Oxidation Of Ammonia Nitrogen Research Articles

Electrochemical Detection of Ammonia in Water Using NiCu Carbonate Hydroxide-Modified Carbon Cloth Electrodes: A Simple Sensing Method.

Excessive ammonia nitrogen can potentially compromise the safety of drinking water. Therefore, developing a rapid and simple detection method for ammonia nitrogen in drinking water is of great importance. Nickel-copper hydroxides exhibit strong catalytic capabilities and are widely applied in ammonia nitrogen oxidation. In this study, a self-supported electrode made of nickel-copper carbonate hydroxide was synthesized on a carbon cloth collector via a straightforward one-step hydrothermal method for rapid ammonia nitrogen detection in water. It exhibits sensitivities of 3.9 μA μM-1 cm-2 and 3.13 μA μM-1 cm-2 within linear ranges of 1 μM to 100 μM and 100 μM to 400 μM, respectively, using a simple and rapid i-t method. The detection limit is as low as 0.62 μM, highlighting its excellent anti-interference properties against various anions and cations. The methodology's simplicity and effectiveness suggest broad applicability in water quality monitoring and environmental protection, particularly due to its significant cost-effectiveness.

Moving-bed biofilm reactor (MBBR) alleviates the negative effect of methylisothiazolinone on the nitrification-denitrification process

Methylisothiazolinone (MIT) is an emerging contaminant used as a biocide in housecleaning and skin care products. Therefore, MIT can reach civil wastewater treatment plants due to domestic usage, thus potentially inhibiting the biological process. This study aims to investigate, for the first time, the effect of MIT on the nitrification-denitrification process in a moving-bed biofilm reactor (MBBR). After a preliminary study performed in a fed-batch reactor, two MBBRs were simultaneously operated in semi-continuous mode for 136 days evaluating a concentration of MIT in the influent of 0.1 and 1.0 mg/L. A parallel study was also conducted under anaerobic conditions to evaluate the effect of MIT on methane production and volatile fatty acid accumulation. At a concentration of 0.1 mg MIT/L, the nitrification process experienced an initial complete inhibition. Subsequently, nitrifying bacteria gradually recovered, reaching approximately 49 % oxidation of ammonia nitrogen, a removal improved up to 64 % at 1.0 mg MIT/L. Although denitrification dealt with a temporary inhibition, the process ultimately achieved a 100 % decrease in nitrite and nitrate concentrations when the MIT concentration was increased from 0.1 to 1.0 mg/L. The cumulative methane yield reached approximately 134 mL CH4/g VS for the control group and was similar to the methane production obtained in the presence of MIT. A MIT removal of 100 % was achieved under aerobic, anoxic, and anaerobic conditions.

In-situ oxidation of ammonia nitrogen to N2 in low temperature groundwater through Cl• − mediated peroxymonosulfate – Fe3O4 / chlorine process

The conventional ammonia in-situ treatment technology fails to achieve complete NH4+-N degradation, while the high concentration of native iron in groundwater further complicates its removal process, potentially leading to adverse environmental consequences. This study investigates the introduction of peroxymonosulfate (PMS) into groundwater containing high concentrations Fe2+ (Fe3O4 as a ferrous source), which can act as persistent catalysts, and Cl-, causing the degradation of ammonia through chlorine free radical-based advanced oxidation processes (PMS- Fe3O4/Cl-), and evaluates the advantages and limitations of employing the PMS- Fe3O4/Cl- system for ammonia treatment. The rapid reaction between SO4•- and Cl- resulted in the formation of Cl• as primary products. Cl• initiates a cascade of subsequent reactions with pH-dependent secondary active products. Under optimal conditions, the ammonia removal efficiency reached 97.44 % using the PMS- Fe3O4/Cl- system within 120 min of operation, which can be attributed to the selective oxidation of ammonia by chlorine reactive species. And this finding was substantiated by observations from experiments involving free radical quenching and EPR spectra coupled with DMPO. The HCO3– and humic acid (HA) in water can significantly affect the removal of ammonia, owing to their capability of quenching SO4•- and Cl•. Meanwhile, the levels of generated toxic chlorates in our system remain within acceptable limits. The PMS- Fe3O4/Cl- system exhibited outstanding transport capacity and stability in simulated columns, demonstrating excellent ammonia oxidation efficiency in natural groundwater, thereby confirming its promising practical potential. All experiments were executed at a temperature of 12 ℃, thereby verifying the remarkable efficacy of the PMS- Fe3O4/Cl- system in removing ammonia even under microtherm conditions.

