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PubMed2004

Rate of nitrate production during a two-stage nitrification batch reaction.

The two steps of nitrification, namely the oxidation of ammonia to nitrite and nitrite to nitrate, often need to be considered separately in process studies. It has been assumed that these two reactions can be described by single Monod models. In this paper, the suitability of the single Monod model for describing nitrite oxidation to nitrate is discussed. The measured rate of nitrate production during a batch reaction is presented. For the system studied it was found that nitrate production actually increased after the completion of ammonia oxidation. It is suggested that the reason for the increase was a combination of: (i) likely competition for oxygen when both substrates were present, and (ii) a decrease in ammonia inhibition of nitrite oxidisers with the removal of ammonia. The result is that a single Monod expression (based on nitrite as the substrate) could not be used to describe nitrate production. In these types of systems the consequence of oxygen limitation and substrate inhibition should also be considered.

Ammonia↗
PubMed2005

[Effects of urease and nitrification inhibitors on alleviating the oxidation and leaching of soil urea's hydrolyzed product ammonium].

With simulation test of in-situ soil column, this paper studied the effects of urease inhibitor hydroquinone (HQ), nitrification inhibitors coated calcium carbide (ECC) and dicyandiamide (DCD),and their different combinations on the persistence, oxidation, and leaching of soil urea's hydrolyzed product ammonium. The results showed that compared with other treatments, the combination of HQ and DCD could effectively inhibit the oxidation of the ammonium, and make it as exchangeable form reserve in soil in a larger amount and a longer period. The inhibition of this oxidation not only decreased the accumulation of oxidized product NO3- in soil, but also decreased the potential of NO3- leaching, making the NO3- only leach to 5-10 cm in depth, and the leached amount significantly decreased.

Acetylene↗
PubMed2005

Role of nitrification inhibitor DMPP (3, 4-dimethylpyrazole phosphate) in NO(3-)-N accumulation in greengrocery( Brassica campestris L. ssp. chinensis) and vegetable soil.

The influence of nitrification inhibitor (NI) 3, 4-dimethylpyrazole phosphate (DMPP) on nitrate accumulation in greengrocery (Brassica campestris L. ssp. chinensis) and vegetable soil at surface layer were investigated in field experiments in 2002 and 2003. Results showed that NI DMPP took no significant effect on yields of edible parts of greengrocery, but it could significantly decrease NO(3-)-N concentration in greengrocery and in vegetable soil at surface layer. In addition, NI DMPP could reduce the NO(3-)-N concentration during the prophase stage of storage.

Biological Transport↗
PubMed2005

Comparison of nitrification performance and microbial community between submerged membrane bioreactor and conventional activated sludge system.

A submerged membrane bioreactor (SMBR) and a conventional activated sludge system (CAS) were compared in parallel over a period of more than 260 days on treating synthetic ammonia-bearing inorganic wastewater without sludge purge under decreased hydraulic retention times (HRTs). Conversion of NH4(+)-N to NO3(-)-N was achieved with an efficiency of over 98% at an HRT > or = 10 h in the SMBR, while similar performance was obtained at an HRT > or = 20 h in the CAS. Denaturing gradient gel electrophoresis (DGGE) of polymerase chain reaction (PCR) amplified 16S rDNA was used to monitor variations of community structures in the two systems. With the prolongation of operation, the number of DGGE bands in the SMBR gradually increased from the initial 11 bands to the final 22 bands, whereas that in the CAS varied in a range between 13 and 183 Sequence analysis indicates that Nitrosomonas sp. and Nitrospira sp. were the dominating nitrification species responsible for ammonia and nitrite oxidation, respectively. Heterotrophic bacteria like Pseudomonas sp. and Flavobacteria sp. existed in both of the systems although only inorganic wastewater was fed. Substantive accumulation of extracellular polymeric substances (EPS) in the SMBR was confirmed by scanning electron microscopy and EPS analysis.

Ammonia↗
PubMed2005

Processes in vertical-flow reed beds: nitrification, oxygen transfer and soil clogging.

Vertical-flow reed beds (VF) with intermittent feeding are extremely reliable regarding aerobic processes. For a save operation with high nitrification rates and without soil clogging it is essential to preserve aerobic conditions in the filter. The challenge is to keep aerobic conditions in the filter without oversizing the system (economical aspects). It is very difficult to determine the current oxygen content in the filters because it ultimately results from complex interactions of a large number of different influencing parameters such as loading rate, degree of clogging, temperature, and hydraulic behaviour of the reed bed. To gain better knowledge of this complex system, different tests and examinations were carried out over several years. Focusing on the questions of identification and the description of conversion and transport processes (water/gas), a full-scale treatment plant under clogged and non-clogged conditions was investigated in detail. Additionally soil column test were carried out. The results make it possible to describe some of the processes and their interactions in the filter body. Recommendations for a safe and controlled operation can be derived.

