Nitrate Utilization Rates Research Articles

A distillery by-product as an external carbon source for enhancing denitrification in mainstream and sidestream treatment processes

The use of fusel oil as an 'alternative' carbon source for denitrification in the mainstream and sidestream treatment processes was studied. Research comprised two kinds of batch experiments as well as acclimation of process biomass to external carbon sources. In the conventional nitrate utilization rate (NUR) measurements (one-phase experiments with non-acclimated biomass), the NUR with fusel oil was 1.4-1.7 g N/(kg VSS·h which was comparable to NUR with ethanol and with slowly biodegradable fraction of the settled wastewater. When fusel oil was added at the beginning of the anoxic phase, preceded by an anaerobic phase (in two-phase experiments with non-acclimated biomass), the NURs of 2.5-2.9 g N/(kg VSS·h) were comparable to the tests without the addition of any external carbon sources. The addition of fusel oil and ethanol resulted in a significant enhancement of the denitrification efficiency in lab-scale sequencing batch reactors treating sludge reject water. The NURs continuously increased from below 1 g N/(kg VSS·h) to over 10 g N/(kg VSS·h) over the entire 4-week operational period, indicating gradual acclimation to the substrate. The overall total N removal efficiency reached ∼90%.

A Distillery By-Product as an External Carbon Source for Enhancing Denitrification in Mainstream and Sidestream Treatment Processes

The use of fusel oil as an ‘alternative’ carbon source for denitrification in the mainstream and sidestream treatment processes was studied. Research comprised two kinds of batch experiments as well as acclimation of process biomass to external carbon sources. In the conventional nitrate utilization rate (NUR) measurements (one-phase experiments with non-acclimated biomass), the NUR with fusel oil was 1.4–1.7 g N/(kg VSS·h which was comparable to NUR with ethanol and with slowly biodegradable fraction of the settled wastewater. When fusel oil was added at the beginning of the anoxic phase, preceded by an anaerobic phase (in two-phase experiments with non-acclimated biomass), the NURs of 2.5–2.9 g N/(kg VSS·h) were comparable to the tests without the addition of any external carbon sources. The addition of fusel oil and ethanol resulted in a significant enhancement of the denitrification efficiency in lab-scale sequencing batch reactors treating sludge reject water. The NURs continuously increased from below 1 g N/(kg VSS·h) to over 10 g N/(kg VSS·h) over the entire 4-week operational period, indicating gradual acclimation to the substrate. The overall total N removal efficiency reached ∼90%.

Comparison of the Effects of Conventional and Alternative External Carbon Sources on Enhancing the Denitrification Process

Food industry effluents are considered a potential alternative for methanol when seeking external carbon sources to enhance denitrification in municipal wastewater treatment plants (WWTPs). The aim of this study was to determine the immediate effects of dosing different carbon sources on the denitrification capability of process biomass from the Wschod WWTP in Gdansk (northern Poland). Five carbon sources, including settled wastewater, methanol, and three industrial effluents (distillery, brewery, and fish-pickling process) were tested in two kinds of batch experiments. The acclimation period of biomass to methanol also was investigated in bench-scale systems. During the conventional batch experiments, with the industrial effluents, the observed nitrate utilization rates (NURs) ranged from 2.4 to 6.0 g N/(kg VSS x h), which were only slightly lower than the rates associated with the use of the readily biodegradable fraction in the municipal (settled) wastewater [4.6 to 7.8 g N/(kg VSS x h)]. The conventional NURs observed with methanol and non-acclimated process biomass were low [i.e., 0.4 to 1.5 g N/(kg VSS x h)], and a minimum 2-week acclimation period of biomass to methanol in the bench-scale systems was needed to reach the level of 4.0 g N/(kg VSS x h). In other experiments, dosing the distillery and fish-pickling effluents at the beginning of the anoxic phase (preceded by the anaerobic phase) resulted in considerably higher (over 20%) NURs compared with the same experiments with the other carbon sources.

