Technology For Removal Research Articles

Catalytic Oxidation of BTX (Benzene, Toluene, and Xylene) Using Metal Oxide Perovskites

AbstractThe high toxicity, volatility, and dispersion of the light aromatics, benzene, toluene, and xylene (BTX) pose a serious threat to the environment and human health. Compared to incineration, catalytic oxidation technologies for BTX removal offer benefits such as low energy consumption, high efficiency, and low pollution. ABO3–type perovskite catalysts (ABO3–PCs) are particularly promising materials for the catalytic oxidation of BTX due to their high activity and thermal stability, as well as their adjustable elemental composition and flexible structure allowing their properties to be improved. Nonetheless, the full potential of ABO3–PCs for the oxidation of BTX has yet to be reached. This review systematically and critically analyses progress in the catalytic oxidation of BTX by ABO3–PCs. Catalytic performance is assessed for each category of perovskite, including non–doped, doped (A–, B–, or A/B–site doped), and loading type (noble metal, metal oxide, and matrix composite), with structure–activity relationships are established. A kinetic model and proposed mechanism for the catalytic oxidation of BTX are also presented. Finally, the challenges and opportunities of ABO3–PCs applied to BTX oxidation and other reactions are highlighted.

Advancement of membrane separation technology for organic pollutant removal.

In the face of growing global freshwater scarcity, the imperative to recycle and reuse water becomes increasingly apparent across industrial, agricultural, and domestic sectors. Eliminating a range of organic pollutants in wastewater, from pesticides to industrial byproducts, presents a formidable challenge. Among the potential solutions, membrane technologies emerge as promising contenders for treating diverse organic contaminants from industrial, agricultural, and household origins. This paper explores cutting-edge membrane-based approaches, including reverse osmosis, nanofiltration, ultrafiltration, microfiltration, gas separation membranes, and pervaporation. Each technology's efficacy in removing distinct organic pollutants while producing purified water is scrutinized. This review delves into membrane fouling, discussing its influencing factors and preventative strategies. It sheds light on the merits, limitations, and prospects of these various membrane techniques, contributing to the advancement of wastewater treatment. It advocates for future research in membrane technology with a focus on fouling control and the development of energy-efficient devices. Interdisciplinary collaboration among researchers, engineers, policymakers, and industry players is vital for shaping water purification innovation. Ongoing research and collaboration position us to fulfill the promise of accessible, clean water for all.

Efficiency Improvement and Market Value Analysis of Guide Vane Electrostatic Precipitators

Urbanization and industrialization accelerate, the issue of atmospheric environmental pollution has become increasingly severe, particularly the impact of indoor air quality on human health and well-being. This study introduces a novel guide vane electrostatic precipitator that significantly enhances dust removal efficiency through optimized airflow channels and electrostatic field design. Experimental data demonstrate that this device can effectively reduce PM2.5 concentrations, improving dust removal efficiency by approximately 10% compared to traditional electrostatic dust removal technologies. Applications in various scenarios, including hotels, dust workshops, and steel foundries, indicate that the device not only improves air quality, enhancing employee productivity and well-being, but also features low energy consumption and intelligent operation. Furthermore, it holds considerable potential market value, contributing to the promotion of green and low-carbon development objectives. This research provides a comprehensive analysis and evaluation of the structure, working principle, mechanism of efficiency improvement, practical application effects, and market value of the guide vane electrostatic precipitator, looking forward to its application prospects in the field of air purification.

Microaeration promotes volatile siloxanes conversion to methane and simpler monomeric products

The ubiquitous use of volatile siloxanes in a myriad of product formulations has led to a widespread distribution of these persistent contaminants in both natural ecosystems and wastewater treatment plants. Microbial degradation under microaerobic conditions is a promising approach to mitigate D4 and D5 siloxanes while recovering energy in wastewater treatment plants. This study examined D4/D5 siloxanes biodegradation under both anaerobic and microaerobic conditions (PO2 = 0, 1, 3 %) using wastewater sludge. Results show that the use of microaeration in an otherwise strictly anaerobic environment significantly enhances siloxane conversion to methane. 16S rRNA gene sequencing identified potential degraders, including Clostridium lituseburense, Clostridium bifermentans and Synergistales species. Furthermore, chemical analysis suggested a stepwise siloxane conversion preceding methanogenesis under microaerobic conditions. This study demonstrates the feasibility of microaerobic siloxane biodegradation, laying groundwork for scalable removal technologies in wastewater treatment plants, ultimately highlighting the importance of using bio-based approaches in tackling persistent pollutants.

