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PubMed1997

Pyridine degradation and heterocyclic nitrification by Bacillus coagulans.

A gram-positive, pyridine-degrading microorganism identified as Bacillus coagulans has been isolated from contaminated soil by enrichment culture technique. Pyridine was used as sole source of carbon, nitrogen, and energy. Bacillus coagulans has a unique potential to reduce nitrogen from aromatic ring to ammonia and subsequently heterotrophically to nitrite and nitrate. The maximum degradation of pyridine was 94.1% within 72 h at 30 degrees C with a 7.57-h doubling time. The study suggests possible existence of aromatic degradation and heterotrophic nitrification in Bacillus coagulans.

Bacillus↗
PubMed2005

Characteristics of ammonium removal by heterotrophic nitrification-aerobic denitrification by Alcaligenes faecalis No. 4.

Alcaligenes faecalis no. 4 has heterotrophic nitrification and aerobic denitrification abilities. By taking the nitrogen balance under different culture conditions, 40-50% of removed NH4+-N was denitrified and about one-half of removed NH4+-N was converted to intracellular nitrogen. The maximum ammonium removal rate of no. 4 (28.9 mg-N/l/h) and its denitrification rate at high-strength NH4+-N of about 1200 ppm in aerated batch experiments at a C/N ratio of 10 were 5-40 times higher than those of other bacteria with the same ability. Only a few percent of the removed ammonium was converted to nitrite, and the main denitrification process was speculated to be via hydroxylamine which was produced by ammonium oxidation.

Aerobiosis↗
PubMedDate not supplied

Susceptibility of ammonia-oxidizing bacteria to nitrification inhibitors.

Activity of nitrification inhibitors to several typical ammonia-oxidizing bacteria isolated recently, i. e. Nitrosococcus, Nitrosolobus, Nitrosomonas, Nitrosospira and Nitrosovibrio species was assayed using 2-amino-4-methyl-trichloromethyl-1,3,5-triazine (MAST), 2-amino-4-tribromomethyl-6-trichloromethyl-1,3,5-triazine (Br-MAST), 2-chloro-6-trichloromethylpyridine (nitrapyrin) and others, and compared to confirm the adequate control of ammonia-oxidizing bacteria by the inhibitors. The order of activity of the inhibitors to 13 species of ammonia-oxidizing bacteria examined was approximately summarized as Br-MAST > or = nitrapyrin > or = MAST > other inhibitors. Two Nitrosomonas strains, N. europaea ATCC25978 and N. sp. B2, were extremely susceptible to Br-MAST, exhibiting a pI50 > or = 6.40. These values are the position logarithms of the molar half-inhibition concentration. The 16S rRNA gene sequence similarity for the highly susceptible 4 strains of genus Nitrosomonas was 94% to 100% of Nitrosomonas europaea, although those of the less susceptible 3 strains of ammonia-oxidizing bacteria, Nitrosococcus oceanus C-107 ATCC19707, Nitrosolobus sp. PJA1 and Nitrosolobus multiformis ATCC25196, were 77.85, 91.53 and 90.29, respectively. However, no clear correlation has been found yet between pI50-values and percent similarity of 16S rRNA gene sequence among ammonia-oxidizing bacteria.

Ammonia↗
PubMed2006

Feasibility of controlling nitrification in predenitrification plants using DO, pH and ORP sensors.

Experimental studies were carried out on a bench-scale nitrogen removal system with a predenitrification configuration to gain insights into the spatial and temporal variations of DO, pH and ORP in such systems. It is demonstrated that these signals correlate strongly with the operational states of the system, and could therefore be used as system performance indicators. The DO concentration in the first aerobic zone, when receiving constant aeration, and the net pH change between the last and first aerobic zones display strong correlations with the influent ammonia concentration for the domestic wastewater used in this study. The pH profile along the aerobic zones gives good indication on the extent of nitrification. The experimental results also showed a good correlation between ORP values in the last aerobic zone and effluent ammonia and nitrate concentrations, provided that DO in this zone is controlled at a constant level. These results suggest that the DO, pH and ORP sensors could potentially be used as alternatives to the on-line nutrient sensors for the control of continuous systems. An idea of using a fuzzy inference system to make an integrated use of these signals for on-line aeration control is presented and demonstrated on the bench-scale system with promising results. The use of these sensors has to date only been demonstrated in intermittent systems, such as sequencing batch reactor systems.

