RESUMO
Microplastics (Mps) have emerged as a pervasive environmental concern, with their presence detected not only in freshwater ecosystems but also in drinking and bottled water sources. While extensive research has centered on understanding the origins, migration patterns, detection techniques, and ecotoxicological impacts of these contaminants, there remains a notable research gap about the strategies for Mps removal. This study reviews existing literature on chemical approaches for mitigating microplastic contamination within wastewater systems, focusing on coagulation precipitation, electrocoagulation, and advanced oxidation methods. Each approach is systematically explored, encompassing their respective mechanisms and operational dynamics. Furthermore, the comparative analysis of these three techniques elucidates their strengths and limitations in the context of MPs removal. By shedding light on the intricate mechanisms underlying these removal methods, this review contributes to the theoretical foundation of microplastic elimination from wastewater and identifies future research trajectories and potential challenges.
Assuntos
Microplásticos , Águas Residuárias , Poluentes Químicos da Água , Águas Residuárias/química , Águas Residuárias/análise , Microplásticos/análise , Poluentes Químicos da Água/análise , Purificação da Água/métodos , Eliminação de Resíduos Líquidos/métodosRESUMO
The deep removal of organic pollutants is challenging for coagulation technology in drinking water and wastewater treatment plants to satisfy the rising water standards. Iron (III) chloride (FeCl3) is a popular inorganic coagulant; although it has good performance in removing the turbidity (TB) in water at an alkaline medium, it cannot remove dissolved pollutants and natural organic matter such as humic acid water solution. Additionally, its hygroscopic nature complicates determining the optimal dosage for effective coagulation. Biochar (BC), a popular adsorbent with abundant functional groups, porous structure, and relatively high surface area, can adsorb adsorbates from water matrices. Therefore, combining BC with FeCl3 presents a potential solution to address the challenges associated with iron chloride. Consequently, this study focused on preparing and characterizing a novel biochar/ferric chloride-based coagulant (BC-FeCl3) for efficient removal of turbidity (TB) and natural organic matter, specifically humic acid (HA), from synthetic wastewater. The potential solution for the disposal of produced sludge was achieved by its recovering and recycling, then used in adsorption of HA from aqueous solution. The novel coagulant presented high TB and HA removal within 10 min of settling period at pH solution of 7.5. Furthermore, the recovered sludge presented a good performance in the adsorption of HA from aqueous solution. Adsorption isotherm and kinetics studies revealed that the Pseudo-second-order model best described kinetic adsorption, while the Freundlich model dominated the adsorption isotherm.
Assuntos
Carvão Vegetal , Cloretos , Compostos Férricos , Substâncias Húmicas , Águas Residuárias , Substâncias Húmicas/análise , Carvão Vegetal/química , Adsorção , Cloretos/química , Compostos Férricos/química , Águas Residuárias/química , Poluentes Químicos da Água/química , Poluentes Químicos da Água/análise , Esgotos/química , Eliminação de Resíduos Líquidos/métodos , Purificação da Água/métodosRESUMO
A new facile route to decorate polyurethane foams (PUF) with dense and uniform silver nanoparticles (AgNPs) to ensure efficient and long-term water disinfection is proposed. The antibacterial sponge was fabricated by sequential treatment with chitosan hydrogels grafting, polydopamine (PDA) coating, and finally in situ growth of AgNPs on the surface of substrate. The morphologies, chemical composition, crystalline nature, mechanical property, and swelling capacity of the composite were characterized. Its silver release behavior and bactericidal performances against Escherichia coli (E. coli) were evaluated. Results show that the composite demonstrated higher mechanical strength (compression strength, 51.34 kPa) and a rapid swelling rate with an equilibrium swelling ratio of 18.2 g/g. It possessed a higher loading amount of AgNPs (35.87 mg/g) than that of PUF@Ag (8.21 mg/g) and restricted the cumulative silver release of below 0.05% after 24-h immersion in water. Besides, it presented efficient bactericidal activity with complete reduction of E. coli with 10 min of contact time. The strong bactericidal action was probably governed by strengthening the contact between AgNPs immobilized on the substrate and bacteria cells. Furthermore, the composite demonstrated exceptional reusability for five cycles and exhibited a superior processing capacity in the flow test. Finally, the composite could effectively disinfect the natural water sample like a river in 30 min under real conditions.
