Simultaneous Nitritation Research Articles

Simultaneous nitritation and p-nitrophenol removal using aerobic granular biomass in a continuous airlift reactor

The chemical and petrochemical industries produce wastewaters containing ammonium and phenolic compounds. Biological treatment of these wastewaters could be problematic due to the possible inhibitory effects exerted by phenolic compounds. The feasibility of performing simultaneous nitritation and p-nitrophenol (PNP) biodegradation using a continuous aerobic granular reactor was evaluated. A nitrifying granular sludge was bioaugmented with a PNP-degrading floccular sludge, while PNP was progressively added to the feed containing a high ammonium concentration. Nitritation was sustained throughout the operational period with ca. 85% of ammonium oxidation and less than 0.3% of nitrate in the effluent. PNP biodegradation was unstable and the oxygen limiting condition was found to be the main explanation for this unsteadiness. An increase in dissolved oxygen concentration from 2.0 to 4.5 mg O2 L(-1) significantly enhanced PNP removal, achieving total elimination. Acinetobacter genus and ammonia-oxidising bacteria were the predominant bacteria species in the granular biomass.

Complete autotrophic denitrification in a single reactor using nitritation and anammox gel carriers

A novel aerobic denitrification reactor, aerobic denitrification using nitrifying and anoxic ammonium-oxidizing (anammox) bacteria immobilized on gel carriers in a single stage (AIGES), was developed. Two types of gel carriers, a nitritation gel carrier and an anammox gel carrier, were installed in single reactor, and the denitrification performance of simultaneous nitritation and anammox was evaluated. The denitrification performance increased gradually with increased aeration rate, reaching a denitrification rate of 1.4 kg N m(-3) d(-1) 2 weeks after the nitritation and anammox gel carriers were mixed. A high average denitrification efficiency of 82% was confirmed. Stable aerobic denitrification performance was observed for more than half a year. In the startup period of AIGES operation, ammonia-oxidizing bacteria were shown by fluorescence in situ hybridization analysis to grow on the surface layer of anammox gel cubes. These results indicated that anammox gel carriers promptly adapted to an aerobic environment by altering the microbial ecosystem.

Effect of influent C/N ratio on nitrogen removal using PHB as electron donor in a post‐denitritation SBR

AbstractBackgroundThe post‐denitritation sequencing batch reactor (SBR) is widely‐used and can achieve high levels of nitrogen removal. In this study the effect of influent COD/TN (total nitrogen) ratio (i.e. C/N ratio) on nitrogen removal performance was investigated.ResultsThe experimental results showed that polyhydroxybutyrate (PHB) was the internal carbon source for denitritation, so PHB degradation rate following first‐order kinetics was the rate‐limiting step both for simultaneous nitritation–denitritation (SND) in the substrate famine period of the oxic stage and endogenous denitritation in the anoxic stage. Higher influent C/N ratio resulted in more PHB fractions in microorganisms, which facilitated a higher efficiency of SND and a faster endogenous denitritation rate (DNR). Consequently, mean TN removal ratio in oxic stage dropped from 32.81% to 8.61%, and average endogenous DNR in the anoxic stage fell from 1.50 to 0.27 mgN h‐1 gVSS‐1, when influent C/N ratio changed from 6.82 to 1.89. Furthermore, PHB fraction in the biomass did not drop drastically when influent C/N ratio dropped for a short‐term period, which facilitated better resistance to shock loads.ConclusionHigh influent C/N ration benefits nitrogen removal in this process, and an influent C/N ratio of 4.00 was suitable for advanced nitrogen removal. © 2013 Society of Chemical Industry

Advanced nitrogen removal from landfill leachate without addition of external carbon using a novel system coupling ASBR and modified SBR

In order to achieve advanced nitrogen removal from landfill leachate without the addition of external carbon sources, a novel system coupling an anaerobic sequencing batch reactor (ASBR) and sequencing batch reactor (SBR) was proposed for the treatment of real landfill leachate with NH4+-N and chemical oxygen demand (COD) concentrations of 1100mg/L and 6000mg/L, respectively. ASBR could remove 80% of the influent COD under a volumetric loading rate of 5kg COD/(m3d). Denitritation and simultaneous nitritation–denitritation were responsible for 50% of the TN removal in SBR under alternate anoxic/aerobic modes. Furthermore, advanced nitrogen removal was realized with a total inorganic nitrogen (TIN) removal efficiency of 99% at the expense of endogenous denitritation during a 26h period, which led to effluent COD and TN values of 550–650mg/L and 15–25mgN/L, respectively. For the combined system, removal efficiencies of COD and total nitrogen (TN) were above 90% and 95%, respectively.

