Influent NO3 Research Articles

Nitrate reduction by nano-Fe/Cu particles in packed column

In this work the application of a modified surface nano zero valent iron (NZVI) as bimetallic Fe/Cu particles to remove high concentration of NO3−-N through packed sand column has been studied. Dispersed nano-Fe/Cu particles has been synthesized in water mixed ethanol solvent system (1:4v/v) and described by XRD pattern, TEM and SEM images and BET analyze. Batch experiments have been conducted to investigate the effect of percentage coating of Fe0 by Cu on the nitrate removal. Research on packed sand column (120cm length, 6.5cm inner diameter) has been done under conditions of Nano-Fe/Cu concentration (2, 5, and 8gl−1 of solution), high initial NO3−-N concentration (100, 200, and 300mgl−1) and pore water velocity through sand (0.125, 0.250, and 0.375mms−1) in seven sets. Results of batch experiments indicated the efficient coating percentage of Fe0 by Cu in NO3−-N reduction was 2.5% (w/w). In addition, increase of pore velocity of water through packed sand has negative effect on the nitrate reduction rate. In contrast, increasing the injected mass of nano particles and the influent NO3−-N concentration would increase the rate of NO3−-N reduction. The best condition to reduce NO3−-N has been observed at end of sand column as 75% of influent concentration when nano-Fe/Cu concentration=8gl−1, high initial NO3−-N concentration=100mgl−1 and pore water velocity through sand=0.125mms−1.

Sulfide removal from industrial wastewaters by lithotrophic denitrification using nitrate as an electron acceptor

Sulfide is present in wastewaters as well as in biogas and can be removed by several physicochemical and biotechnological processes. Nitrate is a potential electron acceptor, readily available in most wastewater treatment plants and it can replace oxygen under anoxic conditions. A lab-scale reactor was operated for treatment of sulfide containing wastewater with nitrate as an electron acceptor and is used to evaluate the effects of volumetric loading rates, hydraulic retention time (HRT) and substrate concentrations on the performance of the lithotrophic denitrification process for treating industrial fermentation wastewaters. Sulfide is removed more than 90% at the loading rates between 0.055 and 2.004 kg S(-2)/m(3) d, when the influent sulfide concentration is kept around 0.163 kg/m(3) and the HRT decreased from 86.4 to 2 h. Nitrogen removal differed between 23 and 99% with different influent NO(3)(-)-N concentration and loading rates of NO(3)(-)/S(-2) ratio. The stoichiometry of sulfide oxidation with nitrate is calculated assuming different end-products based on thermodynamic approach and compared with experimental yield values. The calculated maximum volumetric and specific sulfide oxidation rates reached 0.076 kg S(-2)/m(3) h and 0.11 kg S(-2)/kg VSS h, respectively. The results are obtained at industrially relevant conditions and can be easily adapted to either biogas cleaning process or to sulfide containing effluent streams.

High-rate nitrogen removal by the Anammox process at ambient temperature

The purpose of this study is to investigate the nitrogen removal performance of the anaerobic ammonium oxidation (Anammox) process and the microbial community that enables the Anammox system to function well at ambient temperatures. A reactor with a novel spiral structure was used as the gas-solid separator. The reactor was fed with synthetic inorganic wastewater composed mainly of NH4+-N and NO2--N, and operated for 92 days. Stable nitrogen removal rates (NRR) of 16.3 and 17.5 kg-N m(-3) d(-1) were obtained at operating temperatures of 33±1 and 23±2°C, respectively. To our knowledge, such a high NRR at ambient temperatures has not been reported previously. In addition, the experiments presented herein confirm that high influent NO2--N concentration of 460 mg L(-1) did not noticeably inhibit the Anammox activity. Furthermore, the freshwater Anammox bacterium KU2, which was identified as the dominant bacterial species in the consortium by 16S rRNA gene analysis, is considered to be responsible for the stable nitrogen removal performance at ambient temperatures.