Assuntos
Quitosana , Escherichia coli , Hidrogéis , Indóis , Nanopartículas Metálicas , Polímeros , Poliuretanos , Prata , Poliuretanos/química , Quitosana/química , Prata/química , Hidrogéis/química , Nanopartículas Metálicas/química , Escherichia coli/efeitos dos fármacos , Indóis/química , Polímeros/química , Desinfecção/métodos , Antibacterianos/química , Antibacterianos/farmacologia , Purificação da Água/métodosRESUMO
Urban flood risk assessment is a complex task, as it requires extensive knowledge about hydrological features of the catchment, hydraulic characteristics of the drainage network and social characteristics of residential areas. How to accurately and efficiently quantify regional risk has always been a challenge in this field. To solve the problem, this study is developed to propose a novel integrated urban flood risk assessment approach based on one-two dimensional coupled hydrodynamic model and improved projection pursuit method. Two open source software like urban storm flood management model (SWMM) and TELEMAC-2D are introduced to build the one-two coupling hydrodynamic model through proprietary programming, which can accurately simulate urban inundation process. Based on the simulation results of hydrodynamic model and literature review, a set of urban flood risk assessment index system containing physical mechanism and statistical mechanism related index is established, including a total of 12 indicators covering three dimensions like hazard factor, exposure factor and vulnerability factor. Then an Improved Projection Pursuit (IPP) method coupling k-means clustering algorithm is proposed to determine the index weight. The novel integrated urban flood risk assessment approach is implemented in Suyu district, China. The results demonstrate that the accuracy and efficiency of evaluation urban flood risk assessment are greatly improved by the integrated approach. In conclusion, this research offers a novel methodology for urban flood risk assessment and contributes to decision-making in environmental management.
Assuntos
Inundações , Hidrodinâmica , Medição de Risco/métodos , China , Modelos Teóricos , Cidades , AlgoritmosRESUMO
Heterogeneous iron-based catalysts have drawn increasing attention in the advanced oxidation of persulfates due to their abundance in nature, the lack of secondary pollution to the environment, and their low cost over the last a few years. In this paper, the latest progress in the research on the activation of persulfate by heterogeneous iron-based catalysts is reviewed from two aspects, in terms of synthesized catalysts (Fe0, Fe2O3, Fe3O4, FeOOH) and natural iron ore catalysts (pyrite, magnetite, hematite, siderite, goethite, ferrohydrite, ilmenite and lepidocrocite) focusing on efforts made to improve the performance of catalysts. The advantages and disadvantages of the synthesized catalysts and natural iron ore were summarized. Particular interests were paid to the activation mechanisms in the catalyst/PS/pollutant system for removal of organic pollutants. Future research challenges in the context of field application were also discussed.
Assuntos
Ferro , Sulfatos , Poluentes Químicos da Água , Catálise , Ferro/química , Sulfatos/química , Poluentes Químicos da Água/química , Oxirredução , Eliminação de Resíduos Líquidos/métodosRESUMO
Cyanobacteria fouling in ultrafiltration (UF) drinking water treatment poses a significant threat to the stability and sustainability of the process. Both phycocyanin found in cyanobacteria and the polymer membrane exhibit strong fluorescence, which could be readily detected using front-face excitation-emission matrix (FF-EEM) spectroscopy. In this study, FF-EEM was employed for the nondestructive and in situ characterization of algae fouling evolution in UF, while also analyzing fouling mechanisms and reversibility. The results indicated that phycocyanin fluorescence on the membrane surface showed a linear correlation with the specific algal cell count on the membrane surface before reaching saturation. As fouling progressed, membrane fluorescence decreased, which was associated with the extent of the surface coverage on the membrane. The plateau in membrane fluorescence indicated full coverage, coinciding with the cake filtration mechanism, cake compression, and deterioration of fouling reversibility. These findings highlight the promise of FF-EEM as a valuable tool for monitoring and evaluating fouling of cyanobacteria in UF systems.