Bacteria, Aerobic↗
PubMed2005

Nitrification parameter measurement for plant design: experience and experimental issues with new methods.

Nitrification kinetics are important for process design, optimization, and capacity rating of activated sludge wastewater treatment plants. A Water Environment Research Foundation (WERF) project on Methods for Wastewater Characterization in Activated Sludge Modeling (WERF, 2003) focused significantly on the development of procedures for measuring the nitrifier maximum specific growth rate, micro(AUT). In addition, the importance of (and lack of data for) the nitrifier decay rate, b(AUT), was identified. This paper describes three bench-scale methods for measuring micro(AUT): the Low F/M SBR, Washout and High F/M methods. During the WERF project, the importance of pH and temperature control was investigated briefly; this paper summarizes further experimental work performed to address these issues. A summary of micro(AUT) measurements in a number of locations and using the different measurement techniques is provided.

Computer Simulation↗
PubMed2005

Partial nitrification of wastewater from an aminoplastic resin producing factory.

Nitrification via nitrite was studied in two aerobic reactors treating wastewater from an aminoplastic resin producing factory at HRT varying between 1.37-1.89 and 2.45-3.63 days. Both eactors were fed with concentrations of 366, 450, 1099 and 1899 mg N-NH4+/L. In general in the reactor operated at a lower HRT, the nitritation percentage decreased from 87.2 to 21.6%, while the nitratation percentage remained always lower than 2.5% (except in the last period) when the ammonium concentration was increased. This behaviour could be due to the inhibition of the ammonium and nitrite oxidation produced by high free ammonia concentrations up to 179.3 mg N-NH3/L. In the reactor operated at a higher HRT, the nitritation percentage decreased and the nitratation percentage increased from 88.6 to 39.6% and from 0.65 to 35.7%, respectively, due to an increase of the dissolved oxygen concentration from 0.76 to 1.02 mg O2/L. However, when ammonium was fed at a concentration of 1898.7 mg N-NH4+/L, the nitritation increased and the nitratation decreased, probably as a result of the accumulation of free ammonia up to 2.04 mg N-NH3/L, meaning that nitrite oxidizers were inhibited. Nitrite build-up was observed after each modification of ammonium concentration in the feed.

Aerobiosis↗
PubMed2006

[Nitrification and denitrification in BACF for treating high ammonia source water].

A high ammonia micropolluted source water advanced treatment for ammonia removal by biological activated carbon filter was tested. The removal rate of ammonia was high than 95% when influent concentration was under 1.0 mg/L. The removal rate decreased with the influent concentration increased when the ammonia concentration was in range of 1.5 - 4.9 mg/L and the influent DO was under 10 mg/L, and the minimum removal rate was about 30%. The key factor of restrict nitrification in BACF was the influent DO. When the influent ammonia concentration was high, the DO in water was depleted quickly by nitrify and hetetrophic bacteria in 0.4 m deep of filter and the filter layer was divided to aerobic zone and anoxic zone. The denitrification was occurred in the anoxic zone, and because of very low concentration of electron donor led to accumulation of the denitrification intermediates such as NO2-. Aerobic bacteria was existed in the anoxic zone.

Ammonia↗
PubMed2006

[Start-up experiment on nitrification of mid-low ammonia concentration wastewater in SBR biofilm reactor].

The start-up experiment on nitrification of mid-low NH4+ -N concentration wastewater was carried out in four SBR biofilm reactors for the establishment of completely autotrophic nitrogen removal process by the control of DO and HRT and different medias. The results show that on the conditions of temperature 30 degrees C +/-2 degrees C, ammonia concentration 60-120 mg/L, DO 0.8 - 1.0 mg/L and hydraulic retention time 24 h, the inoculating general active aerobic sludge and anaerobic sludge was nitrified stably after 130 days, and the YJZH media was more suitable for microorganism coherence.

Ammonia↗
PubMed1990

Stimulation of ammonification and nitrification in soils by the insecticides monocrotophos and quinalphos.

The application (up to 5 kg ha-1) of monocrotophos or quinalphos to four types of agricultural soils significantly stimulated the mineralization of peptone-nitrogen and the oxidation of ammonium-nitrogen. In soils treated with 2.5 kg ha-1 of either insecticide, the rate of ammonification and nitrification was fairly rapid after 2 and 4 weeks of incubation. The enhancement of both transformations, mediated by microorganisms, was significantly more in the quinalphostreated soils. The results suggest that a balance between the effect of insecticides on insect pests and their impact on beneficial microbial activities in soil must be determined.

Ammonia↗
PubMedDate not supplied

[Complete nitrification in soil columns perfused with nitrite].

