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PubMed1980

Acceleration by montmorillonite of nitrification in soil.

A soil naturally containing montmorillonite (M) was amended with 10% M and sequentially perfused with glyeme, with fresh glyeme being added every 16--17d after nitrification of the previously added glycine-nitrogen had reached a plateau. In some systems, the old perfusates were replaced each time with a fresh glycine solution; in others, the initial perfusate was not replaced but only adjusted each time to the original 200 ml volume and a comparable glycine concentration (140 micrograms NH2-N/ml). The incorporation of M enhanced the rates of heterotrophic degradation of glycine and subsequent autotrophic nitrification, but these stimulatory effects decreased with each successive perfusion. The reasons for these decreases are not known, but they did not appear to be related to inorganic nutrition, as perfusion with a mixed cation solution after five perfusion cycles did not significantly enhance nitrification in either the check or M-amended soils during three subsequent perfusions with glycine. The enhancement of nitrification by M appeared to be a result, in part, of the greater buffering capacity of the M-amended soil, as indicated by lesser reductions in the pH of perfusates from the M-amended soil, by titration curves of the soils, and by the greater and longer stimulation of nitrification in the check soil amended with 1% CaCO3, which had a greater buffering capacity than did M. The stimulation by CaCO3 may also have been partially the result of providing CO2 for the autotrophic nitrifyers. Significant concentrations of nitrite accumulated only in perfusates from soil amended with CaCO3. Air-drying and remoistening the soils enhanced nitrification of subsequently added glycine, especially in the check soil. The importance of pH-mediation, of the production of inhibitors, and/or of feed-back inhibition was indicated by the lower rate and extent of nitrification in systems wherein the perfusates were not replaced between successive additions of glycine. Although the results of these studies confirmed previous observations that M enhances the rate of nitrification in soil, the mechanisms responsible for this stimulation are still not known.

Bentonite↗
PubMed2006

Low nitrification rates in acid Scots pine forest soils are due to pH-related factors.

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 microg g-1 dry soil week-1), but were not detected in soils with low nitrification rates (<0.5 microg 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.

Bacteria↗
PubMed2005

Quantification of ammonia-oxidizing bacteria and factors controlling nitrification in salt marsh sediments.

To elucidate the geomicrobiological factors controlling nitrification in salt marsh sediments, a comprehensive approach involving sediment geochemistry, process rate measurements, and quantification of the genetic potential for nitrification was applied to three contrasting salt marsh habitats: areas colonized by the tall (TS) or short (SS) form of Spartina alterniflora and unvegetated creek banks (CBs). Nitrification and denitrification potential rates were strongly correlated with one another and with macrofaunal burrow abundance, indicating that coupled nitrification-denitrification was enhanced by macrofaunal burrowing activity. Ammonia monooxygenase (amoA) gene copy numbers were used to estimate the ammonia-oxidizing bacterial population size (5.6 x 10(4) to 1.3 x 10(6) g of wet sediment(-1)), which correlated with nitrification potentials and was 1 order of magnitude higher for TS and CB than for SS. TS and CB sediments also had higher Fe(III) content, higher Fe(III)-to-total reduced sulfur ratios, higher Fe(III) reduction rates, and lower dissolved sulfides than SS sediments. Iron(III) content and reduction rates were positively correlated with nitrification and denitrification potential and amoA gene copy number. Laboratory slurry incubations supported field data, confirming that increased amounts of Fe(III) relieved sulfide inhibition of nitrification. We propose that macrofaunal burrowing and high concentrations of Fe(III) stimulate nitrifying bacterial populations, and thus may increase nitrogen removal through coupled nitrification-denitrification in salt marsh sediments.

Ammonia↗
PubMed2006

Boosting nitrification by membrane-attached biofilm.