Start-up and stabilization of an Anammox process from a non-acclimatized sludge in CSTR

Development of an Anammox (anaerobic ammonium oxidation) process using non-acclimatized sludge requires a long start-up period owing to the very slow growth rate of Anammox bacteria. This article addresses the issue of achieving a shorter start-up period for Anammox activity in a well-mixed continuously stirred tank reactor (CSTR) using non-acclimatized anaerobic sludge. Proper selection of enrichment conditions and low stirring speed of 30 +/- 5 rpm resulted in a shorter start-up period (82 days). Activity tests revealed the microbial community structure of Anammox micro-granules. Ammonia-oxidizing bacteria (AOB) were found on the surface and on the outer most layers of granules while nitrite-oxidizing bacteria (NOB) and Anammox bacteria were present inside. Fine-tuning of influent NO2(-)/NH4+ ratio allowed Anammox activity to be maintained when mixed microbial populations were present. The maximum nitrogen removal rate achieved in the system was 0.216 kg N/(m(3) day) with a maximum specific nitrogen removal rate of 0.434 g N/(g VSS day). During the study period, Anammox activity was not inhibited by pH changes and free ammonia toxicity.

Enriquecimento de bactérias anaeróbias oxidadoras de amônia - anammox

Bactérias anaeróbias oxidadoras de amônia (bactérias Anammox, do inglês anaerobic ammonium oxidizing bacteria) foram enriquecidas em reator em batelada sequencial (RBS), a partir de lodo proveniente de um sistema convencional de lodos ativados tratando esgoto doméstico de Belo Horizonte (MG). Após três meses de cultivo, atividade Anammox foi detectada no sistema pelo consumo de quantidades estequiométricas de NO2- e NH4+. Análises de hibridação in situ fluorescente (FISH, do inglês fluorescent in situ hybridization) confirmaram a presença de bactérias Anammox, provavelmente Candidatus Brocadia anammoxidans, e revelaram que estas representavam 53% do total de células (após 6 meses de cultivo). O desempenho do reator ao longo dos sete meses de operação demonstrou remoção quase que total de nitrito, baseada em concentração afluente de 61 a 95 mg N-NO2-/L. A eficiência máxima de remoção de amônia alcançada foi de 95%, a partir de concentração afluente de 55 a 82 mg N-NH4+/L.

Sorptive Media Biofiltration for Inorganic Nitrogen Removal from Storm Water

Passive biological filtration for nitrate removal from storm-water drainage is challenged by highly transient mass loadings, the need to adequately supply an electron donor, and potential inhibition by dissolved oxygen (DO). An approach to optimizing nitrate removal is to employ a filter medium containing a mixture of ion exchange and electron donor particles, where the former serve to retain nitrate at high loadings and enable biological denitrification to be more effective. Bench scale filtration experiments were conducted using a 50:50 volume mixture of expanded clay particles (Filtralite P) and elemental sulfur pastille. Nitrate reduction was 98% under steady flowrate operation at 30min residence time and 2.1mg∕L influent NO3–N. Step increases in flowrate by factors of 5.2, 11, and 25 resulted in maximum effluent NO3–N of 0.93, 1.54, and 1.87mg∕L, respectively. Substantial nitrate breakthrough occurred even when effluent DO remained close to zero. The results suggest methods by which mixed media denitrification filters can be more effectively designed and operated.

