Ammonia Removal Efficiency Research Articles

Anode modification of sediment microbial fuel cells (SMFC) towards bioremediating mariculture wastewater

Remediation of mariculture wastewater is of great practical importance. In this study, sediment microbial fuel cells (SMFCs) were adopted and carbon felt anodes were modified to enhance COD and ammonia removal in mariculture system. The results showed that the SMFC anode with 5 % (w/w) graphene oxide (GO) coating performed best in pollutants removal and electricity generation. The maximum power density approached 132 mW/m2, nearly 4.5 times higher than the unmodified anode. The removal efficiency of COD and ammonia reached 82.1 % and 95.8 % respectively, both improved compared with the control and chemical modification. The modified anode effectively enriched the electrogenic Sulfurovum and Lactobacillus and thus led to a significant improvement in the electrochemical performance of SMFC. This study demonstrates the successful application of SMFCs with GO modified anodes in the in-situ removing pollutants and SMFCs present obvious remediation potential on the contaminated mariculture inhabitant.

Enhanced removal of ammonia in Fe(VI)/Br− oxidation system: Kinetics, transformation mechanism and theoretical calculations

This work systematically examined the capability of ferrate (Fe(VI)) for ammonia oxidation, revealing for the first time that bromide ions (Br−) played an important role in promoting the removal of ammonia in Fe(VI) system. In the presence of 10.0 mM Br−, the removal efficiency of ammonia was nearly 3.4 times that of the control, and 1.0 mM ammonia was almost completely removed after two rounds addition of 1.0 mM Fe(VI) in 60 min. PMSO probe test, electron paramagnetic resonance spectra and radical quenching experiments were employed to interpret the underlying promotion mechanism of Br−, and it was proposed that the formation of active bromine (HOBr/OBr−) played a dominant role in the enhanced oxidative removal of ammonia by Fe(VI). Further kinetic model simulations revealed that HOBr/OBr− and Fe(VI) were the two major reactive species in Fe(VI)/Br− system, accounting for 66.7% and 33.0% of ammonia removal, respectively. As the target contaminant, ammonia could quickly consume the generated HOBr/OBr−, thereby suppressing the formation of brominated disinfection byproducts. Finally, NO3− was identified as the dominant transformation product of ammonia, and density functional theory (DFT) calculations revealed that six reaction stages were involved in ammonia oxidation with the first step as the rate-limiting step. This work would enable the full use of coexisting bromides for effective removal of ammonia from natural waters or wastewaters by in situ Fe(VI) oxidation method.

A novel CuBi2O4/polyaniline composite as an efficient photocatalyst for ammonia degradation

A novel polyaniline (PANI) coupled CuBi2O4 photocatalyst was successfully synthesized via in situ polymerization of aniline with pre-synthesized CuBi2O4 composites. The structure and morphology of the synthesized CuBi2O4/PANI composite photocatalyst were characterized by X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) and the photocatalytic performance were evaluated through degradation process of ammonia in water under visible light irradiation. The resultant CuBi2O4/PANI composite showed exceptional stability as its structure and morphology persisted even after being immersed in water for 2 days. The composite photocatalyst exhibited improved charge transport properties due to the electrical conductivity of the PANI protective layer, leading to enhanced photoelectrochemical activity in water and removal of ammonia. PANI with CuBi2O4 (10% wt) heterostructure was applied for photodegradation of ammonia and exhibited a 96% ammonia removal efficiency (30 mg/l with 0.1 g photocatalyst and 180 min), as compared to PANI (78%) and CuBi2O4 (70%). The degradation was attributed to the efficient charge transfer (e− and h+) and formation of reactive oxygen species upon simulated sunlight exposure. The present work suggests that the CuBi2O4/PANI photocatalyst can be synthesized in a simple process and provides an excellent adsorption capacity, high photocatalytic activity, long term stability, and reusability making it a promising alternative for ammonia removal from wastewater.