Nitrification is a key step for reliable biological nitrogen removal. In order to enhance nitrification in the activated sludge (AS) process, membrane-attached biofilm (MAB) was incorporated in a conventional activated sludge tank. Simultaneous organic carbon removal and nitrification of the MAB incorporated activated sludge (AS + MAB) process was investigated with continuous wastewater treatment. The effluent TOC concentration of AS and the AS + MAB processes were about 6.3 mg/L and 7.9 mg/L, respectively. The TOC removal efficiency of both AS and AS + MAB were above 95% during the wastewater treatment, indicating excellent organic carbon removal performance in both processes. Little nitrification occurred in the AS process. On the contrary, successful nitrification was obtained with the AS + MAB process with nitrification efficiency of about 90%. The volumetric and surface nitrification rates were about 0.14 g/Ld and 6.5 g/m2d, respectively. The results clearly demonstrated that nitrification in the conventional AS process was boosted by MAB. Furthermore, the microfaunal population in the AS + MAB process was different from that in the AS process. The high concentration of rotifers in the AS + MAB process was expected to decrease the generation of excess sludge in the process.

Bacteria↗
PubMed2003

Inhibition of nitrification in soil by metal diethyldithiocarbamates.

Nitrification acts as a key process in determining fertilizer use efficiency by crops as well as nitrogen losses from soils. Metal dithiocarbamates in addition to their pesticidal properties can also inhibit biological oxidation of ammonium(nitrification) in soil. Metal [M = V(III), Cr(III), Mn(II), Fe(III), Ni(II), Cu(II), Zn(II) and Co(II)] diethyldithiocarbamates (DEDTC) were synthesized by the reaction of sodium diethyldithiocarbamate with metal chloride in dichloromethane/water mixture. These metal diethyldithiocarbamates were screened for their ability to inhibit nitrification at different concentrations( 10 microg/g soil, 50 microg/g soil and 100 microg/g soil). With increasing concentration of the complex, capacity to retard nitrification increased but the extent of increase varied for different metals. At 100 microg/g soil, different complexes showed nitrification inhibition from 22.36% to 46.45% . Among the diethyldithiocarbamates tested, Zn(DEDTC)2 proved to be the most effective nitrification inhibitor at 100 microg/g soil. Manganese, iron and chromium diethyldithiocarbamates also proved to be effective nitrification inhibitors than the others at 100 microg/g soil. The order of percent nitrification inhibition in soil by metal diethyldithiocarbamates was: Zn(II) > Mn(II) > Fe(III) > Cr(III) > V(III) > Co(II) > Ni(II) > Cu(II).

Ammonia↗
PubMed1992

Heterotrophic nitrification and aerobic denitrification in Alcaligenes faecalis strain TUD.

Heterotrophic nitrification and aerobic and anaerobic denitrification by Alcaligenes faecalis strain TUD were studied in continuous cultures under various environmental conditions. Both nitrification and denitrification activities increased with the dilution rate. At dissolved oxygen concentrations above 46% air saturation, hydroxylamine, nitrite and nitrate accumulated, indicating that both the nitrification and denitrification were less efficient. The overall nitrification activity was, however, essentially unaffected by the oxygen concentration. The nitrification rate increased with increasing ammonia concentration, but was lower in the presence of nitrate or nitrite. When present, hydroxylamine, was nitrified preferentially. Relatively low concentrations of acetate caused substrate inhibition (KI = 109 microM acetate). Denitrifying or assimilatory nitrate reductase were not detected, and the copper nitrite reductase, rather than cytochrome cd, was present. Thiosulphate (a potential inhibitor of heterotrophic nitrification) was oxidized by A. faecalis strain TUD, with a maximum oxygen uptake rate of 140-170 nmol O2.min-1.mg prot-1. Comparison of the behaviour of A. faecalis TUD with that of other bacteria capable of heterotrophic nitrification and aerobic denitrification established that the response of these organisms to environmental parameters is not uniform. Similarities were found in their responses to dissolved oxygen concentrations, growth rate and ammonia concentration. However, they differed in their responses to externally supplied nitrite and nitrate.

Aerobiosis↗
PubMed2004

Bioaugmentation for nitrification at cold temperatures.

