Mechanism Of Simultaneous Removal Research Articles

Molecular insights into the simultaneous removal mechanisms of As(Ⅴ) and Cd(II) in iron tailings slag-biochar composites

Arsenic and cadmium contamination frequently coexist in the real environment. However, it remains a challenge for their simultaneous removal due to their distinct physicochemical properties at low cost. To this end, a cost-effective magnetic biochar adsorbent (ITBNa800) was prepared using biomass waste and iron tailings slag. This composite adsorbent exhibits excellent performance in the simultaneous removal of aqueous As(V) and Cd(II) even at high concentrations with removal efficiencies of up to 99.98% and 96.04%, respectively. Electrostatic action, precipitation, and complexation were adsorption mechanisms. As(V) and Cd(II) were synergistic and competitive adsorption. As(V) removal was mainly due to physical and chemical adsorption, and 42.40%-58.59% of As(V) had been converted to As(III). Cd(II) removal was mainly due to chemical adsorption. Iron oxide and aluminum oxide in ITBNa800 were the keys to As(V), As(III), and Cd(II) adsorption. DFT calculations revealed iron oxide complex As(V), As(III), and Cd(II) molecular clusters through bidentate binuclear, bidentate binuclear, and monodentate binuclear pathways, respectively. Aluminum oxide complex Cd(II) molecular cluster through a bidentate mononuclear pathway. We hope the ITBNa800 adsorbent and its involved mechanism could offer inspiration in the simultaneous treatment of As and Cd pollution.

Mechanisms of simultaneous removal of multiple chlorinated hydrocarbons in aquifers by in-situ microemulsion

The chlorinated hydrocarbons (CHs) are typically released to the aquifer as complex mixture, and the contaminant type takes the critical action on the in-situ microemulsion formation and solubilization behaviors. However, few interst has been paid to the solubilization behaviors of microemulsion for multiply CHs and the factors affecting selective solubilization. The current work investigated the effect of hydrogeochemical conditions on microemulsion competitive solubilization, and focused on the selective desorption and removal performance of in-situ microemulsion drenching under the various drenching situations. The results elucidated that the apparent solubility of CH was enhanced with adding inorganic salts and the decreasing temperature. In-situ microemulsion showed a preference for dissolving the more polar CHs (CF) in chlorinated hydrocarbon mixture. The selective solubilization was strengthened with increasing temperature, independent of alcohols and salts. The removal efficiency of microemulsion drenching for multiply CHs could achieve 96.0 %, improving with the tinier particle media and lower flow rates. Compared to other CHs, CF was more likely to be desorbed from aquifer medium in multicomponent systems. Furthermore, the selective desorption for multiply CHs was associated with flow rates, media size and residual saturation of contaminants. The inhibition for preferential desorption was more intense to the increase of injection velocity, media size and residual saturation. This insight of selective solubilization behavior can be used to advances the application of in-situ microemulsion drenching for site remediation of multiply CHs.

Induced crystallization for the simultaneous removal of hardness-iron–manganese in groundwater: An experimental study

Hardness, iron, and manganese are common groundwater pollutants, that frequently surpass the established discharge standard concentrations. They can be effectively removed, however, through induced crystallization. This study has investigated the effectiveness of the simultaneous removal of hardness-iron-manganese and the crystallization kinetics of calcium carbonate during co-crystallization using an automatic potentiometric titrator. The impacts pH, dissolved oxygen (DO), and ion concentration on the removal efficiency of iron and manganese and their influence on calcium carbonate induced crystallization were assessed. The results suggest that pH exerts the most significant influence during the removal of hardness, iron, and manganese, followed by DO, and then the concentration of iron and manganese ions. The rate of calcium carbonate crystallization increased with pH, stabilizing at a maximum of 10−10 m/s. Iron and manganese can be reduced from an initial level of 4 mg/L to <0.3 mg/L and 0.1 mg/L, respectively. The removal rate of iron, however, was notably higher than that of manganese. The DO concentration correlates positively with the removal of iron and manganese but has minimal impact on the calcium carbonate crystallization process. During the removal of iron and manganese, competitive interactions occur with the substrate, as increases in the concentration of one ion will inhibit the removal rate of the other. Characterization of post-reaction particles and mechanistic analysis reveals that calcium is removed through the crystallization of CaCO3, while most iron is removed through precipitation as Fe2O3 and FeOOH. Manganese is removed via two mechanisms, crystallization of manganese oxide (MnO2/Mn2O3) and precipitation. Overall, this research studies the removal efficiency of coexisting ions, the crystallization rate of calcium carbonate, and the mechanism of simultaneous removal, and provides valuable data to aid in the development of new removal techniques for coexisting ions.