Identifying Potential Sources of Phthalate Contamination in the Leaves of Stevia Rebaudiana (Bertoni) and the Development of Removal Technology.

Steviosides extracted from the leaves of the plant Stevia rebaudiana are increasingly used in the food industry as natural low-calorie sweeteners. Phthalates in food are often assumed to arise from food containers or packaging materials. Here, experiments were carried out to identify the potential sources of DMP, DBP, DIBP, and DEHP in the leaves of stevioside through investigation of their content in native stevioside tissues, soils, and associated agronomic materials. The results show that phthalate contamination was present in all the samples tested, and the influence of regional factors at the provincial level on the content of plasticizers in stevia leaves was not significant. Phthalates in stevia leaves can be absorbed into the plant body through leaves and roots. Using resin removal, the phthalate content in stevioside glycosides was reduced to less than 0.05 ppm, and some indicators were far lower than the limit standard in EU food.

Novel Ag3PO4/ZnWO4-modified graphite felt electrode for photoelectrocatalytic removal of harmful algae: Performance and mechanism

A novel Ag3PO4/ZnWO4-modified graphite felt electrode (AZW@GF) was prepared by drop coating method and applied to photoelectrocatalytic removal of harmful algae. Results showed that approximately 99.21% of chlorophyll a and 91.57% of Microcystin-LR (MCLR) were degraded by the AZW@GF-Pt photoelectrocatalytic system under the optimal operating conditions with a rate constant of 0.02617 min−1 and 0.01416 min−1, respectively. The calculated synergistic coefficient of photoelectrocatalytic algal removal and MC-LR degradation by the AZW@GF-Pt system was both larger than 1.9. In addition, the experiments of quenching experiments and electron spin resonance (ESR) revealed that the photoelectrocatalytic reaction mainly generated •OH and •O2- for algal removal and MC-LR degradation. Furthermore, the potential pathway for photoelectrocatalytic degradation of MC-LR was proposed. Finally, the photoelectrocatalytic cycle algae removal experiments were carried out on AZW@GF electrode, which was found to maintain the algae removal efficiency at about 91% after three cycles of use, indicating that the photoelectrocatalysis of AZW@GF electrode is an effective emergency algae removal technology.

Thiol-functionalized cellulose for mercury polluted water remediation: Synthesis and study of the adsorption properties

Mercury pollution poses a global health threat due to its high toxicity, especially in seafood where it accumulates through various pathways. Developing effective and affordable technologies for mercury removal from water is crucial. Adsorption stands out as a promising method, but creating low-cost materials with high selectivity and capacity for mercury adsorption is challenging.Here we show a sustainable method to synthesize low-cost sulfhydrylated cellulose with ethylene sulfide functionalities bonded glucose units. Thiol-functionalized cellulose exhibits exceptional adsorption capacity (1325 mg g−1) and selectivity for Hg(II) over other heavy metals (Co, Cu, Zn, Pb) and common cations (Ca++, Mg++) found in natural waters. It performs efficiently across a wide pH range and different aqueous matrices, including wastewater, and can be regenerated and reused multiple times without significant loss of performance. This approach offers a promising solution for addressing mercury contamination in water sources.

A CO2 removal technology based on mineral carbonation and the stability of product carbon storage in a cement matrix

Toward a decarbonized society, the cement industry is continuously striving to enforce energy conservation technologies and develop low-carbon cement. The use of mineral carbonation in the cement and concrete sector and the associated value chain are central in the carbon recycling system, and the importance of CO2 removal technologies has been recognized. This paper proposes a mineral direct air carbon capture and storage in product technology newly designed by a mineral carbon capture reactor through direct feeding of atmospheric CO2. Additionally, a novel concrete mix for use as CO2-storing (CDS) concrete is proposed. This mix contains recarbonates generated using treated water with high Ca content at a ready-mixed concrete plant. The CDS concrete, with a recarbonate content in the range of 2–10% of cement, exhibited very similar initial and mechanical properties compared with ordinary concrete. The CO2 release from the recarbonate in a cement matrix under acidic corrosion and the thermal decomposition were assessed, and the findings are discussed.