Biological treatment of municipal wastewater using fixed rope media technology: Impact of aeration scheme

This paper characterized a new fixed rope media system to upgrade decentralized and small-scale wastewater treatment plants. A primary effluent of municipal wastewater was treated using two pilot-scale reactors equipped with full-scale sized fixed rope media technology, one of the reactors was aerated using a coarse bubble tube and the other using a custom fine bubble aeration system. The study examined the impact of the aeration scheme and intensities and the COD/NH 3 -N ratio on ammonia and COD removal rates, excessive biofilm growth, slough-off, and microbial communities’ composition. The average biofilm ammonia and COD removal rates ranged from 0.23 ± 0.15 to 0.38 ± 0.26 gNH 3 -N/m 2 .d and 1.35 ± 0.95 to 3.05 ± 1.21 gCOD/m 2 .d, respectively. The fine and coarse bubble reactors showed comparable carbon oxidation rates; however, the fine bubble reactor showed a higher nitrification rate than the coarse bubble reactor at lower aeration intensities despite the similar dissolved oxygen concentration. Correspondingly, an increase in COD/NH 3 -N and excessive biofilm growth decreased the NH 3 -N removal performance but did not affect the COD removal efficiency. Further analysis of the microbial communities composition revealed that the reactors supported a relatively substantial amount of AOB (55 and 63%) and denitrifying bacteria (36 and 21%) with a relatively lower NOB (7 and 8%) and anammox (1 and 8%) species in the fine and coarse bubble aeration reactors, respectively. Overall this study demonstrated the feasibility of one stage fixed rope media to treat COD and ammonia and meet treatment objectives, thus providing an alternative solution to decentralized and smaller plant upgrades. • Ammonia and COD removal efficiency of innovative fixed rope media technology was evaluated. • Different aeration schemes showed minimal impact on the DO concentration but impacted removal performances. • C/N ratio influenced NH 3 -N removal but not COD removal. • Slough off did not impact COD removal; however, it enhanced ammonia removal. • Reactor with the fine bubble aeration supported a relatively higher fraction of denitrifying bacteria.

Establishment and optimization of partial nitrification/anammox/partial nitrification/anammox (PN/A/PN/A) process based on multi-stage ammonia oxidation: Using response surface method as a tool

The presence of nitrite-oxidizing bacteria (NOB) when treating low-strength ammonia wastewater was a challenge in the application of the PN/A process. The partial nitrification/ANAMMOX/partial nitrification/ANAMMOX (PN/A/PN/A) process based on multiple oxidations of ammonia was proposed to solve this problem. The influence of independent variables such as nitrite concentration was analyzed based on the response surface method (RSM). The model showed that nitrite concentration has an adverse impact on ammonia removal efficiency and nitrite accumulation rate. The model provided optimal parameters for the PN/A/PN/A process: the dissolved oxygen concentration was 0.60 mg/L, and the cycle duration was 90 min. Advanced nitrogen removal was achieved by maintaining the nitrite concentration below 10.0 mg/L. The nitrogen removal efficiency was 81.44 ± 4.15 %, and the nitrogen removal rate was 0.18 ± 0.02 kg N/(m3⋅d). Potential functions of microorganisms were analyzed by functional annotation of prokaryotic taxa (FAPROTAX) and the correlation network analysis was performed.

Kinetics and mechanisms of enhanced ammonia abatement under synchronous process of electrochemistry and adsorption.

As a kind of common nitrogen pollutants, ammonia seriously pollutes water and soil environments and threatens human health. The treatment of water contaminated with ammonia was carried out in an electrochemical-adsorption system (ECAS). This paper discusses the capacity, kinetics, and mechanism of ammonia electrosorption, which is accurately described by a pseudo-first-order model, indicating that physical adsorption is the dominating mechanism. A high adsorption capacity of 4.086mgN/g was attributed to the formation of a large number of adsorption sites and the highly acidic nature of dealumination of zeolites during electrolysis. Fast directional migration of ammonia in the electric field weakened the negative effect of boundary layer on adsorption and accelerated adsorption procedure. Brunauer, Emmett, and Teller measurements and scanning electron microscopy indicated that the formation of new channels and surface erosion, which resulted in a large surface area and pore volume of zeolites and a low resistance towards ion migration. As a whole, this study achieved efficient ammonia removal without the addition of chemical reagents to avoid secondary pollution.

