Removal Reaction Research Articles

Structure of Mg30 explored via in-beam γ -ray spectroscopy

Background: In the "island of inversion", ground states of neutron-rich $sd$-shell nuclei exhibit strong admixtures of intruder configurations from the $fp$ shell. The nucleus $^{30}$Mg, located at the boundary of the island of inversion, serves as a cornerstone to track the structural evolution as one approaches this region. Purpose: Spin-parity assignments for excited states in $^{30}$Mg, especially negative-parity levels, have yet to be established. In the present work, the nuclear structure of $^{30}$Mg was investigated by in-beam $\gamma$-ray spectroscopy mainly focusing on firm spin-parity determinations. Method: High-intensity rare-isotope beams of $^{31}$Mg, $^{32}$Mg, $^{34}$Si, and $^{35}$P bombarded a Be target to induce nucleon removal reactions populating states in $^{30}$Mg. $\gamma$ rays were detected by the state-of-the-art $\gamma$-ray tracking array GRETINA. For the direct one-neutron removal reaction, final-state exclusive cross sections and parallel momentum distributions were deduced. Multi-nucleon removal reactions from different projectiles were exploited to gain complementary information. Results: With the aid of the parallel momentum distributions, an updated level scheme with revised spin-parity assignments was constructed. Spectroscopic factors associated with each state were also deduced. Conclusions: Results were confronted with large-scale shell-model calculations using two different effective interactions, showing excellent agreement with the present level scheme. However, a marked difference in the spectroscopic factors indicates that the full delineation of the transition into the island of inversion remains a challenge for theoretical models.

Layered Na5V12O32 nanowires with enhanced properties of removing Pb2+ in aqueous solution by chemical reaction

Sodium vanadate (Na5V12O32) nanowires, produced by hydrothermal synthesis are thoroughly investigated for removal of harmful lead ions (Pb2+) from aqueous solution. The removal reaction is visually detected by the color change of the Na5V12O32 nanowires from green to gray. After the reaction, Na5V12O32 is changed to Pb2V2O7. Theoretical DFT calculations show that adsorption and cation-exchange of Pb2+ occur on the surface layers of Na5V12O32 nanowires. It is found that the Pb2+ removal rate reaches 93.6 % after two hours and the Pb2+ concentration is decreased from 187.7 mg·L−1 to 2.1 mg·L−1 within six hours. The highest removal capacity of Na5V12O32 nanowires on Pb2+ is about 2170 mg g−1. With a content of 80 mg/L of Na5V12O32, the Pb2+ concentration in solution is reduced 10 mg/L to 7.3 μg/L, a thousand-fold decrease. This investigation presents a highly potential method for removal of heavy metal ions from aqueous solutions using vanadate nanowires.

A Mini Review on Bismuth-Based Z-Scheme Photocatalysts.

Recently, the bismuth-based (Bi-based) Z-scheme photocatalysts have been paid great attention due to their good solar energy utilization capacity, the high separation rate of their photogenerated hole-electron pairs, and strong redox ability. They are considerably more promising materials than single semiconductors for alleviating the energy crisis and environmental deterioration by efficiently utilizing sunlight to motivate various photocatalytic reactions for energy production and pollutant removal. In this review, the traits and recent research progress of Bi-based semiconductors and recent achievements in the synthesis methods of Bi-based direct Z-scheme heterojunction photocatalysts are explored. The recent photocatalytic applications development of Bi-based Z-scheme heterojunction photocatalysts in environmental pollutants removal and detection, water splitting, CO2 reduction, and air (NOx) purification are also described concisely. The challenges and future perspective in the studies of Bi-based Z-scheme heterojunction photocatalysts are discussed and summarized in the conclusion of this mini review.