Syzygium cumini-mediated synthesis of rGO/Ag-Au nanostructures: Efficient catalysts for rapid degradation of organic dyes

BackgroundThe increasing human health risk caused by contamination of water by both natural and synthetic dye pollutants has become a crucial issue and poses an immense urge to find a sustainable approach for the removal of dye contaminants from wastewater. Photocatalysis performed in the presence of nanomaterials holds huge promise as an efficient and environmentally safe oxidation technology for organic dye removal from waste water. MethodsOur preparation methodology utilizes the extract derived from the endocarp of Syzygium cumini (SC) effects for concurrent reduction of GO and metal ions to form rGO/Ag-Au. The prepared rGO/Ag-Au nanostructures effectively breakdown organic dye pollutants like methylene blue (MB) and methyl orange (MO) dyes. Significant findingsA robust interaction between the rGO matrix and the Ag-Au nanoparticles was established by structural characterization, while morphological investigation displayed the nanoscale Ag-Au particles uniformly coated over the rGO sheet surface. The catalytic efficiency of the rGO/Ag-Au nanocomposite toward methylene blue (MB) and methyl orange (MO) chromophores decomposition was assessed with the aid of sodium borohydride (NaBH4). The decoration of well-spaced Ag-Au nanoparticles over the rGO sheet created firm catalytic active sites in the rGO/Ag-Au composite. With the improved catalytic active surface, the MB/MO dye was completely removed in a very short time of 2.5 to 5 min. The rGO/Ag-Au composite exhibited exceptional catalytic prowess in the disintegration of both dyes, leading to complete degradation. The remarkable efficacy in the dye degradation process can be attributed to the predominance of both electrostatic as well as π-π interactions between the nanocomposite and the dyes. As a result, the current study has developed an easy-to-use and green method for creating rGO/Ag-Au composites, offering a workable way to dispose of hazardous organic dyes in an affordable and efficient way.

Enhanced synergistic performance of g-C3N4/MoS2 with hollow structure for tetracycline photocatalytic degradation in complex environments: Performance and mechanism

The toxicity of antibiotic and heavy metal combined pollutants is greater than single antibiotic, achieving its synergistic removal is the key. In this work, a novel g-C3N4/MoS2 photocatalyst with hollow structure (CN/MS-V-3) was fabricated by one-step solvothermal method. As expected, CN/MS-V-3 showed an outstanding removal efficiency for tetracycline and Cu2+ of 98.49% and 99.90%, respectively. The excellent photocatalytic degradation performance for tetracycline in compound wastewater mainly ascribed to the enhanced visible-light capture ability by hollow structure of CN/MS-V-3, formation 1O2 and ·OH, and the cycle of Cu2+/Cu+ and Mo2+/Mo4+ induced the fast electrons transport. The contamination of Cu2+ in wastewater can play as an accelerator in the CN/MS-V-3 reaction system to improve the degradation performance of tetracycline. DFT results indicated that CN/MS-V-3 heterojunction was formed by combination of side surface MoS2–V and g-C3N4, and the Cu adsorption onto CN/MS-V-3 showed a potential formation of Cu–N and Cu–S bonds. In addition, the tetracycline degradation pathways and evaluation of toxicity of intermediates were also proposed. This work not only provides a promising technology for antibiotic and heavy metal combined contamination removal, but also a clever use of Cu variable valence to accelerate electron cycling to improve the removal performance of the CN/MS-V-3.

