RESUMEN
Anaerobic digestion (AD) is a key technology for converting organic matters to methane-rich biogas. However, nutrient imbalance can destabilize the whole digestion. To realize stable operation of AD and improve its efficiency, this work considers a new strategy to control the intermediate concentrations of poor AD under nutrient stress. For this purpose, long-term digestion under different nutrient conditions was investigated. Results showed that the feedstock with a low C/N ratio (= 6) caused VFA accumulation (2072 ± 632 mg/L), leading to the inhibition of methane production. Employing a substrate with a higher C/N ratio (= 11) and/or adding NH4HCO3 (200 mg NH4+-N/Ladd) could alleviate the VFA inhibition, but excessive dosage of NH4HCO3 would induce ammonia inhibition. Through the established digestion balance between free ammonia nitrogen (FAN) between 0 and 25 mg/L, volatile fatty acid (VFA) 510-2100 mg/L, and alkalinity (ALK) 3300-7800 mg/L, an efficient methane yield of 150-250 mL/g VS was achieved and stable operation of AD under nutrient stress (low C/N ratio) was realized. Metabolic reconstruction between Euryarchaeota sp. MAG162, Methanosarcina mazei MAG53 and Mesotoga infera MAG119 highlighted that microbial niche balance was developed as a result of digestion balance, which is beneficial for stable operation of AD. These findings improved our understanding of the interaction mechanism between intermediates and microbial niches for stability control in AD.
Asunto(s)
Ácidos Grasos Volátiles , Metano , Anaerobiosis , Metano/metabolismo , Ácidos Grasos Volátiles/metabolismo , Reactores Biológicos , Amoníaco/metabolismo , Biocombustibles , Nitrógeno/metabolismoRESUMEN
Capturing the carbon in volatile fatty acids (VFA) produced from the anaerobic digestion (AD) of sewage sludge has the potential to not only provide economic benefits but also reduce greenhouse gas production. This study demonstrates a chemical-free method to collect VFA from an AD instead of methane that involves electrochemical pretreatment (EPT) of sludge. Experimental results show that applying 15 V EPT for 45 min enhances acidogenesis and selectively inhibits methanogenesis, leading to a substantial VFA accumulation (2563.1 ± 307.9 mg COD/L) and achieving 2.5 times more carbon fixation than via methane production. Interfacial thermodynamic analysis shows that EPT induces a decrease in both the repulsive electrostatic energy (from 152.9 kT to 12.2 kT) and the energy barrier (from 57.0 kT to 2.6 kT) in the sludge, leading to increased sludge aggregation and entrapment of microorganisms. Molecular docking sheds lights on how the methanogens interacts with the organic matter released from EPT (e.g., alanine-tRNA ligase), showing that these interactions potentially interfere with the proteins that are associated with the activities of the methanogens and the electron transfer pathways, thereby impeding methanogenesis. Integrating EPT into AD therefore facilitates the recovery of valuable VFA and the capture of carbon from freshwater sludge, providing notable economic and environmental benefits in sewage sludge treatment.
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Ácidos Grasos Volátiles , Metano , Aguas del Alcantarillado , Aguas del Alcantarillado/química , Anaerobiosis , Ácidos Grasos Volátiles/metabolismo , Metano/metabolismo , Eliminación de Residuos Líquidos/métodos , Carbono , Reactores Biológicos , Técnicas Electroquímicas , Simulación del Acoplamiento MolecularRESUMEN
There have been extensive applications of waste activated sludge (WAS) in anaerobic co-digestion (AcoD). Nonetheless, mechanisms through which AcoD systems maintain stability, particularly under nutrient-stressed conditions, are under-appreciated. In this study, the role of WAS in a nutrient-stressed WAS-food waste AcoD system was re-evaluated. Our findings demonstrated that WAS-based co-digestion increased methane production (by 20-60%) as WAS bolsters such systems' resilience via establishing a core niche-based microbial balance. The carbon utilization investigation suggested a microbial niche balance is attainable if two conditions are satisfied: 1) hydrolysis efficiency is greater than 50%; and 2) both the acidogenesis-to-hydrolysis and acetogenesis-to-hydrolysis efficiencies surpass 0.5. Metagenomic assembly genome (MAG) analysis indicated that the versatile metabolic characteristics strengthened the microbial niche balance, rendering the system resilient and efficient through a syntrophic mode, contributing to both acidogenesis and acetogenesis. The findings of this study provide new insights into the ecological effects of WAS on AcoD.
