2000 Jan, 30(1), 33 - 7 Biodetoxification of silver-cyanide from electroplating industry wastewater; Patil YB et al.; A bacterial consortium capable of utilizing metal-cyanides as a source of nitrogen was used to develop a microbiological process for the detoxification of silver-cyanide from electroplating wastewater . When the treatment was carried out in a 27-l rotating biological contactor (R3C) in continuous mode, the system could achieve > 99.5% removal of 0.1 mmol l(-1) silver-cyanide (approximately 5 mg l(-1) cyanide and 10 mg l(-1) silver) in 10 h with sugarcane molasses (0.1 ml l(-1)) as carbon source . The silver ions set free during biodegradation were efficiently adsorbed by the bacterial biomass . The RBC-treated effluent was found to be safe for discharge into the environment, as confirmed by chemical analysis and fish bioassay studies.
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