Comparative study of infrared nanosecond laser surface paint removal for carbon fiber reinforced polymer and glass fiber reinforced polymer

Carbon fiber reinforced polymer (CFRP) and glass fiber reinforced polymer (GFRP) are widely used in aerospace applications due to their excellent properties. Green and efficient laser cleaning technology has a broad development prospect in the paint removal treatment of aerospace composites. However, the lack of theoretical analysis and guidance has prevented the industrial application of laser paint removal technology. An infrared nanosecond laser is used to clean the paint layer on the surface of CFRP and GFRP, and the best paint removal process parameters are explored. Surface micromorphology and 3D morphology of CFRP and GFRP after cleaning are observed to reveal the cleaning quality. The FTIR spectrum is used to verify the cleanliness of the paint layer. In addition, the contact angle and bonding force are tested, and the experimental results show that the surface wettability of both surfaces is enhanced after cleaning, and the paint adhesion of both surfaces is improved after repainting. Temperature monitoring, acoustic signal monitoring and high-speed photography monitoring are used to monitor the two cleaning processes respectively. The temperature, amplitude intensity, and plasma size of the two in the cleaning process are compared and analyzed. Based on the monitoring results, it is found that the cleaning mechanism of fiber-reinforced composites includes thermal ablation, vibration effect and plasma impact effect.

Comparison of electrochemical advanced oxidation processes for the treatment of complex synthetic dye mixtures

Many industries use complex synthetic organic dye mixtures in their dyeing processes, producing wastewater effluents with complex dye mixtures. In this study, electrochemical advanced oxidation processes like electrochemical oxidation (ECO), ECO with electrogenerated H2O2 (ECO-H2O2), electro-Fenton (EF), and photo electro-Fenton (PEF) with UVC irradiation were compared to discolor and mineralize a mixture of Methyl Orange, Methyl Red, and Toluidine Blue O with a boron-doped diamond anode and a gas-diffusion cathode. While ECO and ECO-H2O2 required long times to achieve a complete discoloration, the dyes were quickly degraded by EF and PEF due to the oxidation with ∙OH formed from Fenton’s reaction. Almost complete mineralization was rapidly achieved by PEF for a solution with 424 mg O2 L−1 of chemical oxygen demand (COD) at a current density of 66.6 mA cm−2 due to the synergistic action of the UVC irradiation. Additionally, the treated effluent was evaluated using the DFZ (Deutsche Farb Zah) parameter for water condition, offering a new perspective and distinguishing this work from previous studies focused on electrified technologies for dye removal. The same behavior has been found for the mixture of such dyes in an industrial effluent upon PEF treatment, even showing faster discoloration and COD reduction as result of the additional removal with active chlorine formed from Cl− oxidation. Ion-exclusion HPLC analysis of the treated synthetic effluent revealed the formation of final carboxylic acids like malic, acetic, oxalic, and formic. Released nitrate, ammonia, and nitrite were detected as nitrogenated by-products from the initial N of the dyes.

Purification of process solutions from mercury by sorption

At JSC «Uralelectromed», selenium-containing raw materials and industrial products are processed, resulting in solutions containing a mixture of mercury with concentrations as follows (g/dm3): 157–210 Se; 0.004–0.02 Hg; 0.15–0.20 Te; 2–3 As; 0.15–0.20 Sb; and 45–50 S. To produce branded selenium, the mercury concentration in the solution must be kept below 0.001 g/dm3. Various methods, such ashydrometallurgical and electrochemical processes, are known for mercury purification from solutions. JSC «Uralelectromed» has selected sorption technology for mercury removal using the weak-base macroporous anionite Lewatit MP-68 (Germany), which allows for control over the degree of solution purification. In pursuit of import substitution for the Western European sorbent Lewatit MP-68, we investigated several pre-selected industrial sorbents for extracting mercury anionic complexes produced in Russia (AM-2B, AN-31, AV 17-8, VP-3Ap), China (Seplite MA 940 and LSC 710), and India (Tulsion CH-95 and CH-97). Initially, in static mode, we determined the distribution coefficient (Cd), the degree of element extraction (ε), the static exchange capacity of the resins (SEC, g/dm3), and the mercury/selenium separation coefficient (DHg/Se) which led to the selection of the best samples: AV 17-8, Seplite MA 940, AM-2B, and CH-97, with SEC values of 0.95–0.97 g/dm3 (SEC = 0.98 g/dm3 of resin Lewatit MP-68). Subsequently, in dynamic mode, we ranked the ionites by decreasing dynamic exchange capacity (DEC / TDEC): AV 17-8 ≥ Lewatit MP-68 > AM-2B > Seplite MA 940 > Tulsion CH-97. Resins AV 17-8, Seplite MA 940, and AM-2B demonstrated similar dynamic sorption characteristics; under comparable conditions, mercury breakthrough occurred after processing at least 950 specific volumes of the initial solution. In contrast, with Lewatit MP-68 ionite, mercury breakthrough occurred after no more than 750 specific volumes, indicating the need to increase the number of sorption steps in the solution purification cascade. Considering the totality of ion-exchange properties, for further industrial testing, it is recommended to use the domestically produced resin AV 17-8 instead of the foreign sorbent Lewatit MP-68 in the sorption purification process of selenic acid to remove mercury, thereby ensuring the production of branded selenium.

