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1.
Activity of ammonia-oxidizing bacteria (AOB) to simultaneous variation in Zn2+ concentration (0.01-3.5 mg/L), temperature (23-33 °C), and AOB concentration (3-30 × 106 gene copies/mL) in a steel industry wastewater treatment plant was evaluated. Two equations were developed to describe the lag period (i.e., AOB acclimation) and ammonia oxidation rate (i.e., growth of the AOB) depending on the variables. AOB concentration and temperature both had significant effects on lag period and the ammonia oxidation rate. Zn2+ concentration only had a significant effect on ammonia oxidation rate at 5% α-level. There was a significant interaction between AOB concentration and temperature for both lag period and ammonia oxidation rate. The effects of the variables were not significant when AOB concentration was higher than 2.0 × 107 copies/mL. There was no visible shift or changes in AOB communities based on DGGE analysis with amoA gene primers. 相似文献
2.
During the process of producing cassava starch from Manihot esculenta roots, large amounts of cyanoglycosides were released, which rapidly decayed to CN− following enzymatic hydrolysis. Depending on the varying cyanoglycoside content of the cassava varieties, the cyanide concentration
in the wastewater was as high as 200 mg/l. To simulate anaerobic stabilization, a wastewater with a chemical oxygen demand
(COD) of about 20 g/l was prepared from cassava roots and was fermented in a fixed-bed methanogenic reactor. The start-up
phase for a 99% degradation of low concentrations of cyanide (10 mg/l) required about 6 months. After establishment of the
biofilm, a cyanide concentration of up to 150 mg CN−/l in the fresh wastewater was degraded during anaerobic treatment at a hydraulic retention time of 3 days. All nitrogen from
the degraded cyanide was converted to organic nitrogen by the biomass of the effluent. The cyanide-degrading biocoenosis of
the anaerobic reactor could tolerate shock concentrations of cyanide up to 240 mg CN−/l for a short time. Up to 5 mmol/l NH4Cl (i.e. 70 mg N/l = 265 mg NH4Cl/l) in the fresh wastewater did not affect cyanide degradation. The bleaching agent sulphite, however, had a negative effect
on COD and cyanide removal. For anaerobic treatment, the maximum COD space loading was 12 g l−1 day−1, equivalent to a hydraulic retention time of 1.8 days. The COD removal efficiency was around 90%. The maximum permanent cyanide
space loading was 50 mg CN− l−1 day−1, with tolerable shock loadings up to 75 mg CN− l−1 day−1. Under steady-state conditions, the cyanide concentration of the effluent was lower than 0.5 mg/l.
Received: 15 August 1997 / Received revision: 10 October 1997 / Accepted: 14 October 1997 相似文献
3.
During cassava starch production, large amounts of cyanoglycosides were released and hydrolysed by plant-borne enzymes, leading
to cyanide concentrations in the wastewater as high as 200 mg/l. For anaerobic degradation of the cyanide during pre-acidification
or single-step methane fermentation, anaerobic cultures were enriched from soil residues of cassava roots and sewage sludge.
In a pre-acidification reactor this culture was able to remove up to 4 g potassium cyanide/l of wastewater at a hydraulic
retention time (t
HR) of 4 days, equivalent to a maximal cyanide space loading of 400 mg CN− l−1 day−1. The residual cyanide concentration was 0.2–0.5 mg/l. Concentrated cell suspensions of the mixed culture formed ammonia and
formate in almost equimolar amounts from cyanide. Little formamide was generated by chemical decay. A concentration of up
to 100 mmol ammonia/l had no inhibitory effect on cyanide degradation. The optimal pH for cyanide degradation was 6–7.5, the
optimal temperature 25–37 °C. At a pH of 5 or lower, cyanide accumulated in the reactor and pre-acidification failed. The
minimal t
HR for continuous cyanide removal was 1.5 days. The enriched mixed culture was also able to degrade cyanide in purely mineralic
wastewater from metal deburring, either in a pre-acidification reactor with a two-step process or in a one-step methanogenic
reactor. It was necessary to supplement the wastewater with a carbon source (e.g. starch) to keep the population active enough
to cope with any possible inhibiting effect of cyanide.
