Mitigation of Salinity Buildup and Recovery of Wasted Salts in a Hybrid Osmotic Membrane Bioreactor–Electrodialysis System

The osmotic membrane bioreactor (OMBR) is an emerging technology that uses water osmosis to accomplish separation of biomass from the treated effluent; however, accumulation of salts in the wastewater due to water flux and loss of draw solute because of reverse salt flux seriously hinder OMBR development. In this study, a hybrid OMBR–electrodialysis (ED) system was proposed and investigated to alleviate the salinity buildup. The use of an ED (3 V applied) could maintain a relatively low conductivity of 8 mS cm^–1 in the feed solution, which allowed the OMBR to operate for 24 days, about 6 times longer than a conventional OMBR without a functional ED. It was found that the higher the voltage applied to the ED, the smaller area of ion-exchange membrane was needed for salt separation. The salts recovered by the ED were successfully reused as a draw solute in the OMBR. At an energy consumption of 1.88–4.01 kWh m^–3, the hybrid OMBR-ED system could achieve a stable water flux of about 6.23 L m^–2 h^–1 and an efficient waste salt recovery of 1.26 kg m^–3. The hybrid OMBR-ED system could be potentially more advantageous in terms of less waste saline water discharge and salt recovery compared with a combined OMBR and reverse osmosis system. It also offers potential advantages over the conventional OMBR+post ED treatment in higher water flux and less wastewater discharge

Self-Supplied Ammonium Bicarbonate Draw Solute for Achieving Wastewater Treatment and Recovery in a Microbial Electrolysis Cell-Forward Osmosis-Coupled System

This study has presented a proof-of-concept system for the self-sustained supply of ammonium-based draw solute for wastewater treatment through coupling a microbial electrolysis cell (MEC) and forward osmosis (FO). The MEC produced an ammonium bicarbonate draw solute via recovering ammonia from a synthetic organic solution, which was then applied in the FO for extracting water from the MEC anode effluent. The recovered ammonium could reach a concentration of 0.86 mol L^–1, and with this draw solution, the FO extracted 50.1 ± 1.7% of the MEC anode effluent. The lost ammonium during heat regeneration could be supplemented with additional recovered ammonium in the MEC. The MEC achieved continuing treatment of both organic and ammonium in the returned feed solution mixed with fresh anolyte, although at lower efficiency compared to that with completely fresh anolyte. These results encourage further investigation to optimize the coordination between MEC and FO with improved performance

Electrochemical phosphorus release and recovery from wastewater sludge: A review

Phosphorus (P) is abundant in wastewater sludge and can be a secondary P source that will contribute to a circular economy. Electrochemical systems are an emerging technology that can be used to release and recover P from wastewater sludge. This paper introduces and analyzes the state-of-the-art electrochemical methods for P release and recovery from wastewater sludge, both qualitatively and quantitatively. Electrochemical P release, which involves mobilizing P from the solid phase into the aqueous phase, is categorized into three major mechanisms, electro-biological release, anodic P release, and cathodic P release. Anodic P release has been most widely studied with a median P release rate of 92.4 mg d−1. Correlation analysis revealed that the type of feed sludge, sludge P contents, sludge loading rate, and current density have a significant impact on the P release performance. The released P is subsequently separated from the heavy metal laden sludge and then recovered via different electrochemical systems such as three-chamber cells, two-chamber cells, and their variations. Those systems can achieve P recovery efficiency of 50 ∼ 80% and a recovery rate of 2.0 × 102∼1.8 × 103 mg P d−1. Energy consumption of electrochemical P recovery is estimated at 50 ∼ 200 kWh kg−1 P but only 27.3% of literature reported such data. This work provides insights into the development and challenges of electrochemical P release & recovery from wastewater sludge and discusses the challenges that need to be addressed to advance the viability of electrochemical P recovery approach.</p

Integrating Forward Osmosis into Microbial Fuel Cells for Wastewater Treatment, Water Extraction and Bioelectricity Generation

A novel osmotic microbial fuel cell (OsMFC) was developed by using a forward osmosis (FO) membrane as a separator. The performance of the OsMFC was examined with either NaCl solution or artificial seawater as a catholyte (draw solution). A conventional MFC with a cation exchange membrane was also operated in parallel for comparison. It was found that the OsMFC produced more electricity than the MFC in both batch operation (NaCl solution) and continuous operation (seawater), likely due to better proton transport with water flux through the FO membrane. Water flux from the anode into the cathode was clearly observed with the OsMFC but not in the MFC. The solute concentration of the catholyte affected both electricity generation and water flux. These results provide a proof of concept that an OsMFC can simultaneously accomplish wastewater treatment, water extraction (from the wastewater), and electricity generation. The potential applications of the OsMFC are proposed for either water reuse (linking to reverse osmosis for reconcentration of draw solution) or seawater desalination (connecting with microbial desalination cells for further wastewater treatment and desalination)

Wattle-Bark-Tannin-Derived Carbon Quantum Dots as Multi-Functional Nanomaterials for Intelligent Detection of Cr⁶⁺ Ions, Bio-Imaging, and Fluorescent Ink Applications