Wood chips and wheat straw as alternative biofilter media for denitrification reactors treating aquaculture and other wastewaters with high nitrate concentrations

This study evaluated wood chips and wheat straw as inexpensive and readily available alternatives to more expensive plastic media for denitrification processes in treating aquaculture wastewaters or other high nitrate waters. Nine 3.8-L laboratory scale reactors (40cm packed height×10cm diameter) were used to compare the performance of wood chips, wheat straw, and Kaldnes plastic media in the removal of nitrate from synthetic aquaculture wastewater. These upflow bioreactors were loaded at a constant flow rate and three influent NO3–N concentrations of 50, 120, and 200mg/L each for at least 4 weeks, in sequence. These experiments showed that both wood chips and wheat straw produced comparable denitrification rates to the Kaldnes plastic media. As much as 99% of nitrate was removed from the wastewater of 200mg NO3–N/L influent concentration. Pseudo-steady state denitrification rates for 200mg NO3–N/L influent concentrations averaged (1360±40)gN/(m3d) for wood chips, (1360±80)gN/(m3d) for wheat straw, and (1330±70)gN/(m3d) for Kaldnes media. These values were not the maximum potential of the reactors as nitrate profiles up through the reactors indicated that nitrate reductions in the lower half of the reactors were more than double the averages for the whole reactor. COD consumption per unit of NO3–N removed was highest with the Kaldnes media (3.41–3.95) compared to wood chips (3.34–3.64) and wheat straw (3.26–3.46). Effluent ammonia concentrations were near zero while nitrites were around 2.0mg NO2–N/L for all reactor types and loading rates. During the denitrification process, alkalinity and pH increased while the oxidation–reduction potential decreased with nitrate removal.Wood chips and wheat straw lost 16.2% and 37.7% of their masses, respectively, during the 140-day experiment. There were signs of physical degradation that included discoloration and structural transformation. The carbon to nitrogen ratio of the media also decreased. Both wood chips and wheat straw can be used as filter media for biological denitrification, but time limitations for the life of both materials must be considered.

Carbon and nitrogen removal from low-strength domestic wastewater with a two-stage submerged biological filter

The aim of the present study was to evaluate the secondary and tertiary treatment of low -strength domestic wastewater with submerged biological filters (BFs). The experiments were carried out with a two-stage pilot plant consisting of two subsequent filter columns. In the first aerated reactor, the removal of carbon and nitrification was accomplished (secondary nitrification); while, in the second anoxic reactor a post-denitrification process with methanol as external carbon source was performed. During the 3 months of experimental period, in average terms, Total Suspended Solids (TSS) concentrations of 156 mg/L were reduced to 5 mg/L; Chemical Oxygen Demand (COD) concentrations of 179 mg/L were reduced to 43 mg/L. In the secondary nitrification, mean influent NH4 + concentrations of 6.1 mg/L were reduced to average values of 1.8 mg/L. During the post-denitrification, mean influent NO3 − concentrations of 12.0 mg/L were reduced to average values of 6.1 mg/L. The overall process produced a backwashing effluent with an average concentration of about 175 mg/L of TSS.

The behavior of the DNPAOs at the anaerobic-anoxic process according to the change of the influent NO3−−N loading

This study was conducted to investigate the ratios of phosphorus release to COD uptake, phosphorus release to nitrate removaland phosphorus uptake to phosphorus release by denitrifying phosphate accumulating organisms in the system composed of an anaerobic reactor and an anoxic reactor as the change of the influent nitrate loading. The influent concentrations of COD, NH4+−N and PO4−P were 300, 20 and 6 mg/L, respectively, whereas the influent nitrate concentrations were varied at 10, 15, 20 and 30 mg/L. As aresult, the ratio of phosphorus release to carbon uptake was increased in accordance with nitrate supply. The denitrifying phosphate accumulating organisms simultaneously took up phosphate and removed nitrate from the anoxic reactor. With above 20 mg/L of sufficient NO3−−N supply, phosphate was taken up excessively by the DNPAOs in anoxic condition, resulting in the ratio of phosphorus uptake to nitrate removal to be 1.97. The large amount of both uptake and release of phosphorus occurred above 20 mg/L of nitrate supply, achieving the ratio of phosphorus uptake to phosphorus release to be 1.05. Conversely, if nitrate as the electron acceptor was limited, the ratio was found to be low.