Ammonia↗
PubMedDate not supplied

Simultaneous nitrification-denitrification and clarification in a pseudoliquified activated sludge system.

This paper describes results from a pilot study of a novel wastewater treatment technology, which incorporates nutrient removal and solids separation to a single step. The pseudoliquified activated sludge process pilot system was tested on grit removal effluent at flowrates of 29.4 to 54.7 m3/d, three different solid residence times (SRT) (15, 37, and 57 days), and over a temperature range of 12 to 28 degrees C. Despite wide fluctuations in the influent characteristics, the system performed reliably and consistently with respect to organics and total suspended solids (TSS) removals, achieving biochemical oxygen demand (BOD) and TSS reductions of > 96% and approximately 90%, respectively, with BOD5 and TSS concentrations as low as 3 mg/L. Although the system achieved average effluent ammonia concentrations of 2.7 to 3.2 mg/L, nitrification efficiency appeared to be hampered at low temperatures (< 15 degrees C). The system achieved tertiary effluent quality with denitrification efficiencies of 90 and 91% total nitrogen removal efficiency at a total hydraulic retention time of 4.8 hours and an SRT of 12 to 17 days. With ferric chloride addition, effluent phosphorous concentrations of 0.5 to 0.8 mg/L were achieved. Furthermore, because of operation at high biomass concentrations and relatively long biological SRTs, sludge yields were over 50% below typical values for activated sludge plants. The process was modeled using activated sludge model No. 2, as a two-stage system comprised an aerobic activated sludge system followed by an anoxic system. Model predictions for soluble BOD, ammonia, nitrates, and orthophosphates agreed well with experimental data.

Ammonia↗
PubMed2006

Simultaneous nitrification and denitrification in an aerobic reactor with granular sludge originating from an upflow anaerobic sludge bed reactor.

Anaerobic granular sludge, obtained from an upflow anaerobic sludge bed reactor at a brewery waste treatment station, was cultured for 3 months under aeration conditions until the diameter of sludge was in the range 1.8 to 2.6 mm. The aerobic granular sludge gathered acquired the ability of catalyzing simultaneous nitrification and denitrification (SND) and was applied in the study of the process of nitrogen removal in a bioreactor. The ratio between chemical oxygen demand (COD) and ammonium-nitrogen (NH4(+)-N) concentration in the influent was found to be an important factor influencing the process of SND. The final percentage removal of NH4(+)-N reached 100% under the optimal condition of 500 mg/L COD and 0.39 NH4(+)-N/COD. Intermediate products, such as nitrite-nitrogen and nitrate-nitrogen, were also analyzed to clarify the SND process with the aerobic granular sludge.

Ammonia↗
PubMed2006

Simultaneous nitrification and denitrification with anoxic phosphorus uptake in a membrane bioreactor system.

The performance of an innovative membrane bioreactor (MBR) process using anoxic phosphorus uptake with nitrification and denitrification for the treatment of municipal wastewater with respect to operational performance and effluent quality is addressed in this paper. The system was operated at steady-state conditions with a synthetic acetate-based wastewater at a hydraulic retention time (HRT) of 12 hours and on degritted municipal wastewater at a total system HRT of 6 hours. The MBR system was able to achieve 99% biochemical oxygen demand (BOD), chemical oxygen demand (COD), and ammonia-nitrogen (NH4(+)-N); 98% total Kjeldahl nitrogen (TKN); and 97% phosphorus removal, producing effluent BOD, COD, NH4+-N, TKN, nitrate-nitrogen, nitrite-nitrogen, and phosphate-phosphorus of <3, 14, 0.2, 0.26, 5.8, 0.21, and <0.01 mg/L, respectively, at the 6-hour HRT. The comparison of the synthetic and municipal wastewater run is presented in this paper. Steady-state mass balance on municipal wastewater was performed to reveal some key features of the modified MBR system.