The response mechanism and dynamic succession of microbial community in activated sludge system under dexamethasone stress

The mass production and widespread use of dexamethasone (DEX) during the COVID-19 pandemic inevitably led to the increase of residue concentrations in wastewater treatment plants. In this study, the effects of DEX at different concentrations on the activated sludge system were investigated. The results indicated that organic matter removal and ammonia nitrogen oxidation were inhibited. The effluent COD and TN gradually increased with increasing DEX concentration. The extracellular polymeric substance was secreted as a protective barrier against DEX stress, ensuring the integrity of the cell membrane. According to assembly mechanism analysis, the relative importance of homogeneous selection in deterministic processes gradually increased under DEX stress, which acts as the main driving force to alter the distribution of abundance and rare taxa, causing the decrease of rare taxa and community diversity, thus forming more homogeneous and similar community structure. These negative consequences, coupled with the inhibition in autotrophic nitrifiers such as Nitrosomonas and Ellin6067, and the decrease in gene abundance of nitrification metabolism including AmoCAB and Hao, were directly responsible for the obvious deterioration of NH4+-N oxidation capacity. This study provided reliable experimental data about the effects of DEX on activated sludge systems, which is conducive to reducing the environmental risk of DEX and maintaining the stable operation of the activated sludge system.

Selective oxidation of ammonia nitrogen to nitrogen gas by Fe2+/PMS/Cl−: The role of reactive chlorine species

Ammonia nitrogen (NH4+-N) can pose a threat to ecosystems and human health. Many methods have been used for the removal of NH4+-N. In particular, reactive chlorine species (RCS, including Cl·, Cl2·−, and ClO·) show superior performance for the selective oxidation of NH4+-N to nitrogen gas (N2). Herein, Fe2+/peroxymonosulfate (PMS)/Cl− process was proposed to generate RCS for the conversion of NH4+-N to N2, in which Fe2+ was used as the activator of PMS in the presence of Cl−. Fe2+, PMS, and Cl− concentrations could affect the removal of NH4+-N in Fe2+/PMS/Cl− process. Fe2+/PMS/Cl− exhibited good performance in removing NH4+-N at pH 3.5–8.0. At all investigated conditions, NH4+-N was mainly converted to N2, and N2 selectivity was more than 90 %. Under optimal conditions, 50 % of NH4+-N was removed in 5 min, and the removal efficiency reached the maximum of 96 % within 120 min with the high N2 selectivity of 100 %. The electron spin resonance tests, scavenging experiments, and probe experiments demonstrated the generation of RCS in Fe2+/PMS/Cl− reaction system. Experimental results and model analysis consistently proved that ClO· and Cl· were crucial radicals during the selective oxidation of NH4+-N, especially ClO·. Fe2+/PMS/Cl− system could remove NH4+-N and COD simultaneously in real wastewater. This study can provide an efficient strategy for the removal of NH4+-N.

A novel photo-assisted activated persulfate strategy for selective oxidation of ammonia nitrogen to dinitrogen using sodium silicate and sodium sulfite as regulators