Ecological restoration performance enhanced by nano zero valent iron treatment in constructed wetlands under perfluorooctanoic acid stress

Perfluorooctanoic acid (PFOA) of widespread use can enter constructed wetlands (CWs) via migration, and inevitably causes negative impacts on removal efficiencies of conventional pollutants due to its ecotoxicity. However, little attention has been paid to strengthen performance of CWs under PFOA stress. In this study, influences of nano zero valent iron (nZVI), which has been demonstrated to improve nutrients removal, were explored after exemplifying threats of PFOA to operation performance in CWs. The results revealed that 1 mg/L PFOA suppressed the nitrification capacity and phosphorus removal, and nZVI distinctly improved the removal efficiency of ammonia and total phosphorus in CWs compared to PFOA exposure group without nZVI, with the maximum increases of 3.65 % and 16.76 %. Furthermore, nZVI significantly stimulated dehydrogenase (390.64 % and 884.54 %) and urease (118.15 % and 246.92 %) activities during 0–30 d and 30–60 d in comparison to PFOA group. On the other hand, nitrifying enzymes were also promoted, in which ammonia monooxygenase increased by 30.90 % during 0–30 d, and nitrite oxidoreductase was raised by 117.91 % and 232.10 % in two stages. Besides, the content of extracellular polymeric substances (EPS) under nZVI treatment was 72.98 % higher than PFOA group. Analyses of Illumina Miseq sequencing further certified that nZVI effectively improved the community richness and caused the enrichment of microorganisms related to nitrogen and phosphorus removal and EPS secreting. These results could provide valuable information for ecological restoration and decontamination performance enhancement of CWs exposed to PFOA.

Post-hydrolysis ammonia stripping as a new approach to enhance the two-stage anaerobic digestion of poultry manure: Optimization and statistical modelling

Post-hydrolysis ammonia stripping was investigated as a new approach to enhance the methane potential of high ammonia substrates, such as poultry manure. The objective of the proposed approach is to address some of the noticeable disadvantages in the existing ammonia-stripping techniques i.e., treatment of raw samples and side-stream stripping. Poultry manure (PM) and a co-substrate (mixed wastes from a cheese factory and a coffee house, referred to as MS) characterized by a high carbon-to-nitrogen ratio were mixed at five different ratios: PM:MS of 100:0, 75:25, 50:50, 25:75, and 0:100. Samples were hydrolyzed for six days to promote ammonia conversion from organic nitrogen and then the samples with higher ammonia levels (>2000 mg NH3–N/L) were stripped with air at initial pH values of 9 and 10 and temperatures of 40 and 55 °C. Biochemical methane potential (BMP) test results showed that post-hydrolysis ammonia stripping had alleviated ammonia inhibition and improved methane potential up to 200% when compared with untreated samples. The ammonia removal efficiency was mostly affected by pH. On the other hand, methane potential was highest in the samples treated at a higher temperature as their biodegradability was enhanced when compared with the samples treated at lower temperatures. Post-BMP characterization showed that the proposed approach had also limited the increase of ammonia in the digestate which ensured proper growth of methanogenic microorganisms.

Oxygen Vacancy‐Rich La0.5Sr1.5Ni0.9Cu0.1O4–δ as a High‐Performance Bifunctional Catalyst for Symmetric Ammonia Electrolyzer