DENITRIFICATION OF AGRICULTURAL DRAINAGE USING WOOD-BASED REACTORS

Two denitrification reactor designs, utilizing alternate layers of fine and coarse wood particles, were monitored for their ability to achieve passive, maintenance-free nitrate removal in agricultural tile drainage. A lateral flow design was tested over a 26-month period on drainage from a cornfield in southern Ontario, and an upflow design was tested over a 20-month period on drainage from a golf course, also in southern Ontario. At the cornfield site, flow through the reactor averaged 7.7 L/min at an average influent NO3 concentration of 11.8 mg N/L, and removal averaged 3.9 mg N/L. At the golf course site, flow through the reactor averaged 7.8 L/min at an average influent NO3 concentration of 3.2 mg N/L, and removal averaged 1.7 mg N/L. Areal removal rates averaged 2.5 g N/m2/d in the cornfield reactor and 0.95 g N/m2/d in the golf course reactor, and are about an order of magnitude higher than rates reported for other passive treatment systems such as constructed wetlands even though average operating temperatures were relatively low (7°C to 9°C). Mass balance calculations indicate that carbon consumption from denitrification was <2% per year; thus, these reactors have the potential to operate for a number of years without the need for media replenishment. Both reactors were successful in achieving maintenance-free operation during all seasonal conditions, including unassisted startup after drought and freeze periods. Reactors such as these have the potential for a range of applications in agricultural settings because of their low cost and low maintenance characteristics. They are most usefully applied in the treatment of base flows rather than peak flows and can be readily used in combination with other treatment systems such as constructed wetlands.

Modeling Floodplain Filtration for the Improvement of River Water Quality

A mathematical model was developed to describe a treatment method of floodplain filtration for the improvement of river water quality. The process consists of spraying poor quality river water onto the river floodplains and thus allowing soil filtration to treat water before it gets back again into the main river stream. This technique can be readily employed in Korea because it exploits the characteristics of the climate and rivers in the country, as described in an experimental study of Chung et al. The model was analyzed by numerical methods and validated by comparing the simulated values with experimental data. A scenario analysis of the model was also performed in order to have a better understanding of the floodplain filtration process. Our results show that the model was able to predict the reduction in organic matter and NO 3 − in river water through the floodplain filtration. Furthermore, it was found that only a few decimeters of top soil profile were enough to degrade most of the organic matter under wider operational conditions than those reported in the literature. Also, it was found that significant infiltration of atmospheric oxygen took place near the soil surface. The N2O emission and the NO 3 − leaching increased with the increase in the influent NO 3 − concentration. However, the N2O emission due to floodplain filtration was not expected to exceed 0.1 mL/m2-day.

Thiobacillus denitrificans immobilized biotrickling filter for NO2 removal

Nitrogen dioxide (NO2) removal efficiency of a biotrikling filter was evaluated under different operating conditions. Activated alumina (AA) was used as the immobilization matrix for Thiobacillus denitrificans (T. denitrificans) in the biotrickling filter. Batch studies were conducted to find out the degradation kinetics of nitrate and nitrite for a concentration range of 600–10,000 mg/L expressed as nitrogen. Nitrite exhibited maximum degradation rate followed by nitrate. Electron acceptor in the form of NO2 gas showed least removal efficiency. Bio-kinetic parameters for T. denitrificans, by utilizing nitrate and nitrite as electron acceptors, were also evaluated. The μmax (Maximum specific growth rate) and YT (Yield coefficient) values for T. denitrificans in the presence of nitrate and nitrite were 1.03 h−1, 0.275 and 0.63 h−1, 0.1316 respectively. Column study was conducted to find the adsorption and desorption potential of activated alumina. The adsorbed NO2 from AA could easily be desorbed using distilled water with an efficiency of 76±0.8%. Once fed batch studies were conducted to evaluate the NO2 removal efficiency by a biotrickling filter. With an influent NO2 gas concentration of 2,735 ppm, the reactor could achieve a removal efficiency of 99% within 2 min from gas phase and within 96 h from the liquid phase, with an average biomass concentration of 200 mg/g of AA. The mechanism of NO2 gas removal in the biotrickling filter seems to be the dissolution of NO2 in water to form NO 3 − , conversion of NO 3 − to NO2 −, and finally to N2 gas.