Numerical modeling of nitrogen removal processes in biofilters with simultaneous nitritation and anammox

This study developed a simple numerical model for nitrogen removal in biofilters, which was designed to enhance simultaneous nitritation and anaerobic ammonium oxidation (anammox). It is the first attempt to simulate anammox together with two-step nitrification in natural treatment systems, which may have different kinetic parameters and temperature effects from conventional bioreactors. Prediction accuracy was improved by adjusting kinetic coefficients over the startup period of the biofilters. The maximum rates of nitritation and nitrite oxidation increased linearly over time during the startup period. Simulations confirmed successful enhancement of simultaneous nitritation and anammox (SNA) in the biofilters, with anammox contributing 35% of ammonium removal. Effluent ammonium concentration was affected by influent ammonium concentration and the maximum nitritation rate, and was insensitive to the maximum nitrite oxidation rate and anammox substrate factor. Ammonium removal via SNA was likely limited by biomass of aerobic ammonia oxidizing bacteria in the biofilters. The developed model is a promising tool for studying the dynamics of nitrogen removal processes including SNA in natural treatment systems.

Enhancing simultaneous nitritation and anammox in recirculating biofilters: Effects of unsaturated zone depth and alkalinity dissolution of packing materials

This study investigated effects of unsaturated zone depth on nitrogen removal via simultaneous nitritation and anammox in three vertical flow recirculating biofilters. The biofilters had different depths (25, 40, and 60cm) of an unsaturated zone and the same depth (35cm) of a saturated zone. Unsaturated zone depth could be regulated to maintain suitable dissolved oxygen concentrations and enhance entrapment of carbon dioxide for co-occurrence of aerobic ammonia oxidation and anammox in the saturated zones. The biofilters with the larger unsaturated zones had higher ammonium and total inorganic nitrogen removal rates (16.2–33.5gN/m3/d and 4.6–16.7gN/m3/d, respectively) than the biofilter with the smallest unsaturated zone (11.9–18.1gN/m3/d and 4.4–7.9gN/m3/d, respectively). Electric arc furnace slag and marble chips were packed in the unsaturated and saturated zones, respectively, as low-cost materials to supplement alkalinity and buffer pH. Laboratory experiments showed that the maximum alkalinity dissolution efficiency was 513mg CaCO3/kg marble chips and 761mg CaCO3/kg electric arc furnace slag. Marble chips and electric arc furnace slag could increase dairy wastewater pH up to 7 and 9, respectively. The laboratory results are also useful for utilization of furnace slag and marble chips in constructed wetlands.

Effects of pH and temperature on coupling nitritation and anammox in biofilters treating dairy wastewater

Simultaneous nitritation and anammox is a novel process for nitrogen removal from wastewater. This study operated two innovative biofilters to examine the effects of pH and temperature on the nitritation–anammox process. Marble chips were packed in the biofilters to buffer pH and supplement alkalinity. Electric arc furnace slag was added to marble chips in one biofilter to further increase pH to favor nitritation over nitratation. After a 5-month startup period, the biofilters were batch loaded with dairy wastewater and drained weekly over seven months. Fluorescence in situ hybridization analysis found that aerobic ammonium oxidizing and anammox bacteria accounted for 69–74% of the bacterial populations in the biofilters, which were substantially higher than those reported earlier for constructed wetlands and biofilters. Ammonium removal rate was significantly higher in the biofilter at pH 8.1 (7.8±1.2gN/m3d) than that in the other biofilter at pH 7.6 (6.4±1.3gN/m3d). Free ammonia concentration should be controlled along with pH to avoid toxicity to anammox bacteria. There was no significant correlation of nitrogen removal with the seasonal variation of temperature. Temperature effects were further examined for another five months by heating one of the biofilters. Ammonium removal rate was greater (23.7±3.3gN/m3d) in the heated biofilter at 28.8±1.1°C than that in the unheated biofilter (7.6±2.4gN/m3d) where temperature fluctuated at 21.2±3.2°C. The effects of constant temperature were superior to pH effects on nitritation–anammox. The nitritation–anammox process is more sensitive to temperature than nitritation and anammox individually. This study demonstrated that waste products (marble chips and furnace slag) can be used in biofilters to effectively raise pH and enhance nitritation–anammox for nitrogen removal from dairy wastewater.