Removal of Congo red and malachite green from aqueous solution using heterogeneous Ag/ZnCo-ZIF catalyst in the presence of hydrogen peroxide

AbstractThe bimetallic Zn/Co zeolitic imidazole frameworks (ZnCo-ZIFs) were successfully synthesized by a simple solvothermal method at room temperature. Silver elements were afterward doped onto the bimetallic frameworks to form Ag/ZnCo-ZIFs via a facile impregnation method in acetone solvent. The as-synthesized material was used as a heterogeneous catalyst for the removal reaction of Congo red (CR) and malachite green (MG) in the presence of hydrogen peroxide (H2O2). Effects of catalyst dosage, H2O2 concentration, initial concentration of the contaminants, reaction temperature, and reaction time were conducted in this work. The results showed that more than 94% and 98% removal of CR and MG were, respectively, achieved within 45 and 30 min. The presence of Ag also enhanced the removal efficiency of CR and MG. The main mechanism of removal reaction of the organic contaminants could be oxidation via hydroxyl radicals. Moreover, the catalytic activity of the material remained over 90% after four recycling cycles. Due to the efficient reactivity as well as high stability, Ag/ZnCo-ZIFs can be a potential heterogeneous catalyst to remove hazardous dyes from aqueous solution.

Integration of ozonation and an anaerobic expanded granular sludge bed reactor for micropollutant removal from sewage.

Conventional sewage treatment systems are generally not designed to remove micropollutants, requiring the development of new technologies, such as the combination of biological processes with advanced oxidative processes. The configuration of an anaerobic expanded granular sludge bed (EGSB) reactor stands out for its use of granular biomass and high sludge bed expansion. Ozonation is an advanced oxidative process that stands out as one of the most promising technologies for the degradation of micropollutants. Thus, the present work aimed to evaluate the removal of drugs through the application of ozonation as a polishing process for the effluent of an EGSB reactor that was fed with synthetic sewage. Ozonation was shown to be efficient in the degradation of these compounds, reaching removals above 90%. It was found that the degradation profile of each drug varied according to its chemical structure since some drugs are more susceptible to oxidation than others and since the concentrations of pharmaceuticals are also related to their removal. Moreover, the assessment of risks to the environment and human health confirmed the need to assess the best scenario for risk reduction considering all drugs, since even with almost complete removal of some compounds, the effluents still showed toxicity. Thus, the high removal efficiencies found for the evaluated micropollutants showed that this technique has the potential to be used to improve the quality of biological reactor effluents or even to be combined in effluent reuse systems.

A Study on Oxidation of Tetramethylammonium Hydroxide (TMAH) using UV/Persulfate

Objective : In order to efficiently remove TMAH from the wastewater generated by the TFT-LCD manufacturing process, the oxidation of TMAH was tested by applying an UV/persulfate. The optimum reaction conditions for high concentration TMAH oxidation were investigated by evaluating and comparing the removal efficiency according to the factors affecting TMAH oxidative degradation.Methods : In this study, TMAH was decomposed by sulfate radical (SO4-∙) and hydroxyl radical (OH∙) generated from persulfate activated by UV. Factors affecting on the treatment efficiency were try to be optimized by comparing and evaluating the removal efficiency depending on the initial pH, oxidant concentration, and initial TMAH concentration.Results and Discussion : Depending on initial pH (2, 7, 12), persulfate addition (0, 50, 100, 150, 200 mM), initial TMAH concentration (100, 300, 500, 700 mg/L) degradation rates of TMAH were compared. When UV/persulfate was applied, the removal efficiency of TMAH was close to 90% regardless of the initial pH and, at initial pH 12, was the highest with 89%. It was confirmed that the generation pattern of intermediate formed were different depending on the initial pH. When the oxidizing agent was not added, there was little change in TMAH concentration. The removal efficiency was highest when 100 mM persulfate was added. However the efficiency was rather low when 150 mM persulfate was added. When the initial TMAH concentration was 100 mg/L, it was decreased within 150 minutes. As the initial concentration increased, the removal efficiency and reaction rate constant decreased.Conclusions : As a results, during the oxidation of 750 mg/L TMAH by using UV/persulfate, the removal efficiency was highest with initial pH 12 and 100 mM of persulfate addition.

