Comprehensive comparison of integrated fixed-film activated sludge (IFAS) and AAO activated sludge methods: Influence of different operational parameters.

Due to limited land availability in municipal wastewater treatment plants, integrated fixed-film activated sludge (IFAS) technology offers significant advantages in improving nitrogen removal performance and treatment capacity. In this study, two systems, IFAS and Anaerobic-Anoxic-Oxic Activated sludge process (AAO), were compared by adjusting parameters such as hydraulic retention time (HRT), nitrifying solution recycle ratio, sludge recycle ratio, and dissolved oxygen (DO). The objective was to investigate pollutant removal capacity and differences in microbial community composition between the two systems. The study showed that, at an HRT of 12 h, the IFAS system exhibited an average increase of 5.76%, 8.85%, and 12.79% in COD, NH4+-N, and TN removal efficiency respectively, compared to the AAO system at an HRT of 16 h. The TP concentration in the IFAS system reached 0.82 mg/L without the use of additives. The IFAS system demonstrated superior effluent results under lower operating conditions of HRT, nitrification solution recycle ratio, and DO. The 16S rDNA analysis revealed higher abundance of denitrification-related associated flora, including Proteobacteria, Bacteroidetes, and Planctomycetota, in the IFAS system compared to the AAO system. Similarities were observed between microorganisms attached to the media and activated sludge in the anaerobic, anoxic, and oxic tanks. q-PCR analysis indicated that the incorporation of filler material in the IFAS system resulted in similar abundance of nitrifying bacteria genes on the biofilm as in the oxic tank. Additionally, denitrifying genes showed higher levels due to aeration scouring and the presence of alternating aerobic-anaerobic environments on the biofilm surface, enhancing nitrogen removal efficiency.

Bio-Inspired Flexible Fluoropolymer Film for All-Mode Light Extraction Enhancement.

Enhancing the light extraction efficiency is a prevalent but vital challenge for most solid-state lighting technologies, especially for deep ultraviolet light-emitting diodes (DUV-LEDs). In this paper, inspired by the microstructure of the butterfly's eye, we propose and fabricate a flexible fluoropolymer film (FFP film) to tackle this issue for all-mode, full-wavelength light extraction enhancement for most solid-state lighting technologies compatibly. The experimental results demonstrate that compared with one mounted with a smooth FFP film, the light output power of DUV-LED is enhanced up to 26.7% by mounting the FFP film with 325 nm radius nanocones at a driving current of 200 mA. Importantly, thanks to the super-flexible feature of the FFP film, it can both cover the top surface and sidewalls of the DUV-LED chip, leading to the improvement of transverse electric and transverse magnetic mode light extraction by 20.5 and 21.8%, respectively. Finite element analysis (FEA) simulations of the electric field distribution of DUV-LEDs with the FFP film reveal the underlying physics. The present strategy is proposed from the view of the packaging level, which is cost-effective, able to be manufactured at a large scale, and compatible with the solid-state lighting technologies.

Enhanced light extraction of deep ultraviolet light-emitting diodes by using optimized aluminum reflector.

Deep ultraviolet light-emitting diodes (DUV-LEDs) have become a promising UV light source for sterilization, disinfection, and purification. However, the challenge in practical application of DUV-LEDs still remains in their low light efficiency. In this paper, we propose an optimized aluminum (Al) reflector for the light extraction enhancement of DUV-LEDs. The optical model of DUV-LEDs was established, and the optical simulations were performed to achieve the optimized reflector. The DUV-LEDs exhibit the highest light efficiency when the reflector has the optimized feature sizes with an angle of 60°, a height of 2.0 mm, and an internal radius of 2.5 mm. Furthermore, the optimized reflector with different reflectance was fabricated and applied for the packaging of DUV-LEDs. Consequently, the light output powers of DUV-LEDs are enhanced by 28.8%, 37.0%, and 43.8%, respectively, by using the different reflectors at the driving current of 100 mA. It is attributed to the remarkable reflection effect of the Al reflector, which increases the light extraction of the sidewall emission from the DUV-LED chip.

Internal strain induced significant enhancement of deep ultraviolet light extraction efficiency for AlGaN multiple quantum wells grown by MOCVD.