Industrial wastewater as an external carbon source for optimization of nitrogen removal at the “Wschod” WWTP in Gdansk (Poland)

Carbon source alternatives for denitrification belong to the highest research area priorities as they allow to optimize N removal within the existing capacities. In particular, some food industry effluents appear to be good candidates for such alternatives due to their high C/N ratios and high content of readily biodegradable organic fraction. The aim of this study was to determine the immediate effects of dosing different types of industrial wastewater on the denitrification capability of process biomass originating from the "Wschod" WWTP in Gdansk (northern Poland). Three types of industrial wastewater (effluents from a distillery, brewery and fish-pickling factory) were tested in two kinds of batch experiments. The results of this study revealed that the investigated industrial wastewater can be a potential external carbon source to improve denitrification efficiency. The observed single nitrate utilization rates (NURs) were ranging from 2.4 to 6.0 g N/(kg VSS.h) and were comparable to the rates associated with the utilization of readily biodegradable COD in the settled wastewater. When the NURs were measured during anoxic P uptake, the P uptake rates did not appear to be adversely affected by the addition of any carbon source.

Indole production by Pseudomonas stutzeri strain NAP-3 during anaerobic naphthalene biodegradation in the presence of dimethyl formamide

We previously reported on the denitrifier Pseudomonas stutzeri strain NAP-3 that degrades naphthalene without oxygen. In our present studies, naphthalene biodegradation by NAP-3 was slow or nearly absent when acetate was not present, suggesting a stimulating effect by the non-fermentable substrate. NAP-3 was sensitive to the amount of naphthalene in the culture; with naphthalene removal and nitrate utilization rates higher when present at 20 mg L− 1 compared to 40 mg L− 1. Electron equivalents represented by transformation of electron donor could be met assuming nitrate reduction to nitrite, except for the incubation with 40 mg L− 1 naphthalene which required complete denitrification. Transient production of the nitrogen-containing bicyclic indole was found by gas chromatograph mass spectrophotometry (GC/MS). Indole production was repeatable and affected by naphthalene concentration; with the 20 mg L− 1 culture producing the most indole. The production of indole was strictly biotic and required the presence of both naphthalene and the commonly-used solubilizing agent N, N dimethyl formamide (DMF). The source of nitrogen in indole was confirmed to be DMF through a series of growth experiments with NAP-3. No indole was produced in incubations fed naphthalene plus nitrate, nitrite or ammonia, either alone or in combination, when DMF was absent. Further, no production of indole was observed when heptamethyl nonane was used as an alternative solubilizing agent. We speculate that indole production proceeds through a pathway similar to the chorismic acid pathway for indole synthesis with incorporation of nitrogen from DMF. No other potential compounds of the chorismic pathway were found by GC/MS when naphthalene was the sole carbon source. NAP-3 grew statistically significantly on anthranilate, but not using salicylate or indole as the sole carbon source.

Storage and growth of denitrifiers in aerobic granules: Part I. model development

A mathematical model, based on the Activated Sludge Model No.3 (ASM3), is developed to describe the storage and growth activities of denitrifiers in aerobic granules under anoxic conditions. In this model, mass transfer, hydrolysis, simultaneous anoxic storage and growth, anoxic maintenance, and endogenous decay are all taken into account. The model established is implemented in the well-established AQUASIM simulation software. A combination of completely mixed reactor and biofilm reactor compartments provided by AQUASIM is used to simulate the mass transport and conversion processes occurring in both bulk liquid and granules. The modeling results explicitly show that the external substrate is immediately utilized for storage and growth at feast phase. More external substrates are diverted to storage process than the primary biomass production process. The model simulation indicates that the nitrate utilization rate (NUR) of granules-based denitrification process includes four linear phases of nitrate reduction. Furthermore, the methodology for determining the most important parameter in this model, that is, anoxic reduction factor, is established.

Denitrification potential enhancement by addition of external carbon sources in a pre-denitrification process

The aim of this study is to investigate the denitrification potential enhancement by addition of external carbon sources and to estimate the denitrification potential for the predenitrification system using nitrate utilization rate (NUR) batch tests. It is shown that the denitrification potential can be substantially increased with the addition of three external carbon sources, i.e. methanol, ethanol, and acetate, and the denitrification rates of ethanol, acetate, and methanol reached up to 9.6, 12, and 3.2 mgN/(g VSS·h), respectively, while that of starch wastewater was only 0.74 mgN/(g VSS·h). By comparison, ethanol was found to be the best external carbon source. NUR batch tests with starch wastewater and waste ethanol were carried out. The denitrification potential increased from 5.6 to 16.5 mg NO 3-N/L owing to waste ethanol addition. By means of NUR tests, the wastewater characteristics and kinetic parameters can be estimated, which are used to determine the denitrification potential of wastewater, to calculate the denitrification potential of the plant and to predict the nitrate effluent quality, as well as provide information for developing carbon dosage control strategy.

