A Roadmap for Achieving Energy-Positive Sewage Treatment Based on Sludge Treatment Using Free Ammonia

This letter proposes an innovative roadmap for achieving energy-positive sewage treatment based on sludge treatment using free ammonia (FA, i.e., NH₃). This FA technology is able to enhance anaerobic energy recovery in the form of methane via pretreatment of primary sludge and/or secondary sludge. It can also achieve stable mainstream nitrogen removal via nitrite instead of nitrate, thereby increasing organics availability for energy recovery. Energy evaluation suggests that the FA technology could transform sewage treatment plants from energy consumers (energy consumption at 0.27 kWh/m³ sewage treated) to energy exporters (energy export at 0.14 kWh/m³ sewage treated). Economic and environmental evaluations indicate that the FA technology would reduce sewage treatment cost and CO₂ emission by $0.056/m³ sewage treated and 0.40 kg CO₂/m³ sewage treated, respectively. This FA technology is a sustainable and closed-loop technology, which requires negligible chemical/energy input with FA being a byproduct of sewage treatment. It is also easy to implement in any existing and new sewage treatment plants by adding a simple sludge mixing tank

Diastereoselective Construction of Indole-Bridged Chroman Spirooxindoles through a TfOH-Catalyzed Michael Addition-Inspired Cascade Reaction

The first highly diastereoselective Michael addition/condensation/Friedel–Crafts alkylation cascade reaction of 3-indolyl-substituted oxindoles with <i>ortho</i>-hydroxychalcones was established, which afforded a wide range of polycyclic indole-bridged chroman spirooxindoles with novel and complex scaffolds in moderate to excellent yields

Reducing N₂O Emission from a Domestic-Strength Nitrifying Culture by Free Nitrous Acid-Based Sludge Treatment

An increase of nitrite in the domestic-strength range is generally recognized to stimulate nitrous oxide (N₂O) production by ammonia-oxidizing bacteria (AOB). It was found in this study, however, that N₂O emission from a mainstream nitritation system (cyclic nitrite = 25–45 mg of N/L) that was established by free nitrous acid (FNA)-based sludge treatment was not higher but much lower than that from the initial nitrifying system with full conversion of NH₄⁺-N to NO₃^–-N. Under dissolved oxygen (DO) levels of 2.5–3.0 mg/L, N₂O emission from the nitritation stage was 76% lower than that from the initial stage. Even when the DO level was reduced to 0.3–0.8 mg/L, N₂O emission from the nitritation stage was still 40% lower. An investigation of the mechanism showed that FNA treatment caused a shift of the stimulation threshold of nitrite on N₂O emission. At the nitritation stage, the maximal N₂O emission factor occurred at ∼16 mg of N/(L of nitrite). However, it increased with increasing nitrite in the range of 0–56 mg of N/L at the initial stage. FNA treatment decreased the biomass-specific N₂O production rate, suggesting that the enzymes relevant to nitrifier denitrification were inhibited. Microbial analysis revealed that FNA treatment decreased the microbial community diversity but increased the abundances of AOB and denitrifiers

Diastereoselective Construction of Indole-Bridged Chroman Spirooxindoles through a TfOH-Catalyzed Michael Addition-Inspired Cascade Reaction

The first highly diastereoselective Michael addition/condensation/Friedel–Crafts alkylation cascade reaction of 3-indolyl-substituted oxindoles with <i>ortho</i>-hydroxychalcones was established, which afforded a wide range of polycyclic indole-bridged chroman spirooxindoles with novel and complex scaffolds in moderate to excellent yields

Free Nitrous Acid (FNA)-Based Pretreatment Enhances Methane Production from Waste Activated Sludge