Cationic covalent organic framework for efficient removal of PFOA substitutes from aqueous solution

Perfluorooctanoic acid (PFOA) substitutes such as hexafluoropropylene oxide dimer acid (GenX) and hexafluoropropylene oxide trimer acid (HFPO-TA) are toxic as environmental contaminants, and efficient adsorbents are required to remove them from waters. In this study, the novel cationic covalent organic framework (COF) was developed via an imine condensation reaction for efficient removal of GenX and HFPO-TA from aqueous solution. The prepared COFs exhibited a 2D ordering hexagonal structure with AA stacking and two classes of pores (mesopore and micropore). The introduction of quaternary ammonium on COF exhibited little effect on its morphology and crystal structure. The cationic COF with quaternary ammonium showed high adsorption capacity for GenX (2.06 mmol/g) and HFPO-TA (2.16 mmol/g), more efficient than conventional activated carbons and resins. The effects of pH and natural organic matter on the removal efficiency of GenX and HFPO-TA on COF were also investigated. Interestingly, the previously adsorbed GenX on the cationic COF was replaced by the longer-chain HFPO-TA, and the underlying competitive mechanism was further clarified by performing a density functional theory calculation. This study highlights the exceptional potential of COFs through topology structural design for the efficient removal of per- and polyfluoroalkyl substances from aqueous solution.

Design of a continuous-flow single-channel reactor using optimal experimental data from batch reactor for turbidity removal by electrocoagulation

Electrocoagulation was used for turbidity removal from surface water in an internal loop airlift batch reactor. The turbidity removal efficiency of 72.05 % and energy consumption of 0.210 kW h/m3 were achieved using initial conductivity of 1,494 μS/cm, applied voltage of 5 V, treatment time of 6.5 min and inter-electrode distance of 14 mm as optimal experimental conditions. These optimal experimental data were used to design a continuous-flow single-channel (CFSC) reactor for surface water treatment by Electrocoagulation. Furthermore, experimental study under previous optimal experimental data was carried out in the CFSC reactor and the performance of two reactors was compared. Then, hydrodynamic behaviour of the CFSC reactor was studied using Residence Time Distribution (RTD). According to the results, the amount of electro-dissolved aluminum and the energy consumption were lower in the CFSC reactor than in batch system. Despite these decreases, turbidity removal efficiency was more effective in the CFSC reactor than in batch reactor. This performance is attributed to the high mixing level within the reactor as well as the reuse of the tiny flocs for particles destabilization. According to the RTD results, the hydrodynamic behaviour of the CFSC reactor shows neither short-circuiting nor dead zones, but presents small deviation from plug flow. Dispersion models were used to characterize flow within the CFSC reactor. As a result, tanks-in-series model with J = 59 and axial dispersion model with Peclet = 116 are determined as models corresponding to the hydrodynamic behaviour of the CFSC reactor.

An improved kinetic model for dephosphorization of laundry wastewater by electrocoagulation

Electrocoagulation (EC) dephosphorization kinetics plays an important role in design and amplification of EC reactors for phosphate removal. However, the existing EC dephosphorization kinetic models including both statistical model and adsorption model, fail to establish a direct law between the electric field characteristics and the dephosphorization process, which limit their efficient applications in practice. In this study, three classic adsorption isotherm models, i.e., Langmuir, Freundlich and Dubinin-Radushkevich model, were compared to describe the phosphorus adsorption in EC reactor. The experimental data is better fitted with Langmuir model than the other two models, indicating that adsorbed molecules are monolayered dispersed. Afterwards, an advanced EC dephosphorization kinetic model is developed by combining Faraday's law with Langmuir model. Laundry wastewater is used to illustrate the effects of current densities, plate spacing and initial phosphorus concentrations on the model parameters. Finally, the relationships among current efficiency, current density, plate spacing, initial concentration are established by using response surface methodology. Our new EC kinetic model successfully describe the phosphorus removal process of laundry wastewater, which might pave the way for the optimal design of EC reactor.