A promising catalyst for catalytic oxidation of chlorobenzene and slipped ammonia in SCR exhaust gas: Investigating the simultaneous removal mechanism

As the emission limits for NOx become further stringent, development of a synergistic control technology to prevent emissions of slipped ammonia (NH3) and chlorinated organics from steel production and waste incineration is both a prospect and a challenge for the environmental issues. In this work, the designed ruthenium-based catalyst (RuNb/ST) showed the excellent chlorobenzene (CB)/NH3 synergistic removal performance and N2/CO2 selectivity above 300 ℃. The activity of NH3 and CB were suppressed at relatively low temperature due to the competitive adsorption of CB and NH3. Whereas, there was a significant improvement in the N2/CO2 selectivity at relatively high temperature. The removal mechanism was studied by experiments, in which the accumulation of chlorine species, the role of NO2 and the oxidation of CB were considerable. In contrast to the carrier, the vast majority of the chloride ions adsorbed onto the active sites after dissociating from CB could be efficiently removed in form of Cl2 via the Deacon Reaction catalyzed by RuO2. CB was predominantly converted into CO2 and H2O with a fraction persisting as organics. Partial of organics were attacked by Cl ions to generate organic chlorine-containing by-products. The presence of NO2 molecule was found to promote the cleavage of the benzene ring within CB, and expedited the carbon migration towards the ultimate product of CO2, resulting in a notable reduction of byproducts.

Performances and mechanisms of simultaneous removal of nitrate and phosphate by biofilter assembled with sponge iron/copper and corn cobs

Sponge iron (SI) is a potential material for removing nitrate and phosphate from water. We decorated the SI with copper (Cu) to enhance its removal performance. To gain insight into the nitrate and phosphate removal utilizing SI/Cu and microbial coupling systems, three biofilters filled with corn cob (CC), corn cob + sponge iron (CS) and corn cob + sponge iron/copper (CSCu) were constructed. The results showed that the effluent NO3–-N and PO43−-P concentrations of CSCu remained consistently below 1 and 0.1 mg/L. The introduction of SI/Cu led to the enrichment of the Dechloromonas genus, making it the dominant microbial group, occupying 42.65% of the effective sequences. Modification of SI with Cu increased nitrogen cycle-related functional genes abundance in CSCu, with a 634% increase in nirS compared to CS. These findings proved that SI/Cu was a promising material, providing an approach to concomitantly removing nitrate and phosphate.

Control of chemical and microbial pollutants in liquid-solid phases of sewer pipes by Fe(II)-activated persulfate: Performance and mechanism of simultaneous removal

Most of the problems such as odor and corrosion in sewage systems originate from the biochemical reactions of liquid and solid phases in the pipes. Suppressing the activity of microorganisms and biofilms in the sewers is conducive to maintaining the proper operation of the sewer system. This study verified the removal of microorganisms and sulfides from wastewater and the inhibition of biofilm activity by peroxodisulfate (PDS) with the activation of ferrous ions (Fe(II)). Fe(II)/PDS can achieve efficient microbial inactivation within a reaction time of 20 min after a single dosing (Up to 95% removal of planktonic bacteria in the liquid phase), and the sulfide reduction can be maintained for more than 5 days, providing the possibility of intermittent dosing. The sulfide concentration can be maintained below 4 mg/L by intermittent dosing (average dosing interval is 10 days) during the long-term operation of the reactor. Dissolved organic matter (DOM) changes in sewage predict biofilm destruction. Changes in the biofilm microscopic morphology, extracellular polymer substances (EPS) fraction, biofilm functional groups, and microbial community revealed the effects of Fe(II)/PDS on the solid–liquid phase material fraction and biofilm structure of the sewage pipeline. The mechanism of biofilm disruption was analyzed based on the identification of strongly oxidizing active species in the Fe(II)/PDS system. This study shows that it is feasible to develop an efficient and cost-effective sulfide and microbial control strategy using Fe(II) with PDS in sewage systems.