Ammonia↗
PubMed2006

Evaluation of the persistence of micropollutants through pure-oxygen activated sludge nitrification and denitrification.

The persistence of pharmaceuticals, hormones, and household and industrial chemicals through a pure-oxygen activated sludge, nitrification, denitrification wastewater treatment facility was evaluated. Of the 125 micropollutants that were tested in this study, 55 compounds were detected in the untreated wastewater, and 27 compounds were detected in the disinfected effluent. The persistent compounds included surfactants, fire-retardant chemicals, pesticides, fragrance compounds, hormones, and one pharmaceutical. Physical-chemical properties of micropollutants that affected partitioning onto wastewater solids included vapor pressure and octanol-water partition coefficients.

Ammonia↗
PubMed2000

Single-step nitrification models erroneously describe batch ammonia oxidation profiles when nitrite oxidation becomes rate limiting.

Nitrification involves the sequential biological oxidation of reduced nitrogen species such as ammonium-nitrogen (NH(4)(+)-N) to nitrite-nitrogen (NO(2)(-)-N) and nitrate-nitrogen (NO(3)(-)-N). The adequacy of modeling NH(4)(+)-N to NO(3)(-)-N oxidation as one composite biochemical reaction was examined at different relative dynamics of NH(4)(+)-N to NO(2)(-)-N and NO(2)(-)-N to NO(3)(-)-N oxidation. NH(4)(+)-N to NO(2)(-)-N oxidation and NO(2)(-)-N to NO(3)(-)-N oxidation by a mixed nitrifying consortium were uncoupled using selective inhibitors allylthiourea and sodium azide. The kinetic parameters of NH(4)(+)-N to NO(2)(-)-N oxidation (q(max,ns) and K(S,ns)) and NO(2)(-)-N to NO(3)(-)-N oxidation (q(max,nb) and K(S,nb)) were determined by a rapid extant respirometric technique. The stoichiometric coefficients relating nitrogen removal, oxygen uptake and biomass synthesis were derived from an electron balanced equation. NH(4)(+)-N to NO(2)(-)-N oxidation was not affected by NO(2)(-)-N concentrations up to 100 mg NO(2)(-)-N L(-1). NO(2)(-)-N to NO(3)(-)-N oxidation was noncompetitively inhibited by NH(4)(+)-N but was not inhibited by NO(3)(-)-N concentrations up to 250 mg NO(3)(-)-N L(-1). When NH(4)(+)-N to NO(2)(-)-N oxidation was the sole rate-limiting step, complete NH(4)(+)-N to NO(3)(-)-N oxidation was adequately modeled as one composite process. However, when NH(4)(+)-N to NO(2)(-)-N oxidation and NO(2)(-)-N to NO(3)(-)-N oxidation were both rate limiting, the estimated lumped kinetic parameter estimates describing NH(4)(+)-N to NO(3)(-)-N oxidation were unrealistically high and correlated. These findings indicate that the use of single-step models to describe batch NH(4)(+) oxidation yields erroneous kinetic parameters when NH(4)(+)-to-NO(2)(-) oxidation is not the sole rate-limiting process throughout the assay. Under such circumstances, it is necessary to quantify NH(4)(+)-N to NO(2)(-)-N oxidation and NO(2)(-)-N to NO(3)(-)-N oxidation, independently.

Ammonia↗
PubMed2001

Process using DO and ORP signals for biological nitrification and denitrification: validation of a food-processing industry wastewater treatment plant on boosting with pure oxygen.