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Cianobactérias , Purificação da Água , Ultrafiltração/métodos , Ficocianina , Membranas Artificiais , Filtração , Purificação da Água/métodosRESUMO
The effects of biological factors including dissolved oxygen (DO), pH, carbon/nitrogen (C/N) and hydraulic retention times (HRT) on the performance of simultaneous nitrification and denitrification (SND) in a moving bed sequencing batch reactor (MBSBR) were investigated. A low DO was found to be advantageous to the SND in that nitrification was not inhibited, while pH and C/N ratio were shown to have positive effects on SND, and HRT needed to be controlled in a suitable range. A desirable SND efficiency was obtained at a DO of 2.5 mg L-1, pH of approximately 8.0, C/N ratio of 10 and HRT of 10 h in the MBSBR. High-throughput sequencing analysis showed that different operating conditions impacted microbial communities, resulting in different nitrogen removal mechanisms. Autotrophic and heterotrophic nitrification together contributed to the good nitrification performance, while denitrification was conducted by combined anoxic and aerobic processes. Furthermore, the results of principal component analyses (PCA) and the abundance of the predominant nitrification and denitrification genera both showed that DO and HRT might be regarded as the dominant variable factors influencing community structure analysis during SND, while the linear discriminant analysis (LDA) effect size (LEfSe) algorithm showed differences in abundance among the biofilm microbial communities with different DO. Overall, the results of this study improve our understanding of the bacterial community structure with different operating conditions in MBSBRs.
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Processos Autotróficos , Reatores Biológicos/microbiologia , Desnitrificação , Microbiota , Nitrificação , Eliminação de Resíduos LíquidosRESUMO
Anaerobic biological phosphorus removal has proposed a new direction for the removal of phosphorus from wastewater, and the discovery of phosphate reduction makes people have a more comprehensive understanding of microbial phosphorus cycling. Here, from the perspective of thermodynamics, the bioreduction reaction of phosphate was analyzed and its mechanism was discussed. The research progress of phosphate reduction and the application prospects of anaerobic biological phosphorus removal from wastewater were introduced, pointing out the situation and guiding the further research in this field.
Assuntos
Bactérias/metabolismo , Reatores Biológicos/microbiologia , Fosfatos/metabolismo , Fosfinas/metabolismo , Fósforo/metabolismo , Esgotos/química , Eliminação de Resíduos Líquidos/métodos , Purificação da Água/métodos , Anaerobiose , TermodinâmicaRESUMO
With the development of researches, the treatments of wastewater have reached a certain level. Whereas, heavy metals in wastewater cause special concern in recent times due to their recalcitrance and persistence in the environment. Therefore, it is important to get rid of the heavy metals in wastewater. The previous studies have provided many alternative processes in removing heavy metals from wastewater. This paper reviews the recent developments and various methods for the removal of heavy metals from wastewater. It also evaluates the advantages and limitations in application of these techniques. A particular focus is given to innovative removal processes including adsorption on abiological adsorbents, biosorption, and photocatalysis. Because these processes have leaded the new trends and attracted more and more researches in removing heavy metals from wastewater due to their high efficency, pluripotency and availability in a copious amount. In general, the applicability, characteristic of wastewater, cost-effectiveness, and plant simplicity are the key factors in selecting the most suitable method for the contaminated wastewater.
Assuntos
Recuperação e Remediação Ambiental/métodos , Metais Pesados/química , Eliminação de Resíduos Líquidos/métodos , Poluentes Químicos da Água/química , Purificação da Água/métodos , Adsorção , Filtração/métodos , Troca Iônica , Processos Fotoquímicos , Águas ResiduáriasRESUMO
On the basis of achieving shortcut nitrification in a lab-scale SBR, the effects of constant pH and unsteady pH at different free ammonia concentrations on shortcut nitrification for landfill leachate treatment was investigated. The results indicate that under the condition of DO of 0.5 ± 0.2 mg/L and temperature of 30 ± 2 °C, the absolute value of nitrite accumulation increased significantly with the increase in free ammonia (FA) concentration from 5.30 to 48.67 mg/L; however, the nitrite accumulation rate remained almost constant at a constant pH of 8.0 ± 0.1. Ammonia oxidation and the nitrite accumulation become slow with the pH decreased from 8.0 ± 0.1 to 7.5 ± 0.2, and the activities of ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB) were severely inhibited when the pH further decreased to 6.5. More importantly, this study confirmed that the pH decrease from 8.0 to 6.5 within a short time exhibited significant negative effect on the ammonia oxidation rather than the FA concentration.
Assuntos
Amônia/metabolismo , Nitrificação , Poluentes Químicos da Água/química , Poluentes Químicos da Água/metabolismo , Bactérias/efeitos dos fármacos , Bactérias/metabolismo , Concentração de Íons de Hidrogênio , Nitritos/metabolismo , Oxirredução , TemperaturaRESUMO
To reveal the succession procedure of ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB) community structure in sequencing biofilm batch reactor (SBBR), the molecular biological techniques of denaturing gradient gel electrophoresis (DGGE), cloning, and real-time PCR were applied. DGGE showed that the structural diversity of the bacterial community increased during the biofilm formation period, and some kinds of populations had been highly preponderant consistently. The results of cloning and sequencing revealed that Nitrosomonas was the dominant species. The real-time PCR analysis indicated that the amount of the AOB increased significantly after the cultivation period, and the NOB gradually decreased. The AOB content on the 25th day was 17 times that of the 6th day. It also showed the biofilm formed successfully with accumulating nitrite and prepared to achieve the achievement of simultaneous nitrification and denitrification in SBBR. Furthermore, the ammonia-oxidizing rate was in correspondence with the NH4 (+)-N removal efficiency.
