The main goal of the current study was to investigate the membrane fouling mechanism of aerobic granular sludge (AGS) with various AGS sizes. In this regard, AGSs were sieved into 6 levels: 0∼0.5, ...0.5∼0.7, 0.7∼1, 1∼1.2, 1.2∼1.7 mm and larger than 1.7 mm, then filtrated by a small dead-end filtration cell. Interestingly, there appeared a critical AGS size (1∼1.2 mm) for membrane fouling. Above 1.2 mm, flux increased and fouling reduced with size, due to the loose cake layer and high permeability caused by larger AGS. Below 1 mm, for smaller AGS, higher flux and lower fouling appeared, because less extracellular polymeric substance (EPS) formed and adhered onto AGS foulants. In the critical size, membrane fouling was serious to the most extent, on account of the dual role of the compact structure of cake fouling layer and the adhesion of EPS. Moreover, this critical AGS size also possessed the highest cake layer, pore blocking and irreversible fouling, which generally existed in various operational conditions. Besides, the results of SEM, AFM, hydrophilicity and ATR-FTIR also proved that the existence of the maximum membrane fouling at the critical AGS size. This study provides a deep understanding of the membrane fouling mechanisms of AGS in membrane filtration and is beneficial for developing a new membrane fouling mitigation strategy by terms of regulating AGS size.
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•Membrane fouling mechanisms of AGS with various AGS sizes were studied.•Interestingly, there appeared a critical AGS size (1–1.2 mm) for membrane fouling.•Above or below critical AGS size, fouling reduced as the size increase or decrease.•For the fouling resistance, pore blocking was higher than cake layer.•The micromorphology of fouled membrane was used to analyze critical AGS size.
During public health emergencies, the work of prevention and control must be normalised, and coordination between economic development and epidemic prevention is crucial. However, in China, there is ...a lack of research on participatory governance in public health emergencies, particularly from a legal perspective. Existing studies are insufficient in terms of using legal texts and exploring legal governance in a normative sense, and there is an inadequate in‐depth exploration of issues such as the legitimacy, path, motivation, and other aspects of participation. This article addresses these gaps by analysing the issues of participatory governance in public health emergencies from a legal perspective, using practical cases as examples. The research has shown that there are significant differences among the three types of organisations regarding their internal motivation, external incentives, and legal basis, and therefore it is necessary to distinguish different participation paths. Finally, we propose several measures to promote the active and sustained participation of organisation in governance, including cultivating the ability of organisations, emphasising organizational demands, seeking consensus, strengthening the guiding role of legislation, and broadening the channels of engagement.
Highlights
Participatory governance in public health emergencies is a process in which various types of organisations can actively participate in governance while receiving legal protection.
It might be helpful to develop a concrete path for participatory governance that considers the rule of law perspective.
The incentive factors for various organisations to participate in governance are different, public organisations have a legal responsibility, private organisations are based on social responsibility and market promotion, and the third sector pursues regulatory convenience and social support.
The rule of law is crucial for the long‐term governance of public health emergencies and should be adopted to ensure sustainability and innovation.
•AGS-MBR greatly lowered fouling rate in comparison with that of the conventional MBR.•A new scouring model was developed to explain the AGS scouring mechanism.•The AGS scouring stress is ...proportional to the total amount of AGS on the membrane.•A contribution quantification model was built to evaluate fouling mitigation factors.•AGS scouring had a contribution rate of 39.97% for membrane fouling mitigation.