The simultaneous removal of carbonaceous and nitrogenous pollution by the activated sludge process is becoming common in industrial and municipal wastewater treatment plants. An oxygenation monitoring process has been developed, which is based on the dynamic analysis of ORP and DO signals and allows the detection of specific characteristic points at the end of the biological nitrification and denitrification. The aim of this study is to validate this process in a food-processing industry WWTP (slaughterhouse) having large variations of carbonaceous and nitrogenous loads. In order to treat during the peak period, pure oxygen is used. The first part of the study provides a precise diagnosis of the WWTP operation by the analysis of the ORP and DO signals. It is particularly easy to estimate the level of nitrogen treatment actually achieved and the oxygen requirements, and to detect the over- or under-oxygenated phases. Thanks to the monitoring process, the aerobic period of each cycle is reduced to the optimal duration, providing a reduction of 30% on the energy consumption compared to a traditional schedule. We have demonstrated that the use of pure oxygen associated with the existing air system is particularly relevant for the peak period. The revamping of an existing plant to simultaneously treat the carbon and the ammonia in the same basin is now technically feasible.

Abattoirs↗
PubMed2001

Nitrification-denitrification of UASB effluents highly loaded with nitrogen in an activated sludge reactor operated with short cycled aeration.

A conventional activated sludge reactor operated with short cycled aeration was used for total nitrogen removal of UASB anaerobic reactor effluent containing nitrogen (up to 1,200 mg NKT/L) and organic matter (up to 2,000 mg COD/L). Initially the reactor was fed with synthetic water to progressively introduce the UASB effluent. This favored the acclimation of the microorganisms to the real environment. The results obtained throughout this study showed that initially the tested technology is feasible and can report significant cuts on operation and maintenance when compared to conventional activated sludge processes. Total nitrogen removal up to 66% was attained treating the effluent of an UASB process designed for treating the wastewater of a potato starch factory. Total nitrogen removal capacities ranging between 0.1 and 0.58 kg of nitrogen per cubic metre per day are reported. Short-cycled aeration allowed for a more efficient use of the oxygen supply for nitrification and the organic carbon content present in the wastewater for denitrification. This operating protocol has demonstrated serious advantages in terms of operation costs and simplicity when total nitrogen removal is wanted. Most of the existing activated sludge processes, i.e. single continuous flow reactors, can be updated for total nitrogen removal essentially at no cost, the inversion (aeration control system) is rapidly returned as reduction in energy expenditure.

Bacteria, Anaerobic↗
PubMed2003

Nitrification preservation in activated sludge during curative bulking chlorination.

The bulking that occurs in biological wastewater treatment plants using activated sludge is very often controlled by the injection of sodium hypochlorite into the return activated sludge (RAS) stream. In the present study undertaken at two pilot plants fed with synthetic wastewater, the impact of the pass frequency of the sludge at the chlorine dosing point on the nitrifying flora is analysed. The pass frequency is one for the pilot plant 1 and two for the pilot plant 2. A dose of chlorine of 4.85 +/- 0.05 g/kg/MLVSS per day was applied at both pilots. The preservative effect on nitrifying activity of the lowest concentration of chlorine at the dosing point and therefore of the highest pass frequency was evidenced. Among other tools, a simple method of measurement of the oxygen uptake rate enabled us to monitor the effect of chlorination on nitrification before recording an increase in the ammonia concentration in the bulking.

Bacteria↗
PubMed2003

Nitrification in biofilters under variable load and low temperature.

The evolution of European legislation has led to the rehabilitation of many wastewater treatment plants, sometimes through the installation of a biological complementary treatment stage. Among these sites, some plants in mountain areas are considering a biofiltration process. The design of such plants, especially for winter, appears to be tricky because of the very low influent temperature, the high performance requested for ammonia removal and the important and short term variations of the influent loads. The monitoring of a site during two consecutive winters has allowed us to study some aspects of the treatment. The major results are: a maximal nitrification capacity of about 0.59 kg of formed N-NO3- x m(-3) of material x d(-1) with an influent temperature around 7 degrees C at the plant inlet; a nitrifying biomass growth rate, expressed as nitrifying capacity increase, of 0.03 kg of N-NO3- x m(-3) of material x d(-2); quick and short terms load variations require a specific operation of the filters prior to the load increase, in order to grow enough active biomass to be able to treat the peak load immediately.