AbstractIn this study, strontium and copper dual‐doped La2NiO4 annealed in Ar (La0.5Sr1.5Ni0.9Cu0.1O4‐δ‐Ar, LSNC‐Ar) with K2NiF4 structure is strategically designed as an ammonia oxidation reaction (AOR) and hydrogen evolution reaction (HER) bifunctional catalyst for high‐efficiency ammonia electrolysis. The selective substitution of lanthanum with high content strontium improves the electronic conductivity and increases the oxygen vacancy concentration. Doping of Cu into the B‐site of the perovskite induces a synergistic interplay of Ni and Cu, leading to excellent AOR activity. Due to the excellent AOR and HER activity of doped La2NiO4, a symmetric ammonia electrolyzer based on LSNC‐Ar (SAE‐LSNC‐Ar) is assembled and investigated for the removal of ammonia. In addition, the performance of the SAE is comparable to the ammonia electrolyzer based on a PtIr/C anode and Pt/C cathode at low voltage. This is the first report using an oxide with the K2NiF4 structure as an efficient AOR catalyst. The assembled SAE‐LSNC‐Ar shows ≈95% ammonia removal efficiency in real landfill leachate, which is the highest among electrochemical removal of ammonia in landfill leachate. This study paves an attractive route to explore materials with the K2NiF4 structure as highly efficient AOR/HER bifunctional catalysts for the electrolysis of ammonia.

A novel Pseudomonas aeruginosa strain performs simultaneous heterotrophic nitrification-aerobic denitrification and aerobic phosphate removal

Nitrogen and phosphate removal from wastewater relies on different functional bacteria. In this study, a novel strain affiliated with Pseudomonas aeruginosa was isolated from activated sludge by gradient dilution and performed heterotrophic nitrification-aerobic denitrification and aerobic phosphate removal (HNADPR). The strain showed an ammonium removal efficiency of 87% and a phosphate removal efficiency of 97% under optimal conditions, such as C/N ratio of 10, P/N ratio of 0.1, temperature of 30°C, and pH of 7.5–8.5. The modified Gompertz model could fit well the heterotrophic ammonium nitrification, aerobic nitrite/nitrate denitrification, and aerobic phosphate removal processes. Functional gene amplification indicated that ammonium removal followed the complete HN-AD pathway (NH4+ → NH2OH → NO2− → NO3− → NO2− → NO → N2O → N2). Phosphate removal only occurred under aerobic conditions and ceased under anaerobic conditions. In successive aerobic cycles, the strain persistently took up phosphate. In wastewater, phosphate was aerobically converted into cell membrane, intracellular and extracellular polymeric substrates (EPS). Phosphorus in the form of phosphate monoester was pooled in EPS. A hypothetic aerobic phosphate removal model for strain SNDPR-01 is proposed to improve our understanding of the novel bacterial function of HNADPR.

Water and green ammonia recovery from anaerobic digestion effluent by two-stage membrane distillation

A water and green ammonia recovery strategy for anaerobic digestion (AD) effluent treatment through a two-stage membrane distillation (2s-MD) was put forward in this study. In the 1st-stage, the MAP (monoammonium phosphate solution, NH4H2PO4)/DAP (diammonium phosphate solution, (NH4)2HPO4) loop, was used as the recyclable ammonia absorbent to recover ammonia from AD effluent. The multicycle ammonia absorption-regeneration experiments illustrated that the ammonia removal efficiency was stable (~81 %) and the recovered ammonia solution was 1.05 mol/L. In the 2nd-stage, the water recovery experiments from AD effluent with different ammonia concentrations were conducted. The results indicated that the water recovered from ammonia-removed AD effluent could be adopted as the general industrial or agricultural water. Finally, the economic evaluation demonstrated that the application of MAP solution as the recyclable ammonia absorbent was more economically efficient than the sulfuric acid solution. The treatment cost and net profit of AD effluent treatment by 2s-MD were $ 1.73/m3 and $ 0.83/m3, respectively. The 2s-MD can be acted as a valuable candidate strategy for sustainable green ammonia and water recovery from AD effluent.