Received: 29 April 1998 / Received revision: 8 June 1998 / Accepted: 14 June 1998 相似文献
4.
Partial nitrification to nitrite using low dissolved oxygen concentration as the main selection factor 总被引:6,自引:0,他引:6
Partial nitrification to nitrite (nitritation) can be achieved in a continuous process without sludge retention by wash out
of nitrite oxidising bacteria (NOB) while retaining ammonia oxidising bacteria (AOB), at elevated temperatures (the SHARON
process) and, as demonstrated in this paper, also at low dissolved oxygen (DO) concentrations. Enriched AOB was attained at
a low DO concentration (0.4 mg l−1) and a dilution rate of 0.42 day−1 in a continuous process. A higher oxygen affinity of AOB compared to NOB seemed critical to achieving this. This was verified
by determining the oxygen half saturation constant, K
o, with similar oxygen mass transfer resistances for enriched AOB and NOB as 0.033 ± 0.003 mg l−1 and 0.43 ± 0.08 mg l−1, respectively. However, the extent of nitritation attained was found to be highly sensitive to process upsets. 相似文献
5.
G. I. Karavaiko T. F. Kondrat’eva E. E. Savari N. V. Grigor’eva Z. A. Avakyan 《Microbiology》2000,69(2):167-173
The role played by a bacterial community composed ofPseudomonas putida, strain 21;Pseudomonas stutzeri, strain 18; andPseudomonas sp., strain 5, and by physical and chemical factors in the degradation of CN− and SCN− was studied. It was shown that the degradation of CN− is determined both by the action of bacteria and by abiotic physical and chemical factors (pH, O2, temperature, the medium agitation rate, etc.). The contribution of chemical degradation was found to increase drastically
at pH below 9.0; when air was blown through the medium (irrespective of the pH value); under active agitation of the medium;
and when the medium surface interfacing air was increased. Even at elevated pH values (9.0-9.2), suboptimal for bacterial
growth, the microbial degradation could account for at most 20–25 mg/1 of CN−, regardless of its initial concentration. When CN− and SCN− were concurrently present in the medium, the former compound was the first to be degraded by microorganisms. The rate of
bacterial degradation of SCN− under continuous cultivation in a chain of reactors was found to depend on its concentration, the medium flow rate, agitation
rate, and the pattern of carbon source supply and could exceed 1 g/(l day). CN− and SCN− are utilized by bacteria solely as nitrogen sources. The mechanism of CN− and SCN− degradation by the microbial community is discussed.
Deceased. 相似文献
6.
Low Nitrification Rates in Acid Scots Pine Forest Soils Are Due to pH-Related Factors 总被引:1,自引:0,他引:1
In a previous study, ammonia-oxidizing bacteria (AOB)-like sequences were detected in the fragmentation layer of acid Scots
pine (Pinus sylvestris L.) forest soils (pH 2.9–3.4) with high nitrification rates (>11.0 μg g−1 dry soil week−1), but were not detected in soils with low nitrification rates (<0.5 μg g−1 dry soil week−1). In the present study, we investigated whether this low nitrification rate has a biotic cause (complete absence of AOB)
or an abiotic cause (unfavorable environmental conditions). Therefore, two soils strongly differing in net nitrification were
compared: one soil with a low nitrification rate (location Schoorl) and another soil with a high nitrification rate (location
Wekerom) were subjected to liming and/or ammonium amendment treatments. Nitrification was assessed by analysis of dynamics
in NH4
+-N and NO3
−-N concentrations, whereas the presence and composition of AOB communities were assessed by polymerase chain reaction–denaturing
gradient gel electrophoresis and sequencing of the ammonia monooxygenase (amoA) gene. Liming, rather than ammonium amendment, stimulated the growth of AOB and their nitrifying activity in Schoorl soil.
The retrieved amoA sequences from limed (without and with N amendment) Schoorl and Wekerom soils exclusively belong to Nitrosospira cluster 2. Our study suggests that low nitrification rates in acidic Scots pine forest soils are due to pH-related factors.
Nitrosospira cluster 2 detected in these soils is presumably a urease-positive cluster type of AOB. 相似文献
7.