Persulfate (PS)-based advanced oxidation processes (SR-AOPs) is a promising approach for the removal of ammonia nitrogen (NH3-N) from wastewater, but it suffered from the low removal efficiency and the excessive oxidation of NH3-N to nitrate (NO3−) or nitrite (NO2−) in the absence of in-situ generated chlorine radicals. Therefore, it is still a challenge to improve the efficiency of NH3-N removal and the selectivity of NH3-N oxidation products towards dinitrogen (N2) by SR-AOPs without chlorine radicals. Herein, a novel photo-assisted activation of SR-AOPs involving sodium silicate (Na2SiO3) and sodium sulfite (Na2SO3) was developed for NH3-N removal from wastewater. In this system, Na2SiO3 was acted as a green buffer to maintain NH3-N in the form of un-ionized ammonia (NH3) with strong reducibility, promoting the efficiency of NH3-N removal as well as ensuring the neutral effluent by receiving the H+ from PS activation. Na2SO3 could inhibit the excessive oxidation of NH3-N by regulating the redox potential of the solution and generating hydrated electrons (eaq−) under light (hv) irradiation, enhancing the selectivity of NH3-N oxidation products towards N2. 100 % of NH3-N removal efficiency and more than 98 % of N2 selectivity were obtained after 30 min at the initial pH of 3–9 and the initial NH3-N concentration of 30 mg N/L. Based on the quenching experiment, EPR test and probe experiment, the HO and SO4− were the main reactive oxygen species (ROS) to be responsible for NH3-N oxidation. This study proposed a new approach for treatment of wastewater containing NH3-N by SR-AOPs.

Micro-aeration and low influent C/N are key environmental factors for achieving ANAMMOX in livestock farming wastewater treatment plants

Anaerobic ammonium oxidation (ANAMMOX)-mediated system is a cost-effective green nitrogen removal process. However, there are few examples of successful application of this advanced wastewater denitrification process in wastewater treatment plants, and the understanding of how to implement anaerobic ammonia oxidation process in full-scale is still limited. In this study, it was found that the abundance of anaerobic ammonia-oxidizing bacteria (AnAOB) in the two livestock wastewater plants named J1 and J2, respectively, showed diametrically opposed trends of waxing and waning with time. The microbial communities of the activated sludge in the two plants at different time were sampled and analyzed by high-throughput sequencing of 16S rRNA genes. Structural equation models (SEMs) were used to reveal the key factors affecting the realization of the ANAMMOX. Changes in the concentration of dissolved oxygen and C/N had a significant effect on the relative abundance of anaerobic ammonia oxidation bacteria (AnAOB). The low concentration of DO (0.2∼0.5 mg/L) could inhibit the activity of nitrifying bacteria (NOB) to achieve partial oxidation of ammonia nitrogen and provide sufficient substrate for the growth of AnAOB, similar to the CANON (Completely Autotrophic Nitrogen removal Over Nitrite). Unlike CANON, heterotrophic denitrification is also a particularly critical part of the livestock wastewater treatment, and a suitable C/N of about 0.6 could reduce the competition risk of heterotrophic microorganisms to AnAOB and ensure a good ecological niche for AnAOB. Based on the results of 16S rRNA and microbial co-occurrence networks, it was discovered that microorganisms in the sludge not only had a richer network interaction, but also achieved a mutually beneficial symbiotic interaction network among denitrifying bacteria (Pseudomonas sp., Terrimonas sp., Dokdonella sp.), AnAOB (Candidatus Brocadia sp.) at DO of 0.2∼0.5 mg/L and C/N of 0.6. Among the top 20 in abundance of genus level, AnAOB had a high relative abundance of 27.66%, followed by denitrifying bacteria of 3.67%, AOB of 0.64% and NOB of 0.26%, which is an essential indicator for the emergence of an AnAOB-dominated nitrogen removal cycle. In conclusion, this study highlights the importance of dissolved oxygen and C/N regulation by analyzing the mechanism of ANAMMOX sludge extinction and growth in two plants under anthropogenic regulation of AnAOB in full-scale wastewater treatment systems.