Removal of pharmaceutical and personal care products (PPCPs) from waterbody using a revolving algal biofilm (RAB) reactor

The occurrence of Pharmaceutical and Personal Care Products (PPCPs) in the aquatic environment has raised concerns due to their accumulation in the ecosystem. This study aims to explore the feasibility of using a Revolving Algal Biofilm (RAB) reactor for PPCPs removal from waterbody. Five model PPCP compounds including ibuprofen, oxybenzone, triclosan, bisphenol A and N, N-diethyl-3-methylbenzamide (DEET) were mixed and added to the culture medium. It shows that PPCP removal efficiencies of the RAB reactor ranged from 70% to 100%. The degradation of PPCPs by the RAB reactor contributed > 90% PPCP removal while < 10% PPCPs removal was due to accumulation in the algal biomass. The nutrients removal performance of the RAB reactor was not affected by exposing to the PPCPs. The extracellular polysaccharides content of the biomass increased when exposing to PPCPs, while the extracellular proteins content remained constant. The Chl a content maintained constant in the PPCPs-treated biomass, but decreased in the biomass without PPCP treatment. It was also found that the microbial consortium of the RAB reactor was enriched with PPCPs degradation microorganisms with the progressing of feeding PPCPs. Collectively, this work demonstrates that the RAB system is a promising technology for removing PPCPs from wastewater.

In situ observation of catalytic CeO2-nanocube (100) surface with carbon contamination by environmental TEM: a model for soot combustion

An environmental transmission electron microscopy (ETEM) was applied to the in situ observation of carbon contamination removal reaction on (100) crystal plane of catalytic CeO2 nanocubes. The distance between the surface of CeO2 and carbon layer (width) was quantitatively measured versus time at eleven points on three CeO2 nanocubes by observation at an oxygen pressure of 3.0 × 10−1 Pa at 400 °C. The carbon contamination removal rate in the time range of 100 to 460 s was 0.01 ± 0.002 nm s−1, not depending on the place. However, in the later stage, the rates of 0.057 ± 0.01 nm s−1 and 0.24 ± 0.02 nm s−1 were obtained for carbon contamination of different areas in the specimen even if the same crystal plane (100) was in contact with carbon. Carbon on the crystal surface in the inner area of the CeO2 aggregate was eliminated more quickly than contamination in the outer area. The result means that the local-environmental influence in nanoparticle aggregates is taken into account in a heterogeneous catalytic reaction as well as contamination reduction using ETEM.

Treatment of high-strength sewage by textile fibers-based sequencing batch biofilm reactor for simultaneous removal of organics and nutrients

This study investigates the effectiveness of SBBR with low-cost textile fibers-based bio-carrier namely polypropylene fibers for the treatment of real sewage. The influent loading rates of COD, TN, and TP were averaged at 0.2780, 0.0170, and 0.0077 kg/m3.d, respectively. The removal efficiencies of BOD, COD, TN, and TP recorded in SBBR were 98%, 93%, 82%, and 44%, respectively at an aeration time of 4 h. The TN and TP removal achieved in SBBR were 2.05 and 2.75 times, respectively higher than SBR. The COD removal efficiency was more than 90% under all SRT conditions (10, 14, 18, 22, and 26 d) in SBBR, and the highest efficiency of 93% was obtained at an SRT of 22 days. As the SRT increased, the nitrogen and phosphorus removal decreased, because the denitrification rate and phosphorus release and uptake rate decreased at longer SRT. Simultaneous nitrification and denitrification (SND) efficiency was 85% in SBBR and 44% in SBR, indicating the co-existence of aerobic nitrifiers and anoxic denitrifiers in the biofilm reactor. In SBBR, the nitrogen mass balance showed 74% of nitrogen removed by denitrification, 9% was removed through sludge wasting process, and 13% was removed in effluent at an SRT of 22 days and DO concentration of 3 mg/L. The t-test results suggest that the performance of SBBR was better than SBR in nitrogen and phosphorus removal at a 95% confidence interval.