Nitrifying granules cultivation in a sequencing batch reactor at a low organics-to-total nitrogen ratio in wastewater 总被引:4,自引:0,他引:4
It is possible to cultivate aerobic granular sludge at a low organic loading rate and organics-to-total nitrogen (COD/N) ratio
in wastewater in the reactor with typical geometry (height/diameter = 2.1, superficial air velocity = 6 mm/s). The noted nitrification
efficiency was very high (99%). At the highest applied ammonia load (0.3 ± 0.002 mg NH4+–N g total suspended solids (TSS)−1 day−1, COD/N = 1), the dominating oxidized form of nitrogen was nitrite. Despite a constant aeration in the reactor, denitrification
occurred in the structure of granules. Applied molecular techniques allowed the changes in the ammonia-oxidizing bacteria
(AOB) community in granular sludge to be tracked. The major factor influencing AOB number and species composition was ammonia
load. At the ammonia load of 0.3 ± 0.002 mg NH4+–N g TSS−1 day−1, a highly diverse AOB community covering bacteria belonging to both the Nitrosospira and Nitrosomonas genera accounted for ca. 40% of the total bacteria in the biomass. 相似文献
8.
Ammonia concentration determines differential growth of ammonia-oxidising archaea and bacteria in soil microcosms 总被引:4,自引:0,他引:4
The first step of nitrification, oxidation of ammonia to nitrite, is performed by both ammonia-oxidising archaea (AOA) and ammonia-oxidising bacteria (AOB) in soil, but their relative contributions to ammonia oxidation and existence in distinct ecological niches remain to be determined. To determine whether available ammonia concentration has a differential effect on AOA and AOB growth, soil microcosms were incubated for 28 days with ammonium at three concentrations: native (control), intermediate (20 μg NH4+-N per gram of soil) and high (200 μg NH4+-N per gram of soil). Quantitative PCR demonstrated growth of AOA at all concentrations, whereas AOB growth was prominent only at the highest concentration. Similarly, denaturing gradient gel electrophoresis (DGGE) analysis revealed changes in AOA communities at all ammonium concentrations, whereas AOB communities changed significantly only at the highest ammonium concentration. These results provide evidence that ammonia concentration contributes to the definition of distinct ecological niches of AOA and AOB in soil. 相似文献
9.
Kinetic analysis on the two-step processes of AOB and NOB in aerobic nitrifying granules 总被引:1,自引:0,他引:1
Fang Fang Bing-Jie Ni Xiao-Yan Li Guo-Ping Sheng Han-Qing Yu 《Applied microbiology and biotechnology》2009,83(6):1159-1169
Complete granulation of nitrifying sludge was achieved in a sequencing batch reactor. For the granular sludge, batch experiments
were conducted to characterize the kinetic features of ammonia oxidizers (AOB) and nitrite oxidizers (NOB) in the granules
using the respirometric method. A two-step nitrification model was established to determine the kinetic parameters of both
AOB and NOB. In addition to nitrification reactions, the new model also took into account biomass maintenance and mass transfer
through the granules. The yield coefficient, maximum specific growth rate, and affinity constant for ammonium for AOB were
0.21 g chemical oxygen demand (COD) g−1 N, 0.09 h−1, and 9.1 mg N L−1, respectively, whereas the corresponding values for NOB were 0.05 g COD g−1 N, 0.11 h−1, and 4.85 mg N L−1, respectively. The model developed in this study performed well in simulating the oxygen uptake rate and nitrogen conversion
kinetics and in predicting the oxygen consumption of the AOB and NOB in aerobic granules. 相似文献
10.
The contribution of ammonia-oxidizing archaea (AOA) to nitrogen removal in wastewater treatment plants (WWTPs) remains unknown.