Construction of the multi-layer TiO2-NTs/Sb-SnO2/PbO2 electrode for the highly efficient and selective oxidation of ammonia in aqueous solution: Characterization, performance and mechanism

Electrochemical oxidation is a promising technology to convert ammonia nitrogen to environmental-friendly gaseous nitrogen, but the high cost of the precious metal as an electrode limits its application. Herein, the multi-layer TiO2-NTs/Sb-SnO2/PbO2 electrode, a cheap and efficient dimensionally stable anode (DSA), was constructed for selective electrocatalytic oxidation of ammonia. The surface morphology, crystalline structure, and composition of the TiO2-NTs/Sb-SnO2/PbO2 electrode were investigated by the field emission scanning electron microscope (SEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The synergistic effect of the multi-layer structures of the electrode contributed to a stable structure and efficient electrocatalytic activity. Accelerated lifetime measurements and electrode recycling tests proved that the electrode possessed outstanding stability and long life with continuously used for 935 h. Compared with the commercial Ti/RuO2-IrO2, the TiO2-NTs/Sb-SnO2/PbO2 electrode displayed a more excellent performance of chlorine evolution and higher removal efficiency of ammonia. Under the optimal conditions, 30 mg/L of ammonia nitrogen could be completely removed with 92.3% selective conversion to gaseous nitrogen after 60 min. Moreover, the difference between oxygen evolution potential and chlorine evolution potential exceeded 0.45 V on the TiO2-NTs/Sb-SnO2/PbO2 electrode, which enhanced the anodic chlorine evolution reaction. Hypochlorite radical (ClO•) was supposed as the dominant oxidant to transform ammonia in water, which could promote ammonia removal and the selectivity of gaseous nitrogen with minimizing by-products formation such as nitrite and nitrate, etc. Therefore, this study suggests that the constructed multi-layer TiO2-NTs/Sb-SnO2/PbO2 electrode might be a promising anode for the electrochemical oxidation of ammonia nitrogen to N2 in an aqueous solution.

Synergistic removal of ammonia nitrogen by UV photo-electrocatalytic process: Heterogeneous reaction pathways and mechanism

UV photo-electrocatalytic process has emerged as a promising approach for the abatement of ammonia nitrogen in wastewater. However, the radical chemistry for ammonia nitrogen removal in this process requires further clarification. The heterogeneous reaction pathways and mechanism of ammonia nitrogen oxidation in the UV photo-electrocatalytic process were investigated in this study. Photocurrents of the Ti/RuO2-IrO2-TiO2 electrodes with good electrocatalytic behavior were enhanced by UV radiation. Compared with the electrocatalytic process, the removal rates of ammonia nitrogen were improved by 12.4%∼20% at the Cl− concentration of 50 mM in the photo-electrocatalytic process. The ammonia nitrogen was mainly transferred into N2, meanwhile, the formation of nitrogenous by-products, active chlorine, and chloramines was inhibited in the photo-electrocatalytic process. The contribution of UV radiation was to photo-decompose the active chlorine and chloramines, generating free radicals. The removal efficiency of ammonia nitrogen reached more than 64% after the elimination of free radicals. The electro-generated HOCl was the principal species for ammonia nitrogen removal, and the synergistic effect for the acceleration of ammonia nitrogen oxidation resulted from the photo-generated chlorine radicals. This investigation provides insight into the electrochemistry, photochemistry, and radical chemistry for the heterogeneous catalytic degradation of ammonia nitrogen by UV photo-electrocatalytic process.

Functional biological anode as electron acceptor for direct oxidation of ammonia nitrogen to N2 in an anaerobic single-chamber reactor

A functional biological anode (nonwoven-wrapped functional microbial carbon felt bag) was constructed to realize the ammonia oxidation to nitrogen gas in a single-chamber anaerobic microbial electrochemical system (MES). The applied potential has a significant impact on oxidation products of ammonia. As the applied potential was reduced from +0.8 V to +0.3 V (vs. Ag/AgCl), the ammonia oxidation rate increased from 65.2% to 94.7% and the TN removal rate increased from almost 0 to 88.0% on the bio-anode. At +0.3 V ammonia could be converted to N2 on the bio-anode and hydrogen is generated on the cathode. The zeolite adsorbent added inside the anodic carbon felt bag was also a key factor to accelerate nitrogen removal in the MES. The dominant genera of SWB02 sp., Nitrospira sp. and Bryobacter sp. played a crucial role in ammonia oxidation according to 16S rRNA analysis. This paper provides a new idea for NH4+-N removal and hydrogen production from wastewater.