Identification of a denitrifying bacterium and verification of its anaerobic ammonium oxidation ability

A strain D3 of denitrifying bacterium was isolated from an anammox reactor, and identified as Pseudomonas mendocina based on the morphological and physiological assay, Vitek test, Biolog test, (G + C) mol% content, and 16S rDNA phylogenetic analysis. As a typical denitrifying bacterium, strain D3 achieved the maximal nitrate reduction rate of 26.2 mg/(L x d) at the nitrate concentration of 88.5 mg N/L. The optimal pH and growth temperature were 7.84 and 34.9 degrees C, respectively. Strain D3 was able to oxidize ammonia under anaerobic condition. The maximum nitrate and ammonium utilization rates were 6.37 mg/(L x d) and 3.34 mg/(L x d), respectively, and the consumption ratio of ammonia to nitrate was 1:1.91. Electron microscopic observation revealed peculiar cell inclusions in strain D3. Because of its relation to anammox activity, strain D3 was presumed to be anammoxosome. The present investigation proved that denitrifying bacteria have the anammox ability, and the results have engorged the range of anammox populations.

A kinetic study of hydrogenotrophic denitrification

The progress of hydrogenotrophic denitrification in batch assays with a mixed culture was examined. The aim was to study the performance of the culture for hydrogenotrophic denitrification of drinking water at various NO 3 − concentrations. The kinetics of the process were studied in batch experiments. The rates of the process were found to be inhibited at high nitrate concentrations. The nitrite concentration remained at very low values throughout the process but it still affected biomass growth. A kinetic model was developed and its kinetic parameters were determined from the batch experiments. The growth kinetics could be very well described by using expressions for double nutrient limitation (nitrate, nitrite) with inhibition from nitrate. The proposed model is capable of describing accurately enough cellular growth, nitrate and nitrite utilization and utilization rates under anoxic conditions in the presence of various concentrations of nitrate in the range of 7 to about 200 mg N/l.

Incorporating membrane gas diffusion into a membrane bioreactor for hydrogenotrophic denitrification of groundwater

A hydrogenotrophic denitrification system, comprising a suspended growth membrane bioreactor (MBR) with membrane hydrogen gas diffusion, was developed to remove nitrate from groundwater. A hollow fiber gas permeable membrane module was designed for hydrogen delivery and a commercially available hollow fiber membrane module was used for solid/liquid separation. The MBR was operated at an SRT of 20 days and at room temperature. Four nitrate loading rates of 24, 48, 96 and 192 NO3(-)-N mg I(-1) d(-1) were applied to the system. As the nitrate loading was raised, pH increased due to increased denitrification and release of OH- ions. The oxidation reduction potential (ORP) remained fairly stable when full denitrification was achieved, but increased when nitrate loading rates reached 192 NO3(-)-N mg I(-1) d(-1) and residual nitrate was present in the reactor. Nitrate removal was complete (100%) in the first three nitrate loadings and 72% in the system with 192 NO3(-)-N mg I(-1) d(-1). Nitrate utilization rates of 30.6, 23.4, and 37.7 g NO3(-)-N m(-3) d(-1) were achieved in the first three loadings. Average effluent dissolved organic carbon (DOC) concentration of approximately 8 mg l(-1) was observed in all four nitrate loading regimes, possibly owing to the generation and release of soluble microbial bi-products (SMP).

The Polish perspective on adopting EU standards nitrogen removal at large WWTPs - case studies

The most challenging issue for existing large WWTPs (>100,000 PE) in Poland will be achievement of the new effluent standards for total nitrogen. Consequently, reliable and accurate information concerning the dimensioning of anoxic compartments is necessary. This study focused on validating to what extent the denitrification rates determined from batch tests were comparable with the rates calculated based on a mass balance over a full-scale activated sludge reactor. The experiments were conducted at two large WWTPs in northern Poland: "Wschod" in Gdansk and "Debogorze" in Gdynia. Two types of batch tests were used to determine the denitrification capability of activated sludge. Lower nitrate utilization rates observed during the full-scale experiments could potentially result from the local disturbances such as nitrate limitation ("Wschod" WWTP) or oxygen penetration to the anoxic zone ("Debogorze" WWTP). These factors should be taken into consideration during the design phase of the anoxic compartments.

