The impact of different voltage application modes on biodegradation of chloramphenicol and shift of microbial community structure

● Presented coupled system enhanced biodegradation of antibiotic chloramphenicol. ● HRT and electrical stimulation modes were key influencing factors. ● Electrical stimulation had little effect on the chloramphenicol metabolic pathway. ● Microbial community structure varied with the voltage application mode. Exoelectrogenic biofilms have received considerable attention for their ability to enhance electron transfer between contaminants and electrodes in bioelectrochemical systems. In this study, we constructed anaerobic-aerobic-coupled upflow bioelectrochemical reactors (AO-UBERs) with different voltage application modes, voltages and hydraulic retention times (HRTs). In addition, we evaluated their capacity to remove chloramphenicol (CAP). AO-UBER can effectively mineralize CAP and its metabolites through electrical stimulation when an appropriate voltage is applied. The CAP removal efficiencies were ~81.1%±6.1% (intermittent voltage application mode) and 75.2%±4.6% (continuous voltage application mode) under 0.5 V supply voltage, which were ~21.5% and 15.6% greater than those in the control system without voltage applied, respectively. The removal efficiency is mainly attributed to the anaerobic chamber. High-throughput sequencing combined with catabolic pathway analysis indicated that electrical stimulation selectively enriched Megasphaera, Janthinobacterium, Pseudomonas, Emticicia, Zoogloea, Cloacibacterium and Cetobacterium, which are capable of denitrification, dechlorination and benzene ring cleavage, respectively. This study shows that under the intermittent voltage application mode, AO-UBERs are highly promising for treating antibiotic-contaminated wastewater.     

Electro-conductive crosslinked polyaniline/carbon nanotube nanofiltration membrane for electro-enhanced removal of bisphenol A

● A crosslinked polyaniline/carbon nanotube NF membrane was fabricated. ● Electro-assistance enhanced the removal rate of the NF membrane for bisphenol A. ● Intermittent voltage-assistance can achieve nearly 100% removal of bisphenol A. ● Membrane adsorption–electro-oxidation process is feasible for micropollutant removal. Nanofiltration (NF) has attracted increasing attention for wastewater treatment and potable water purification. However, the high-efficiency removal of micropollutants by NF membranes is a critical challenge. Owing to the adsorption and subsequent diffusion, some weakly charged or uncharged micropollutants, such as bisphenol A (BPA), can pass through NF membranes, resulting in low removal rates. Herein, an effective strategy is proposed to enhance the BPA removal efficiency of a crosslinked polyaniline/carbon nanotube NF membrane by coupling the membrane with electro-assistance. The membrane exhibited a 31.9% removal rate for 5 mg/L BPA with a permeance of 6.8 L/(m²·h·bar), while the removal rate was significantly improved to 98.1% after applying a voltage of 2.0 V to the membrane. Furthermore, when BPA coexisted with humic acid, the membrane maintained 94% removal of total organic carbon and nearly 100% removal of BPA at 2.0 V over the entire filtration period. Compared to continuous voltage applied to the membrane, an intermittent voltage (2.0 V for 0.5 h with an interval of 3.5 h) could achieve comparable BPA removal efficiency, because of the combined effect of membrane adsorption and subsequent electrochemical oxidation. Density functional theory calculations and BPA oxidation process analyses suggested that BPA was adsorbed by two main interactions: π–π and hydrogen-bond interactions. The adsorbed BPA was further electro-degraded into small organic acids or mineralized to CO₂ and H₂O. This work demonstrates that NF membranes coupled with electro-assistance are feasible for improving the removal of weakly charged or uncharged micropollutants.     

Bacteria inactivation by sulfate radical: progress and non-negligible disinfection by-products

● Status of inactivation of pathogenic microorganisms by SO₄^•− is reviewed. ● Mechanism of SO₄^•− disinfection is outlined. ● Possible generation of DBPs during disinfection using SO₄^•− is discussed. ● Possible problems and challenges of using SO₄^•− for disinfection are presented. Sulfate radicals have been increasingly used for the pathogen inactivation due to their strong redox ability and high selectivity for electron-rich species in the last decade. The application of sulfate radicals in water disinfection has become a very promising technology. However, there is currently a lack of reviews of sulfate radicals inactivated pathogenic microorganisms. At the same time, less attention has been paid to disinfection by-products produced by the use of sulfate radicals to inactivate microorganisms. This paper begins with a brief overview of sulfate radicals’ properties. Then, the progress in water disinfection by sulfate radicals is summarized. The mechanism and inactivation kinetics of inactivating microorganisms are briefly described. After that, the disinfection by-products produced by reactions of sulfate radicals with chlorine, bromine, iodide ions and organic halogens in water are also discussed. In response to these possible challenges, this article concludes with some specific solutions and future research directions.     