Photocatalytic selective oxidation of ammonium to dinitrogen by FeOx-MgO activated persulfate under solar-light irradiation

The selective oxidation of ammonium nitrogen (NH4+-N) to dinitrogen (N2) by advanced oxidation processes (AOPs) is of paramount significance, but it is still a great challenge. In this study, a novel composite (FeOx-MgO) was synthesized to activate persulfate (PS) for selective oxidation of ammonium (NH4+) to N2 under simulated solar-light irradiation (hv). The results demonstrated that the conversion of NH4+ to ammonia (NH3) on the basic sites of FeOx-MgO was a key step for the selective oxidation of NH4+. Fe(IV) species formed in FeOx-MgO/PS/hv system could enhance both the efficiency and N2 selectivity of the NH4+-N oxidation through the oxidation of ammonia hydride to N2. The 100 % NH4+-N removal and over 95.5 % N2 selectivity could be achieved after 30 min when initial pH was in range of 2–10, and the initial NH4+-N concentration was 30 mg N/L. This study could provide a promising technology for the selective oxidation of NH4+-N to N2 in water and wastewater.

The formation and distinct characteristics of aerobic granular sludge with filamentous bacteria in low strength wastewater

In low strength wastewater, aerobic granular sludge (AGS) with filamentous bacteria is often found and regarded as unstable AGS. However, in this study, a new view is proposed that AGS with filamentous bacteria (FAGS) may be the result of low strength wastewater selection. FAGS was found when AGS was cultivated for 30 days. By increasing the settling time, FAGS could keep the mixed liquid suspension (MLSS) at 0.89 g/L. FAGS showed excellent ammonia nitrogen removal performance. The ammonia nitrogen oxidation rate and denitrification rate of FAGS were 1.72 and 1.20 times higher than that of AGS, respectively. FAGS have large specific surface area (15.99 m2/g), high extracellular polymeric substances (EPS) content (>200 mg/gVSS), and strong stability (integrity coefficient: 2 ∼ 8%). Furthermore, FAGS showed higher potential than AGS in many aspects such as carbon metabolism, nitrogen metabolism, and toxicant degradation.

Biological Nitrogen Removal by A Membrane-Aerated Biofilm Reactor: An Attempt to Treat Urine Wastewater with High Sustainability

Human urine contains the majority of nutrients in domestic wastewater, therefore treatment of source-separated urine by sustainable methods would become a low-cost and eco-friendly alternative to conventional urban wastewater treatment system. In this work, a waste stream composed of real urine and hygiene wastewater was prepared, which had characteristic of high nitrogen content and low available C/N ratio. Membrane-aerated biofilm reactor (MABR) is an emerging technology utilizing microporous or nonporous aeration membranes as the substrate for biofilm attachment, and this configuration could promote the growth of autotrophic nitrifying bacteria and the efficiency of nitrogen removal process. The waste stream was treated with a home-made MABR system to remove the organic carbon and nitrogen pollutants. Over a four-month operation period with the incoming waste stream concentration progressively elevated, the system achieved 90-95% removal of TOC, 50-73% oxidation of ammonium-nitrogen, and 24-63% removal of total nitrogen from the influent, without external carbon source input. The results indicated that MABR has the potential for urine wastewater treatment with low consumption in energy and materials.

Effects of Aeration Rates and Patterns on Shortcut Nitrification and Denitrification

The effects of aeration rates and aeration patterns on the oxidation of ammonia-nitrogen into nitrite were investigated. The influent high ammonia-nitrogen synthetic wastewater resembled to those of the catalytic process of the petrochemical refinery. The method involved the biological shortcut nitrification and denitrification lab-scale’s sequencing batch reactor (SBR) process based on intermittent aerations and aeration patterns. All the operations were carried out in a 20 L working volume SBR bioreactor, and the influent synthetic wastewater’s concentration was always 1000 mg/L ammonia-nitrogen NH4-N concentration at a C/N (carbon/nitrogen) ratio of 2.5:1. Effective shortcut nitrification to nitrite was registered at 1.1 mg-O2/L (i.e. 9 L-air/min) with 99.1% nitrification efficiency, 99.0% nitritation rate and 2.6 mg-NO3--N/L nitrate concentration. The best results with 99.3% nitrification efficiency were recorded when operating at 1.4 mg-O2/L (i.e. 12 L-air/min). According to these experiments, it results that the nitrite accumulation rate was related to aeration rate and cycle’s duration. However, at 1.7 mg-O2/L (i.e. 15 L-air/min), the system was limited by an increase in nitrate concentration with more than 5 mg/L which could be a point of reverse to conventional nitrification. The best total nitrogen (TN) removal was about 71.5%.