Highly efficient removal of amoxicillin from water by three-dimensional electrode system within granular activated carbon as particle electrode

Amoxicillin (AMX) is a widely used broad-spectrum antibiotic. In this study, a three-dimensional electrode system (3DES) was constructed with granular activated carbon (GAC) packed between the anode and cathode electrodes to degrade AMX. Under optimal conditions of 3DES (current density of 5 mA/cm2, 17 mM NaCl as the electrolyte, an initial pH of 5.56, and a GAC-quartz sand volume ratio of 9:1), the removal efficiency of AMX reached 98.98 % after 2 h of treatment. It was also shown that the total organic carbon (TOC) removal efficiency (R) and reaction rate constant (k) of 3DES were 47.6 % and 0.22 h−1, respectively, much higher than the sum of the two-dimensional electrode system (2DES) and adsorption process (30.7 % and 0.12 h−1). Thus, there existed the synergy between electrolysis and adsorption in 3DES, which enhanced the TOC removal efficiency and removal rate by up to 35.5 % and 46.8 %, respectively. Electrochemical characterization was explored using an electrochemical workstation. It demonstrated that GAC played an important role in reducing the mass transfer resistance, and the mass transfer rate of 3DES was 2.24 times that of the 2DES. It was also deduced that AMX adsorbed on the surface of GAC directly participated in the electrochemical oxidation to achieve the in-situ regeneration of activated carbon. The results of Scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and Brunauer-Emmett-Teller (BET) of GAC verified it again. In summary, 3DES has good electrochemical performance, and it is an efficient, cost-effective, and environmentally friendly system for AMX degradation.

Mechanism of removing ferrum impurity in lanthanum refined by electron beam melting

Removal feasibility of Fe impurity form La metal by electron beam melting (EBM) was analyzed, the removal mechanism was discussed, and the verification experiments were carried out in this study. The research results indicate that, the evaporation coefficient of Fe in La metal is 35–175 at 1800–3000 K, and Fe impurity can be removed by EBM; the removal efficiency of Fe impurity is improved with the increasing EBM power, the Fe concentration is significantly decreased from 1482 to 0.1 μg/g under 50 kW and 2400 s; the reaction of Fe removal by EBM follows the first-order rate law, and Fe impurity is removed by evaporation as a single atom; transport from the La melt to the liquid boundary layer of the Fe atom is rate-controlling step in the EBM when the EBM power is 30–50 kW.

Indigenous microbial communities in Albertan sediments are capable of anaerobic benzene biodegradation under methanogenic, sulfate-reducing, nitrate-reducing, and iron-reducing redox conditions.

Alberta is a major center for oil and gas production, and correspondingly harbors hundreds of unresolved contamination sites by environmental hazards such as benzene (C6 H6 ). Due to its cost-effectiveness, bioremediation has become a promising strategy for C6 H6 removal. Contamination sites typically take on an anaerobic context, which complicates the energetics of contamination sites and is a subject that is scarcely broached in studies of Albertan sediments. This study examines the innate potential for indigenous microbial communities in Albertan sediments to remove C6 H6 in a multitude of reduced conditions. Community profiles of these sediments were analyzed by 16S rRNA gene amplicon sequencing, and removal rates and reaction stoichiometries were observed by gas chromatography and ion chromatography. Organisms belonging to known primary degrader taxa were identified, including Geobacter (iron-reducing), and Peptococcaceae (nitrate-reducing). Furthermore, benzene removal patterns of the cultures were similar to those observed in previously reported microcosms, with lag times between 70 and 168days and removal rates between 3.27 and 12.70µM/day. Such information could support a more comprehensive survey of Albertan sediment consortia, which may eventually be utilized in informing future remediation efforts in the province. PRACTITIONER POINTS: ●Clay and sand sediments originating from Northern Alberta could remove benzene under methanogenic, sulfate-reducing, iron-reducing, and nitrate-reducing conditions. ●Degradation profiles were broadly comparable to those of reported cultures from other geographical locales. ●Key degrader taxa observed included Geobacter (Fe3+ -reducing) and Peptococcaceae ( -reducing). ●Knowledge gained can be the start of a more extensive survey of Albertan sediments. Eventually, this collection of information can be used to generate robust C6 H6 -degrading cultures that can be implemented for bioaugmentation and be implemented in informing remediation strategies in soil and water matrices for priority contamination cases such as leaking underground storage tanks and orphan wells.