Summer plankton production and nutrient consumption patterns in the Mertz Glacier Region of East Antarctica

Abstract We report on a biological and nutrient survey conducted off the eastern Adelie and George V Coasts of East Antarctica in late December 2000 and January 2001. The region was dominated by the Mertz Glacier Tongue (MGT) and its associated polynya that controlled the amount of open water through the season and influenced stratification near forming and melting ice. As in other regions of the Southern Ocean, large concentrations of nitrate, phosphate and silicic acid were found. Chlorophyll levels varied from 0.3 mg m−3 in pack-ice and slope regions to greater than 10 mg m−3 in a Phaeocystis bloom encountered among grounded ice northeast of the MGT. Net utilization rates of nutrients were derived from the deficit between measured concentrations and estimated winter values. Nitrate (N+N) and silicic acid utilization rates ranged from 2 to 12 and 14 to 30 mmol m−2 d−1, respectively, and were greatest in Commonwealth Bay. The ratio of nitrate to phosphate utilization was low ( 10. Lower silicic acid to N+N ratios were found in regions with substantial populations of Phaeocystis sp. in the eastern, grounded ice region. However, there was significant variation in the silicic acid to N+N utilization that may be induced by mixed-layer iron levels that varied from

Denitrifying Characteristics of the Multiple Stages Enhanced Biological Nutrient Removal Process with External Carbon Sources

This research investigated denitrifying activity of activated sludge with three external carbon sources (sodium acetate, methanol and glucose) via a series of batch experiments. Activated sludge used was cultivated in a multiple stages enhanced biological nutrient removal (EBNR) process that exhibited high removal efficiency of effective carbon, nitrogen, and phosphorus. Results showed type of external carbon source had a significant influence on specific nitrate utilization rate, nitrite accumulation, adaptive time of microorganisms, and nitrate removal efficiency. Sodium acetate addition resulted in high phosphate concentration in effluent; meanwhile methanol caused increasing turbidity and carbon breakthrough problem. When glucose was fed to be the external carbon source, accumulative nitrite concentration was higher than that with sodium acetate or methanol addition. When sodium acetate, methanol and glucose were used to be the electron donor, average dosages for nitrate elimination were 6.97, 5.85, and 5.65 mg-COD/mg-N, respectively. Because the final polyhydroxyalkanoates (PHAs) concentrations contained within the biomass were more than the original level and no phosphate re-release was observed, glycogen-accumulating organisms (GAOs) might exist in the multiple stages EBNR process and increased carbon dosage for further nitrate removal.

Modeling Enhanced In Situ Denitrification in Groundwater

A two-dimensional numerical solute transport model was developed for simulating an enhanced in situ denitrification experi- ment performed in a nitrate-contaminated aquifer on Cape Cod, Massachusetts. In this experiment, formate ~HCOO 2 ! was injected for a period of 26 days into the carbon-limited aquifer to stimulate denitrification. Calibration of the vertical-profile site model was demon- strated through error analysis and comparison with formate, nitrate, and nitrite concentration data monitored along a transect of three multilevel groundwater sampling wells for 75 days after initial injection. Formate utilization rates were approximately 142 and 38 mM/day for nitrate and nitrite reduction, respectively. Nitrate and nitrite utilization rates were approximately 29 and 8 mM/day, respectively. Nitrate utilization rates under enhanced conditions were 1 order of magnitude greater than previously reported naturally occurring rates. The nitrite production rate was approximately 29 mM/day. Persistence of nitrite was attributed to a combination of factors, including electron donor ~formate! limitation late in the experiment, preferential utilization of nitrate as an electron acceptor, and greater nitrite production relative to nitrite utilization.