Metagenomic analyses reveal nitrogen metabolism responses to copper and chromium contamination in sludge-based microbial communities

In this study, we used metagenomic sequencing to explore the effects of chromium (Cr) and copper (Cu) on microbial communities and function by analyzing pathway of nitrogen metabolism based on KEGG annotation. High concentrations of Cr (VI) and Cu (II) reduced the removal efficiency of total nitrogen and ammonium in the system. Metagenomic analyses showed that the taxonomic composition of nitrogen metabolism-associated microorganisms (NMAM) was mainly composed of Betaproteobacteria, Alphaproteobacteria, Gammaproteobacteria, Sphingobacteria, Deltaproteobacteria, Flavobacteria and Nitrospira. Different concentrations of Cr (VI) and Cu (II) led to great changes in NMAM in activated sludge and enriched dominant microbes, respectively, suggesting specific response strategies in microbial communities. NMDS (Non-metric multidimensional scaling) analyses revealed the impact of different Cr (VI) and Cu (II) concentrations on NMAM β diversity, and indicated that Cr (VI) treatment induced greater variations in NMAM communities than Cu (II). We also identified a significant association (p < 0.05) between enzymes of nitrogen metabolism pathway and corresponding NMAM. This study revealed that under Cu (II) and Cr (VI) stress, the sludge nitrification pathway was inhibited, especially for ammonia monooxygenase and hydroxylamine dehydrogenase. These combined effects led to a decrease in sludge efficiency for nitrogen removal. These findings underscore the influence of heavy metals in water treatment.

Study and actual application of the electrochemical reactor in flow-through mode based on channel confinement

The method of enhancing mass transfer and improving reaction efficiency by confinement has attracted much attention in the electrochemical research field. In this research, to make low diffusion-limited electrochemical reactors fieldable, a new electrochemical reactor in flow-through mode was established with the mass-produced Ti/RuO2–IrO2 felt fibers as the electrodes. The effects of voltage, current, and electrode thickness were explored in this study. When the flow mode was switched from flow-by to flow-through, the single-pass degradation effect of rhodamine B rose from 4.4% to 74.8% under the same operating conditions. Meanwhile, a mass transfer model was established based on the results of removal efficiency and electrode channel parameters. The model was in good agreement with the new electrode parameters verification (R2 > 0.970). With this model, it could derive specific results on the effect of pore size change on the treatment effect. The impact of enhancing mass transfer by confining the pore sizes is most clearly gained at a certain range (less than 100 μm). Furthermore, a pilot-scale electrochemical reactor in flow-through mode was built, and excellent performance was shown in the treatment of actual waste leachate. The removal efficiencies of total nitrogen, ammonia, and nitrate were 80.9%, 88.6%, and 64.5% in 30 min, respectively. It will be a promising technology with good prospect.

Biohythane production from swine manure and pineapple waste in a single-stage two-chamber digester using gel-entrapped anaerobic microorganisms

A mixture of swine manure and pineapple waste was used to check the feasibility of producing biohythane in a newly-developed single-stage anaerobic fermentation system that having immobilized H2 and CH4-producing microbes in a two-chamber digester. Tested hydraulic retention times (HRT) were from 96 h to 6 h. HRT 6 h resulted in peak gas production performance with hydrogen production rate 1240 and methane production rate 812 mL/L-d. Besides, the synergistic function of generation and consumption of volatile fatty acids in this hybrid biosystem had a significant impact on biohythane composition with acetate and butyrate being the dominant liquid metabolites. Chemical oxygen demand and ammonium removal efficiencies were 52.4 and 78.8%, respectively during steady-state conditions. Based on the experimental findings, prospects for field applications of single-stage biohythane fermentation were suggested.

Achieving Ammonium Removal Through Anammox-Derived Feammox With Low Demand of Fe(III).