Anaerobic digestion of waste activated sludge (WAS) is currently enjoying renewed interest due to the potential for methane production. However, methane production is often limited by the slow hydrolysis rate and/or poor methane potential of WAS. This study presents a novel pretreatment strategy based on free nitrous acid (FNA or HNO₂) to enhance methane production from WAS. Pretreatment of WAS for 24 h at FNA concentrations up to 2.13 mg N/L substantially enhanced WAS solubilization, with the highest solubilization (0.16 mg chemical oxygen demand (COD)/mg volatile solids (VS), at 2.13 mg HNO₂–N/L) being six times that without FNA pretreatment (0.025 mg COD/mg VS, at 0 mg HNO₂–N/L). Biochemical methane potential tests demonstrated methane production increased with increased FNA concentration used in the pretreatment step. Model-based analysis indicated FNA pretreatment improved both hydrolysis rate and methane potential, with the highest improvement being approximately 50% (from 0.16 to 0.25 d^–1) and 27% (from 201 to 255 L CH₄/kg VS added), respectively, achieved at 1.78–2.13 mg HNO₂–N/L. Further analysis indicated that increased hydrolysis rate and methane potential were related to an increase in rapidly biodegradable substrates, which increased with increased FNA dose, while the slowly biodegradable substrates remained relatively static

Triclosan in sludge: Exploring its journey from the sewage treatment plants to land application and potential impacts on the environment

Triclosan (TCS) is an anti-microbial widely used in personal care and medical antibacterial products. Despite the widespread occurrence of TCS in municipal sewage sludge, understanding toward the fate of TCS within sewage treatment and environmental risks in the eventual land application is still limited. This review summarizes the TCS loads and transfer mechanisms in the sewage treatment process, sludge management process, land application, and its potential environmental impacts. TCS transfer from sewage to sludge mainly occurs in the primary sedimentation process, representing 2.50 to 4.58 times more compared to the secondary sedimentation process. This transfer is facilitated through adsorption because of the presence of humic acid-like and protein-like substances in sludge. Both anaerobic digestion and aerobic composting contribute to the degradation of TCS with aerobic composting being more effective, exhibiting TCS degradation rates 1.04–2.87 times higher than those observed in anaerobic digestion. After sludge land application, TCS majorly dissipates in the soil through biodegradation by fungi and bacteria, potentially posing environmental risks, such as inhibiting the seedling growth of plant species. Additionally, the degradation of TCS, coupled with the formation and subsequent degradation of MeTCS, is observed, with MeTCS exhibiting a higher half-life and greater toxicity than its parent compound (TCS). Overall, this research offers vital insights to enhance understanding of TCS’s migration and degradation processes in sewage treatment and soil. It also provides guidance in environmental protection and sustainable resource management.</p

An Unexpected FeCl₃‑Catalyzed Cascade Reaction of Indoles and <i>o</i>‑Hydroxychalcones for the Assembly of Chromane-Bridged Polycyclic Indoles

An unexpected FeCl₃-catalyzed cascade reaction of simple indoles and <i>o</i>-hydroxychalcone was reported, leading to densely functionalized and strained chromane-bridged polycyclic indoles in moderate to good yields. This reaction not only establishes a new transformation of indoles and <i>o</i>-hydroxychalcones but also provides an efficient method for the synthesis of structurally complex and congested chromane-bridged polycyclic indoles

Pressure-Triggered Fluorescence Intensity Ratio Variations of YNbO₄:Bi³⁺/Ln³⁺ (Ln = Eu or Sm) for High-Sensitivity Optical Pressure Sensing

Optical pressure sensing by phosphors is a growing area of research. However, the main pressure measurement methods rely on the movement of the central peak position, which has significant drawbacks for practical applications. This paper demonstrates the feasibility of using the fluorescence intensity ratio (FIR) of different emission peaks for pressure sensing. The FIR (IBi3+/ILn3+) values of the synthesized YNbO4:Bi3+/Ln3+ (Ln = Eu or Sm) phosphors are all first-order exponentially related to pressure, and YNbO4:Bi3+/Ln3+ (Ln = Eu or Sm) phosphors have high pressure-sensing sensitivities (Sp and Spr), which are 6 times higher than those from our previously reported work. In addition, the changes in FIR values during the decompression process were also calculated, and the trend was similar to that during the compression process. The YNbO4:Bi3+,Eu3+ phosphor has better pressure recovery performance. In summary, the YNbO4:Bi3+/Ln3+ (Ln = Eu or Sm) phosphors reported in this paper are expected to be applied in the field of optical pressure sensing, and this study provides a new approach and perspective for designing new phosphors for pressure measurement