Micro-pressure swirl reactor (MPSR) for efficient COD and nitrogen removal of high-concentration wastewater.

A micro-pressure swirl reactor (MPSR) was developed for carbon and nitrogen removal of wastewater, in which dissolved oxygen (DO) gradient and internal circulation could be created by setting the aerators along one side of the reactor, and micro-pressure could be realized by sealing most of the top cap and increasing the outlet water level. In this study, velocity and DO distribution in the reactor was measured, removal performance treating high-concentration wastewater was investigated, and the main functional microorganisms were analyzed. The experiment results indicated that there was stable swirl flow and spatial DO gradient in MPSR. Operated in sequencing batch reactor mode, distinct biological environments spatially and temporally were created. Under the average influent condition of chemical oxygen demand (COD) concentration of 2,884 mg/L and total nitrogen (TN) of 184 mg/L, COD removal efficiency and removal loading was 98% and 1.8 kgCOD/(m3·d) respectively, and TN removal efficiency and removal loading reached up to 90% and 0.11 kgTN/(m3·d) respectively. With efficient utilization of DO and simpler configuration for simultaneous nitrification and denitrification, the MPSR has the potential of treating high-concentration wastewater at lower cost.

Effect of low temperature on abiotic and biotic nitrate reduction by zero-valent Iron

The effect of low temperatures on abiotic and biotic nitrate (NO3−) reduction by zero-valent iron (ZVI) were examined at temperatures below 25 °C. The extent and rate of nitrate removal in batch ZVI reactors were determined in the presence and absence of microorganisms at 3.5, 10, 17, and 25 °C. Under anoxic conditions, NO3− reduction rates in both ZVI-only and ZVI-cell reactors declined as temperature decreased. In ZVI-only reactor, 62% and 17% of initial nitrate concentration were reduced in 6 days at 25 and 3.5 °C, respectively. The reduced nitrate was completely recovered as ammonium ions (NH4+) at both temperatures. The temperature-dependent abiotic reduction rates enabled us to calculate the activation energy (Ea) using the Arrhenius relationship, which was 50 kJ/mol. Nitrate in ZVI-cell reactors was completely removed within 1–2 days at 25 and 10 °C, and 67% of reduction was achieved at 3.5 °C. Only 18–25% of the reduced nitrate was recovered as NH4+ in the ZVI-cell reactors. Soluble iron concentrations (Fe2+ and Fe3+) in the ZVI reactors were also measured as the indicators of anaerobic corrosion. In the ZVI-cell reactors, soluble iron concentrations were 1.7 times higher than that in ZVI-only reactors at 25 °C, suggesting that the enhanced nitrate reduction in the ZVI-cell reactors may be partly due to increased redox activity (i.e., corrosion) on iron surfaces. Anaerobic corrosion of ZVI was also temperature-dependent as substantially lower concentrations of corrosion product were detected at lower incubation temperatures; however, microbially induced corrosion (MIC) of ZVI was much less impacted at lower temperatures than abiotic ZVI corrosion. This study demonstrated that ZVI-supported microbial denitrification is not only more sustainable at lower temperatures, but it becomes more dominant reaction for nitrate removal in microbial-ZVI systems at low temperatures.

Membrane aerated biofilm reactors for mainstream partial nitritation/anammox: Experiences using real municipal wastewater