Aerobic granular sludge (AGS) has been proven to have a low fouling potential in membrane bioreactor (MBR). Nevertheless, AGS scouring effect on mitigating membrane fouling remains poorly investigated. The main objective of this study is to examine AGS-MBR performance, to reveal the AGS scouring mechanism and quantify its contribution rate to membrane fouling mitigation, from the views of theory and experiment. Above all, AGS-MBR exhibited a low fouling rate ((transmembrane pressure (TMP) kept below 20 kPa) without membrane cleaning and a higher removal of organics and nutrients than conventional MBR during 80 days’ sludge granulation process. Then, flocculent sludge (FS) with various AGS ratios was applied to simulate the sludge granulation phase. When AGS ratio increased from 0% to 100%, the permeate flux gradually elevated from 40.0 L m−2h−1 to 92.9 L m−2h−1, and fouling resistance decreased from 9.0 × 10−12m−1 to 3.9 × 10−12m−1 benefiting from the loose structure and high porosity of AGS fouling layer. Meanwhile, the scouring effect produced by AGS on the membrane fouling mitigation was investigated. Based on the momentum conservation, a new hydrodynamic model was developed to explain the scouring mechanism of AGS. The scouring stress, proportional to the total amount of AGS depositing on the membrane surface, effectively reinforced the collision between AGS and FS, and reduced their deposition on the membrane surface by friction with the membrane; thus it was further conducive to membrane fouling mitigation. Moreover, a novel contribution quantification model was proposed for analyzing the contribution rate of AGS scouring effect to mitigate membrane fouling. AGS scouring possessed a significant contribution rate (39.9%) for fouling mitigation, compared with AGS structure (50.3%) and hydraulic stress (9.7%). In final, this study provides an in-depth understanding to mitigate the MBR membrane fouling by the unique advantages of sludge granulation.
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•The immobilization process improves the enzyme stability, reusability, and efficiency.•The immobilization methods and immobilized carriers for laccases are summarized.•The pollutant ...removal mechanisms by immobilized laccases and influencing factors are reviewed.•The relationship among adsorption, enzymatic and pollutant removal are analyzed.•The application of immobilized laccases for water treatment in recent years is showed.
Laccase is a promising biocatalyst for micro-pollutants removal and water purification. However, laccase can only play its significant catalytic role after effective immobilization. The immobilization process improves the laccase stability, in terms of thermal, pH, storage and operation. Furthermore, the reusability of immobilized laccase makes it more advantageous in the practical applications of water purification, in comparison with free laccase. The laccase immobilization is a promising water purification technology. In this review, the immobilization methods and immobilized carriers are summarized. Then, the pollutant removal mechanism by immobilized laccases, and its influencing factors are reviewed. Afterwards, the relationship among carrier adsorption, enzymatic degradation and pollutant removal efficiency are analyzed. Finally, the application of immobilized laccase for water purification in recent years is demonstrated. This review is expected to provide a valuable guideline for enzymatic water purification.
This study utilized physical adsorption and filtration of carbon nanotubes (CNTs) and laccases to fabricate biomimetic dynamic membrane (BDM) for the advanced treatment of dye wastewater. In BDM, the ...adsorption, enzymatic degradation and membrane separation demonstrated a synergism effect on pollutant removal. At first, the fabrication methods of BDM were investigated, and the mixed filtration for laccases and CNTs showed a better performance than the stepwise filtration. Furthermore, the operation parameters of BDM, including CNTs and laccase loading amounts, dye concentration, agitation speed and transmembrane pressure (TMP), were studied. Suitable CNTs and laccase amounts could reduce filtration resistance and increase catalysis efficiency, while moderate TMP and agitation speed were in favor of boosting the BDM structure for catalysis and permeability. Optimized operation parameters (CNT loading amount = 20 g m−2, laccase loading amount = 74.6 g m−2, agitation speed = 100 rpm, and TMP = 1.0 bar) sustained a high removal rate, and the flux was over 120 L m−2 h−1, even for 7 operation cycle’ tests. BDM exhibited an excellent dye removal rate, stable flux and great antifouling capacity, on the ground that adsorption saturation and foulant may be alleviated “online and in-situ” by the enzymatic degradation. Afterwards, the bionic layer on BDM, after absorption saturation and catalyst deactivation, could be eliminated rapidly by carrying out a simple backwash cleaning operation, then a new one could be fabricated immediately. Therefore, BDM is a good candidate for functional membrane materials in future water treatment.
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•BDM was fabricated by physical adsorption and forward filtration of laccase and CNTs.•Adsorption, enzymatic degradation and membrane separation had a synergism effect.•Mixed filtration was more conductive for BDM fabrication than stepwise filtration.•Backwash could rapidly remove the inactive BDM and refabricate a new one.•BDM had high removal rate and great flux (over 120 L m−2 h−1) for 7 cycle’ tests.