Evaluating microcystinase A-based approach on microcystins degradation during harvested cyanobacterial blooms

Addressing notorious and worldwide Microcystis blooms, mechanical algae harvesting is an effective emergency technology for bloom mitigation and removal of nutrient loads in waterbodies. However, the absence of effective methods for removal of cyanobacterial toxins, e.g., microcystins (MCs), poses a challenge to recycle the harvested Microcystis biomass. In this study, we therefore introduced a novel approach, the “captured biomass-MlrA enzymatic MC degradation”, by enriching microcystinase A (MlrA) via fermentation and spraying it onto salvaged Microcystis slurry to degrade all MCs. After storing the harvested Microcystis slurry, a rapid release of extracellular MCs occurred within the initial 8 h, reaching a peak concentration of 5.33 μg/mL at 48 h during the composting process. Upon spraying the recombinant MlrA crude extract (about 3.36 U) onto the Microcystis slurry in a ratio of 0.1% (v/v), over 95% of total MCs were degraded within a 24-h period. Importantly, we evaluated the reliability and safety of using MlrA extracts to degrade MCs. Results showed that organic matter/nutrient contents, e.g. soluble proteins, polysaccharides, phycocyanin and carotenoids, were not significantly altered. Furthermore, the addition of MlrA extracts did not significantly change the bacterial community composition and diversity in the Microcystis slurry, indicating that the MlrA extracts did not increase the risk of pathogenic bacteria. Our study provides an effective and promising method for the pre-treatment of harvested Microcystis biomass, highlighting an ecologically sustainable framework for addressing Microcystis blooms.

Ultrasound based technology for removal of scale from downhole production tubing, an experimental verification

Deposition and blockages due to scale formation inside the production tubing are the most common problems experienced during the production of oil and gas, and this significantly leads to a decline in the production rate. Progressive scale formation limits production which subsequently leads to abandonment of the well. There is a great cost attached to preventing the occurrence and remediation of scales. Chemical and mechanical techniques for scale removal in production tubing have drawbacks like environmental concerns, equipment damage, and incomplete removal of stubborn scale. In contrast, ultrasound-based methods offer potential benefits such as non-destructiveness, enhanced efficiency, reduced chemical usage, and increased safety for workers. Despite the extensive research about the application of ultrasound to improve oil recovery, there remains a significant gap in the comprehensive exploration of optimum ultrasound parameters (frequency, power, radiation time, interval time, and location) for the removal of in-situ built scales in a simulated production tubing under different flow rates. This study addresses this gap by investigating the impact of ultrasound parameters on its performance for removal of calcium carbonate (CaCO3) and gypsum scales in a simulated production tubing system under different flow rate (100% and 50%). The ultrasound parameters include frequency (in the range of 20 kHz–120 kHz), power (50 W and 100 W), operation time, and location (externally attached and inserted into the production tubing).Initial tests revealed that adjusting the operating frequency improves the impedance matching, resulting in enhanced scale removal. The experiments also explored the influence of flow rate on scale removal, showing a general increase in removal with higher flow rates, specially at operating frequencies 20 kHz and 28 kHz. It was also demonstrated that the higher frequencies of 40 kHz, 68 kHz, and 120 kHz exhibit limited removal efficiency. The effectiveness of scale removal exhibited nonlinear variation over time, with the 28 kHz, 100 W transducer demonstrating the most significant improvement.In-pipe ultrasonic rod, operating at a constant frequency of 26 kHz, was employed to assess its performance for scale removal. Pulsed treatment was introduced to manage rod heating issues. Results demonstrated that both interval times and flow rates influenced CaCO3 removal, with shorter intervals yielding better results. The ultrasonic rod's efficacy was also observed in removing gypsum scale layers, suggesting potential applications in treating scales with various strengths. The results of this study can contribute to a better understanding of how the frequency, power, operating time and interval, and flow rate influence ultrasonic scale removal. The experimental findings provide valuable insights in optimizing practical applications for removal of scales from production tubing.