This study investigated the abundance of archaeal (AOA) and bacterial (ammonia-oxidizing bacteria (AOB)) amoA genes in eight of Bangkok’s municipal WWTPs. AOA amoA genes (3.28 × 107 ± 1.74 × 107–2.23 × 1011 ± 1.92 × 1011 copies l−1 sludge) outnumbered AOB amoA genes in most of the WWTPs even though the plants’ treatment processes, influent and effluent characteristics, removal efficiencies,
and operation varied. An estimation of the ammonia-oxidizing activity of AOA and AOB suggests that AOA involved in autotrophic
ammonia oxidation in the WWTPs. Statistical analysis shows that the numbers of AOA amoA genes correlated negatively to the ammonium levels in effluent wastewater, while no correlation was found between the AOA
amoA gene numbers and the oxygen concentrations in aeration tanks. An analysis of the AOB sequences shows that AOB found in the
WWTPs limited to only two AOB clusters which exhibit high or moderate affinity to ammonia. In contrast to AOB, AOA sequences
of various clusters were retrieved, and they were previously recovered from a variety of environments, such as thermal and
marine environments. 相似文献
11.
In this study, sludge was taken from a municipal wastewater treatment plant that contained a nearly equal number of archaeal
amoA genes (5.70 × 106 ± 3.30 × 105 copies mg sludge−1) to bacterial amoA genes (8.60 × 106 ± 7.64 × 105 copies mg sludge−1) and enriched in three continuous-flow reactors receiving an inorganic medium containing different ammonium concentrations:
2, 10, and 30 mM NH4+–N (28, 140, and 420 mg N l−1). The abundance and communities of ammonia-oxidizing archaea (AOA) and ammonia-oxidizing bacteria (AOB) in enriched nitrifying
activated sludge (NAS) were monitored at days 60 and 360 of the operation. Early on, between day 0 and day 60 of reactor operation,
comparative abundance of AOA amoA genes to AOB amoA genes varied among the reactors depending on the ammonium levels found in the reactors. As compared to the seed sludge, the
number of AOA amoA genes was unchanged in the reactor with lower ammonium level (0.06 ± 0.04 mgN l−1), while in the reactors with higher ammonium levels (0.51 ± 0.33 and 0.25 ± 0.10 mgN l−1), the numbers of AOA amoA genes were deteriorated. By day 360, AOA disappeared from the ammonia-oxidizing consortiums in all reactors. The majority
of the AOA sequences from all NASs at each sampling period fell into a single AOA cluster, however, suggesting that the ammonium
did not affect the AOA communities under this operational condition. This result is contradictory to the case of AOB, where
the communities varied significantly among the NASs. AOB with a high affinity for ammonia were present in the reactors with
lower ammonium levels, whereas AOB with a low affinity to ammonia existed in the reactors with higher ammonium levels. 相似文献
12.
Population dynamics of ammonia-oxidizing bacteria (AOB) in a full-scale aerated submerged biofilm reactor for micropolluted
raw water pretreatment was investigated using molecular techniques for a period of 1 year. The ammonia monooxygenase (amoA) gene fragments were amplified from DNA and RNA extracts of biofilm samples. Denaturing gradient gel electrophoresis (DGGE)
profile based on the amoA messenger RNA approach exhibited a more variable pattern of temporal dynamics of AOB communities than the DNA-derived approach
during the study. Phylogenetic analysis of excised DGGE bands revealed three AOB groups affiliated with the Nitrosomonas oligotropha lineage, Nitrosomonas communis lineage, and an unknown Nitrosomonas group. The population size of betaproteobacterial AOB, quantified with 16S ribosomal RNA gene real-time polymerase chain
reaction assay, ranged from 6.63 × 105 to 2.67 × 109 cells per gram of dry biofilm and corresponded to 0.23–1.8% of the total bacterial fraction. Quantitative results of amoA gene of the three specific AOB groups revealed changes in competitive dominance between AOB of the N. oligotropha lineage and N. communis lineage. Water temperature is shown to have major influence on AOB population size in the reactor by the statistic analysis,
and a positive correlation between AOB cell numbers and ammonia removal efficiency is suggested (r = 0.628, P < 0.05). 相似文献
13.