Biomineralization behavior and mechanism of microbial-mediated removal of arsenate from water

The microbial-mediated removal of arsenate by biomineralization received much attention, but the molecular mechanism of Arsenic (As) removal by mixed microbial populations remains to be elucidated. In this study, a process for the arsenate treatment using sulfate-reducing bacteria (SRB) containing sludge was constructed, and the performance of As removal was investigated at different molar ratios of AsO43- to SO42-. It was found that biomineralization mediated by SRB could achieve the simultaneous removal of arsenate and sulfate from wastewater but only occurred when microbial metabolic processes were involved. The reducing ability of the microorganisms for the sulfate and arsenate was equivalent, so the precipitates produced at the molar ratio of AsO43- to SO42−of 2:3 were most significant. X-ray absorption fine structure (XAFS) spectroscopy was the first time used to determine the molecular structure of the precipitates which were confirmed to be orpiment (As2S3). Combined with the metagenomics analysis, the microbial metabolism mechanism of simultaneous removal of sulfate and arsenate by the mixed microbial population containing SRB was revealed, that is, the sulfate and As(V) were reduced by microbial enzymes to produce S2- and As(III) to further form As2S3 precipitates. This research provided a reference and theoretical foundation for the simultaneous removal of sulfate and arsenic mediated by SRB-containing sludge in wastewater treatment.

Simultaneous removal of antibiotics and antibiotic resistance genes in wastewater by a novel nonthermal plasma/peracetic acid combination system: Synergistic performance and mechanism

In this study, a novel and green method combining plasma with peracetic acid (plasma/PAA) was developed to simultaneously remove antibiotics and antibiotic resistance genes (ARGs) in wastewater, which achieves significant synergistic effects in the removal efficiencies and energy yield. At a plasma current of 2.6 A and PAA dosage of 10 mg/L, the removal efficiencies of most detected antibiotics in real wastewater exceeded 90 % in 2 min, with the ARG removal efficiencies ranging from 6.3 % to 75.2 %. The synergistic effects of plasma and PAA could be associated with the motivated production of reactive species (including •OH, •CH3, 1O2, ONOO-, •O2- and NO•), which decomposed antibiotics, killed host bacteria, and inhibited ARG conjugative transfer. In addition, plasma/PAA also changed the contributions and abundances of ARG host bacteria and downregulated the corresponding genes of two-component regulatory systems, thus reducing ARG propagation. Moreover, the weak correlations between the removal of antibiotics and ARGs highlights the commendable performance of plasma/PAA in the simultaneous removal of antibiotics and ARGs. Therefore, this study affords an innovative and effective avenue to remove antibiotics and ARGs, which relies on the synergistic mechanisms of plasma and PAA and the simultaneous removal mechanisms of antibiotics and ARGs in wastewater.