This study investigated the potential of Membrane-Aerated Biofilm Reactors (MABRs) for mainstream nitrogen removal via partial nitration/anaerobic ammonium oxidation (anammox). Four laboratory-scale MABRs were operated with real municipal wastewater characterized by low concentrations of nitrogen (varying between 31 and 120 mg–NH4–N L−1) and the presence of biodegradable organic carbon (soluble COD (sCOD) between 7 and 230 mg-O2 L−1). Two reactors were operated with different aeration strategies (intermittent vs. continuous), the other two with differences in biomass retention (recirculation or removal of detached biomass). Keeping a constant HRT caused instabilities due to difficulties with setting the optimal oxygen flux for the respective surface loadings (1.6–6 g–NH4–N m−2 d−1). Operating the MABRs with a constant surface loading (2 g–NH4–N m−2 d−1) resulted in higher and more stable total nitrogen (TN) removal independent of the aeration strategy. The intermittently aerated MABR improved from an average TN removal of 23%–69%, the continuously aerated MABR from 20% to 50% TN removal. Independent of the feeding strategy, the continuously aerated reactor removed slightly more ammonium (80–95%) compared to the intermittently aerated reactor (74–93%).Limiting the oxygen supply by intermittent aeration proofed successful to favor partial nitritation and anammox. Continuous aeration did not achieve stable suppression of nitrite oxidizing bacteria (NOB). Of the removed ammonium, approx. 26% were left in the effluent as nitrate (only 10% with intermittent aeration).Recirculation of the detached biomass resulted in reattachment onto the biofilm or membrane surface. This recirculation led to significantly higher biomass retention times and thus to better performance. Removing detached biofilm from the reactor caused a slightly lower TN removal of 33% compared to 45% with reattachment, while average ammonium removal was 58% compared to 63%, respectively. Scouring events had a significant impact on the overall operation, resulting in short term losses of TN removal capacities of 50–100%.The microbial community composition was different depending on the aeration strategy and biomass retention. The continuously aerated reactor contained significantly more AOB than the intermittently aerated MABR. The reactor with biomass retention contained less ammonium oxidizing bacteria (AOB), compared to the reactor with low biomass retention. In all MABRs, anammox bacteria established in the biofilm after an initial drop in abundance.

Manipulating denitrifying sulfide removal of Pseudomonas sp. C27 with nitrite as sole nitrogen source: Shotgun proteomics analysis

Pseudomonas sp. C27 can effectively conduct denitrifying sulfide removal (DSR) reactions via autotrophic denitrification, heterotrophic denitrification and coupled-cycle pathway. This study is the first to cultivate strain C27 using nitrite as the sole nitrogen source, and to conduct shotgun proteomics analysis and investigate the characteristics of DSR growth of strain C27 with nitrate or nitrite as sole nitrogen source. Shotgun proteomics analysis identified a total of 42 specially expressed proteins of C27 in the nitrite medium, based on which, together with chemical analysis data, a supplementary pathway of sulfur metabolism for C27 from sulfate to thiosulfate via intermediate adenosine-5′-phosphosulfate and 3′-phosphoadenosine-5′-phosphosulfate was proposed. Based on the newly revised scheme, the use of nitrite as sole nitrogen source expands the assessible regime of DSR reactions by C27 and provides the potential to recover renewable chemicals such as pyruvate and succinate from the coupled-cycle pathway.

ALLODUST augmented activated sludge single batch anaerobic reactor (AS-SBAnR) for high concentration nitrate removal from agricultural wastewater

Nitrate is among the most widespread contaminants that threaten water bodies and waterways. Under favourable environmental conditions, high nitrate concentrations in water can contribute to eutrophication, thus presenting a high potential for risk to ecosystems and human health. Low-cost allophanic soil material and carbon-based bio-wastes have great potential to reduce nutrient concentrations from contaminated waters. This study investigated the mechanisms that underpin the reduction of nitrate concentrations and nitrous oxide (N2O) emission in the presence of novel developed media in an activated sludge process. A new operating approach, employing a newly developed media (ALLODUST), was evaluated for enhanced NO−3-N removal from agricultural wastewater. Two anaerobic-aerobic batch reactors were developed, where the coupled bottom aeration method was used for efficient agitation and aeration in the aerobic reactor. The reactor was run at high NO−3-N concentrations (110 mg L−1), under anoxic conditions at low- to long-term contact times (2, 12, and 22 h), while the aerobic period (clarification) was constant for all the experimental designs (2 h). ALLODUST retained its integrity and stability over the long-term operation. Low ALLODUST concentrations (5.95 g L−1) removed 87% of the NO−3-N from the wastewater within 12 h. Further exploration revealed that the same amount of the media was optimal for decreasing N2O emissions from the anaerobic activated sludge reactor by 80%.