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Metano , Aguas del Alcantarillado , Aguas del Alcantarillado/microbiología , Anaerobiosis , Metano/metabolismo , Reactores Biológicos , Hidrólisis , Nutrientes/metabolismo , Carbono/metabolismoRESUMEN
Microplastics and antibiotics not only pollute aquatic environments and threaten human health, but are also tricky to remove. Microplastics adsorb antibiotics, and, before being released into the natural environment, most microplastics pass through some wastewater treatment and/or disinfection (such as chlorination) facilities. It is therefore necessary to understand how these treatment processes may affect or alter microplastics' properties, particularly their ability to adsorb antibiotics, and whether or not the two, when bound together, may present exacerbated harm to the environment. This study used both laboratory tests and molecular dynamics simulation to investigate the mechanism through which chlorinated microplastics (specifically polystyrene) adsorb the antibiotic tetracycline, and showed that chlorination gave the polystyrene a larger interaction area (> 21%) and more free energy (> 14%) to adsorb tetracycline. Van der Waals (vdW) forces played a more dominant role than electrostatics in facilitating tetracycline's adsorption. Moreover, a density functional theory analysis demonstrated that the vdW potentials of the microplastics decreased as more and more hydrogen atoms became replaced by chlorine, suggesting a facilitation of the adsorption of polycyclic antibiotic molecules. The experimental results confirmed the simulation's prediction that a higher degree of chlorination significantly increases the polystyrene's adsorption capacity, whereas pH and salinity had almost no effect on the adsorption. This study demonstrates that disinfection elevates the risk of antibiotics adhering to and accumulating on the surface of microplastics.
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Antibacterianos , Halogenación , Humanos , Microplásticos , Plásticos , Adsorción , Poliestirenos , TetraciclinaRESUMEN
With the rise of the concept of carbon neutrality, the current wastewater treatment process of industrial organic wastewater is moving towards the goal of energy conservation and carbon emission reduction. The advantages of anaerobic digestion (AD) processes in industrial organic wastewater treatment for bio-energy recovery, which is in line with the concept of carbon neutrality. This study summarized the significance and advantages of the state-of-the-art AD processes were reviewed in detail. The application of expanded granular sludge bed (EGSB) reactors and anaerobic membrane bioreactor (AnMBR) were particularly introduced for the effective treatment of industrial organic wastewater treatment due to its remarkable prospect of engineering application for the high-strength wastewater. This study also looks forward to the optimization of the AD processes through the enhancement strategies of micro-aeration pretreatment, acidic-alkaline pretreatment, co-digestion, and biochar addition to improve the stability of the AD system and energy recovery from of industrial organic wastewater. The integration of anaerobic ammonia oxidation (Anammox) with the AD processes for the post-treatment of nitrogenous pollutants for the industrial organic wastewater is also introduced as a feasible carbon-neutral process. The combination of AnMBR and Anammox is highly recommended as a promising carbon-neutral process for the removal of both organic and inorganic pollutants from the industrial organic wastewater for future perspective. It is also suggested that the AD processes combined with biological hydrogen production, microalgae culture, bioelectrochemical technology and other bio-processes are suitable for the low-carbon treatment of industrial organic wastewater with the concept of carbon neutrality in future.