Removal of high NO3Ð concentrations in saline water through autotrophic denitrification by the bacterium Thiobacillus denitrificans strain MP

Autotrophic denitrification by Thiobacillus denitrificans MP isolated from mangrove was investigated in both a sulphur-limestone column reactor and a fermenter. More than 97.5% of the nitrate (NO3-) in the 250 mg NO3(-)-N/L strong influent was removed after 14.3 hours in the column reactor. Influent NO3- was completely depleted in the lower part of the column as the hydraulic retention time increased and a slight pH drop was also observed along the reactor column due to the exhaustion of the buffering ability of the limestone. Trace amounts of oxygen present in the lower part of the reactor column resulted in the accumulation of nitrite and subsequent inhibition of further denitrification. The species composition of the bacterial community in the higher parts of the reactor column was morphologically more diverse than in the lower part. Denitrification by T. denitrificans MP reached an optimal level when the dissolved oxygen was maintained between 1.5-2% of saturation level in the automated fermenter. The stoichiometric ratios of deltaSO4(2-) produced/deltaNO3(-)-N removed were 6.81 and 9.32 in the reactor column and fermenter, respectively. This study suggests that efficient removal of high NO3- concentrations in water or wastewater can be achieved using autotrophic bacteria immobilized on surfaces of sulphur granules in the column system.

Denitrification of High NO3 −-N Containing Wastewater Using Elemental Sulfur; Nitrogen Loading Rate and N2O Production

The effects of both concentration and loading rates of nitrate on denitrification efficiency and N2O production during the autotrophic denitrification with elemental sulfur were evaluated. Experiments were conducted with three continuously fed sulfur packed bed reactors (SPBRs) with different influent nitrate concentrations. The loading rate at which nitrate removal efficiency was greater than 95% decreased from 2.46 to 1.64 kg NO3 −-N m−3 day−1 as the influent NO3 −-N concentration increased from 175 to 700 mg l−1. The nitrate removal rate per unit volume of sulfur layer can be expressed as α (ALR)n, where ALR is the applied loading rate. The range of α and n values were 0.72-0.83 and 0.91-0.94, respectively. The maximum nitrate removal rate was estimated as 3.9 to 4.5 kg NO3 −-N m−3 day−1 depending on the influent NO3 −-N concentration. The loading rate for complete denitrification without N2O production was 1.37 kg NO3 −-N m−3 day−1 at the influent NO3 −-N concentration of 175 mg l−1. N2O production became significant when the influent nitrate concentration increased while the loading rate remained the same. The batch test indicated that the amount of N2O production per unit mass of nitrogen was greater with nitrite than with nitrate showing that N2O production was directly related to the concentration of nitrite and nitrate.