Feammox-based nitrogen removal technology can reduce energy consumption by aeration and emission of carbon dioxide. However, the huge theoretical demand for Fe(III) becomes a challenge for the further development of Feammox. This study investigated an anammox-derived Feammox process with an intermittent dosage of Fe2O3 and proposed a novel approach to reduce the Fe(III) consumption. The results showed that anammox genera Candidatus Brocadia and Candidatus Kuenenia in the seed anammox sludge significantly decreased after cultivation. The formation of N2 was the dominating pathway in Feammox while that of nitrite and nitrate could be neglected. Batch tests showed that specific Feammox activity of ammonium oxidation was 1.14–9.98 mg N/(g VSS·d). The maximum removal efficiency of ammonium reached 52.3% in the bioreactor with a low dosage of Fe(III) which was only 5.8% of the theoretical demand in Feammox. The removal of ammonium was mainly achieved through Feammox, while partial nitrification/anammox also played a role due to the non-power and unintentional oxygen leakage. The super-low oxygen also responded to the low demand of Fe(III) in the bioreactor because it could trigger the cycle of Fe(III)/Fe(II) by coupling Feammox and chemical oxidation of Fe(II) to Fe(III). Therefore, anammox-derived Feammox can achieve the removal of ammonium with low Fe(III) demand at super-low oxygen.

Study on the preparation of manganese oxide filter media for catalytic oxidation removal of ammonium and manganese in high alkalinity groundwater: The effect of copper and cobalt doping

Owing to the low efficiency of catalytic oxidation of ammonium and manganese in high alkalinity groundwater by manganese oxide filter column, the effect of doping copper (Cu) and cobalt (Co) on catalytic activity was investigated. A pilot-scale filter column system was used in this experiment. The catalytic oxidation activities of manganese oxide filter media prepared at different Cu and Co concentrations (0, 0.1, 1.0 mg/L) in raw water were compared. The results showed that the removal efficiency of ammonium by the filter column increased from 65% to 100% due to low Cu doping, while the removal efficiency of manganese decreased from 95% to 60% due to high Cu doping. Low Co doping was beneficial to the start-up period of the filter column and the effluent ammonium concentration reached the standard on the 8th day. In addition, X-ray diffraction (XRD) and Scanning electron microscopy coupled energy dispersive spectroscopy (SEM-EDS) results showed that the high alkalinity of water led to the formation of a large amount of calcium carbonate on the surface of the filter media. Combined with X-ray photoelectron spectroscopy (XPS) analysis, it was found that the conversion of different valence manganese species caused by Cu and Co doping and the Cu and Co elements with different valence were the key factors determining the catalytic activity of manganese oxide filter media. Cu2+/Cu+ and Co3+/Co2+ electron cycles also participated in the electron transfer process of catalytic reaction. This study provides a research idea for solving the pollution problem of ammonium and manganese in high alkalinity water.

Enhanced adsorptive removal of ammonium on the Na+/Al3+ enriched natural zeolite

Biological methods for removing ammonium from surface water are ineffective at low ammonium concentrations and temperatures. Herein, in combination with calcination, natural zeolite (NZ) is modified using sodium aluminate (SA, NaAlO2) to determine its ammonium removal efficiency. The NZ impregnated with a 0.50 M SA solution and treated with calcination at 573 K exhibits the best ammonium removal rate, which increases by 21.20% compared to that with NZ under the same conditions. Regeneration through the NaCl solution impregnation further improves the ammonium removal efficiency of the modified NZ. More adsorption sites are created through Na+–cation exchange and Al3+ engrafting into the NZ skeleton. The average pore size and mesoporous volume percentage are also increased. Ammonium adsorption onto the modified NZs is a diffusion-controlled endothermic process. The isotherm better fits the Freundlich model because of the coarse surface functionalized using SA and calcination. The effect of coexisting ions, pH, and dosage on ammonium adsorption is also determined.

Achieving deep autotrophic nitrogen removal in aerated biofilter driven by sponge iron: Performance and mechanism