Removal of ammonia nitrogen from wastewater by three-dimensional electrode system based on solid waste containing iron

In order to solve the problem of ammonia nitrogen pollution, three-dimensional electrode electrochemical oxidation technology is utilized to transform ammonia nitrogen. The influence of influent pH, power supply and electrolyte concentration on ammonia nitrogen removal by three-dimensional electrode method and its mechanism were discussed by single factor variable analysis. The particle electrode by emission scanning electron microscope (SEM) and energy dispersive spectroscopy (EDS). The results show that the removal efficiency of ammonia nitrogen by three-dimensional electrode is higher than that by two-dimensional electrode. When the aqueous solution is neutral, the direct and indirect oxidation reactions of ammonia nitrogen can reach the best state, and the removal efficiency is the highest. Within a certain range, the electrolytic efficiency will increase with the increase of electrolytic voltage and electrolyte concentration. The reduction of electrode spacing in a certain range can enhance the direct oxidation of ammonia nitrogen and improve the electrolysis efficiency of ammonia nitrogen. Under the conditions of pH 7, power supply voltage 14 V, electrolyte concentration 0.1 mol/L, electrode spacing 1 cm, electrolytic time 50 min, ammonia nitrogen can be completely removed from the three-dimensional electrode.

Cu2ZnSnS4/CeO2 heterojunction with excellent sensing property for ammonia nitrogen in aqueous solution

A novel nanomaterial formed by a Cu2ZnSnS4 (CZTS)/CeO2 heterojunction with excellent electrochemical sensing for ammonia nitrogen was prepared by a microwave irradiation method combined with a hydrothermal method. The properties of the CZTS/CeO2 heterojunction were investigated by a series of characterizations such as Raman spectra, x-ray diffraction, scanning electron microscopy, thermogravimetric analysis, specific surface area (SSA), temperature-programmed desorption of ammonia and UV–vis spectroscopy. Nickel foam was used as a conductive frame electrode in order to enhance the sensitivity of the sensor along with the electrical conductivity, permeability and SSA. It is revealed by electrochemical measurements that the ammonia nitrogen oxidation reaction occurring in the sensing electrode of the CZTS/CeO2 heterojunction demonstrated regulation of I p (mA) = 6.4 × 10−3C (mM)+ 0.1527 (R 2= 0.9987) in a wide concentration range of 0–380.0 mM with a low detection of 6.0 μM according to the signal-to-noise ratio (S/N= 2). The CZTS/CeO2 heterojunction is expected to become a new candidate semiconductor nanomaterial for the electrochemical detection of ammonia nitrogen in an aqueous solution.

An efficient strategy for selective oxidation of ammonia nitrogen into N2 over BiOCl photocatalyst

Selective oxidation of ammonia nitrogen (NH4+-N) into N2 is critical to remove the superfluous nitrogen in the hydrosphere and control the fixed nitrogen inventory for the global nitrogen cycle. Herein, on the basis of chlorine radical chemistry, we report the photocatalytic denitrogenation over BiOCl with high N2 selectivity (>97 %). Efficient Cl– conversion into reactive chlorine species (RCS) is achieved, serving as the predominant reactive species for NH4+-N oxidation. According to the zero-order kinetics of Cl– for RCS generation, as well as the Cl– extraction/insertion over BiOCl, a Cl–-mediated Mars-van Krevelen mechanism is revealed, by which the catalytic performance shifts from the undesired deactivation (because of photocorrosion) towards the remarkably enhanced reactivity. This system exhibits great potential for the denitrogenation of saline wastewater, also provides an interesting strategy to activate inert chemical bond via the chlorine cycle.