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Contaminantes Ambientales , Aguas Residuales , Carbono , Aguas del Alcantarillado , Anaerobiosis , Reactores Biológicos , Nitrógeno/análisis , Eliminación de Residuos Líquidos/métodosRESUMEN
Conventional biological treatment processes cannot efficiently and completely degrade nitroimidazole antibiotics, due to the formation of highly antibacterial and carcinogenic nitroreduction by-products. This study investigated the removal of a typical nitroimidazole antibiotic (ornidazole) during wastewater treatment by a biological sulfidogenic process based on elemental sulfur (S0-BSP). Efficient and stable ornidazole degradation and organic carbon mineralization were simultaneously achieved by the S0-BSP in a 798-day bench-scale trial. Over 99.8 % of ornidazole (200â500 µg/L) was removed with the removal rates of up to 0.59 g/(m3·d). Meanwhile, the efficiencies of organic carbon mineralization and sulfide production were hardly impacted by the dosed ornidazole, and their rates were maintained at 0.15 kg C/(m3·d) and 0.49 kg S/(m3·d), respectively. The genera associated with ornidazole degradation were identified (e.g., Sedimentibacter, Trichococcus, and Longilinea), and their abundances increased significantly. Microbial degradation of ornidazole proceeded by several functional genes, such as dehalogenases, cysteine synthase, and dioxygenases, mainly through dechlorination, denitration, N-heterocyclic ring cleavage, and oxidation. More importantly, the nucleophilic substitution of nitro group mediated by in-situ formed reducing sulfur species (e.g., sulfide, polysulfides, and cysteine hydropolysulfides), instead of nitroreduction, enhanced the complete ornidazole degradation and minimized the formation of carcinogenic and antibacterial nitroreduction by-products. The findings suggest that S0-BSP can be a promising approach to treat wastewater containing multiple contaminants, such as emerging organic pollutants, organic carbon, nitrate, and heavy metals.
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Reactores Biológicos , Ornidazol , Reactores Biológicos/microbiología , Azufre/metabolismo , Sulfuros/metabolismo , Antibacterianos , CarbonoRESUMEN
Two limiting factors of microbial electrochemical denitrification (MED) are the abundance and efficiency of the functional microorganisms. To supply these microorganisms, MED systems are inoculated with denitrifying sludge, but such method has much room for improvement. This study compared MED inoculated with autotrophic denitrifying inoculum (ADI) versus with heterotrophic denitrifying inoculum (HDI). ADI exhibited electroactivity for 50% less of timethan HDI. The denitrification efficiency of the ADI biocathode was42% higherthan that of the HDI biocathode. The HDI biocathode had high levels of polysaccharides while the ADI biocathode was rich in proteins, suggesting that two biocathodes may achieveMED but via differentpathways. Microbial communities of two biocathodes indicated MED of HDI biocathode may rely on interspecies electron transfer, whereas sulfur bacteria of ADI biocathode take electrons directly from the cathode to achieve MED. Utilizing autotrophic sulfur-oxidizing denitrifiers, this study offers a strategy for enhancing MED.
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Desnitrificación , Nitratos , Nitratos/metabolismo , Bacterias/metabolismo , Procesos Autotróficos , Reactores Biológicos/microbiología , Azufre/metabolismo , Nitrógeno/metabolismoRESUMEN
Granular sludge (GS) has superior antibiotic removal ability to flocs, due to GS's layered structure and rich extracellular polymeric substances. However, prolonged exposure to antibiotics degrades the performance and stability of GS. This study investigated how a seawater matrix might help maintain the structural integrity and bioactivity of granules. The results demonstrated that GS had better sulfadiazine (SDZ) removal efficiency in a seawater matrix (85.6 %) than in a freshwater matrix (57.6 %); the multiple ions in seawater enhanced boundary layer diffusion (kiR1 = 0.0805 mg·g-1·min-1/2 and kiR2 = 0.1112 mg·g-1·min-1/2) and improved adsorption performance by 15 % (0.123 mg/g-SS freshwater vs. 0.141 mg/g-SS seawater). Moreover, multiple hydrogen bonds (1-3) formed between each SDZ and lipid bilayer fortified the adsorption. Beyond S-N and S-C bond hydrolyses that took place in freshwater systems, there was an additional biodegradation pathway for GS to be cultivated in a saltwater system that involved sulfur dioxide extrusion. This additional pathway was attributable to the greater microbial diversity and larger presence of sulfadiazine-degrading bacteria containing SadAC genes, such as Leucobacter and Arthrobacter, in saltwater wastewater. The findings of this study elucidate how seawater influences GS properties and antibiotic removal ability.
