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PubMed2003

Online titrimetric and off-gas analysis for examining nitrification processes in wastewater treatment.

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. For a detailed examination, it is desirable to monitor the two-step sequence using online measurements. In this paper, the use of online titrimetric and off-gas analysis (TOGA) methods for the examination of the process is presented. Using the known reaction stoichiometry, combination of the measured signals (rates of hydrogen ion production, oxygen uptake and carbon dioxide transfer) allows the determination of the three key process rates, namely the ammonia consumption rate, the nitrite accumulation rate and the nitrate production rate. Individual reaction rates determined with the TOGA sensor under a number of operation conditions are presented. The rates calculated directly from the measured signals are compared with those obtained from offline liquid sample analysis. Statistical analysis confirms that the results from the two approaches match well. This result could not have been guaranteed using alternative online methods. As a case study, the influences of pH and dissolved oxygen (DO) on nitrite accumulation are tested using the proposed method. It is shown that nitrite accumulation decreased with increasing DO and pH. Possible reasons for these observations are discussed.

Ammonia↗
PubMed2000

Development of chitosan-magnetite aggregates containing Nitrosomonas europaea cells for nitrification enhancement.

A cell suspension of the nitrifying bacterium Nitrosomonas europaea obtained after 96-h cultivation was subjected to magnetic separation using chitosan-conjugated magnetite particles (chitosan-magnetite), which have the ability to form aggregates with microbial cells. An equilibrium condition was obtained at room temperature after 30 min and over 90% of the cells were recovered when the chitosan-magnetite concentration was 200 mg/l. The relationship between the cell concentration in the supernatant in equilibrium and the number of cells adsorbed per 1g chitosan-magnetite was expressed by a Freundlich-type adsorption equation. A high nitrifying bacterium activity yield was obtained with a chitosan-magnetite concentration between 100 and 200 mg/l. Repeated batch culture resulted in more N. europaea cells accumulating on the aggregates and as a consequence their nitrification activity improved further. The chitosan-magnetite/cell aggregates were recovered and employed to remove ammonia from artificial wastewater together with PVA-alginate gel beads containing the denitrifying bacterium Paracoccus denitrificans. A higher ammonia removal rate was achieved under aerobic conditions in comparison with that obtained when N. europaea and P. denitrificans were coimmobilized in PVA-alginate gel beads.

Journal Article↗
PubMed2005

Effect of selected textile effluents on activated sludge nitrification process.

In this study, a recently developed methodology for the assessment of the inhibitory effect on nitrifying biomass was applied to several textile effluents from productive processes. Effluents are classified according to the degree of inhibition as EC50 (concentration producing 50% nitrification inhibition); the investigated textile effluents showed a wide range of EC50 ranging from 20 ml gVSS-1 (83 ml l-1) to values above 100 ml gVSS-1 (300 ml l-1) for effluents produced by rinsing phases. Taking into account biodegradability and toxicity evaluations, most of the effluents showed a good treatability in conventional biological wastewater treatment plant. On the other hand three textile effluents showed significant toxic effects towards nitrifying biomass. In any case, the proposed procedure represents an efficient tool to prevent treatment failures due to toxic discharges.

Bacteria↗
PubMed2003

Nitrification-denitrification of opto-electronic industrial wastewater by anoxic/aerobic process.

This research focused on the biological treatment of high-strength organic nitrogen wastewater, and presented the results from the nitrification and denitrification of an actual industrial wastewater using anoxic/aerobic process. The opto-electronic industrial wastewater often contains a significant quantity of organic nitrogen compounds and has a ratio over 95% in organic nitrogen (Org-N) to total nitrogen (T-N). In this study, a 2-stage anoxic/aerobic process was established and evaluated the efficiency of wastewater treatment. Raw wastewater from an actual TFT-LCD manufacturing plant was obtained as the sample for looking into the feasibility of opto-electronic industrial wastewater treatment. After toxicity identification evaluation (TIE) test of raw wastewater. the inhibition was related to organic nitrogen (TMAH, MEA) and unionized ammonia (free ammonia, NH3) with high pH. Therefore, pH control is important for biological treatment of high-strength organic nitrogen industrial wastewater. Besides. hydraulic retention time (HRT) and mixed liquor recycled rate (MLR) were controlled independently to distinguish between the effects of these two factors. Under suitable HRT ( > 1.7 d) and mixed liquor recycled rate (< 4Q), effluent of NH4-N. NO3-N + NO2-N, and COD can fall below 20 mg/L, 30 mg/L, and 80 mg/L. The anoxic/aerobic process removed 92-98% of the carbon source, and approximately 80% of TKN, 70% of T-N.

Ammonia↗
PubMed1969

Nitrification: importance to nutrient losses from a cutover forested ecosystem.