Long‐Term Performance of In Situ Reactive Barriers for Nitrate Remediation

AbstractNitrate is now recognized as a widespread ground water contaminant, which has led to increased efforts to control and mitigate its impacts. This study reports on the long‐term performance of four pilot‐scale field trials in which reactive porous barriers were used to provide passive in situ treatment of nitrate in ground water. At two of the sites (Killarney and Borden), the reactive barriers were installed as horizontal layers underneath septic system infiltration beds; at a third site (Long Point), a barrier was installed as a vertical wall intercepting a horizontally migrating septic system plume; and at the fourth site (North Campus), a barrier was installed as a containerized subsurface reactor treating farm field drainage water. The reactive media consisted of 15% to 100% by volume of waste cellulose solids (wood mulch, sawdust, leaf compost), which provided a carbon source for heterotrophic denitrification. The field trials have been in semicontinuous operation for six to seven years at hydraulic loading rates ranging from six to 2000 L/day. Trials have been successful in attenuating influent NO3‐ (or NO3‐+ NH4+ at Borden) concentrations averaging from 4.8 mg/L N at North Campus to 57 mg/L N at Killarney, by amounts averaging 80% at Killarney, 74% at Borden, 91 % at Long Point, and 58% at North Campus. Nitrate consumption rates were temperature dependent and ranged from 0.7 to 32 mg L N/day, but did not deteriorate over the monitoring period. Furthermore, mass‐balance calculations indicate that carbon consumption by heterotrophic denitrification has so far used only about 2% to 3% of the initial carbon mass in each case. Results suggest that such barriers should be capable of providing NO3‐ treatment for at least a decade or longer without carbon replenishment.Reactive barriers have now been used to treat nitrate contamination from a variety of sources including septic systems, agricultural runoff, landfill leachate, and industrial operations. This demonstration of successful long‐term operation should allow this technology to become more widely considered for nitrate remediation, particularly at sites where passive treatment requiring a minimum of maintenance is desired.

Alkalinity requirements and the possibility of simultaneous heterotrophic denitrification during sulfur-utilizing autotrophic denitrification

Alkalinity requirement and the possibility of simultaneous heterotrophic denitrification during sulfur-utilizing autotrophic denitrification were evaluated with sulfur packed bed reactors (SPBRs). SPBR showed &amp;gt;99% NO3--N removal efficiency at influent NO3--N concentration of 1,500 mg/L, although 25-40% of the added NO3--N was recovered as N2O. Complete denitrification without N2O production was achieved when the influent NO3--N concentration decreased to 750 mg/L. When nitrified landfill leachate containing 602–687 mg/L of NO3--N was fed to SPBR, denitrification efficiency was greater than 98%. During leachate treatment, alkalinity consumption was 3.25–3.76 g CaCO3/g NO3--N removed. Most of denitrification activity occurred within bottom 11.5 cm of sulfur layer, meaning that effective HRT of 2.34 hours was enough for the complete denitrification at the loading rate of 2.2 kg NO3--N/m3-day. Complete denitrification was also achieved when methanol was added to nitrified leachate without alkalinity addition. In this case, alkalinity produced by heterotrophs was used for sulfur-utilizing denitrification.

Nitrogen removal in a surface-flow wastewater treatment wetland

From December 1993 through November 1994, we conducted a nitrogen mass-balance study on a 0.74-ha, surface-flow wetland that receives water from an oxidation pond in the municipal wastewater treatment system in Arcata, California, USA. Water samples were collected biweekly and analyzed for concentrations of NO3−N (nitrate), NH4−N (total ammonia), and TN (total nitrogen). Flow was calculated from hydraulic head measurements taken at two inlet weirs. Macrophytes and sediment were sampled during summer to estimate N storage in these compartments. The wetland removed 17% of the 16,600 kg of influent N during the annual cycle. Little removal occurred prior to mid-May; whereas from mid-May through November, 37% of influent N was removed. Expressed on an areal basis, net N removal was 1.84 g N·m−2·d−1 during the warmer months of the year and 1.07 g N·m−2·d−1 during the entire 12-month period. Nitrogen storage in the seasonal, above-ground increment of macrophyte biomass was only 7% of overall N removal by the marsh. From 1986 to 1994, 990–2,390 kg of N (or 0.046–0.11 g N·m−2·d−1) accumulated in the sediment—only 4–10% of overall annual N removal. Mean annual TN removal (1.07 g N·m−2·d−1) considerably exceeded mean influent NO3−N loading (0.64 g N·m−2·d−1), and removal of TN was highly correlated with NO3−N mass loading (r=0.89, P<0.001). Thus, sequential nitrification/denitrification appears to occur in the marsh, and denitrification (estimated at 0.95–1.02 g N·m−2·d−1) appears to be the primary N-removal mechanism.