Conventional technologies and recent developments in the nanotechnological approach for the remediation of persistent organic pollutants

ABSTRACT Persistent organic pollutants (POPs) are one of the important concerns in the environmental sciences and ecotoxicology fields. Various deadly illnesses and environmental problems are caused by them. It is a major issue in society that there are no new and effective ways to eliminate POPs from the atmosphere. Nanotechnology is a rapidly developing area that has uses in every aspect of life. A lot of attention is being paid to the investigation of novel synthetic methods for shaping and controlling the size of nanomaterials due to their outstanding uses and qualities. One of the most significant groups of nanoparticles is the magnetic nanoparticles. A novel class of magnetic separation techniques for water treatment has been made possible through the utilization of magnetic nanoparticles as nano adsorbents. Our aim in this study is to give a concise, focused review of POP, emphasize the sources, types, and potentially hazardous impacts they have on living organisms, and to offer some observations on their detection and monitoring strategies. To highlight specific conventional removal technologies of importance, as well as recent advancements such as nanotechnology and magnetic nanoparticles, including their synthesis methods. Finally, hybrid nanotechnology for POP removal has been investigated.

Development of a Low Cost System for The Removal of Heavy Metals from Polluted Water

Water pollution by heavy metals has become one of the most harmful environmental issues. This study developed a low cost heavy metal (lead and chromium) removal system from polluted water using locally available adsorbents, such as sawdust, pawpaw (Carica papaya) seeds and sand. Heavy metals constitute a serious threat to human health and the entire biological system due to their toxic, mutagenic, and carcinogenic nature even at trace concentrations. The objective of this study was to design and construct a low cost heavy metals removal system, test its performance and do a cost analysis of the system. In this process, a filter column made of a plastic container of height 54 cm and diameter 20.4 cm was constructed. Characteristic properties of the adsorbents were obtained from secondary sources and were found to possess functional groups (hydroxyl, carbonyl, aldehyde and amine) capable of binding to metal ions. Optimization was done with a sawdust and pawpaw seeds/sand height ratios of 10:10, 10:15, 15:10, 20:10 and 10:20 cm respectively in the filter column. Results showed that the best removal efficiencies were 99.88% for lead and 85.57% for chromium with a sawdust to pawpaw seeds/sand mixture ratio of 10:20 cm. Statistical analysis showed a significant difference (p < 0.05) in the final concentrations of lead and chromium using the various adsorbent proportions. Cost per liter of treated water was deduced to be 15.5 FCFA. This cost can be afforded by many households with low incomes and thus, this low cost heavy metals removal technology is highly recommended.