Four columns of the same soil were put under the continuous flow of a NaNO2 solution [50 ppm N], so as to follow the evolution of nitrification. The soil, the columns as well as the solution continuous flow regulating system, were prepared as in the previous experiments. The columns, with the exception of No1 (control), contained also the following substances: No2 and 4: 2% de CaCO3 and No3 and 4:0.0015% SO - 4-S. Since the eight day of perfusion all the effluents had an important concentration of nitrate (Figure 1), exceeding in them, the sum of [No-2-N] an [NO-3-N] (Table 1) the concentration of th NO-2-N of the perfusion solution. Finally, the [NO-2-N] was reduced importantly in the effluents, and the (NO-3N), in all of them, stabilized itself as values nearing 50 ppm. Its suggested that at the beginning of the experiment, an endogenous source of NO-2 was functioning, which could explain the observed phenomenon, and that later it ceased to do so. The populational density of NO-2 oxidizers increased, during the experiment, 49 times (Table 2). An increase was also measured in the populational density of NH+4 oxidizers, which amounted to 41 times. This later fact contributes to support the existence of an endogenous provision of NO-2 during the initial part of the experiment.

Bacteria↗
PubMed1983

Effect of microbiological hydrolysis of urea on the nitrification process.

The aim of this study was to determine the causes of previously observed inhibition of stage II of nitrification in nitrifying activated sludge treating industrial wastewaters containing ammonium, urea and nitrates. Experiments made with both industrial wastewaters and synthetic medium containing equivalent concentrations of nitrogen compounds demonstrated that the factor limiting the activity of nitrobacteria is microbiological hydrolysis of urea, the causative agent probably being free ammonia released in the course of this hydrolysis.

Bacteria↗
PubMed1984

Bacterial microflora participating in the removal of nitrogen from industrial wastewaters by nitrification and denitrifaction.

Nitrification and denitrification were used to purify industrial nitrogenous-organic wastewaters containing 1,130 mg N/l (mainly in the form of ammonium and urea) and with mean COD 1,050 mg O2/l. The use of a five-step system consisting of two denitrifying beds and three nitrifying activated sludge reactors gave 99% removal of nitrogen and 54% reduction in COD during total retention time of the wastes of 81 hours. The participation of stage I nitrifying bacteria in the activated sludge was 4.4 to 5.8% and of stage II nitrifying bacteria 21.9 to 53.8%. Denitrifying bacteria in the denitrifying beds accounted for 90% of the isolated population, which was dominated by Alcaligenes faecalis and Paracoccus denitrificans.

Alcaligenes↗
PubMed1984

[Nitrification in soil columns subjected to continuous flow].

Nitrification in columns of soil under continuous flow of substrate was studied. The soil was previously diluted with sterile sand (1 part of soil: 9 parts of sand; w : w) and admixed with 2% CaCO3. Soil columns, 15 cm high, were contained in glass cylinders with a cross sectional area of 39.6 cm2. In the main experiment, a soil column was subjected to the continuous flow of a KNO2 solution (100 ppm NO2- - N) at a flow rate of 46.0 cm3 h-1. An exponential increase of nitrate concentration in the column effluent was observed during the first 4 days (Fig. 1), suggesting an exponential growth of NO2- oxidizers in the soil column, with an apparent generation time of 1, 2 days. At the end of this phase, an almost complete conversion of nitrite to nitrate was reached followed by an important decrease in conversion and by a partial recovery with stabilization at 69 ppm NO3- - N in the column effluent. This phenomenon was presumably due to a rapid rate of O2 demand by the microorganisms which exceeded the supply, and to the subsequent adaptation of the NO2- oxidizers to a situation in which the O2 concentration was the limiting factor. At the end of the experiment, the average population density of NO2- oxidizers in the column was 1.5. 10(7) cells cm-3. In a preliminary experiment, a column of the same soil was continuously perfused with an (NH4)2SO4 solution with 140 ppm NH+4 - N, at a constant rate of 40.8 cm3 h-1 (Fig. 2.).(ABSTRACT TRUNCATED AT 250 WORDS)

Bacteria↗
PubMed1979

Removal of nitrogen from industrial wastewaters by three-step nitrification and denitrification.

The removal of nitrogen from industrial wastewaters carrying about 1,000 mg NH4-N and urea-N/l was investigated on a laboratory scale. The use of a three-step nitryfying activated sludge with adjustment of pH from step to step resulted in 99% oxidation of both forms of nitrogen to nitrites. The efficiency of nitrification was 18 mg N/l/h. Total time of wastewater aeration depended on nitrogen concentration and was 33-54 hours. Complete dentrification of NO2-N was obtained in packed-bed reactor with the use of acetic acid as a carbon source. Efficiency of denitrification was 361 mg N/l/h.

Acetates↗