Oxidation of Hydrogen sulfide, Ammonia nitrogen and Nitrite nitrogen by Bacillus sp. Isolated from West Coast of Korea

In the aquaculture industry, the biological treatment using probiotics for eliminating hydrogen sulfide, ammonia nitrogen and nitrite nitrogen is receiving attention. In this study, Bacillus sp. TO-3, Bacillus sp. TO-10 and Bacillus sp. TO-12 were isolated from the west coast of Korea and oxidation ability of hydrogen sulfide, ammonia nitrogen and nitrite nitrogen were analyzed. Bacillus sp. TO-10 had high oxidation toward hydrogen sulfide by oxidizing 100% and Bacillus sp. TO-3 and TO-12 each had hydrogen sulfide oxidation of 49.53% and 69.03%. Bacillus sp. TO-10 and Bacillus sp. TO-12 had ammonia nitrogen oxidation approximately of 32.7 mg/L, while Bacillus sp. TO-3 had 11.4 mg/L of ammonia nitrogen oxidation. Bacillus sp. TO-3, Bacillus sp. TO-10 and Bacillus sp. TO-12 all had high oxidation toward nitrite nitrogen by oxidizing 100% of 137.46 mg/L nitrite nitrogen. Therefore, Bacillus sp. TO-3, Bacillus sp. TO-10 and Bacillus sp. TO-12 are possible probiotics used as water quality improvement of eliminating hydrogen sulfide, ammonia nitrogen and nitrite nitrogen.

Oxidation of Ammonia Nitrogen with Ozone in Water: A Mini Review

Since ammonia nitrogen is a pollutant causing eutrophication, it must be removed from wastewater to develop sustainable environment and society. Ozonation, which is an oxidation reaction with ozone, is an effective and efficient method for the removal of ammonia nitrogen in wastewater because the reaction can proceed at low temperature and atmospheric pressure. Although the researches in ozonation of ammonia nitrogen have been going on for the last five decades, the reaction mechanism has not yet been well understood and the papers focusing on the reaction mechanism are very few. In this short review paper, the progress in oxidation of ammonia nitrogen with ozone both in non-catalytic and catalytic reactions is summarized to provide a better understanding on the reaction mechanism for ozonation of ammonia nitrogen in water.

Orthophosphate vs. bicarbonate used as a buffering substance for optimizing the bromide-enhanced ozonation process for ammonia nitrogen removal.

Bromide-enhanced ozonation (BEO) process can be a fast and effective solution for the complete removal of total nitrogen (TN) from wastewaters containing from moderate to high concentrations of ammonia nitrogen (AN). Like the traditional biological process of AN oxidation, even BEO requires the presence of buffering agents, in order to oppose the progressive acidification induced by the reaction. This study compares the effect of two buffering substances (namely bicarbonate and mixtures of orthophosphates) in hindering the acidification caused by AN oxidation and, consequently, optimizing the overall efficiency of the process. Tests were carried out with on-purpose made solutions containing concentrations of AN of 5-10 mM. The range of [Br-]/[O3] ratio values was from 12 to 18, so as to make ozone the limiting factor in HOBr generation. The results of this study proved that, in the absence of natural buffering agents, mixtures of orthophosphates must be preferred to the more traditionally employed bicarbonate to control the pH evolution of BEO process. In fact, orthophosphates proved to be capable to guarantee an initial pH of the wastewater in the order of 7.5, thus making the zero-order AN removal rates 15% faster than those observed in the presence of bicarbonate. Furthermore, in the presence of mixtures of orthophosphates, the generation of ozonation byproducts in the oxidized form (nitrate, bromate) was reduced by over 70%. Finally, the fine control of pH obtained with orthophosphates in the BEO of AN makes that process an attractive solution for the treatment of effluents containing AN, thus preventing the discharge of residual nitrogen into aquatic environments and avoiding eutrophication of receiving water bodies.