Biological export flux in the Southern Ocean estimated from a climatological nitrate budget

Abstract Diagnostic budgets for heat and nitrate in the Southern Ocean mixed layer are constructed from monthly variation of properties between 80°S and 35°S. The budgets are evaluated using historical CTD and bottle data, including those from WOCE and US JGOFS cruises in the 1990s. A consistent feature in the nitrate budget at all latitudes is the net loss to biological production in the spring/summer. Typical maximum spring nitrate utilization rates are predicted to be 10–20 mmol N m−2 d−1 near Antarctica (south of 70°S) and 4 mmol N m−2 d−1 north of 70°S. South of 55°S much of the nitrate lost to biological production in spring/summer is offset by apparent nitrate production (remineralization) in the mixed layer during the fall/winter. This predicted remineralization, however, may be an artifact of the model and/or limited wintertime data. The annually averaged, area-integrated biological carbon export flux south of 50°S is dominated by the region north of the Polar Front, and is estimated to be 0.9±1.2 Gt C yr−1, assuming a Redfield ratio C/N=6.6. Integrating over the area south of 40°S this flux is increased to 2.0±1.7 Gt C yr−1. However, if we assume that the predicted fall/winter remineralization is in error, and that unresolved physical processes completely replenish the mixed-layer nitrate, then the annual average, area-integrated biological export flux to 50°S increases from 0.9 to 2.2 Gt C yr−1. These results suggest that the Southern Ocean makes a small contribution (

Nitrogen and carbon isotopic composition of marine and terrestrial organic matter in Arctic Ocean sediments:: implications for nutrient utilization and organic matter composition

Relationships between organic carbon, total nitrogen and organic nitrogen concentrations and variations in δ 13C org and δ 15N org are examined in surface sediments from the eastern central Arctic Ocean and the Yermak Plateau. Removing the organic matter from samples with KOBr/KOH and determining residual as well as total N shows that there is a significant amount of bound inorganic N in the samples, which causes TOC/N total ratios to be low (4–10 depending on the organic content). TOC/N org ratios are significantly higher (8–16). This correction of organic TOC/N ratios for the presence of soil-derived bound ammonium is especially important in samples with high illite concentrations, the clay mineral mainly responsible for ammonium adsorption. The isotopic composition of the organic N fraction was estimated by determining the isotopic composition of the total and inorganic nitrogen fractions and assuming mass-balance. A strong correlation between δ 15N org values of the sediments and the nitrate concentration of surface waters indicates different relative nitrate utilization rates of the phytoplankton in various regions of the Arctic Ocean. On the Yermak Plateau, low δ 15N org values correspond to high nitrate concentrations, whereas in the central Arctic Ocean high δ 15N org values are found beneath low nitrate waters. Sediment δ 13C org values are close to −23.0‰ in the Yermak Plateau region and approximately −21.4‰ in the central Arctic Ocean. Particulate organic matter collected from meltwater ponds and ice-cores are relatively enriched in 13C ( δ 13C org=−15.3 to −20.6‰) most likely due to low CO 2(aq) concentrations in these environments. A maximum terrestrial contribution of 30% of the organic matter to sediments in the central Arctic Ocean is derived, based on the carbon isotope data and various assumptions about the isotopic composition of the potential endmembers.

Enhancement of new production in the northeast subarctic Pacific Ocean during negative North Pacific index events

We examined interannual variability in the 1965–1990 winter‐summer differences in surface nitrate (ΔNO3) in the northeast subarctic Pacific Ocean (Station P, 50°N, 145°W). Increases in ΔNO3, of 30–70% above the mean value occurred during four events (1969, 1971‐1972, 1979, 1983). The ΔNO3 time series was highly correlated (r = 0.86) with the spring‐summer nitrate utilization rate from 1970 to 1980. The ΔNO3 time series was negatively correlated with the North Pacific index (NPI) (r = ‐0.72) and positively correlated with solar radiation in the spring (r = 0.48) and summer (r = 0.46). A simple ecosystem model forced with observed incident solar radiation and mixed‐layer depth during the spring‐summer period predicted increases in export production that were 50% of the observed increase for 1970–1972 and 1977–1979. Comparison between the ΔNO3 and sedimenting particulate organic nitrogen (PON) showed that the high ΔNO3 event of 1983 was associated with a dramatic increase in PON fluxes. A simple ecosystem model underpredicts observed interannual variations in export production, and this result combined with the observed PON fluxes suggests that a combination of increased phytoplankton production and increased f ratio produced the observed increase in ΔNO3. The increase in f‐ratio implies a change in the community structure of the phytoplankton during the elevated ΔNO3 events that appears connected to changes in the NPI.