The nitrate concentration (weighted average) in stream water from an experimentally deforested watershed increased from 0.9 milligram per liter before removal of the vegetation to 53 milligrams per liter 2 years later. This nitrate mobilization, presumably due to increased microbial nitrification, was equivalent to all of the other net cationic increases and anionic decreases observed in tae drainage water.

Calcium↗
PubMed2006

Nitrification in a biofilm at low pH values: role of in situ microenvironments and acid tolerance.

The sensitivity of nitrifying bacteria to acidic conditions is a well-known phenomenon and generally attributed to the lack and/or toxicity of substrates (NH3 and HNO2) with decreasing pHs. In contrast, we observed strong nitrification at a pH around 4 in biofilms grown on chalk particles and investigated the following hypotheses: the presence of less acidic microenvironments and/or the existence of acid-tolerant nitrifiers. Microelectrode measurements (in situ and under various experimental conditions) showed no evidence of a neutral microenvironment, either within the highly active biofilm colonizing the chalk surface or within a control biofilm grown on a nonbuffering (i.e., sintered glass) surface under acidic pH. A 16S rRNA approach (clone libraries and fluorescence in situ hybridizations) did not reveal uncommon nitrifying (potentially acid-tolerant) strains. Instead, we found a strongly acidic microenvironment, evidence for a clear adaptation to the low pH in situ, and the presence of nitrifying populations related to subgroups with low Km s for ammonia (Nitrosopira spp., Nitrosomonas oligotropha, and Nitrospira spp.). Acid-consuming (chalk dissolution) and acid-producing (ammonia oxidation) processes are equilibrated on a low-pH steady state that is controlled by mass transfer limitation through the biofilm. Strong affinity to ammonia and possibly the expression of additional functions, e.g., ammonium transporters, are adaptations that allow nitrifiers to cope with acidic conditions in biofilms and other habitats.

Biofilms↗
PubMed1980

Variation in heterotrophic and autotrophic nitrifier populations in relation to nitrification in organic soils.

The occurrence of heterotrophic and autotrophic nitrifiers in Pahokee muck and the role of these organisms in the ecosystem were assessed by surveying their population densities under different field conditions and by observing the relationship of these populations with aerobic bacteria and soil moisture. Heterotrophic nitrifier populations varied from 2.0 x 10 to 3.8 x 10 bacteria per cm of muck in surface fallow (bare) Pahokee muck during the annual cycle. This population decreased 40-fold between the surface and the 60- to 70-cm depths of soil. Similar variations were noted with autotrophic nitrifier populations. Significant correlations were found between heterotrophic nitrifiers and both soil moisture and aerobic bacteria. These relationships did not exist for the autotrophic nitrifiers. In soil that had been heated to kill the autotrophic nitrifiers, while preserving a population of the heterotrophs, and then amended with sodium acetate or ammonium sulfate or both, no nitrate or nitrite accumulated, although significant increases in heterotrophic nitrifiers were detected. In unheated control soil, nitrate plus nitrite-N increased from 14.3 to 181 mug/g of wet soil, and 48 mug of nitrite-N per g was produced. These data suggest that the autotrophic nitrifiers were the sole population responsible for nitrification in Pahokee muck.

Journal Article↗
PubMed1983

Inhibition of chemoautotrophic nitrification by sodium chlorate and sodium chlorite: a reexamination.

The oxidation of NH(4) by Nitrosomonas europaea was insensitive to 10 mM NaClO(3) (sodium chlorate) but was strongly inhibited by NaClO(2) (sodium chlorite; K(i), 2 muM). The oxidation of NO(2) by Nitrobacter winogradskyi was inhibited by both ClO(3) and ClO(2) (K(i) for ClO(2), 100 muM). N. winogradskyi reduced ClO(3) to ClO(2) under both aerobic and anaerobic conditions, and as much as 0.25 mM ClO(2) was detected in the culture filtrate. In mixed N. europaea-N. winogradskyi cell suspensions, the oxidation of both NH(4) and NO(2) was inhibited in the presence of 10 mM ClO(3) after a 2-h lag period, despite the fact that, under these conditions, ClO(2) was not detected in the filtrate. The data are consistent with the hypothesis that, in mixed culture, NH(4) oxidation is inhibited by ClO(2) produced by reduction of ClO(3) by the NO(2) oxidizer. The use of ClO(3) inhibition of NO(2) oxidation in assays of nitrification by mixed populations necessitates cautious interpretation unless it can be shown that the oxidation of NH(4) is not affected.

Journal Article↗
PubMed1984

Use of nitrifying activity measurements for describing the effect of salinity on nitrification in the Scheldt estuary.