A pyrazine based metal-organic framework for selective removal of copper from strongly acidic solutions

● pz-UiO-66 was synthesized facilely by a solvothermal method. ● Efficient capture of copper from highly acidic solution was achieved by pz-UiO-66. ● pz-UiO-66 exhibited excellent selectivity and capacity for copper capture. ● Pyrazine-N in pz-UiO-66 was shown to be the dominant adsorption site. The selective capture of copper from strongly acidic solutions is of vital importance from the perspective of sustainable development and environmental protection. Metal organic frameworks (MOFs) have attracted the interest of many scholars for adsorption due to their fascinating physicochemical characteristics, including adjustable structure, strong stability and porosity. Herein, pz-UiO-66 containing a pyrazine structure is successfully synthesized for the efficient separation of copper from strongly acidic conditions. Selective copper removal at low pH values is accomplished by using this material that is not available in previously reported metal–organic frameworks. Furthermore, the material exhibits excellent adsorption capacity, with a theoretical maximum copper uptake of 247 mg/g. As proven by XPS and FT-IR analysis, the coordination of pyrazine nitrogen atoms with copper ions is the dominant adsorption mechanism of copper by pz-UiO-66. This work provides an opportunity for efficient and selective copper removal under strongly acidic conditions, and promises extensive application prospects for the removal of copper in the treatment for acid metallurgical wastewater.     

Simple fabrication of carboxymethyl cellulose and κ-carrageenan composite aerogel with efficient performance in removal of fluoroquinolone antibiotics from water

● A composite aerogel was simply obtained to remove various fluoroquinolones (FQs). ● The structural and textural properties of this composite aerogel are improved. ● Its adsorption capacity was improved at a low content of coexisting Cu²⁺ or Fe³⁺ ion. ● Two substructural analogs of FQs are compared to explore the adsorption mechanisms. ● This aerogel after saturated adsorption can be reused directly for Cu²⁺ adsorption. 3D composite aerogels (CMC-CG) composed of carboxymethyl cellulose and κ-carrageenan were designed and fabricated using the one-pot synthesis technique. The optimized CMC-CG showed a good mechanical property and a high swelling ratio due to its superior textural properties with a proper chemically cross-linked interpenetrating network structure. CMC-CG was utilized for the removal of various fluoroquinolones (FQs) from water and exhibited high adsorption performance because of effective electrostatic attraction and hydrogen bonding interactions. Ciprofloxacin (CIP), a popular FQ, was used as the representative. The optimized CMC-CG had a theoretically maximal CIP uptake of approximately 1.271 mmol/g at the pH of 5.0. The adsorption capacity of CMC-CG was improved in the presence of some cations, Cu²⁺ and Fe³⁺ ions, at a low concentration through the bridging effect but was reduced at a high concentration. The investigation of adsorption mechanisms, based on the adsorption kinetics, isotherms and thermodynamic study, Fourier transform infrared spectrometry and X-ray photoelectron spectroscopy analyses before and after adsorption, and changes in the adsorption performance of CMC-CG toward two molecular probes, further indicated that electrostatic attraction was the dominant interaction rather than hydrogen bonding in this adsorption. CMC-CG after saturated adsorption of CIP could be easily regenerated using a dilute NaCl aqueous solution and reused efficiently. Moreover, the disused aerogel could still be reused as a new adsorbent for effective adsorption of Cu²⁺ ion. Overall, this study suggested the promising applications of this composite aerogel as an eco-friendly, cost-effective, and recyclable adsorbent for the efficient removal of FQs from water.     

Removal of ammonium and nitrate through Anammox and FeS-driven autotrophic denitrification

● Simultaneous NH₄⁺/NO₃^– removal was achieved in the FeS denitrification system ● Anammox coupled FeS denitrification was responsible for NH₄⁺/NO₃^– removal ● Sulfammox, Feammox and Anammox occurred for NH₄⁺ removal ● Thiobacillus, Nitrospira , and Ca. Kuenenia were key functional microorganisms An autotrophic denitrifying bioreactor with iron sulfide (FeS) as the electron donor was operated to remove ammonium (NH₄⁺) and nitrate (NO₃⁻) synergistically from wastewater for more than 298 d. The concentration of FeS greatly affected the removal of NH₄⁺/NO₃⁻. Additionally, a low hydraulic retention time worsened the removal efficiency of NH₄⁺/NO₃⁻. When the hydraulic retention time was 12 h, the optimal removal was achieved with NH₄⁺ and NO₃⁻ removal percentages both above 88%, and the corresponding nitrogen removal loading rates of NH₄⁺ and NO₃⁻ were 49.1 and 44.0 mg/(L·d), respectively. The removal of NH₄⁺ mainly occurred in the bottom section of the bioreactor through sulfate/ferric reducing anaerobic ammonium oxidation (Sulfammox/Feammox), nitrification, and anaerobic ammonium oxidation (Anammox) by functional microbes such as Nitrospira, Nitrosomonas, and Candidatus Kuenenia. Meanwhile, NO₃⁻ was mainly removed in the middle and upper sections of the bioreactor through autotrophic denitrification by Ferritrophicum, Thiobacillus, Rhodanobacter, and Pseudomonas, which possessed complete denitrification-related genes with high relative abundances.     