Nitrate respiration associated with detrital aggregates in aerobic bottom waters of the abyssal NE Pacific

Rates of nitrate utilization in tube core respirometers (TCR) placed over aggregates on the seafloor at an abyssal site (Station M) in the eastern North Pacific Ocean increased at times of high particle flux. In the presence of aggregates, both oxygen and nitrate were used in respiration. The ratio of O 2 : NO 3 concentrations in ambient waters was 3.9, while O 2 : NO 3 utilization rates in TCR overlying and TCR aggregate pore waters were 2.6 and 0.6, respectively. We postulated that denitrification was occurring in microzones of the particle-rich oxygenated (135 μM) waters. To test this, nitrate respiration was measured aboard a ship in oxygen-minimum (∼26 μM) water supplemented with particulate matter collected by a surface net tow. Dissolved oxygen consumption occurred immediately, followed by nitrate utilization while oxygen was still present. Calculations from cell densities indicated 0.6 μM of the original 42 μM of nitrate was assimilated into bacterial biomass during 36 h of incubation, suggesting the major portion of the utilized nitrate was used in respiration. Nitrate utilization rates in the in situ incubation study and those of the shipboard experiment were 3.1 and 2.7 μM d -1, respectively. The results of the present studies suggest nitrate respiration occurs in microzones of aggregates in oxygenated bottom waters at times of high particle flux and causes some loss of fixed nitrogen.

第四紀後期の海洋環境と生物生産 堆積有機物の炭素・窒素安定同位体比による古海洋解析

Recently stable carbon and nitrogen isotopic ratios (δ13C and δ15N) of the sedimentary organic matter have become to be applied to reconstruct past changes of the biogeochemical processes in surface waters, although they were used only as the mixing tracers of terrestrial organic matter into coastal sediments during 1970's and 80's. While both of the δ13C and δ15N values of the organic matter produced in the surface water change due to the isotopic fractionation processes during the uptake of inorganic substance (CO2 and NO3- etc.) by phytoplankton, the reconstructed paleoceanograhic factors are completely different between the δ13C and δ15N, such as the [CO2] aq and the phytoplankton growth rate for the δ13C and the nitrate availability for δ15N, reflecting the difference in Σ CO2 and nitrate budgets in the sea surface water.Because the magnitude of carbon isotopic fractionation during the photosynthesis of phytoplankton are influenced by [CO2] aq in the surface water, many recent studies of the organic δ13C in the sediment cores discuss about past changes in pCO2 in the surface water. However, the phytoplankton growth rate also governs the δ13C values of phytoplankton, andtherefore, it is actually very difficult to extract purely the [CO2] aq data from the organic δ13C values. On the other hand, δ15N of sediment is now believed to reflect the past changes in nitrate utilization rates in the surface water (i.e. biological pumping efficiency). Because the isotope fractionation during the nitrate uptake by phytoplankton makes theδ15N values of the remaining nitrate much higher in the surface water body, the relativelylow δ15N values of organic matter can be used to trace a upwelling center of the surface water.The δ13C and δ15N values in the particulate organic matter change largely during their sinking and sedimentation processes. Both of the two isotopic values in the sinking particledecrease downward irrespective of their sample sites, probably due to the selective decomposition of amino acids which have relatively higher δ13C and δ15N values than the bulk organic matter. Contrary to this, the δ13C and δ15N values increase again on the sediment surface. Because the changes in δ13C and δ15N values of organic matter in the sinking and sedimentation processes are universal and somewhat constant processes, it seems reasonable to apply the downcore δ13C and δ15N variations to reconstruct the past changes in the surface water processes.

Response of Nitrobacter to toxicity of drilling chemicals

The effect of drilling chemicals on nitrate utilization and logarithmic rate of growth of Nitrobacter was investigated using varying concentrations of the chemicals. Results indicated that all the drilling chemicals tested were inhibitory to nitrate utilization and caused decrease in growth rate of Nitrobacter. An increase in nitrite utilization by Nitrobacter with increase in exposure time to the chemicals was observed. Nitrite utilization decreased with increase in concentration of the chemicals. Some concentrations of drilling chemicals stimulated the growth rate of Nitrobacter as exposure time increased. Inhibition of nitrite utilization was greatest with Carbotrol and least with Chaux (lime) and Huile-clean. These results showed that drilling chemicals inhibit an aspect of nitrification in the biosphere thereby negatively affecting soil and water fertility.