Assuntos
Bactérias/classificação , Bactérias/crescimento & desenvolvimento , Biofilmes/crescimento & desenvolvimento , Reatores Biológicos/microbiologia , Biota , Amônia/metabolismo , Bactérias/metabolismo , Fenômenos Fisiológicos Bacterianos , Clonagem Molecular , Eletroforese em Gel de Gradiente Desnaturante , Nitritos/metabolismo , Oxirredução , Reação em Cadeia da Polimerase em Tempo Real , Fatores de TempoRESUMO
Biochar has effect on phosphorus adsorption, release, and transformation. This study compared the influence of biochar derived from animal (AB) and plant (PB) during paper mill sludge composting. Results indicated AB not only accelerated sludge decomposition but also had significantly higher levels of available phosphorus (AP) than PB and CK (no biochar), with AP contents in the order of AB > PB > CK. Compared to CK, AB was found to increase the relative abundance of thermophilic bacteria, and PB diversified the microbial community. Based on Pearson and RDA results, TOC/TN ratio (C/N) and organic matter (OM) explained above 50% of the variance in microbial community and phosphorus fractions. Thermophilic bacteria with high levels of OM and C/N promoted the conversion among labile and moderately labile organic phosphorus, moderately labile inorganic phosphorus, and AP. Biochar could enhance the AP conversion pathway, leading to increased levels of AP.
RESUMO
The proper management of phosphorus (P) from wastewater is crucial for sustainable development consideration. Herein, we developed a strategy which combines adsorption via tailored adsorbents and electrochemically-driven struvite precipitation (ESP) for P recovery. Novel polydopamine-modified Ce-MOF/chitosan composite beads (PDA@Ce-MOF-CS) were prepared by a facile in situ growth of Ce-MOF crystals incorporated natural polymers and PDA coating. The physicochemical properties of PDA@Ce-MOF-CS were characterized. Both batch and fixed-bed column experiments were conducted to evaluate its adsorption performances. Representatively, PDA@Ce-MOF-CS performed good selectivity for P removal and exhibited a maximum adsorption capacity of 161.13 mg P/g at pH 3 and 318 K. Meanwhile, the developed adsorbent showed great reusability after ten regeneration cycles as well as good adsorption stability. The dominant mechanism for efficient P adsorption included electrostatic attraction, surface precipitation and ligand exchange. Interestingly, PDA@Ce-MOF-CS exhibited a remarkable adsorption capacity of 92.86 mg P/g by treating real P-rich electroplating wastewater, and the desorbed P in the eluate could be effectively recovered and converted into a solid fertilizer as struvite via ESP. Overall, this work provided a new research direction for P recovery from wastewater as struvite by combined technologies with the help of macroscopic MOF architectures.
Assuntos
Quitosana , Poluentes Químicos da Água , Estruvita , Fósforo , Quitosana/química , Águas Residuárias , Adsorção , Poluentes Químicos da Água/análise , Cinética , Fosfatos/químicaRESUMO
Transition metal oxides are widely pursued as potent electrocatalysts for the oxygen evolution reaction (OER). However, single-metal chromium catalysts remain underexplored due to their intrinsic activity limitations. Herein, we successfully synthesize mixed-valence, nitrogen-doped Cr2O3/CrO3/CrN@NC nanoelectrocatalysts via one-step targeted pyrolysis techniques from a binuclear Cr-based complex (Cr2(Salophen)2(CH3OH)2), which is strategically designed as a precursor. Comprehensive pyrolysis mechanisms were thoroughly delineated by using coupled thermogravimetric analysis and mass spectrometry (TG-MS) alongside X-ray diffraction. Below 800 °C, the generation of a reducing atmosphere was noted, while continuous pyrolysis at temperatures exceeding 800 °C promoted highly oxidized CrO3 species with an elevated +6 oxidation state. The optimized catalyst pyrolyzed at 1000 °C (Cr2O3/CrO3/CrN@NCs-1000) demonstrated remarkable OER activity with a low overpotential of 290 mV in 1 M KOH and excellent stability. Further density functional theory (DFT) calculations revealed a much smaller reaction energy barrier of CrO3 than the low oxidation state species for OER reactivity. This work reveals fresh strategies for rationally engineering chromium-based electrocatalysts and overcoming intrinsic roadblocks to enable efficient OER catalysis through a deliberate oxidation state and compositional tuning.