Different from anammox, the combination of Fe (III) reduction coupled to anaerobic ammonium oxidation (Feammox) and nitrate/nitrite dependent ferrous oxidation (NDFO) do not require to control nitrite accumulation. Furthermore, sponge iron can avoid continuous iron supplementation in practice and is a good iron source for the occurrence of Feammox and NDFO in wastewater treatment. Therefore, a biofilter using sponge iron as carrier treating low nitrogen wastewater was built. In this study, the performances of nitrogen removal were explored under different hydraulic retention times (HRT) and gas-water ratios in sponge iron biofilter. And the pathways of nitrogen removal were analyzed by activity tests. The results showed ammonia removal efficiency reached 94.1% and total inorganic nitrogen removal efficiency was up to 70.6% at HRT of 19 h and gas-water ratio of 18. Compared to nitrogen removal by adsorption under non-aeration, the activity tests showed that total inorganic nitrogen loss was caused by Feammox and NDFO after aeration. The results of microbial communities showed that appearances of nitrifier-Nitrosomonadaceae, Feammox bacteria-Clostridiaceae and NDFO bacteria-Gallionellaceae resulted in deep nitrogen removal after aeration, in which Nitrosomonadaceae and Clostridiaceae contributed to ammonia removal and Gallionellaceae contributed to nitrite/nitrate reduction to nitrogen gas. Therefore, it was feasible to achieve deep autotrophic nitrogen removal and Fe (II) and Fe (III) cycle in sponge iron biofilter.

Electrooxidation of ammonia on A-site deficient perovskite oxide La0.9Ni0.6Cu0.35Fe0.05O3-δ for wastewater treatment

Wastewater can contain high amounts of ammonia which can pose as a great safety threat if released into natural waters. The electrochemical oxidation of ammonia offers a viable strategy to remove high concentrations and provides an attractive method for wastewater treatment. However, finding a highly efficient and low-cost catalyst is imperative for overcoming the sluggish nature of ammonia oxidation reaction. Herein, a modified A- and B-site perovskite is proposed as a catalyst for the oxidation of ammonia, making it suitable as an anode in an ammonia electrolyser. A series of La1-yNi0.6Cu0.4-xFexO3-δ (x = 0, 0.05 and 0.10; y = 0, 0.05 and 0.10) perovskite materials were synthesised by a conventional sol–gel method. Amongst those tested oxides, La0.9Ni0.6Cu0.35Fe0.05O3-δ was found to have superior activity towards the electrooxidation of ammonia due to an optimised amount of Fe doping and the presence of oxygen vacancies introduced by an A-site deficiency. Subsequently, La0.9Ni0.6Cu0.35Fe0.05O3-δ was employed as an anode in an ammonia electrolyser where the ammonia removal efficiency reached 95.4 % in simulated wastewater after 80 hr and a substantial reduction in real wastewater was also observed. These results demonstrate that the A-site deficient perovskite materials are a viable electrode for the removal of ammonia in a practical energy setting and paves way for future applications.

Waste-derived volatile fatty acid production and ammonium removal from it by ion exchange process with natural zeolite

ABSTRACT Volatile fatty acids (VFAs) produced during anaerobic digestion (AD) of organic waste are a promising alternative carbon source for various biological processes; however, their applications are limited due to the presence of impurities such as ammonium (NH4 +). This study investigates the potential for removal of ammonium using a naturally occurring zeolite (clinoptilolite) from chicken manure (CKM) derived VFA effluent recovered from an anaerobic membrane bioreactor (MBR). Experiments were conducted for both synthetic and actual VFA (AD-VFA) solutions, and the effects of different parameters were investigated with batch and continuous studies. It was observed that the Langmuir-type isotherm provided the best fit to the equilibrium data in the isotherm investigations carried out with the AD-VFA solution. The maximum adsorption capacity (qm) was found as 15.7 mg NH4 +/g clinoptilolite. The effect of some operational parameters on process performance such as pH, initial NH4 + loading and potassium ion (K+) concentration was investigated. The pH had a negligible effect on ammonium removal for a pH range of 3–7, while the removal efficiency of ammonium decreased with the increase of initial NH4 + loading and K+ concentration. At the optimum conditions determined in batch experiments, the ammonium removal from synthetic and AD-VFA solutions were compared and average ammonium removal efficiencies of 93 and 94% were found in 12 h equilibrium time for synthetic and AD-VFA solutions, respectively. Overall findings indicated that clinoptilolite has excellent potential for ion exchange when combined with biological processes such as acidogenic fermentation of VFAs to purify the solution from high-ammonium content.