Integration of anammox into the aerobic granular sludge process for main stream wastewater treatment at ambient temperatures

Anaerobic ammonium oxidation, nitrification and removal of COD was studied at ambient temperature (18 °C ± 3) in an anoxic/aerobic granular sludge reactor during 390 days. The reactor was operated in a sequencing fed batch mode and was fed with acetate and ammonium containing medium with a COD/N ratio of 0.5 [g COD/gN]. During influent addition, the medium was mixed with recycled effluent which contained nitrate in order to allow acetate oxidation and nitrate reduction by anammox bacteria. In the remainder of the operational cycle the reactor was aerated and controlled at a dissolved oxygen concentration of 1.5 mg O 2/l in order to establish simultaneous nitritation and Anammox. Fluorescent in-situ hybridization (FISH) revealed that the dominant Anammox bacterial population shifted toward Candidatus “Brocadia fulgida” which is known to be capable of organotrophic nitrate reduction. The reactor achieved stable volumetric removal rates of 900 [g N 2–N/m 3/day] and 600 [g COD/m 3/day]. During the total experimental period Anammox bacteria remained dominant and the sludge production was 5 fold lower than what was expected by heterotrophic growth suggesting that consumed acetate was not used by heterotrophs. These observations show that Anammox bacteria can effectively compete for COD at ambient temperatures and can remove effectively nitrate with a limited amount of acetate. This study indicates a potential successful route toward application of Anammox in granular sludge reactors on municipal wastewater with a limited amount of COD.

N-004 INORGANIC NITRITE ATTENUATES ANGIOTENSIN II INDUCED CONTRACTION OF THE RENAL MICROCIRCULATION VIA XANTHINE OXIDASE-DEPENDENT NO PRODUCTION

Background Reduced nitric oxide (NO) bioavailability in the kidney increases reactivity of preglomerular vessels, and may contribute to hypertension. Inorganic nitrite is emerging as a substrate for NOS-independent generation of NO, and physiological and therapeutic effects have been demonstrated in renal and cardiovascular disease. Today the influence of nitrite on renal microvascular function is not known. Methods Isolated and perfused renal afferent arterioles of mice (C57BL/6J) were used to investigate the effects of nitrite (10−9 to 10−4 mol/L, each dose applied for 2 min) on the luminal diameter. Effects of nitrite (10−5 mol/L) on NO production (using DAF-FM), and isotonic contractions to Ang II (10−12 to 10−6 mol/L, each dose applied for 2 min) were measured with or without simultaneous NOS-inhibition with L-NAME (10−4 mol/L). Results Nitrite increased luminal diameter in a dose dependent manner (6 ± 1% at 10−4 mol/L). Nitrite at 10−5 mol/L, applied for 15 min, dilated arterioles (6 ± 2%) and was associated with an increase in NO production (7 ± 1%). Ang II constricted arterioles in a concentration-dependent manner with a maximal response of 31 ± 3%. Simultaneous nitrite treatment (10−5 mol/L) attenuated the contractile response to Ang II (17 ± 4%). Simultaneous treatment with L-NAME enhanced Ang II-mediated contraction (56 ± 4%), and nitrite attenuated the response (25 ± 2%). The nitrite-mediated attenuation on Ang II+L-NAME-induced contraction was abolished by the NO scavenger cPTIO (66 ± 2%), the guanylyl cyclase inhibitor ODQ (58 ± 4%), as well as the xanthine oxidase inhibitor oxypurinol (63 ± 3%). Conclusion Inorganic nitrite undergoes xanthine oxidase-mediated reduction to NO in the microcirculation of the kidney, and attenuates Ang II mediated contraction. This novel function of nitrite in regulating preglomerular resistance may contribute to the reported effects in cardiovascular health and disease.

Simultaneous nitritation and denitritation of domestic wastewater without addition of external carbon sources at limited aeration and normal temperatures