The effect of cyanide (CN−) on voltage-activated or cAMP-induced passive chloride conductance (G
Cl
) was analyzed in isolated toad skin. Comparatively low concentrations of CN− inhibited G
Cl
almost completely and fully reversibly, regardless of whether it was applied from the mucosal or serosal side. The IC50 was 180 ± 12 μm for voltage-activated G
Cl
and 305 ± 30 μm for the cAMP-inducted conductance. At [CN] <100 μm, the initial inhibition frequently declined partly in the continuous presence of CN−. Inhibition was independent of the presence of Ca2+. Inhibition was stronger at more alkaline pH, which suggests that dissociated CN− is the effective inhibitor. The onset of the inhibition of voltage-activated or cAMP-induced G
Cl
by CN− occurred with half-times of 34 ± 10 sec, whereas reversibility upon washout was twice as fast (18 ± 7 sec). If [CN−] <200 μm was applied under inactivating conditions (serosa −30 mV), the reduction of G
Cl
was stronger upon subsequent voltage-activation than under steady-state activated conditions. This effect was essentially
complete less than 30 sec after apical addition of CN−, but G
t
recovered thereafter partially in the continuous presence of CN−. Dinitrophenol inhibited G
Cl
similarly, while omission of oxygen did not affect it. These observations, as well as the time course of inhibition and the
full reversibility, suggest that interference of CN− with oxidative phosphorylation and subsequent metabolic depletion is not the reason for the inhibition of G
Cl
. We propose that the inhibition is directly on G
Cl
, presumably by competition with Cl− at a rate-limiting site in the pathway. Location and molecular nature of this site remain to be identified.
Received: 8 February 1999/Revised: 22 September 1999 相似文献
14.
Nitrification in fixed-bed reactors treating saline wastewater 总被引:2,自引:0,他引:2
Utomo Sudarno Stephan Bathe Josef Winter Claudia Gallert 《Applied microbiology and biotechnology》2010,85(6):2017-2030
Halophilic nitrifiers belonging to the genus Nitrosomonas and Nitrospira were enriched from seawater and marine sediment samples of the North Sea. The maximal ammonia oxidation rate (AOR) in batch
enrichments with seawater was 15.1 mg N L−1 day−1. An intermediate nitrite accumulation was observed. Two fixed-bed reactors for continuous nitrification with either polyethylene/clay
sinter lamellas (FBR A) or porous ceramic rings (FBR B) were run at two different ammonia concentrations, three different
ammonia loading rates (ALRs), ± pH adjustment, and at an increased upflow velocity. A better overall nitrification without
nitrite accumulation was observed in FBR B. However, FBR A revealed a higher AOR and nitrite oxidation rate of 6 and 7 mg N L−1 h−1, compared to FBR B with 5 and 5.9 mg N L−1 h−1, respectively. AORs in the FBRs were at least ten times higher than in suspended enrichment cultures. Whereas a shift within
the ammonia-oxidizing population in the genus Nitrosomonas at the subspecies level occurred in FBR B with synthetic seawater at an increasing ALR and a decreasing pH, the nitrite oxidizing
Nitrospira population apparently did not change. 相似文献
15.
Community structure and population dynamics of ammonia oxidizers in composting processes of ammonia-rich livestock waste 总被引:2,自引:0,他引:2
Takeshi Yamada Shinya Araki Wakako Ikeda-Ohtsubo Keiko Okamura Akira Hiraishi Hideyo Ueda Yasuichi Ueda Keisuke Miyauchi Ginro Endo 《Systematic and applied microbiology》2013
This study investigated the relationship between the population dynamics of ammonia-oxidizing bacteria (AOB) and archaea (AOA), and changes in the concentrations of nitrogenous compounds during ammonia-rich livestock waste-composting processes. The data showed that ammonia in beef and dairy cow livestock waste-composting piles was slowly oxidized to nitrite and nitrate after approximately 21–35 days under thermophilic or moderately thermophilic and mesophilic conditions. Real-time quantitative PCR (qPCR) assays showed a relative abundance of betaproteobacterial AOB during ammonia oxidation but did not detect AOA in any composting stage. Furthermore, real-time qPCR and terminal-restriction fragment length polymorphism (T-RFLP) analyses for the AOB in two composting processes (beef and dairy cow livestock waste) out of the three studied found that thermophilic or moderately thermophilic uncultured betaproteobacterial AOB from the “compost AOB cluster” contributed to ammonia oxidation during hot composting stages. Non-metric multidimensional scaling analyses of the data from T-RFLP showed that only a few analogous species predominated during composting of beef, dairy cow and pig livestock wastes, and thus, the AOB community structures in the three composting piles operating under different conditions were similar. AOB-targeted clone library analyses revealed that uncultured members of the “compost AOB cluster”, which could be clearly distinguished from the authentic species of the genus Nitrosomonas, were the major constituents of the AOB populations. These results suggested that a limited and unique species of AOB played a role in ammonia oxidation during the composting of ammonia-rich livestock waste. 相似文献
16.