Nitrifying activity measurements, carried out on freshly collected samples from an estuarine environment, show that the composition of the nitrifier population undergoes a progressive modification during the mixing of freshwater masses in seawater, with increasing tolerance to salt. As a result, the overall effect of increasing salinity on nitrification is much less severe than the direct effect of salt on the freshwater nitrifying population.

Fresh Water↗
PubMed1990

Direct determination of nitrification in marine waters by using the short-lived radioisotope of nitrogen, N.

Biological oxidation of radiolabeled NH(4) (half-life = 10 min) was observed within minutes in assays of an estuarine ammonium oxidizer and in natural populations of nitrifiers in coastal waters. Our estimates of turnover of the ammonium pool and rates of nitrification based on experiments using N are consistent with previous values in the literature based on longer-term N tracer experiments or on indirect methods and thus provide corroboration for the estimates by other researchers.

Journal Article↗
PubMed1991

Bacterial nitrification in chloraminated water supplies.

Nitrifying bacteria were detected in 64% of samples collected from five chloraminated water supplies in South Australia and in 20.7% of samples that contained more than 5.0 mg of monochloramine per liter. Laboratory experiments confirmed that nitrifying bacteria are relatively resistant to the disinfectant. Increased numbers of the bacteria were associated with accelerated decays of monochloramine within distribution systems. The combination of increased concentrations of oxidized nitrogen with decreased total chlorine residuals can be used as a rapid indicator of bacterial nitrification.

Chloramines↗
PubMed1998

Ammonium removal by the oxygen-limited autotrophic nitrification-denitrification system

The present lab-scale research reveals the potential of implementation of an oxygen-limited autotrophic nitrification-denitrification (OLAND) system with normal nitrifying sludge as the biocatalyst for the removal of nitrogen from nitrogen-rich wastewater in one step. In a sequential batch reactor, synthetic wastewater containing 1 g of NH4+-N liter-1 and minerals was treated. Oxygen supply to the reactor was double-controlled with a pH controller and a timer. At a volumetric loading rate (Bv) of 0. 13 g of NH4+-N liter-1 day-1, about 22% of the fed NH4+-N was converted to NO2--N or NO3--N, 38% remained as NH4+-N, and the other 40% was removed mainly as N2. The specific removal rate of nitrogen was on the order of 50 mg of N liter-1 day-1, corresponding to 16 mg of N g of volatile suspended solids-1 day-1. The microorganisms which catalyzed the OLAND process are assumed to be normal nitrifiers dominated by ammonium oxidizers. The loss of nitrogen in the OLAND system is presumed to occur via the oxidation of NH4+ to N2 with NO2- as the electron acceptor. Hydroxylamine stimulated the removal of NH4+ and NO2-. Hydroxylamine oxidoreductase (HAO) or an HAO-related enzyme might be responsible for the loss of nitrogen.

Journal Article↗
PubMed1998

Molecular Analysis of Bacterial Communities in a Three-Compartment Granular Activated Sludge System Indicates Community-Level Control by Incompatible Nitrification Processes.

Bacterial community structure and the predominant nitrifying activities and populations in each compartment of a three-compartment activated sludge system were determined. Each compartment was originally inoculated with the same activated sludge community entrapped in polyethylene glycol gel granules, and ammonium nitrogen was supplied to the system in an inorganic salts solution at a rate of 5.0 g of N liter of granular activated sludge-1 day-1. After 150 days of operation, the system was found to comprise a series of sequential nitrifying reactions (K. Noto, T. Ogasawara, Y. Suwa, and T. Sumino, Water Res. 32:769-773, 1998), presumably mediated by different bacterial populations. Activity data showed that all NH4-N was completely oxidized in compartments one and two (approximately half in each), but no significant nitrite oxidation was observed in these compartments. In contrast, all available nitrite was oxidized to nitrate in compartment three. To study the microbial populations and communities in this system, total bacterial DNA isolated from each compartment was analyzed for community structure based on the G+C contents of the component populations. Compartment one showed dominant populations having 50 and 67% G+C contents. Compartment two was similar in structure to compartment one. The bacterial community in compartment three had dominant populations with 62 and 67% G+C contents and retained the 50% G+C content population only at a greatly diminished level. The 50% G+C content population from compartment one hybridized strongly with amo (ammonia monooxygenase) and hao (hydroxylamine oxidoreductase) gene probes from Nitrosomonas europaea. However, the 50% G+C content population from compartment two hybridized strongly with the hao probe but only weakly with the amo probe, suggesting that the predominant ammonia-oxidizing populations in compartments one and two might be different. Since different activities and populations come to dominate in each compartment from an identical inoculum, it appears that the nitrification processes may be somewhat incompatible, resulting in a series of sequential reactions and different communities in this three-compartment system.