RESUMO
Membrane aerated biofilm reactor (MABR) is challenged by biofilm thickness control and phosphorus removal. Air scouring aided by computational fluid dynamics (CFD) was employed to detach outer biofilm in sequencing batch MABR treating low C/N wastewater. Biofilm with 177-285 µm thickness in cycle 5-15 achieved over 85 % chemical oxygen demand (COD) and total inorganic nitrogen (TIN) removals at loading rate of 13.2 gCOD/m2/d and 2.64 gNH4+-N/m2/d. Biofilm rheology measurements in cycle 10-25 showed yield stress against detachment of 2.8-7.4 Pa, which were equal to CFD calculated shear stresses under air scouring flowrate of 3-9 L/min. Air scouring reduced effluent NH4+-N by 10 % and biofilm thickness by 78 µm. Intermittent aeration (4h off, 19.5h on) and air scouring (3 L/min, 30 s before settling) in one cycle achieved COD removal over 90 %, TIN and PO43--P removals over 80 %, showing great potential for simultaneous carbon, nitrogen and phosphorus removals.
Assuntos
Biofilmes , Reatores Biológicos , Carbono , Hidrodinâmica , Membranas Artificiais , Nitrogênio , Fósforo , Ar , Análise da Demanda Biológica de Oxigênio , Purificação da Água/métodos , Simulação por Computador , Reologia , Águas Residuárias/químicaRESUMO
Slow dissolution/hydrolysis of insoluble/macromolecular organics and poor sludge filterability restrict the application potential of anaerobic membrane bioreactor (AnMBR). Bubble-free membrane microaeration was firstly proposed to overcome these obstacles in this study. The batch anaerobic digestion tests feeding insoluble starch and soluble peptone with and without microaeration showed that microaeration led to a 65.7-144.8% increase in methane production and increased critical flux of microfiltration membrane via driving the formation of large sludge flocs and the resultant improvement of sludge settleability. The metagenomic and bioinformatic analyses showed that microaeration significantly enriched the functional genes and bacteria for polysaccharide and protein hydrolysis, microaeration showed little negative effects on the functional genes involved in anaerobic metabolisms, and substrate transfer from starch to peptone significantly affected the functional genes and microbial community. This study demonstrates the dual synergism of microaeration to enhance the dissolution/hydrolysis/acidification of insoluble/macromolecular organics and sludge filterability for AnMBR application.
Assuntos
Reatores Biológicos , Filtração , Membranas Artificiais , Esgotos , Reatores Biológicos/microbiologia , Esgotos/microbiologia , Anaerobiose , Filtração/métodos , Metano/metabolismo , Hidrólise , Amido/metabolismoRESUMO
This paper reports the preparation of calcium alginate gels-functionalized PUF decorated with AgNPs (CA/PUF@Ag) by in situ reduction of Ag+ ions to form AgNPs with weakly reducing glycerol in CA/PUF composite. The water-adsorbing capacity, chemical structure, crystalline nature, elemental composition and morphologies of the composite were characterized. The Ag release behavior of CA/PUF@Ag was investigated. The inhibition zone test, time-dependent co-culture assay, test tube test, and antibacterial filtration experiment with Escherichia coli as an indicator of bacterial contamination were conducted to explore the antimicrobial efficacy. Results indicated that the CA/PUF@Ag prepared at 0.25 % w/v of SA could absorb more water with a higher swelling ratio of 8.0 g/g than that of PUF@Ag (6.0 g/g), which was subsequently squeezed by minimal pressure stimuli. The CA/PUF@Ag had a larger initial AgNPs loading amount (8.48 mg/g), lower Ag release concentration (44.35 µg/L) and lower Ag release rate (0.27 %) after 14 days tests than those of PUF@Ag (7.93 mg/g, 80.87 µg/L and 0.60 % respectively). The CA/PUF@Ag was highly reusable because bacterial cells in the squeezed water recovered from the composite were completely inactivated over five cycles of operation, and exhibited good antibacterial efficacy as an antibacterial filter in a flow test.