In this work, combined analysis of internal strain effects on optical polarization and internal quantum efficiency (IQE) were conducted for the first time. Deep ultraviolet light extraction efficiency of AlGaN multiple quantum wells (MQWs) have been investigated by means of polarization-dependent photoluminescence (PD-PL) and temperature-dependent photoluminescence (TD-PL). With the increase of compressive internal strain applied to the MQWs by an underlying n-AlGaN layer, the degree of polarization (DOP) of the sample was improved from -0.26 to -0.06 leading to significant enhancement of light extraction efficiency (LEE) as the PL intensity increased by 29.2% even though the internal quantum efficiency declined by 7.7%. The results indicated that proper management of the internal compressive strain in AlGaN MQWs can facilitate the transverse electric (TE) mode and suppress the transverse magnetic (TM) mode which could effectively reduce the total internal reflection (TIR) and absorption. This work threw light upon the promising application of compressively strained MQWs to reduce the wave-guide effect and improve the LEE of deep ultraviolet light emitting diodes (DUV LEDs).

Interface Anchored Effect on Improving Working Stability of Deep Ultraviolet Light-Emitting Diode Using Graphene Oxide-Based Fluoropolymer Encapsulant.

The graphene oxide (GO)-based fluoropolymer is first proposed as an interface encapsulant to improve the light extraction efficiency and achieve the ultralong working stability of deep ultraviolet light-emitting diodes (DUV-LEDs), benefitting from its superior interface performance based on an anchored effect. For the GO-based fluoropolymer composite, the anchored structure is designed to effectively and tightly rivet the quartz lens on the DUV-LED chip by using the interface reaction between GO embedded in fluoropolymer and 3-aminopropyltriethoxy-silane grafted on the surfaces. Experimental results show that on the basis of the interface anchored effect, the air voids in the interface layer of DUV-LED are reduced by 84%, leading to an improvement of the light output power by 15% and a decrease of the junction temperature by 5%, by virtue of the sealing characteristics of the 0.10 wt % GO-based fluoropolymer. In addition, the steady working time is dramatically improved by 660% and it was attributed to the good interface anchored bonding of the 0.10 wt % GO-based fluoropolymer. This novel graphene oxide-based fluoropolymer is believed to provide a feasible and effective interface encapsulant to improve the performance of DUV-LEDs.

Improvement of Interface Thermal Resistance for Surface-Mounted Ultraviolet Light-Emitting Diodes Using a Graphene Oxide Silicone Composite.

In this study, based on silicone composites with graphene oxide (GO) as a filler, a novel packaging strategy was proposed to reduce the interface thermal resistance of surface-mounted ultraviolet light-emitting diodes (UV-LEDs) and provide a potentially effective way for enhancing the long-term stability of devices. The 4 wt % GO-based composite showed an excellent performance in the thermal conductivity, and the interface thermal resistance was reduced by 34% after embedding the 4 wt % GO-based composite into the air gaps of bonding interfaces in the UV-LEDs, leading to a reduction of junction temperature by 1.2 °C under the working current of 1000 mA. Meanwhile, a decrease of thermal stress in bonding interfaces was obtained based on the finite element analysis. What is more, it was found that the lifetime of UV-LEDs with the proposed structure could be obviously improved. It is believed to provide a simple and effective approach for improving the performance of surface-mounted UV-LEDs.

Ag-Decorated Localized Surface Plasmon-Enhanced Ultraviolet Electroluminescence from ZnO Quantum Dot-Based/GaN Heterojunction Diodes by Optimizing MgO Interlayer Thickness.

We demonstrate the fabrication and characterization of localized surface plasmon (LSP)-enhanced n-ZnO quantum dot (QD)/MgO/p-GaN heterojunction light-emitting diodes (LEDs) by embedding Ag nanoparticles (Ag-NPs) into the ZnO/MgO interface. The maximum enhancement ration of the Ag-NP-decorated LEDs in electroluminescence (EL) is 4.3-fold by optimizing MgO electron-blocking layer thickness. The EL origination was investigated qualitatively in terms of photoluminescence (PL) results. Through analysis of the energy band structure of device and carrier transport mechanisms, it suggests that the EL enhancement is attributed to the increased rate of spontaneous emission and improved internal quantum efficiency induced by exciton-LSP coupling.

Physical and chemical properties of waste-activated sludge after microwave treatment.

In this study, we investigate the physical and chemical properties of waste-activated sludge after treatment with microwave irradiation. The results indicate that microwave energy and contact time strongly influence the physical and chemical properties of sludge. According to the settling velocity and particle size measurements, the microwave energy of 900 W with a contact time of 60s may be the optimal condition for improving the ability of the sludge to settle. Results of the experiments have shown that supernatant turbidity, soluble chemical oxygen demand, volatile suspended solid solubilization, extracellular polymeric substances content, and inorganic nitrogen increase significantly with contact time. Based on these results, we find that the microwave irradiation treatment specified by the contact time not only improves settleability, but also disintegrates sludge and destroys microbial cells. Possible mechanisms of microwave treatment are also discussed.