Journal Article↗
PubMed2005

Relationship of temporal and spatial variabilities of ammonia-oxidizing bacteria to nitrification rates in Monterey Bay, California.

Temporal and spatial dynamics of ammonia-oxidizing bacteria (AOB) were examined using genes encoding 16S rRNA and ammonia monooxygenase subunit A (AmoA) in Monterey Bay, Calif. Samples were collected from three depths in the water column on four dates at one mid-bay station. Diversity estimators for the two genes showed a strong positive correlation, indicating that overlapping bacterial populations had been sampled by both sets of clone libraries. Some samples that were separated by only 15 m in depth had less genetic similarity than samples that were collected from the same depth months apart. Clone libraries from the Monterey Bay AOB community were dominated by Nitrosospira-like sequences and clearly differentiated from the adjacent AOB community in Elkhorn Slough. Many Monterey Bay clones clustered with previously identified 16S rRNA and amoA groups composed entirely of marine sequences, supporting the hypothesis that these groups are specific to the marine environment and are dominant marine AOB. In addition, novel, phylogenetically distinct groups of AOB sequences were identified and compared to sequences in the database. Only one cluster of gammaproteobacterial AOB was detected using 16S rRNA genes. Although significant genetic variation was detected in AOB populations from both vertical and temporal samples, no significant correlation was detected between diversity and environmental variables or the rate of nitrification.

Ammonia↗
PubMed1967

Oxygen-nitrogen relationships in autotrophic nitrification.

Oxygen utilization by the autotrophic nitrifiers Nitrosomonas and Nitrobacter was studied. Experimental evidence is presented which reflects the effect of carbon dioxide fixation on overall oxygen utilization in autotrophic nitrification. Measurement of dissolved oxygen and inorganic nitrogen changes indicates that oxygen-nitrogen ratios in inorganic nitrogen oxidation are equal to 3.22 parts (expressed in milligrams per liter) of oxygen per part of ammonia nitrogen oxidized to nitrite nitrogen and 1.11 parts of oxygen per part of nitrite nitrogen oxidized to nitrate nitrogen. These values rather than the stoichiometric ratios should be used in nitrogenous oxygen demand calculations.

Ammonia↗
PubMed1968

Activated-sludge nitrification in the presence of linear and branched-chain alkyl benzene sulfonates.

The effects of biodegradable linear alkyl benzene sulfonate and branched-chain alkyl benzene sulfonate detergents on activated-sludge nitrification were investigated by administering a synthetic waste containing up to 23 mg of each detergent per liter to eight bench-scale, batch, activated-sludge units. It was found that both detergents tended to promote complete oxidation of ammonia to nitrate, whereas control units produced approximately equal amounts of nitrite and nitrate. Various hypotheses are offered to explain the phenomenon.

Ammonia↗
PubMed1975

Nitrification on a coral reef.

We report that the algal pavement just behind the reef crest at Enewetak Atoll produces nitrate at measurable rates. In situ and in vitro incubations with N-Serve indicate that the autotrophic pathway involving two separate organisms is effective in this oxidation of ammonia to nitrate. Significant nitrification is indicated throughout the reef environment; Nitrobacter agilis has specifically been identified as at least one of the organisms responsible for the terminal oxidation of nitrite to nitrate.

Ammonia↗
PubMed1990

Nitrification of swine waste.

Complete oxidation of ammonia nitrogen (approximately 1000 mg/L) to nitrite was observed in stabilized swine waste after 49 days in incubation at 400 rpm and 29 degrees C, only if 10% (v/v) activated sludge from a wastewater treatment unit and 1.5% (w/v) CaCO3, were added. Stabilized swine waste contains less than 0.09 most probable number (MPN) per millilitre of nitrosobacteria and 2.3 MPN/mL of nitrobacteria. In activated sludge, the concentrations of these bacteria were 2.4 MPN/mL for nitrosobacteria and 4.2 x 10(5) MPN/mL for nitrobacteria. In the swine waste where ammonia was oxidized to nitrite, the nitrosobacteria growth increased to 5.5 x 10(5) MPN/mL, while the nitrobacteria growth decreased to 2.3 MPN/mL. Inoculation of a freshly stabilized swine waste with 10% (v/v) of the active nitrifying waste and addition of 1.5% (w/v) CaCO3, accelerated the oxidation of ammonia nitrogen to nitrite; the reaction was completed after only 5 days of incubation. Increasing the incubation period to 10 days resulted in the complete oxidation of the accumulated nitrite to nitrate. In the stabilized swine waste, complete nitrification without accumulation of nitrite was obtained in only 5 days of incubation when the waste was inoculated with both enriched nitrifying populations (10(6)-10(7) MPN/mL).

Animals↗