Bioaugmentation of nitrifying bacteria for short solids retention time (short-SRT) nitrification is an attractive alternative for wastewater treatment plants in cold climates or for those in the process of upgrading to include nitrification. One possible source of ammonia for the production of nitrifying bacteria is the liquor generated during the dewatering of anaerobically digested sludges. The objectives of this study was to determine the impact of sudden decrease in temperature on nitrification rates and to determine if nitrification could be accomplished in sequencing batch reactors (SBRs) at 10 degrees C by seeding nitrifying bacteria acclimated to 20 degrees C. In this research, biomass produced during warm nitrification of dewatering liquor was seeded into cold SBRs at various hydraulic retention times from 43.3 to 96 h. The average decreases in nitrification rates were 58%, 71% and 82% for biomass cooled to 10 degrees C when the biomass was acclimated to 20 degrees C, 25 degrees C and 30 degrees C, respectively. The seeded SRTs of the cold SBRs were raised above the minimum solids retention time (SRT(min)) required for nitrification. Full ammonia nitrogen removal was achieved in cold SBRs that were operated at an apparent SRT less than SRT(min).

Bacteria, Anaerobic↗
PubMedDate not supplied

Nitrification modelling in biofilms under inhibitory conditions.

A biofilm model has been developed for simulating nitrification in biofilms under inhibitory conditions. Nitrification inhibition has been modelled using uncompetitive inhibition kinetics. Inhibition kinetic experiments were performed by varying the bulk concentrations of inhibitory compound, aniline. Two sets of results were obtained with a nitrifying biofilm that was unacclimated to aniline and another which was acclimated to aniline. Fitting of the nitrification inhibition biofilm model to the experimental results yielded the nitrification inhibition constant, Ki, for aniline. Both the experiments yielded a value of about 3mg/L for Ki, which was similar to that obtained during nitrification inhibition experiments with suspended growth process carried out in an earlier study. The nitrification inhibition biofilm model is general and can be applied to nitrification inhibition with other toxic compounds.

Aniline Compounds↗
PubMed2002

Biological nitrogen removal from municipal landfill leachate: low-cost nitrification in biofilters and laboratory scale in-situ denitrification.

The slow leaching of nitrogen from solid waste in landfills, resulting in high concentrations of ammonia in the landfill leachate, may last for several decades. The removal of nitrogen from leachate is desirable as nitrogen can trigger eutrophication in lakes and rivers. In the present study, a low-cost nitrification-denitrification process was developed to reduce nitrogen load especially in leachates from small landfills. Nitrification was studied in laboratory and on-site pilot aerobic biofilters with waste materials as filter media (crushed brick in upflow filters and bulking agent of compost in a downflow filter) while denitrification was studied in a laboratory anoxic/anaerobic column filled with landfill waste. In the laboratory nitrification filters, start-up of nitrification took less than 3 weeks and over 90% nitrification of leachate (NH4-N between 60 and 170mg N l(-1), COD between 230 and 1,300 mg l(-1)) was obtained with loading rates between 100 and 130 mgNH4-N l(-1) d at 25 degrees C. In an on-site pilot study a level of nitrification of leachate (NH4-N between 160 and 270 mg N l(-1), COD between 1,300 and 1,600 mg l(-1)) above 90% was achieved in a crushed brick biofilter with a loading rate of 50mg NH4-N l(-1) d even at temperatures as low as 5-10 degrees C. Ammonium concentrations in all biofilter effluents were usually below the detection limit. In the denitrification column. denitrification started within 2 weeks and total oxidised nitrogen in nitrified leachate (TON between 50 and 150mg N l(-1)) usually declined below the detection limit at 25 degrees C, whereas some ammonium, probably originating from the landfill waste used in the column, was detected in the effluent. No adverse effect was observed on the methanation of waste in the denitrification column with a loading rate of 3.8 g TON-N/t-TS(waste) d. In conclusion, nitrification in a low-cost biofilter followed by denitrification in a landfill body appears applicable for the removal of nitrogen in landfill leachate in colder climates.

Biofilms↗
PubMed2003

Nitrification with high nitrite accumulation for the treatment of wastewater with high ammonia concentration.