Ammonia↗
PubMed2003

[Cultivation of aerobic granular sludge for simultaneous nitrification and denitrification in SBR system].

The cultivation of aerobic granular sludge used for nitrogen removal in Sequencing Batch Reactor (SBR) fed with a synthetic municipal wastewater was investigated. The results showed that the aerobic granular sludge with the high activity of simultaneous nitrification and denitrification, could form in the reactor by controlling the addition of carbon source, and the removal rates of COD and NH3-N reached 74.0%-92.8% and 82.3%-98.5%, respectively, in the reactor. The granular formed was averagely 0.5-1.0 mm in diameter, and the Mixed Liquid Suspended Solids (MLSS) and the Sludge Volumetric Index (SVI) in the reactor were above 4.5 g/L and above 32.5, respectively. Compared with the normal aerobic activated sludge process, the system with aerobic granular sludge had a higher concentration of effective biomass and a much stronger ability of nitrogen removal.

Aerobiosis↗
PubMed2003

Temperature effect on aerobic denitrification and nitrification.

Nitrogen loss without organic removal in biofilter was observed and its possible reason was explained. A lower hydraulic loading could improve aerobic denitrification rate. Aerobic denitrification was seriously affected by low temperature(below 10 degrees C). However, nitrification rate remained high when the temperature dropped from 15 degrees C to 5 degrees C . It seemed the autotrophic biofilm in BAF could alleviate the adverse effect of low temperature.

Biodegradation, Environmental↗
PubMed2003

Nitrogen removal from domestic effluent using subsurface flow constructed wetlands: influence of depth, hydraulic residence time and pre-nitrification.

This paper describes two studies into the BOD and TN removal performance of horizontal subsurface flow wetlands (reed beds) in subtropical Australia. The aim of the first study was to determine the influence of HRT and vertical position on BOD and TN concentration and removal performance in a 0.5 m deep reed bed (System 1) by taking samples from three levels (or layers) in the water column at five points along the length of the bed. The aim of the second study was to investigate the TN removal performance of a treatment train consisting of a vertical flow intermittently dosed sand filter preceding a reed bed (System 2). Both systems were dosed with primary settled municipal wastewater (BOD 194 mg L(-1); TN 49 mg L(-1)). System 1 achieved a TN load removal of 58% under a HLR of 22 mm day(-1) (HRT 10.5 days), producing effluent BOD concentrations consistently less than 8 mg L(-1). There was no significant difference in BOD attenuation rate between the three layers. While there were differences in both the nitrification and denitrification rates between the three layers, the TN concentration was found to decline steadily in all layers up to an HRT of 8.7 days. System 2 reduced TN influent load by 33%, less than half of which was removed by the reed bed. The lack of substantial TN removal within this reed bed was attributed to the low concentrations of BOD and consequent lack of dissolved organic carbon to drive the denitrification process.

Australia↗
PubMed2004

Experimental study on nitrification in a submerged aerated biofilter.

The aim of the present work was to evaluate the performance of a semi-pilot scale BAF in order to obtain a highly polished effluent in terms of removal of organic matter, suspended solids and ammonia and to observe the influence of temperature, pH and nitrite accumulation on the nitrification process. The ammonia removal efficiency during summer and winter and the nitrite accumulation in presence of free ammonia were observed. The biomass density was measured at different filter bed heights and the sludge production from the effluent of the backwashing water was evaluated. The results obtained were used to calibrate a mathematical model for the prediction of the ammonia removal profile in the filter bed and of biomass thickness.

Ammonia↗