Simultaneous removal of chlorite and coexisting emerging organic contaminants by sulfite: Kinetics and mechanisms

The inevitable formation of chlorite (ClO2–) and the ineffective degradation of some emerging organic contaminants (EOCs) during chlorine dioxide disinfection have aroused increasing concern about their adverse effects on human health. In this study, the kinetics and mechanisms of simultaneous removal of ClO2– and coexisting EOCs by sulfite (S(IV)) were investigated. Under aerobic conditions, ClO2– and coexisting EOCs could be effectively removed by S(IV) at pH 6.5–7.5, and their removal rates decreased as pH increased. ClO3– was generated in this process but its amount decreased with increasing pH. Many lines of evidence verified that the reaction of ClO2– with HSO3– and H+ generated SO3•− and ClO•, and the generated ClO• was rapidly quenched by S(IV) to form OCl– and SO3•−. Subsequently, SO3•− quickly reacted with O2 to form SO5•−, which was further transformed into SO4•−. SO4•− was the dominant reactive oxidant contributing to the degradation of coexisting EOCs and the formation of ClO3–. Using S(IV) to simultaneously control ClO2– and coexisting EOCs in water treatment is a promising approach because its performance was slightly affected by the water matrix.

A novel constructed wetland based on iron carbon substrates: performance optimization and mechanisms of simultaneous removal of nitrogen and phosphorus.

In recent years, the combination of iron carbon micro-electrolysis (ICME) with constructed wetlands (CWs) for removal of nitrogen and phosphorus has attracted more and more attention. However, the removal mechanisms by CWs with iron carbon (Fe-C) substrates are still unclear. In this study, the Fe-C based CW (CW-A) was established to improve the removal efficiencies of nitrogen and phosphorus by optimizing the operating conditions. And the removal mechanisms of nitrogen and phosphorus were explored. The results shown that the removal rates of COD, NH4+-N, NO3--N, TN, and TP in CW-A could reach up to 84.4%, 94.0%, 81.1%, 86.6%, and 84.3%, respectively. Wetland plants and intermittent aeration have dominant effects on the removal of NH4+-N, while the removal efficiencies of NO3--N, TN, and TP were mainly affected by Fe-C substrates, wetland plants, and HRT. XPS analysis revealed that Fe(0)/Fe2+ and their valence transformation played important roles on the pollutants removal. High-throughput sequencing results showed that Fe-C substrates and wetland plants had considerable impacts on the microbial community structures, such as richness and diversity of microorganism. The relative abundance of autotrophic denitrification bacteria (e.g., Denitatsoma, Thauera, and Sulfuritalea) increased in CW-A than CW-C. The electrons and H2/[H] produced from Fe-C substrates were utilized by autotrophic denitrification bacteria for NO3--N reduction. Microbial degradation was the main removal mechanism of nitrogen in CW-A. Removal efficiency of phosphorus was enhanced resulted from the reaction of phosphate with iron ion. The application of CWs with Fe-C substrates and plants presented great potential for simultaneous removal of nitrogen and phosphorus.

Simultaneous removal of triclosan and Cd(Ⅱ) by bio-reduced graphene oxide and its mechanism

The co-existence of contaminants such as triclosan (TCS) and Cadmium in wastewater is a major public health problem because of their persistence and toxicity. In this study, bio-reduced graphene oxide (B-rGO) synthesized by Lysinibacillus sp. Simultaneously remove TCS and Cd(II), with adsorption capacities of 81.91 and 23.32 mg g−1, for TCS and Cd (Ⅱ), respectively. This was significantly higher than that previously reported for commercially available reduced graphene oxide (C-rGO), which was only 31.94 and 2.01 mg g−1, for TCS and Cd (Ⅱ), respectively. Fourier transform infrared spectroscopy (FTIR) showed that rGO surface-bound extracellular polymeric substances (EPS) played a key role in the observed enhanced contaminant removal, which was verified by scanning electron microscopy (SEM), energy dispersive spectrometry (EDS) and X-ray photoelectron spectroscopy (XPS). In addition, the absorption of both Cd(II) and TCS on B-rGO was confirmed by XPS and high-performance liquid chromatography (HPLC-UV). The adsorption kinetics of both TCS and Cd(II) fitted well to the pseudo-second-order model, while the adsorption isotherms of Cd(II) followed the Langmuir model, and triclosan the Freundlich model. A mechanism of simultaneous removal of TCS was proposed based on π-π interactions and hydrogen bonding, while Cd(II) was removed by a combination of electrostatic and chelation/complexation. Finally, the adsorption of TCS and Cd(II) by B-rGO in real wastewater was shown to be 76.67 and 16.53 mg g−1, respectively, demonstrating that B-rGO has the potential for practical simultaneous removal of TCS and Cd(II) from wastewater.