Start-up and stabilization of an Anammox process from a non-acclimatized sludge in CSTR 总被引:1,自引:0,他引:1
Samik Bagchi Rima Biswas Tapas Nandy 《Journal of industrial microbiology & biotechnology》2010,37(9):943-952
Development of an Anammox (anaerobic ammonium oxidation) process using non-acclimatized sludge requires a long start-up period
owing to the very slow growth rate of Anammox bacteria. This article addresses the issue of achieving a shorter start-up period
for Anammox activity in a well-mixed continuously stirred tank reactor (CSTR) using non-acclimatized anaerobic sludge. Proper
selection of enrichment conditions and low stirring speed of 30 ± 5 rpm resulted in a shorter start-up period (82 days). Activity
tests revealed the microbial community structure of Anammox micro-granules. Ammonia-oxidizing bacteria (AOB) were found on
the surface and on the outer most layers of granules while nitrite-oxidizing bacteria (NOB) and Anammox bacteria were present
inside. Fine-tuning of influent NO2
−/NH4
+ ratio allowed Anammox activity to be maintained when mixed microbial populations were present. The maximum nitrogen removal
rate achieved in the system was 0.216 kg N/(m3 day) with a maximum specific nitrogen removal rate of 0.434 g N/(g VSS day). During the study period, Anammox activity was
not inhibited by pH changes and free ammonia toxicity. 相似文献
17.
Vasil'ev LA Dzyubinskaya EV Kiselevsky DB Shestak AA Samuilov VD 《Biochemistry. Biokhimii?a》2011,76(10):1120-1130
Ubiquinone or plastoquinone covalently linked to synthetic decyltriphenylphosphonium (DTPP+) or rhodamine cations prevent programmed cell death (PCD) in pea leaf epidermis induced by chitosan or CN−. PCD was monitored by recording the destruction of cell nuclei. CN− induced the destruction of nuclei in both epidermal cells (EC) and guard cells (GC), whereas chitosan destroyed nuclei in
EC not in GC. The half-maximum concentrations for the protective effects of the quinone derivatives were within the pico-
and nanomolar range. The protective effect of the quinones was removed by a protonophoric uncoupler and reduced by tetraphenylphosphonium
cations. CN−-Induced PCD was accelerated by the tested quinone derivatives at concentrations above 10−8–10−7 M. Unlike plastoquinone linked to the rhodamine cation (SkQR1), DTPP+ derivatives of quinones suppressed menadione-induced H2O2 generation in the cells. The CN−-induced destruction of GC nuclei was prevented by DTPP+ derivatives in the dark not in the light. SkQR1 inhibited this process both in the dark and in the light, and its effect
in the light was similar to that of rhodamine 6G. The data on the protective effect of cationic quinone derivatives indicate
that mitochondria are involved in PCD in plants. 相似文献
18.
Start-up and inhibition analysis of the Anammox process seeded with anaerobic granular sludge 总被引:4,自引:0,他引:4
Chong-jian Tang Ping Zheng Qaisar Mahmood Jian-wei Chen 《Journal of industrial microbiology & biotechnology》2009,36(8):1093-1100
The longer start-up period of the Anammox process is due to the very low cellular yield and growth rates of Anammox bacteria.