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Antibacterianos , Aguas Residuales , Reactores Biológicos , Aguas del Alcantarillado , Sulfadiazina , Agua de MarRESUMEN
This study investigated the use of sulfate reduction effluent (SR-effluent) to induce sulfidation on nanoscale zerovalent iron (nZVI). SR-effluent-modified nZVI achieved a 100% improvement in Cr(VI) removal from simulated groundwater, a result comparable to cases where other, more typical sulfur precursors (Na2S2O4, Na2S2O3, Na2S, K2S6, and S0) were used. Through a structural equation model analysis, amendment of nanoparticles' agglomeration (standardized path coefficient (std. path coeff.) = -0.449, p < 0.05) and hydrophobicity (std. path coeff. = 0.100, p < 0.05) and direct reaction between iron-sulfur compounds and Cr(VI) (std. path coeff. ranged from -0.195 to 0.322, p < 0.05) were primarily contributing to sulfidation-induced Cr(VI) removal enhancement. Regarding the property improvement of nZVI, the SR-effluent's corrosion radius played a crucial role in tuning the content and distribution of the iron-sulfur compounds based on the core-shell structure of the nZVI and the redox processes at the aqueous-solid interface.
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Hierro , Adsorción , Cromo/química , Hierro/química , Transición de Fase , Sulfatos , Compuestos de AzufreRESUMEN
To efficiently remove organic and inorganic pollutants from leachate concentrate, an in situ coagulation-electrochemical oxidation (CO-EO) system was proposed using Ti/Ti4O7 anode and Al cathode, coupling the "super-Faradaic" dissolution of Al. The system was evaluated in terms of the removal efficiencies of organics, nutrients, and metals, and the underlying cathodic mechanisms were investigated compared with the Ti/RuO2-IrO2 and graphite cathode systems. After a 3-h treatment, the Al-cathode system removed 89.0% of COD and 36.3% of total nitrogen (TN). The TN removal was primarily ascribed to the oxidation of both ammonia and organic-N to N2. In comparison, the Al-cathode system achieved 3-10-fold total phosphorus (TP) (62.6%) and metal removals (>80%) than Ti/RuO2-IrO2 and graphite systems. The increased removals of TP and metals were ascribed to the in situ coagulation of Al(OH)3, hydroxide precipitation, and electrodeposition. With the reduced scaling on the Al cathode surface, the formation of Al3+ and electrified Al(OH)3 lessened the requirement for cathode cleaning and increased the bulk conductivity, resulting in increased instantaneous current production (38.9%) and operating cost efficiencies (48.3 kWh kgCOD -1). The present study indicated that the in situ CO-EO process could be potentially used for treating persistent wastewater containing high levels of organic and inorganic ions.
RESUMEN
Biocompatible metal-free carbon dots (CDs) with good photo-induced strong oxidation capacity in aqueous solutions are scarce for high-performance photocatalytic antibacterial and tumor therapy. In this work, we achieved effective visible light-induced cell death and antibacterial performance based on biocompatible metal-free CDs. The visible-light-induced reducing ability of the surface electron-withdrawing structure of the CDs allowed for the remaining photo-induced holes with high oxidation capacity to oxidize water molecules and generate hydroxyl radicals. Antibiotic-resistant bacteria were effectively inhibited by the CDs under xenon lamp irradiation with 450 nm long pass filter. Moreover, CD-based tumor photocatalytic therapy in mice was achieved using a xenon lamp with 450 nm long pass filter (0.3 W cm-2).