Simultaneous catalytic oxidation mechanism of NO and Hg0 over single-atom iron catalyst

Among the many pollutants emitted from coal-fired power plants, elemental mercury (Hg0) and nitrogen oxides (NOx) are widely concerned and regarded as a global environmental problem. Catalytic oxidation is an effective method to remove the above power plant pollutants. Although the recent pioneering experiment found that single-atom catalysts (SACs) exhibit excellent performance for the oxidation of NO and Hg0, the reaction mechanism for the simultaneous removal of NO and Hg0 has not been thoroughly revealed. In this work, a single-atom iron catalyst supported by a double vacancy doped graphene substrate with four N atoms (Fe1N4) was used to explore the reaction mechanism of O2 simultaneous catalytic of NO and Hg0. By using DFT method and energy span model, all possible paths of simultaneous catalytic oxidation of NO and Hg0 are enumerated. Among the ten paths we found, Termolecular Eley-Rideal (TER) mechanism has the lowest energy barrier. The rate determining reaction barrier is 1.59 eV. Disregarding the contribution of molecular collisions, TER path is more kinetically favorable for the integrated removal of NO and Hg0. Comprehensive consideration of intermolecular collisions, the catalytic oxidation reaction follows the E-R mechanism. The study deepened the understanding of the reaction mechanism of simultaneous removal of NO and Hg0.

Microbial driving mechanism for simultaneous removal of nitrogen and phosphorus in a pure anammox reactor under ferrous ion exposure

The mechanisms of Fe2+ on nitrogen and phosphorus removal and functional bacterial competition in anammox systems was investigated. Under 0.12 mM Fe2+, the performance of nitrogen and phosphorus removal increased by 10.08 % and 151.91 %, respectively, compared with the control stage. Phosphorus removal was achieved through extracellular polymeric substance (EPS) induced biomineralization to form Fe-P minerals, and functional group COC in EPS played a critical role. T-EPSs was the major nucleation site due to it maintaining the supersaturated state (saturation index > 0) of Fe-P minerals for a long time. Population succession showed that Fe2+ weakened the competition between heterotrophic denitrifier (Denitrasoma) and anammox microbe (Candidatus Brocadia) for space and substrates, which was favorable for the enrichment of anammox biomass. Moreover, the variation in gene abundance (such as Hao, Cyt c, and Nir) indicated that Fe2+ improved electron behaviors (generation, transport, and consumption) during the nitrogen metabolism of anammox systems.

Fenton-like oxidation mechanism for simultaneous removal of estriol and ethinyl estradiol by green synthesized Mn3O4 NPs

Manganese tetroxide (Mn3O4) nanomaterials were prepared by green tea extract and applied to catalyze sodium peroxydisulfate (PDS) for the simultaneous degradation of estriol/17a-ethinylestradiol (E3/EE2) with removal efficiencies of 97.5 and 96.4% for E3 and EE2, respectively. XPS also showed that before and after the reaction the divalent manganese content decreased from 50.2 to 34.8%, indicating divalent manganese plays a major role in the catalytic process. EPR quenching and electrochemical studies showed that while initially singlet oxygen (1O2), sulfate (SO4•-), superoxide (O2•-) and hydroxyl (•OH) radicals were all generated in the system, thereafter, the oxidation of E3/EE2 mainly depended on 1O2 and O2•-, where O2•- intermediates participated in the generation of 1O2 in the Fenton-like process. LC-MS analysis showed that degradation products of E3/EE2 were mainly produced via hydroxyl and sulfate degradation pathways. Finally, a mechanism of Fenton-like oxidation of E3/EE2 was proposed.