Synthesis of Core–Shell Magnetic Nanocomposite Fe₃O₄@ Microbial Extracellular Polymeric Substances for Simultaneous Redox Sorption and Recovery of Silver Ions as Silver Nanoparticles

Microbial extracellular polymeric substance (EPS) is a complex high molecular weight compound secreted from many organisms. In this work, magnetic nanocomposite Fe₃O₄@EPS of <i>Klebsiella</i> sp. J1 were first synthesized for silver ions (Ag⁺) wastewater remediation, which synergistically combined the advantages of the easy separation property of magnetic Fe₃O₄ nanoparticles and the superior adsorption capacity of EPS of <i>Klebsiella</i> sp. J1. The physical and chemical properties of Fe₃O₄@EPS were analyzed comprehensively. Fe₃O₄@EPS exhibited the well-defined core–shell structure (size 50 nm) with high magnetic (79.01 emu g^–1). Batch adsorption experiments revealed that Fe₃O₄@EPS achieved high Ag⁺ adsorption capacity (48 mg g^–1), which was also much higher than many reported adsorbents. The optimal solution pH for Ag⁺ adsorption was around 6.0, with the sorption process followed pseudo-second-order kinetics. Ag⁺ adsorption on Fe₃O₄@EPS was mainly attributed to the reduction of Ag⁺ to silver nanoparticles (AgNPs) by benzenoid amine (−NH−), accompanied by the chelation between Ag⁺ and hydroxyl groups, ion exchange between Ag⁺ and Mg²⁺ and K⁺, and physical electrostatic sorption. The repeated adsorption–desorption experiments showed a good recycle performance of Fe₃O₄@EPS. This study has great importance for demonstrating magnetic Fe₃O₄@EPS as potential adsorbent to remove Ag⁺ from contaminated aquatic systems

Effect of End Groups on Optoelectronic Properties of Poly(9,9-dioctylfluorene): A Study with Hexadecylfluorenes as Model Polymers

Monodisperse hexadecyl­(9,9-dioctylfluorene)­s <b>F16</b>, <b>BrF16</b>, and <b>BF16</b>, which comprise H, Br, and boronic pinacol ester end groups, respectively, were synthesized, and the effect of these end groups on the photophysical, electrochemical, and electroluminescent properties of the polymers were investigated. The end groups have no noticeable effect on the energy levels of the polymers. <b>F16</b> and <b>BrF16</b> show high photoluminescence (PL) quantum yields (Φs) in both solution and film states. Film PL Φs (Φ_films) of <b>F16</b> and <b>BrF16</b> are 0.72 and 0.79, respectively. These values are about 1.4–1.5 times of that of <b>BF16</b> and poly­(9,9-dioctylfluorene) (<b>PFO</b>) prepared by Suzuki polycondensation. Moreover, Φ_films of <b>F16</b> and <b>BrF16</b> were kept almost the same after thermal annealing at 120 °C in both air and argon atmospheres. By contrast, the Φ_films of <b>BF16</b> and <b>PFO</b> dramatically decreased to 0.25 and 0.29 after thermal annealing at 120 °C in air. Polymer light-emitting diodes (PLEDs) were fabricated. <b>F16</b>, <b>BrF16</b>, and <b>PFO</b> exhibited maximum luminance efficiencies of 0.60, 0.27, and 0.39 cd·A^–1, respectively, while that of <b>BF16</b> was as low as 0.024 cd·A^–1. Meanwhile, green emission was observed for devices of <b>BrF16</b>, <b>BF16</b>, and <b>PFO</b>, but not for devices of <b>F16</b>. Electron- and hole-only devices were fabricated for elucidating the effect of end groups on charge transporting properties of the polymers. While Br is a mild hole-trapper, boronic ester group traps both holes and electrons, resulting in severely unbalanced hole- and electron-transport. Our results indicate that boronic ester end groups have a detrimental effect on the optoelectronic properties of polyfluorenes larger than Br