Asunto(s)
Carbono , Neoplasias , Animales , Ratones , Carbono/química , Luz , Antibacterianos/farmacología , Antibacterianos/química , Oxidación-Reducción , Metales , AguaRESUMEN
Microplastics (MPs) are substances that pose a risk to both human life and the environment. Their types and production are increasing year on year, and their potential to cause environmental pollution is a worldwide concern. Conventional water treatment processes, particularly coagulation and sedimentation, are not effective at removing all MPs. It is therefore important to assess the morphological changes in the MPs, i.e., the thermoplastic polyurethane (TPU) and polyethylene (PE), during ozonation and the dissolved organic carbon leaching as well as chloroform formation in the subsequent chlorination. The results show that the appearance and surface chemistry of the MPs changed during the ozonation process, most notably for TPU. The trichloromethane (CHCl3) generation during chlorination was 0.168 and 0.152 µmol/L for TPU and PE, respectively, and the ozone pretreatment significantly increased the CHCl3 yield of TPU, while it had a weak effect on PE. Additional disinfection byproducts (DBPs), including CHCl2Br, CHClBr2, and CHBr3, were produced in the presence of bromide ions in the water column, and the total amount of DBPs produced by PE, PE-O, TPU, and TPU-O was significantly increased to 0.787, 0.814, 0.931, and 1.391 µmol/L, respectively. The study provides useful information for the environmental risk assessment of two representative MPs, i.e., TPU and MPs, in disinfection procedures for drinking water.
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Desinfectantes , Ozono , Contaminantes Químicos del Agua , Purificación del Agua , Humanos , Desinfección/métodos , Microplásticos , Plásticos , Halogenación , Purificación del Agua/métodos , Cloroformo , Poliuretanos , Ozono/química , Contaminantes Químicos del Agua/análisis , Desinfectantes/químicaRESUMEN
Nanoplastics (NPs, <1 µm) are of great concern worldwide because of their high potential risk toward organisms in aquatic systems, while very little work has been focused on their tissue-specific toxicokinetics due to the limitations of NP quantification for such a purpose. In this study, NPs with two different sizes (86 and 185 nm) were doped with palladium (Pd) to accurately determine the uptake and depuration kinetics in various tissues (intestine, stomach, liver, gill, and muscle) of tilapia (Oreochromis niloticus) in water, and subsequently, the corresponding toxic effects in the intestine were explored. Our results revealed uptake and depuration constants of 2.70-378 L kg-1 day-1 and 0.138-0.407 day-1 for NPs in tilapia for the first time, and the NPs in tissues were found to be highly dependent on the particle size. The intestine exhibited the greatest relative accumulation of both sizes of NPs; the smaller NPs caused more severe damage than the larger NPs to the intestinal mucosal layer, while the larger NPs induced a greater impact on microbiota composition. The findings of this work explicitly indicate the size-dependent toxicokinetics and intestinal toxicity pathways of NPs, providing new insights into the ecological effects of NPs on aquatic organisms.
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Cíclidos , Tilapia , Contaminantes Químicos del Agua , Animales , Tilapia/metabolismo , Cíclidos/metabolismo , Microplásticos , Intestinos , Hígado/metabolismo , Contaminantes Químicos del Agua/metabolismoRESUMEN
The large number of microplastics (MPs) that appear in the environment has drawn much attention. Few studies, however, have examined the transformation of MPs in water treatment processes and their effects on environmental pollutants. In this study, the alteration of the physicochemical characteristics of polyethylene and thermoplastic polyurethane upon chlorination, as well as the influence of this alteration on contaminants, were investigated. The findings indicated that microplastics underwent significant morphology and O-functional groups changes during chlorination. It is noteworthy that the mechanisms controlling the chlorination treatment of the two MPs are clearly different. The results of aggregation and adsorption experiments showed that the chlorination treatment enhanced the aggregation ability of the MPs in brine and their interaction with Cr(VI). The present discoveries further suggested that water treatment could alter the migration capacity of microplastics and the distribution of contaminants in the aqueous environment by altering the adsorption of microplastics to the contaminants.