Mechanism for the simultaneous removal of Sb(III) and Sb(V) from mining wastewater by phytosynthesized iron nanoparticles

Since antimony (Sb) is a toxic metalloid cost-effective method for the simultaneous removal of the two major Sb species from mining wastewater has attracted much attention. In this study, phytosynthesized iron nanoparticles (nFe) prepared using a eucalyptus leaf extract were successfully used to simultaneously remove Sb(III) and Sb(V) via an adsorption and oxidation mechanism with removal efficiencies of 100 and 97.7% for Sb(III) and Sb(V), respectively. Advanced analysis using X-ray photoelectron spectroscopy (XPS), ion chromatography-atomic fluorescence spectroscopy (IC-AFS), and electrochemical analysis confirmed that Sb(III) was oxidized to Sb(V) by Fe(III) on the nFe surface while Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS) indicated that both Sb(III) and Sb(V) were adsorbed onto nFe. Adsorption of both Sb(III) and Sb(V) best fit the Langmuir adsorption model with R2 of 0.999 and 0.989, respectively and both followed pseudo-second-order kinetics with R2 of 0.999 and 0.981, respectively. Furthermore, the adsorption rate of Sb(III) was faster than that of Sb(V) due to inner-sphere complex formation, and the Fe–O bonds in the asymmetric tetrahedron structure of Sb(III) were easier to break due to a lower energy barrier (0.863 eV). Consequently, a simultaneous removal mechanism of Sb(III) and Sb(V) was proposed. Finally, nFe was used practically to remove Sb in mining wastewater with a removal efficiency of 93.5%, demonstrating that nFe have significant potential to remove Sb in contaminated mining wastewaters.

Nano-Fe1−xS embedded BCAA/Fe3O4 as the stabilized catalyst for simultaneous quinclorac oxidation and Cr(VI) reduction

Quinclorac (QNC) and Cr(VI), are common contaminants in surface waters, posing serious hazard to human and ecological health. Nano FeS, an effective catalyst that has excellent redox properties, is susceptible to over-oxidation and agglomeration problems, which impede its practical application. Herein, nano-Fe1−xS was modified by stable iron oxide (Fe3O4) and biochar (BCAA/Fe1−xS/Fe3O4), which presented the core (Fe1−xS) shell (Fe3O4)-like structure uniformly dispersed on BCAA surface. The composite overcame the disadvantages of nano-Fe1−xS and achieved high removal efficiency of 100% and 99.98% for QNC and Cr(VI), respectively. Based on XPS analysis, Fe(II) content was reduced from 53.3% to 34.2% and S(II) content from 13.0% to 6.5%. Fe(II) species in the composite were the main active substance for QNC degradation and Cr(VI) reduction, and S(II) species also indirectly provided electrons to promote Fe2+/Fe3+ cycling. Then, we identified the intermediates of QNC and active radicals •OH or SO4•− in the system to suggest possible degradation pathways. We further discovered no mutual interference between QNC and Cr(VI) and proposed the possible mechanism for simultaneous removal that QNC degradation by radical attack and Cr(VI) reduction by electrons.

Simultaneous adsorption of As(III) and Cd(II) by ferrihydrite-modified biochar in aqueous solution and their mutual effects

A simply synthetic ferrihydrite-modified biochar (Fh@BC) was applied to simultaneously remove As(III) and Cd(II) from the aqueous solution, and then to explore the mutual effects between As(III) and Cd(II) and the corresponding mechanisms. The Langmuir maximum adsorption capacities of As(III) and Cd(II) in the single adsorbate solution were 18.38 and 18.18 mg g−1, respectively. It demonstrated that Fh@BC was a potential absorbent material for simultaneous removal of As(III) and Cd(II) in aqueous solution. According to the XRF, SEM–EDS, FTIR, XRD, and XPS analysis, the mechanisms of simultaneous removal of As(III) and Cd(II) by Fh@BC could be attributable to the cation exchange, complexation with R-OH and Fe-OH, and oxidation. Moreover, the mutual effect experiment indicated that Cd(II) and As(III) adsorption on Fh@BC in the binary solution exhibited competition, facilitation and synergy, depending on their ratios and added sequences. The mechanisms of facilitation and synergy between Cd(II) and As(III) might include the electrostatic interaction and the formation of both type A or type B ternary surface complexes on the Fh@BC.