The objective of this paper was to determine the best conditions for partial nitrification with nitrite accumulation of simulated industrial wastewater with high ammonia concentration, lowering the total oxygen needed in the nitrification step, which may mean great saving in aeration. Dissolved oxygen (DO) concentration and pH were selected as operational parameters to study the possibility of nitrite accumulation not affecting overall ammonia removal. A 2.5L activated sludge reactor was operated in nitrification mode, feeding a synthetic wastewater simulating an industrial wastewater with high ammonia concentration. During the start-up a pH of 7.85 and a DO of 5.5mg/L were used. The reactor was operated until stable operation was achieved at final nitrogen loading rate (NLR) of 3.3kgN- NH(4)(+)/m(3)d with an influent ammonia concentration of 610mg N-NH(4)(+)/L. The influence of pH was studied in continuous operation in the range of 6.15-9.05, changing the reactor pH in steps until ammonia accumulation (complete nitrification inhibition) took place. The influence of DO was studied in the same mode, changing the DO in steps from 5.5 to 0.5mg/L. The pH was not a useful operational parameter in order to accumulate nitrite, because in the range of pH 6.45-8.95 complete nitrification to nitrate occurs. At pH lower than 6.45 and higher than 8.95 complete inhibition of nitrification takes place. Setting DO concentration in the reactor at 0.7mg/L, it was possible to accumulate more than 65% of the loaded ammonia nitrogen as nitrite with a 98% ammonia conversion. Below 0.5mg/L of DO ammonia was accumulated and over a DO of 1.7mg/L complete nitrification to nitrate was achieved. In conclusion, it is possible under the conditions of this study, to treat high ammonia synthetic wastewater achieving an accumulation of at least 65% of the loaded nitrogen as nitrite, operating at a DO around 0.7mg/L. This represents a reduction close to 20% in the oxygen necessary, and therefore a considerable saving in aeration.

Ammonia↗
PubMed1986

Distinguishing between Nitrification and Denitrification as Sources of Gaseous Nitrogen Production in Soil.

The source of N(2)O produced in soil is often uncertain because denitrification and nitrification can occur simultaneously in the same soil aggregate. A technique which exploits the differential sensitivity of these processes to C(2)H(2) inhibition is proposed for distinguishing among gaseous N losses from soils. Denitrification N(2)O was estimated from 24-h laboratory incubations in which nitrification was inhibited by 10-Pa C(2)H(2). Nitrification N(2)O was estimated from the difference between N(2)O production under no C(2)H(2) and that determined for denitrification. Denitrification N(2) was estimated from the difference between N(2)O production under 10-kPa C(2)H(2) and that under 10 Pa. Laboratory estimates of N(2)O production were significantly correlated with in situ N(2)O diffusion measurements made during a 10-month period in two forested watersheds. Nitrous oxide production from nitrification was most important on well-drained sites of a disturbed watershed where ambient NO(3) was high. In contrast, denitrification N(2)O was most important on poorly drained sites near the stream of the same watershed. Distinction between N(2)O production from nitrification and denitrification was corroborated by correlations between denitrification N(2)O and water-filled pore space and between nitrification N(2)O and ambient NO(3). This technique permits qualitative study of environmental parameters that regulate gaseous N losses via denitrification and nitrification.

Journal Article↗
PubMed1998

Biosensor determination of the microscale distribution of nitrate, nitrate assimilation, nitrification, and denitrification in a diatom-inhabited freshwater sediment

High-resolution NO3- profiles in freshwater sediment covered with benthic diatoms were obtained with a new microscale NO3- biosensor characterized by absence of interference from chemical species other than NO2- and N2O. Analysis of the microprofiles obtained indicated no nitrification during darkness, high rates of nitrification and a tight coupling between nitrification and denitrification during illumination, and substantial rates of NO3- assimilation during illumination. Nitrification during darkness could be induced by purging the bulk water with O2 gas, indicating that the stimulatory effect on nitrification by illumination was caused by algal production of O2. NH4+ addition did not stimulate nitrification during darkness when O2 was restricted to the upper 1-mm layer, and there was thus a low nitrification potential in the permanently oxic top 1 mm of the sediment.