Nitrite inhibition is considered to be the key factor in the instability of the Anammox process during the operation. However,
little attention was paid to the inhibitory effect of pH and free ammonia. This paper presents start-up and inhibition analysis
of an Anammox biofilm reactor seeded with anaerobic granular sludge. Results showed that the start-up period could be divided
into the sludge lysis phase, lag phase, propagation phase, stationary phase and inhibition phase. Optimization control could
be implemented correspondingly to accelerate the start-up of Anammox bioreactors. Effluent pH increased to 8.7–9.1 when the
nitrogen removal rate was higher than 1,200 mg l−1 day−1. The free ammonia concentration was accompanied with a higher level of 64–73 mg l−1. Inhibitory effects of high pH and free ammonia on Anammox bacteria contributed to the destabilization of the Anammox bioreactor
during the first 125 days with influent KHCO3 of 0.5 g l−1. Increasing the suffering capacity in the inlet by dosing 1.25 g KHCO3 l−1 effectively reduced the pH variation, and the nitrogen removal performance of the reactor was further developed. 相似文献
19.
Experimental measurement of sediment nitrification and denitrification in Hamilton Harbour,Canada 总被引:1,自引:0,他引:1
This research examines the role of sediment nitrification and denitrification in the nitrogen cycle of Hamilton Harbour. The
Harbour is subject to large ammonia and carbon loadings from a waste-water treatment plant and from steel industries. Spring
ammonia concentrations rapidly decrease from 4.5 to 0.5 mg 1−1, while spring nitrate concentrations increase from 1 to 2 mg l−1, by mid-summer. A three-layer sediment model was developed. The first layer is aerobic; in it, oxidation of organics and
nitrification occurs. The second layer is for denitrification, and the third layer is for anaerobic processes. Ammonia sources
for nitrification include diffusion from the water column, sources associated with the oxidation of organics, sources from
denitrification and from anaerobic processes. Diffusion of oxygen, ammonia and nitrate across the sediment-water interface
occurs. Temperature effects are modelled using the Arrhenius concept. A combination of zero-order kinetics for nitrate or
ammonia consumption with diffusion results in a half-order reaction, with respect to the water column loss rate to sediments.
From experimental measurement, the rate of nitrification is 200 mg N 1−1 sediment per day, while that of denitrification is 85 mg N 1–1 sediment per day at 20 °C. The Arrhenius activation energy
is estimated as 15 000 cal/ mole-K and 17 000 cal/ mole-K for nitrification and denitrification, respectively, between 10
°C and 20 °C. Calculations of the flux of ammonia with the sediments, using the biofilm model, compare favourably with experimental
observations. The ammonia flux from the water column is estimated to account for 20% of the observed decrease in water column
stocks of ammonia, while the nitrate flux from the water column is estimated to account for 25% of the total nitrogen produced
by the sediments. 相似文献
20.
Changes of microbial characteristics in a full-scale submerged membrane bioreactor system (capacity, 60,000 m3 day−1) treating sewage were monitored over the start-up period (96 days). Fluorescence in situ hybridization analysis showed that
the percentages of ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (nitrobacter-related population) in total
bacteria counted with DAPI staining increased significantly from 1.9% and 0.9% to 4.5% and 2.8%, corresponding to an increase
of the specific ammonium oxidizing rate (from 0.06 to 0.12 kg N kg−1 mixed liquor suspended solids (MLSS) per day) and the specific nitrate forming rate (from 0.05 to 0.10 kg N kg−1 MLSS day−1). Both the denaturing gradient gel electrophoresis of polymerase chain reaction and clone library results showed that the
AOB was dominated by the genus Nitrosomonas, the diversity of which increased markedly with operational time. Most of the day 2 clones were closely related with the
uncultured Nitrosomonas sp. clone Ninesprings-49S amoA gene (AY356450.1) originated from activated sludge, while the day 96 clone library showed a more diverse distribution characterized
by the appearance of the oligotrophic nitrifiers like the Nitrosomonas oligotropha- and Nitrosomonas ureae-like bacteria, perhaps due to the interception by membrane and the low food-to-microorganisms ratio environment. The above
results show that the membrane bioreactor system was characterized by the increased diversity and percentage of nitrifiers,
which made it possible to achieve a stable and high efficient nitrification. Ammonia-oxidizing archaea with the changing population
structures were also detected, but their roles for ammonia oxidation in the system need further studies. 相似文献