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Microplásticos , Contaminantes Químicos del Agua , Cromo , Plásticos , Adsorción , Halogenación , Contaminantes Químicos del Agua/análisisRESUMEN
The complex and rigid floc structure often limits the reutilization of waste activated sludge (WAS). Electrochemical pretreatment (EPT) is one of the most effective technologies that can enhance WAS disintegration. But a comprehensive investigation into how multiple EPT conditions work was rarely reported. The study evaluated the effects of multiple EPT conditions, i.e., different electrolytes (NaCl, Na2SO4, and CaCl2), electrolytes dosage (0 g/L, 0.5 g/L, 1.0 g/L, and 3.0 g/L), EPT current (0 A, 0.5 A, 1.0 A, and 3.0 A) and EPT time (0 min, 30 min, 60 min, and 90 min) on WAS disintegration. The results showed that NaCl was outstanding from other electrolytes in promoting more WAS disintegration. Besides, a relatively higher NaCl dosage, a higher EPT current, and a longer EPT time promoted more reactive chlorine species (RCS), thus enhancing WAS disintegration in terms of extracellular polymeric substances (EPS) structure destruction and biodegradable organic matter release. After EPT for 60 min at NaCl dosage of 1.0 g/L and current of 1.0 A, the EPS multilayer structure destruction, biodegradable organic matters release, and soluble chemical oxygen demand (SCOD) increase in the supernatant were enhanced by 17.2 %, 130.5 %, and 238.7 %, respectively. Then a predictive quadratic model was established and the impact significance of the above EPT factors for enhancing WAS disintegration followed dosage of NaCl > current > EPT time. Furthermore, response surface methodology (RSM) suggested NaCl dosage of 2.75 g/L, current of 2.0 A, and EPT time of 30 min were the optimal EPT conditions, bringing a 42.0 % increase in the net economic benefit of WAS treatment compared to without EPT.
RESUMEN
Using the aerobic granular sludge (AGS) to improve tetracycline (TET) removal in the treatment of mariculture wastewater was investigated in the present study. The AGS rapidly adapted to and was sustained in seawater matrices with a robust granule strength (k = 0.0014) and a more stable sludge yield than the activated sludge (AS) (0.14 vs 0.11 g-VSS/g-CODrem). The compact structure provided the AGS with an anoxic environment, which favored the growth of N (37.3 %) and P removal bacteria (30.4 %) and the expression of functional genes (nos, nor, and nar), resulting in more than 62 % TN and TP removals, respectively. Similar abundances of aromatic compound-degrading bacteria (â¼34 %) in both reactors (AGS and AS) led to comparable TET biodegradation efficiencies (â¼0.045 mg/g-VSS). The greater size and surface area of the AGS expanded the boundary layer diffusion region, leading to 16 % increases in the granule's TET adsorption capacity.
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Aguas del Alcantarillado , Eliminación de Residuos Líquidos , Eliminación de Residuos Líquidos/métodos , Reactores Biológicos , Aerobiosis , Antibacterianos , Tetraciclina/farmacología , Bacterias , NitrógenoRESUMEN
Anticipated growth in living standards has accentuated higher requirements for effluent quality from municipal wastewater treatment. In this study, an air-lifting internal circulating reactor with a high internal circulation ratio (36:1) was established to treat municipal wastewater with a long-term operation. In the bioreactor, the average effluent chemical oxygen demand, total nitrogen, and ammonium nitrogen could be 13.1, 5.7, and lower than 1 mg/L, respectively. Further analysis of nitrogen removal showed that traditional nitrification and denitrification, simultaneous nitrification and denitrification (SND), and nitrogen assimilation accounted for 27.4 %, 68.7 %, and 3.9 % respectively. The proportion of aerobic bacteria (Saprospiraceae) and facultative bacteria (Comamonadaceae) were significantly increased, indicating a higher capacity for organic degradation in the reactor. The relative abundance of denitrifying bacteria and bacterial groups with SND (Comamonadaceae) increased. These results suggested the air-lifting internal circulating reactor could be a viable and efficient option for superior nitrogen removal in wastewater treatment.