Ecological filter walls for efficient pollutant removal from urban surface water

Urban surface water pollution poses significant threats to aquatic ecosystems and human health. Conventional nitrogen removal technologies used in urban surface water exhibit drawbacks such as high consumption of carbon sources, high sludge production, and focus on dissolved oxygen (DO) concentration while neglecting the impact of DO gradients. Here, we show an ecological filter walls (EFW) that removes pollutants from urban surface water. We utilized a polymer-based three-dimensional matrix to enhance water permeability, and emergent plants were integrated into the EFW to facilitate biofilm formation. We observed that varying aeration intensities within the EFW's aerobic zone resulted in distinct DO gradients, with an optimal DO control at 3.19 ± 0.2 mg L−1 achieving superior nitrogen removal efficiencies. Specifically, the removal efficiencies of total organic carbon, total nitrogen, ammonia, and nitrate were 79.4%, 81.3%, 99.6%, and 79.1%, respectively. Microbial community analysis under a 3 mg L−1 DO condition revealed a shift in microbial composition and abundance, with genera such as Dechloromonas, Acinetobacter, unclassified_f__Comamonadaceae, SM1A02 and Pseudomonas playing pivotal roles in carbon and nitrogen elimination. Notably, the EFW facilitated shortcut nitrification-denitrification processes, predominantly contributing to nitrogen removal. Considering low manufacturing cost, flexible application, small artificial trace, and good pollutant removal ability, EFW has promising potential as an innovative approach to urban surface water treatment.

Coupling Partial Nitritation, Anammox and n-DAMO in a membrane aerated biofilm reactor for simultaneous dissolved methane and nitrogen removal

Anaerobic technologies with downstream autotrophic nitrogen removal have been proposed to enhance bioenergy recovery and transform a wastewater treatment plant from an energy consumer to an energy exporter. However, approximately 20–50 % of the produced methane is dissolved in the anaerobically treated effluent and is easily stripped into the atmosphere in the downstream aerobic process, contributing to the release of greenhouse gas emissions. This study aims to develop a solution to beneficially utilize dissolved methane to support high-level nitrogen removal from anaerobically treated mainstream wastewater. A novel technology, integrating Partial Nitritation, Anammox and Methane-dependent nitrite/nitrate reduction (i.e. PNAM) was demonstrated in a membrane-aerated biofilm reactor (MABR). With the feeding of ∼50 mg NH4+-N/L and ∼20 mg/L dissolved methane at a hydraulic retention time of 15 h, around 90 % of nitrogen and ∼100 % of dissolved methane can be removed together in the MABR. Microbial community characterization revealed that ammonia-oxidizing bacteria (AOB), nitrite-oxidizing bacteria (NOB), anammox bacteria, nitrite/nitrate-dependent anaerobic methane oxidation microorganisms (n-DAMO bacteria and archaea) and aerobic methanotrophs co-existed in the established biofilm. Batch tests confirmed the active microbial pathways and showed that AOB, anammox bacteria and n-DAMO microbes were jointly responsible for the nitrogen removal, and dissolved methane was mainly removed by the n-DAMO process, with aerobic methane oxidation making a minor contribution. In addition, the established system was robust against dynamic changes in influent composition. The study provides a promising technology for the simultaneous removal of dissolved methane and nitrogen from domestic wastewater, which can support the transformation of wastewater treatment from an energy- and carbon-intensive process, to one that is energy- and carbon-neutral.

Study on effect of magnetization on wetting characteristics of water with different ions to coal dust

Coal dust is a significant problem in underground coal mining, and more economical and effective methods are needed to control coal dust. Magnetized water dust removal technology is considered to be an effective method to solve the problem of high concentration dust. In order to further understand the role of ions in magnetic fields in water, the optimal magnetic field parameters for solutions containing various ions were determined by surface tension and contact angle measurements. The wettability experiments have shown that the optimal magnetization effect can be obtained by placing NaCl solution with the concentration of 0.04 mol/L in the 150mT magnetic field for 120 s at room temperature. Subsequently, the influence of various ions in water on the wettability of coal was investigated using a combination of FTIR testing and Zeta potential experiments. The results showed that the order of the influence intensity of different ions on the wettability of water was Na+ > Mg2+ > Ca2+ when the Cl– content was 0.04 mol/l, and Cl– > CO32– > SO42– when the Na+ content was 0.04 mol/L. Furthermore, Lorentz forces can influence various ions, accelerating their migration and enhancing their accessibility to water clusters. Different ions exert force on the dipoles within water molecules, which can promote or suppress hydrogen bond cleavage. When the number of hydrogen bond breaks rises, it leads to an increase in the wetting properties of the solution. The research findings provide a theoretical foundation for the use of magnetization technology in dust suppression with mist spray in underground coal mines.