Nitrogen removal via nitrite and simultaneous nitrification-denitrification (SND) are two processes for nitrogen removal from wastewater. The combination of these two processes, i.e., simultaneous nitritation-denitritation or SND via nitrite, is highly beneficial for the domestic wastewater treatment in terms of lower carbon requirements, reduced oxygen demand and less biomass production. A lab-scale sequencing batch reactor (SBR) treating domestic wastewater with low C/N ratios was operated to investigate simultaneous nitritation-denitritation without addition of external carbon sources under limiting aeration and normal temperatures (19±1°C). The results showed that at a longer sludge retention time (SRT) of 50–66 d and an average dissolved oxygen (DO) concentration of 0.65 mg/L, nitritation was successfully achieved with nitrite accumulation rate over 95%. Fluorescence in-situ hybridization (FISH) analysis proved that ammonia oxidizing bacteria (AOB) became dominant nitrifying bacteria. Furthermore, denitritation occurred during the above aerobic period. The average total nitrogen (TN) removal through simultaneous nitritation-denitritation was maintained at 52% with a maximum of 63.1%. Low DO concentration under limited aeration is the key factor to achieve simultaneous nitritationdenitritation. Under long-term operation with low DO concentrations, the altering of nitrifying communities, establishment of anoxic micro-environment for denitrifiers growth and the characteristics of COD and NH4+-N biodegradation promoted the occurrence of simultaneous nitritation-denitritation.

Two rapid and sensitive automated methods for the determination of nitrite and nitrate in soil samples

Abstract Spectrophotometric flow injection methods were developed for the individual determination of nitrite or nitrate, and for the simultaneous determination of nitrite and nitrate, in soil samples. Nitrite was determined directly using a modified version of the Griess–Ilosvay diazo-coupling reaction, measuring at 543 nm the absorbance of the azo–dye complex formed. Simultaneous nitrite and nitrate determinations were based on on-line nitrate reduction in a micro column containing copperised cadmium. A single chromogenic reagent containing all the necessary reactants was used in both methods. For determinations, the chemical and instrumental variables were optimised by univariate analysis and simplex chemometric method. The optimised conditions gave a linear calibration range between 0.05 and 1.6 µg m L − 1 for N–NO 2 − and between 0.05 and 7.0 µg m L − 1 for N–NO 3 − . The detection limits for nitrite and nitrate were 22 µg L − 1 and 44 µg L − 1 respectively. The proposed methods allowed up to 35–40 samples per hour to be analysed with good precision. The simultaneous method was successfully used for the determination of nitrite and nitrate in soil samples (the results obtained were validated against those obtained by reference methods). The proposed methods are simpler and faster than conventional methods and could be routinely used in environmental monitoring laboratories.

Failure of an enriched nitrite-DPAO population to use nitrate as an electron acceptor

The metabolism of denitrifying polyphosphate accumulating organisms (DPAO) is not completely known. Recent reports suggest the existence of two types of DPAOs: those that can use nitrate and nitrite as electron acceptors (nitrate-DPAO) and those that can only use nitrite (nitrite-DPAO). Then, the survival of nitrite-DPAO in nitrate reducing environments is due to the existence of flanking denitrifying species, which reduce nitrate to nitrite. This works aims at a better understanding of the nitrite-DPAO population. For this aim, a nitrite-DPAO population was previously selected in a SBR using nitrite as electron acceptor. Then, nitrate utilisation by nitrite-DPAO was studied within a short-term period (4 days) and within a long-term period (50 days) with simultaneous nitrite and nitrate additions. The results obtained clearly indicate that nitrite-DPAO fail to use nitrate as electron acceptor even after 50 days of periodic dosing of nitrate and agree with the dual DPAO theory. Moreover, this failure casts doubts on the feasibility of nitrite based EBPR systems (i.e. partial nitrification + nitrite-DPAO) because these systems will not be able to denitrify an occasional nitrate inlet, which will remain in the effluent.

Morpholine vapour inhalation and interactions of simultaneous nitrite intake. Biochemical effects on rat spinal cord axons and skeletal muscle.

Male Wistar rats exposed intermittently to 300 ppm (12.5 mumol/l) morpholine vapour 5 days a week for 6 h daily during 4-15 weeks displayed an increasing brain solvent content analyzed by a sensitive gas chromatographic method. Rats drinking water which contained 150 mg NaNO2/l during the vapour exposure period showed initially larger brain solvent concentrations which began to decrease after 8 weeks. Fat solvent concentrations were a fraction of those detected in brain of the solvent-exposed animals or of those in the combined exposure. Nitrite exposure alone caused decreased spinal cord axon acetylcholine esterase activity after 8 weeks while this effect was noted in the combined exposure only at 8 weeks disappearing later on. Axonal succinate dehydrogenase activity was below the controls in the combined exposure throughout the study, and combination also caused persistent increase in the muscle creatine kinase activity. The morpholine-induced effects were less remarkable. The results point at pharmacokinetic interaction between the solvent and nitrite with its own effects on energy metabolism. No N-nitrosomorpholine was found although other metabolic interactions could not be excluded.