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Desnitrificación , Aguas Residuales , Nitrógeno/metabolismo , Cinética , Elevación , Nitrificación , Reactores Biológicos/microbiología , Bacterias/metabolismo , Aguas del Alcantarillado , Eliminación de Residuos Líquidos/métodosRESUMEN
Aerobic granular sludge (AGS) can achieve simultaneous carbon, nitrogen and phosphorus removal owing to its three-dimensional oxygen gradient structure. However, long start-up period and poor operational stability restrict its application and promotion. A novel rapid granulation strategy, viz., the short-term (7 days) addition of ferric chloride at the commissioning stage, was developed and verified in this study. The granulation period was shortened by 9 days, and the formed granules were compact and dense with an Fe3+ concentration of 250â mg L-1. The addition of flocculant not only maintained a high sludge concentration during the initial stages of granulation (5.3â g L-1), but also stimulated the secretion of TB-EPS and increased protein and polysaccharide contents, thereby expediting granule formation. Additionally, ferric chloride induced a diverse microbial community in granules, resulting in the emergence of new genera, such as Thaurea, Brevundimonas and Kinneretia, which improved pollutant removal performance and flocculent aggregation. The removal efficiencies of COD, PO43--P, and NH4+-N stabilized at 94.2, 62.4, and 71.3%, respectively. Therefore, it has been demonstrated that short-term ferric chloride dosing has a synergistic effect on aerobic granulation.
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Reactores Biológicos , Aguas del Alcantarillado , Aguas del Alcantarillado/química , Aerobiosis , Eliminación de Residuos Líquidos/métodos , Nitrógeno/metabolismoRESUMEN
The feasibility of anaerobic membrane bioreactor (AnMBR) for the treatment of N, N-dimethylformamide (DMF)-containing wastewater was theoretically compared with the conventional activated sludge (CAS) process in this study. The electricity consumption and expenditure, bio-energy production and CO2 emission were investigated using the operational results of a lab-scale AnMBR operated in a long-term operation. The AnMBR was capable of producing bio-methane from wastewater and generated 3.45 kWh/m3 of electricity as recovered bio-energy while the CAS just generated 1.17 kWh/m3 of electricity from the post-treatment of excessive sludge disposal. The large quantity of bio-methane recovered by the AnMBR can also be sold as sustainable bioresource for the use of household natural gas with a theoretical profit gain of 29,821 US$/year, while that of the CAS was unprofitable. The AnMBR was also demonstrated to significantly reduce the carbon emission by obtaining a theoretical negative CO2 production of -2.34 kg CO2/m3 with the recycle of bio-energy while that for the CAS was 4.50 kg CO2/m3. The results of this study demonstrate that the AnMBR process has promising potential for the carbon-neutral treatment of high-strength DMF-containing wastewater in the future.
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Aguas del Alcantarillado , Aguas Residuales , Aguas Residuales/análisis , Dimetilformamida , Anaerobiosis , Eliminación de Residuos Líquidos/métodos , Carbono , Dióxido de Carbono , Reactores Biológicos , Metano , ElectricidadRESUMEN
Activated sludge (AS) offers great potential for resource recovery considering its high organic and nutrient content. However, low recovery efficiency and high costs are directing the focus toward the high-valuable resource recovery. This study extracted 71.5 ± 5.9 mg/g VSS of alginate-like exopolysaccharides from AS (ALE/AS) and applied it to mortar as a novel biopolymer agent for crack self-healing. With a mortar crack of 120 µm, addition of 0.5 wt% ALE/AS yielded a high crack closure ratio of 86.5 % within 28 days. In comparison to commercial healing agents, marginal flexural strength reduction with ALE/AS addition (17.9 % vs 30.2-50.5 %) was demonstrated. The abundance of COO- group in GG blocks of ALE/AS resulted in a higher cross-link capacity with Ca2+, while the reduction of hydrophilic residues (e.g., COO- and OH) after complexation engendered a lower swelling capacity, which facilitated self-healing and flexural strength maintenance. Molecular dynamics (MD) revealed that lower Ca2+ diffusivity, arising from the stronger electrostatic interactions between the COO- groups and Ca2+, resulted in a high Ca2+ concentration around the cracks, leading to CaCO3 deposition and healed cracks. The outcomes of this study provided light on ALE-based mortar crack healing and presented a possibility for multi-level AS resource recovery.