Assuntos
Nanopartículas Metálicas , Água , Desinfecção/métodos , Prata/química , Antibacterianos/farmacologia , Nanopartículas Metálicas/química , Escherichia coli , GéisRESUMO
Ultrafiltration (UF) has been proven effective in removing algae during seasonal algal blooms, but the algal cells and the metabolites can induce severe membrane fouling, which undermines the performance and stability of the UF. Ultraviolet-activated sulfite with iron (UV/Fe(II)/S(IV)) could enable an oxidation-reduction coupling circulation and exert synergistic effects of moderate oxidation and coagulation, which would be highly preferred in fouling control. For the first time, the UV/Fe(II)/S(IV) was systematically investigated as a pretreatment of UF for treating Microcystis aeruginosa-laden water. The results showed that the UV/Fe(II)/S(IV) pretreatment significantly improved the removal of organic matter and alleviated membrane fouling. Specifically, the organic matter removal increased by 32.1% and 66.6% with UV/Fe(II)/S(IV) pretreatment for UF of extracellular organic matter (EOM) solution and algae-laden water, respectively, while the final normalized flux increased by 12.0-29.0%, and reversible fouling was mitigated by 35.3-72.5%. The oxysulfur radicals generated in the UV/S(IV) degraded the organic matter and ruptured the algal cells, and the low-molecular-weight organic matter generated in the oxidation penetrated the UF and deteriorated the effluent. The over-oxidation did not happen in the UV/Fe(II)/S(IV) pretreatment, which may be attributed to the cyclic redox Fe(II)/Fe(III) coagulation triggered by the Fe(II). The UV-activated sulfate radicals in the UV/Fe(II)/S(IV) enabled satisfactory organic removal and fouling control without over-oxidation and effluent deterioration. The UV/Fe(II)/S(IV) promoted the aggregation of algal foulants and postponed the shift of the fouling mechanisms from standard pore blocking to cake filtration. The UV/Fe(II)/S(IV) pretreatment proved effective in enhancing the UF for algae-laden water treatment.
RESUMO
The effective inhibition of nitrite-oxidizing bacteria (NOB) is widely acknowledged to be a critical issue for mainstream short-cut biological nitrogen removal. This study demonstrated a stable mainstream nitritation by implementing light irradiation. A sequencing batch reactor with ultraviolet-A (UVA) irradiation was operated for 250 days, and a high nitrite accumulation ratio was achieved and stabilized at about 90 %. UVA irradiation also positively impacts denitrification activity, with total nitrogen removal up to 63 %. Microbial community analysis confirmed that the UVA effectively and stably decreased the abundance of Nitrospira (the only detected NOB) from 6.0 % to 0.1 %, while it showed no effect on Nitrosomonas. The enriched genus Rhodocyclaceae was the major contributor to the increase in denitrification activity in the light-induced nitritation system. The proposed UVA irradiation strategy has the potential to be integrated with an anoxic/aerobic (A/O) or integrated fixed-film activated sludge (IFAS) process for achieving mainstream short-cut biological nitrogen removal.
Assuntos
Compostos de Amônio , Nitritos , Oxirredução , Reatores Biológicos/microbiologia , Esgotos/microbiologia , Nitrogênio , Bactérias , DesnitrificaçãoRESUMO
Resources recovery from landfill leachate (LFL) has been attracting growing attention instead of merely purifying the wastewater. An integrated two-stage membrane distillation (ITMD) was proposed to simultaneously purify LFL and recover ammonia in this study. The results showed that organics could be always effectively rejected by the ITMD regardless of varying feed pH, with COD removal higher than 99%. With feed pH increased from 8.64 to 12, the ammonia migration (50-100%) and capture (36-75%) in LFL were considerably enhanced, boosting the separated ammonia enrichment to 1.3-1.7 times due to the improved ammonium diffusion. However, the corresponding membrane flux of the first MD stage decreased from 13.7 to 10.5 L/m2·h. Elevating feed pH caused the deprotonation of NOM and its binding with inorganic ions, constituting a complex fouling layer on the membrane surface in the first MD stage. In contrast, the membrane permeability and fouling of the second MD were not affected by feed pH adjustment because only volatiles passed through the first MD. More importantly, it was estimated that ITMD could obtain high-quality water and recover high-purity ammonium from LFL with relatively low ammonium concentration at an input cost of $ 2-3/m3, which was very competitive with existing techniques. These results demonstrated that the ITMD can be a valuable candidate strategy for simultaneous water purification and nutrient recovery from landfill leachate.