Journal Article↗
PubMed2006

Biosensor-based control of nitrification inhibitor in municipal wastewater treatment plants.

The effect of potassium cyanide (KCN) on nitrification processes in municipal wastewater treatment plants was studied by batch nitrification tests, which indicated that nitrification processes tend to be inhibited at a lower KCN concentration than the present discharge standard to sewerage. The experiment of the biosensor using nitrifying bacteria was also conducted for continuous monitoring of nitrification inhibitor in influent wastewater, and demonstrated that the biosensor can detect KCN at as low as EC10 of the abovementioned batch nitrification test. Moreover, to determine the effectiveness of application of the biosensor to avoid the impact of KCN due to an accidental spillage in a sewerage system, KCN was intentionally injected into the experimental models of activated sludge process equipped both with and without the biosensor. The model with the biosensor that could detect KCN could divert the wastewater including KCN to a refuge tank, which resulted in the avoidance of upset of the activated sludge process. On the other hand, the model without the biosensor was upset in the nitrification process due to KCN. Such differences demonstrate the effectiveness of the biosensor applied to countermeasures of an accidental spillage of toxic chemicals to avoid upset of nitrification in municipal wastewater treatment plants.

Bioreactors↗
PubMedDate not supplied

Modeling of nitrification inhibition with aniline in suspended-growth processes.

Nitrification inhibition due to aniline was investigated in completely mixed suspended-growth, batch, and continuous processes. Synthetic wastewater was used with aniline as the carbon source. The experiments were conducted at aniline concentrations inhibitory to nitrifier organisms. In the batch tests, degradation took place rapidly (within 4 to 6 hours) for initial aniline concentrations below 100 mg/L, with nitrification picking up as soon as the aniline concentration decreased to less than 3 to 4 mg/L. For initial aniline concentrations of 250 mg/L and higher, complete nitrification did not take place even though the aniline concentration decreased to less than 3 to 4 mg/L. This observation indicated nitrifier inhibition due to aniline. In the continuous experiments, a hydraulic residence time of 8 to 24 hours and a solids retention time of 8 to 24 days were maintained. Complete nitrification took place at bulk aniline concentrations less than 0.5 mg/L, while at higher aniline concentrations, nitrification inhibition took place. The inhibitory effect of aniline on the nitrification process was modeled using uncompetitive inhibition kinetics. Modeling of batch processes yielded the value for the inhibition constant for aniline, Ki, as 3.3 mg/L. Modeling of continuous processes yielded criteria for stable process operation for nitrification under inhibitory conditions, which were also confirmed through experimental results.

Aniline Compounds↗
PubMed2002

Nitrification in reed beds--capacity and potential control methods.

Vertical-flow reed beds (VFBs) are known to be very effective regarding nitrification. However, a generally accepted design formula for dimensioning reed beds for a controlled nitrification process has still not been found. Especially for the purpose of nitrification a vertical-flow reed bed (VFB) has been installed following an existing unaerated pond-system. The paper presents the results concerning the limits of the VFB's performance as well as the main factors influencing the nitrification process gained by balancing the conversion rates under different loads. Even under high loads the VFB provides an excellent nitrification performance, which is mainly influenced by the wastewater temperature. The ammonia oxidation rate is about 90% at temperatures over 10 degrees C; at temperatures below 5 degrees C the average nitrification rate is still approximately 50%. The hydraulic load and the TKN load have almost no impact on this efficiency (the maximum load has been: 180 mm/d, 7.1 g TKN/(m2 x d)). The redox potenial, which is continuously measured in the effluent of the reed bed, proved to be dependent on the current nitrification performance and the oxygen supply of the VFB, and therefore appears to be a suitable control parameter for the operation of VFBs.

Ecosystem↗
PubMed2003

Improving nitrogen removal in predenitrification-nitrification biofilters.