Using natural wattle bark tannin, a kind of stable, nontoxic, fluorescent carbon quantum dots (CQDs) was hydrothermally fabricated and applied as a multifunctional fluorescent nanomaterial for the determination of heavy metal ions (Cr6+ and Co2+), bio-imaging, and fluorescent ink applications. The CQDs could be assembled with polyvinyl alcohol (PVA) through hydrogen bonding to yield a composite fluorescent hydrogel that can be integrated with a smartphone to constitute a novel and convenient intelligent detection system for the rapid (10 s) real-time monitoring of Cr6+. Both the CQDs (with 1.37 μM of LOD (limit of detection)) and CQDs-PVA hydrogel (with 3.36 mg/L of LOD) sensing systems produced fast, sensitive, and selective response to Cr6+ based on the internal filtering effect and electron-transfer effect. The practicability of the CQDs-PVA fluorescence sensor was demonstrated by determining tap water and tanning wastewater samples. Based on their satisfactory fluorescence stability and solubility, the CQDs were further used for HeLa-cell imaging and as fluorescent ink for information encryption. When HeLa cells were incubated for 24 h in CQDs at a high concentration of 200 mg/L, the cell survival remained as high as 90%, and a clear fluorescence image was observed under a laser confocal fluorescence microscope. The CQD solution could be written directly as fluorescent ink on TLC (thin layer chromatography) paper, and the handwritings were invisible after drying, confirming their application potential in the field of information encryption. In summary, the present CQDs derived from wattle bark tannin exhibited excellent stability, sensitivity, and specificity in heavy metal ion sensing and also had great potential in bio-imaging and information encryption applications

The interrupted Pummerer reaction in a sulfoxide‐catalyzed oxidative coupling of 2‐naphthols

A benzothiophene S‐oxide catalyst, generated in situ by sulfur oxidation with H2O2, mediates the oxidative coupling of 2‐naphthols. Key to the catalytic process is the capture and inversion of reactivity of a 2‐naphthol partner, using an interrupted Pummerer reaction of an unusual benzothiophene S‐oxide, followed by subsequent coupling with a second partner. The new catalytic manifold has been showcased in the synthesis of the bioactive natural products, (±)‐nigerone and (±)‐isonigerone. Although Pummerer reactions are used widely, their application in catalysis is rare, and our approach represents a new catalytic manifold for metal‐free C−C bond formation

Use of a Liter-Scale Microbial Desalination Cell As a Platform to Study Bioelectrochemical Desalination with Salt Solution or Artificial Seawater

Bioelectrochemical desalination is potentially advantageous because of bioenergy production and integrated wastewater treatment and desalination. In this work, the performance and energy benefits of a liter-scale upflow microbial desalination cell (UMDC) were evaluated. The UMDC desalinated both salt solution (NaCl) and artificial seawater, and the removal rate of total dissolved solid (TDS) increased with an increased hydraulic retention time, although TDS reduction in artificial seawater was lower than that in salt solution. Our analysis suggested that electricity generation was a predominant factor in removing TDS (more than 70%), and that other factors, like water osmosis and unknown processes, also contributed to TDS reduction. It was more favorable given the high energy efficiency, when treating salt solution, to operate the UMDC under the condition of high power output compared with that of high current generation because of the amount of energy production; while high current generation was more desired with seawater desalination because of lower salinity in the effluent. Under the condition of the high power output and the assumption of the UMDC as a predesalination in connection with a reversal osmosis (RO) system, the UMDC could produce electrical energy that might potentially account for 58.1% (salt solution) and 16.5% (artificial seawater) of the energy required by the downstream RO system. Our results demonstrated the great potential of bioelectrochemical desalination

Hydrothermal Synthesis and Characterization of Aluminum-Free Mn‑β Zeolite: A Catalyst for Phenol Hydroxylation

Zeolite beta, especially heteroatomic zeolite beta, has been widely used in the industries of fine chemicals and petroleum refining because of its outstanding thermal stability, acid resistance, and unique 3-D open-frame structure. In this paper, aluminum-free Mn-β zeolite was hydrothermally synthesized in the SiO₂–MnO₂–(TEA)₂O–NaF–H₂O system. The effect of the chemical composition of the precursor mixture to the crystallization of the Al-free Mn-β zeolite was investigated. The synthesized Al-free Mn-β zeolite was characterized by inductively coupled plasma (ICP), XRD, thermogravimetric/differential thermal analysis (TG/DTA), N₂ adsorption–desorption, FT-IR, UV–vis, X-ray photoelectron spectroscopy (XPS), and scanning electron microscope (SEM). The results show that the synthesized zeolite has a structure of β zeolite with good crystallinity and Mn ions present in the framework of the zeolite. The synthesized Al-free Mn-β zeolite shows great catalytic activity toward the phenol hydroxylation reaction using H₂O₂ as the oxidant. Approximately 35% of phenol conversion and ∼98% of dihydroxybenzene selectivity can be obtained under the optimal conditions

Multitask Lasso Model for Investigating Multimodule Design Factors, Operational Factors, and Covariates in Tubular Microbial Fuel Cells

Microbial fuel cells (MFCs) are a promising technology for simultaneous wastewater treatment and direct electricity generation. To build an effective large-scale MFC in field operation, it is important to identify the critical design and operational factors. However, there are limited studies that focus on developing systematic models to predict MFC performance and conduct variable selection. Herein, a multitask Lasso model (MLM) was employed to characterize the relationship among the input variables (design factors, operational factors, and covariates) and the output variables (normalized energy recovery (NER) and organic removal efficiency) of a tubular MFC with five modules. The proposed MLM can not only select the important input variables to predict the MFC performance but also simultaneously and accurately predict multiple output variables. The important design and operational factors were identified on the basis of the variable selection in the MLM. It was found that cathode moisture, especially the catholyte pump frequency, was significant on NER of the tubular MFC but relatively insignificant on organic removal efficiency. The proposed MLM can be an effective tool to advance the knowledge of potential input variables affecting the MFC performance toward future scaling up