The performance and mechanism of simultaneous removal of calcium and heavy metals by Ochrobactrum sp. GMC12 with the chia seed (Salvia hispanica) gum as a synergist

A bacterium Ochrobactrum sp. GMC12, capable of biomineralization and denitrification, was employed to investigate the performance and mechanism of heavy metals removal. A chia seeds (Salvia hispanica) gum was proposed as a synergist for the first time. The results showed that strain GMC12 reduced Ca2+, Cd2+, Zn2+, and nitrate by 83.38, 98.89, 98.95, and 100% (2.09, 0.29, 0.55, and 0.79 mg L−1 h−1), respectively, over 96 h continuous determination experiments. The concentration gradient test revealed that strain GMC12 would effectively remove Cd2+ and Zn2+ by 99.80 and 99.91% (0.67 and 1.35 mg L−1 h−1), respectively, under the synergistic effect of gum (1.0%, w/v). The SEM-EDS and XRD manifested that Ca2+, HMs ions, and anionic groups coated on the bacteria surface to form CaCO3, Ca5(PO4)3OH, CdCO3, Cd5(PO4)3OH, ZnCO3, and Zn2(PO4)OH. The fluorescence spectrometry and fourier transform infrared (FTIR) spectra illustrated that extracellular polymeric substance (EPS) was the key product for the nucleation site of bacteria, and the gum promoted the accumulation of bio-precipitates and accelerated the removal of HMs. In this research, Ochrobactrum sp. GMC12 exhibited great potential in wastewater treatment and chia seeds gum would go deep into material preparation and wastewater treatment due to its non-toxic nature, high viscosity, and advantageous morphology.

Microbial Driving Mechanism for Simultaneous Removal of Nitrogen and Phosphorus in a Pure Anammox Reactor Under Ferrous Ion Exposure

Microbial Driving Mechanism for Simultaneous Removal of Nitrogen and Phosphorus in a Pure Anammox Reactor Under Ferrous Ion Exposure

Insight into using a novel ultraviolet/peracetic acid combination disinfection process to simultaneously remove antibiotics and antibiotic resistance genes in wastewater: Mechanism and comparison with conventional processes

In this study, the simultaneous removal mechanism of antibiotics and antibiotic resistance genes (ARGs) was investigated using the novel ultraviolet/peracetic acid (UV/PAA) combination disinfection process and conventional disinfection processes were also applied for comparison. The results showed that UV/PAA disinfection with a high UV dosage (UV/PAA-H) was most effective for the removal of tetracyclines, quinolones, macrolides and β-lactams; their average removal efficiencies ranged from 25.7% to 100%, while NaClO disinfection was effective for the removal of sulfonamides (∼81.6%). The majority of ARGs were well removed after the UV/PAA-H disinfection, while specific genes including tetB, tetC, ermA and blaTEM significantly increased after NaClO disinfection. In addition, β-lactam resistance genes (-35.9%) and macrolides resistance genes (-12.0%) remarkably augmented after UV/NaClO disinfection. The highly reactive oxidation species generated from UV/PAA process including hydroxyl radicals (•OH) and carbon-centered organic radicals (R-C•), were responsible for the elimination of antibiotics and ARGs. Correlation analysis showed that tetracycline, sulfonamide and macrolide antibiotics removal showed a positive correlation with the corresponding ARGs, and a low dose of antibiotic residues played an important role in the distribution of ARGs. Metagenomic sequencing analysis showed that UV/PAA disinfection could not only greatly decrease the abundance of resistant bacteria but also downregulate the expression of key functional genes involved in ARGs propagation and inhibit the signal transduction of the host bacteria, underlying that its removal mechanism was quite different from that of NaClO-based disinfection processes. Our study provides valuable information for understanding the simultaneous removal mechanism of antibiotics and ARGs in wastewater during the disinfection processes, especially for the novel UV/PAA combination process.