The effect on NH4-N removal rates in nitrification biofilters of filtered biodegradable COD and particulate COD leaving predenitrification biofilters was studied in a lab scale plant configured with the separated system of biofilters for secondary nitrogen removal from urban wastewaters. Applying a typical COD load of 11 kg/m3 x day to the predenitrification biofilter and maximizing its COD removal by adding nitrates or by operating an improved control of the internal recycle, only 60% removal of filtered biodegradable COD was found. This value corresponds to the complete removal of the readily biodegradable substrate (30% of influent filtered COD) and 36% of filtered slowly biodegradable substrate (50% of influent COD). The remaining 64% of the latter entered the nitrification biofilter, causing competition between heterotrophs and nitrifiers for dissolved oxygen in the inner layers of the biofilm. Consequently the nitrification rate had relatively low values (0.5 kgN/m3 x d) at 14 degrees C despite using dissolved oxygen levels of 6 mg/l. This behaviour may explain the lower nitrification rates obtained in some cases of nitrification biofilters compared to those in tertiary nitrification after activated sludge processes. The particulate COD entering the nitrification biofilter is associated with the suspended solids leaving the denitrification biofilter which are adsorbed by the external layers of the biofilm, increasing its thickness. The activity of the nitrifiers was affected because of a lack of oxygen when the thickness was left to grow considerably. Therefore no significant particulate COD effect is expected to occur as long as backwashing is carried out with the appropriate frequency.

Adsorption↗
PubMed2005

[Stability of shortcut nitrification-denitrification].

The effects of temperature and aeration time on the stability of shortcut nitrification-denitrification are studied specially in some experiments are carried on a sequencing batch reactor (SBR) fed with soybean wastewater. Results show that shortcut nitrification-denitrification achieved by controlling temperature was not stable until the temperature was more than 28 degrees C. In addition, for the first time strong effect of excess aeration on shortcut nitrification-denitrification is observed. When the system run under excess aeration for twelve days, the type of nitrification turned from shortcut nitrification which nitrosation rate (NO2(-)-N/NOx(-) -N) was more than 96% to complete nitrification which nitrosation rate (NO2(-) -N/NOx(-) -N) was less than 39.3%. So, in order to make shortcut nitrification-denitrification run stably, real-time process control must be used.

Bioreactors↗
PubMed2004

Chemical inhibition of nitrification in activated sludge.

Conventional aerobic nitrification was adversely affected by single pulse inputs of six different classes of industrially relevant chemical toxins: an electrophilic solvent (1-chloro-2,4-dinitrobenzene, CDNB), a heavy metal (cadmium), a hydrophobic chemical (1-octanol), an uncoupling agent (2,4-dinitrophenol, DNP), alkaline pH, and cyanide in its weak metal complexed form. The concentrations of each chemical source that caused 1 5, 25, and 50% respiratory inhibition of a nitrifying mixed liquor during a short-term assay were used to shock sequencing batch reactors containing nitrifying conventional activated sludge. The reactors were monitored for recovery over a period of 30 days or less. All shock conditions inhibited nitrification, but to different degrees. The nitrate generation rate (NGR) of the shocked reactors recovered overtime to control reactor levels and showed that it was a more sensitive indicator of nitrification inhibition than both initial respirometric tests conducted on unexposed biomass and effluent nitrogen species analyses. CDNB had the most severe impact on nitrification, followed by alkaline pH 11, cadmium, cyanide, octanol, and DNP. Based on effluent data, cadmium and octanol primarily inhibited ammonia-oxidizing bacteria (AOB) while CDNB, pH 11,and cyanide inhibited both AOB and nitrite-oxidizing bacteria (NOB). DNP initially inhibited nitrification but quickly increased the NGR relative to the control and stimulated nitrification after several days in a manner reflective of oxidative uncoupling. The shocked mixed liquor showed trends toward recovery from inhibition for all chemicals tested, but in some cases this reversion was slow. These results contribute to our broader effort to identify relationships between chemical sources and the process effects they induce in activated sludge treatment systems.

1-Octanol↗