Localized surface plasmon resonance (LSPR) offers a valuable opportunity to improve the efficiency of photocatalysts. However, plasmonic enhancement of photoconversion is still limited, as most of ...metal-semiconductor building blocks depend on LSPR contribution of isolated metal nanoparticles. In this contribution, the concept of collective excitation of embedded metal nanoparticles is demonstrated as an effective strategy to enhance the utilization of plasmonic energy. The contribution of Au-nanochain to the enhancement of photoconversion is 3.5 times increase in comparison with that of conventional isolated Au nanoparticles. Experimental characterization and theoretical simulation show that strongly coupled plasmonic nanostructure of Au-nanochain give rise to highly intensive electromagnetic field. The enhanced strength of electromagnetic field essentially boosts the formation rate of electron-hole pair in semiconductor, and ultimately improves photocatalytic hydrogen evolution activity of semiconductor photocatalysts. The concept of embedded coupled-metal nanostructure represents a promising strategy for the rational design of high-performance photocatalysts.
•Shear-enhanced ultrafiltration was used to pre-treat dairy wastewater.•Complete pore blocking and cake formation are the main fouling mechanisms.•The effect of shear rate, TMP and temperature on ...flux and fouling was studied.•High shear rate can reduce membrane pore blocking and irreversible fouling.
Shear-enhanced ultrafiltration is considered as an important membrane technology that can contribute to pre-treat dairy wastewater and recycle valuable components such as milk proteins. However, to be efficient, it necessitates the establishment of proper methods for the assessment of membrane fouling. Four membrane blocking models proposed by Hermia were used to quantify and assess the membrane fouling of shear-enhanced filtration observed in dairy wastewater treatment. The experiments were performed with various shear rates, mean transmembrane pressure (TMP), temperature and membrane types. Good agreement between complete pore blocking model and experimental data was found, confirming the validity of the Hermia models for assessing the membrane fouling of shear-enhanced filtration system and that only some “sealing” of membrane pores occurs which is due to the high speed shearing effect. Furthermore, the increments of shear rate, TMP, and temperature can decrease the degree of “sealing” of membrane pores and improve filtration performance. In addition, a three-step membrane cleaning mode has achieved very satisfying results in subsequent membrane cleaning. This work confirms that, unlike traditional filtration mode (dead-end and cross flow filtration), high shear dynamic filtration possesses a low degree of membrane fouling and a higher membrane permeability recovery after cleaning.
Metabolic syndrome (MetS) is a chronic disease, including abdominal obesity, dyslipidemia, hyperglycemia, and hypertension. It should be noted that the occurrence of MetS is closely related to ...oxidative stress-induced mitochondrial dysfunction, ectopic fat accumulation, and the impairment of the antioxidant system, which in turn further aggravates the intracellular oxidative imbalance and inflammatory response. As enriched anti-inflammatory and antioxidant components in plants, natural polyphenols exhibit beneficial effects, including improving liver fat accumulation and dyslipidemia, reducing blood pressure. Hence, they are expected to be useful in the prevention and management of MetS. At present, epidemiological studies indicate a negative correlation between polyphenol intake and MetS incidence. In this review, we summarized and discussed the most promising natural polyphenols (including flavonoid and non-flavonoid drugs) in the precaution and treatment of MetS, including their anti-inflammatory and antioxidant properties, as well as their regulatory functions involved in glycolipid homeostasis.
Cancer is one of the primary causes of worldwide human deaths. Most cancer patients receive chemotherapy and radiotherapy, but these treatments are usually only partially efficacious and lead to a ...variety of serious side effects. Therefore, it is necessary to develop new therapeutic strategies. The emergence of nanotechnology has had a profound impact on general clinical treatment. The application of nanotechnology has facilitated the development of nano-drug delivery systems (NDDSs) that are highly tumor selective and allow for the slow release of active anticancer drugs. In recent years, vehicles such as liposomes, dendrimers and polymer nanomaterials have been considered promising carriers for tumor-specific drug delivery, reducing toxicity and improving biocompatibility. Among them, polymer nanoparticles (NPs) are one of the most innovative methods of non-invasive drug delivery. Here, we review the application of polymer NPs in drug delivery, gene therapy, and early diagnostics for cancer therapy.
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