Facile fabrication of dolomite-doped biochar/bentonite for effective removal of phosphate from complex wastewaters

● Dolomite-doped biochar/bentonite was synthesized for phosphate removal. ● DO/BB exhibited a high phosphate adsorption capacity in complex water environments. ● PVC membrane incorporated with DO/BB can capture low concentration phosphate. ● Electrostatic interaction, complexation and precipitation are main mechanisms. The removal of phosphate from wastewater using traditional biological or precipitation methods is a huge challenge. The use of high-performance adsorbents has been shown to address this problem. In this study, a novel composite adsorbent, composed of dolomite-doped biochar and bentonite (DO/BB), was first synthesized via co-pyrolysis. The combination of initial phosphate concentration of 100 mg/L and 1.6 g/L of DO/BB exhibited a high phosphate-adsorption capacity of 62 mg/g with a removal efficiency of 99.8%. It was also stable in complex water environments with various levels of solution pH, coexisting anions, high salinity, and humic acid. With this new composite, the phosphate concentration of the actual domestic sewage decreased from 9 mg/L to less than 1 mg/L, and the total nitrogen and chemical oxygen demand also decreased effectively. Further, the cross-flow treatment using a PVC membrane loaded with DO/BB (PVC-DO/BB), decreased the phosphate concentration from 1 to 0.08 mg/L, suggesting outstanding separation of phosphate pollutants via a combination of adsorption and separation. In addition, the removal of phosphate by the PVC-DO/BB membrane using NaOH solution as an eluent was almost 90% after 5 cycles. The kinetic, isotherm and XPS analysis before and after adsorption suggested that adsorption via a combination of electrostatic interaction, complexation and precipitation contributed to the excellent separation by the as-obtained membranes.     

Cultivars and oil extraction techniques affect Cd/Pb contents and health risks in oil of rapeseed grown on Cd/Pb-contaminated farmland

● Organic solvent extracted fewer Cd/Pb in rapeseed oil than physical pressing. ● Brassica rapa transferred fewer Cd and Pb from seed to oil than Brassica napus . ● Carcinogenic risk mainly from Cd and worth more concern than noncarcinogenic risk. ● Organic solvent specially SLB pose less heath risk for oil than physical pressing. ● Rapeseed oil posed higher carcinogenic risk for rural residents than urban. Substitute planting with rapeseed offers promise for safely using large areas of Cd/Pb-contaminated farmland. Cd/Pb distributions during rapeseed oil production were investigated and health risks posed by the oil were assessed. Tests were performed using three cultivars (Brassica rapa SYH and ZS100 and Brassica napus QY-1) and four oil extraction techniques (mechanical and low-temperature pressing and n-hexane and subcritical low-temperature butane extraction). The amounts of Cd and Pb in oil were 0.73%–8.44% and 3.14%–11.76%, respectively, of the amounts in rapeseed and were strongly affected by the cultivar and oil extraction technique. The heavy metal (HM) concentrations were lower in solvent-extracted oil (particularly subcritical low-temperature butane extracted oil, in which HMs were not detected) than mechanically pressed oil. The Cd and Pb transfer indices were lower (meaning larger proportions of HMs were retained by the rapeseed meal) for B. rapa than B. napus. This was attributed to a high HM binding protein content of B. rapa seed. Health risks to humans were assessed using a probabilistic risk assessment model. The carcinogenic risk was mainly (97.1%–99.9%) caused by Cd and poses more concern than non-carcinogenic risk. Stronger health risks are posed by mechanically pressed than solvent-extracted oil, and higher carcinogenic risks are posed to people living in rural areas than urban areas. Substitute planting with B. rapa and extracting oil with organic solvent (preferably subcritical low-temperature butane) are optimal for safely utilizing Cd/Pb-contaminated soil. Attention should be paid to the health risks posed by Cd in oil to rural populations.     

Adsorption of herring sperm DNA onto pine sawdust biochar: Thermodynamics and site energy distribution

● Adsorption of environmental deoxyribonucleic acid on biochar was studied. ● π−π interaction and electrostatic repulsion worked in the adsorption. ● Thermodynamics indicated the adsorption was spontaneous and endothermic. Environmental deoxyribonucleic acid (eDNA), which includes antibiotic resistance genes, is ubiquitous in the environment. The interactions between eDNA and biochar, a promising material widely used in soil amendment and water treatment, greatly affect the environmental behavior of eDNA. Hitherto few experimental evidences are available yet, especially on the information of thermodynamics and energy distribution to explains the interactions between biochar and eDNA. This study investigated the adsorption of herring sperm DNA (hsDNA) on pine sawdust biochar, with a specific emphasis on the adsorption thermodynamics and site energy distribution. The adsorption of hsDNA on biochar was enhanced by an increase in the pyrolysis and adsorption temperatures. The higher surface area, stronger π−π interaction, and weaker electrostatic repulsion between hsDNA and biochars prepared at high pyrolysis temperatures facilitated the adsorption of hsDNA. The thermodynamics indicated that the adsorption of hsDNA on biochar was spontaneous and endothermic. Therefore, higher temperature was beneficial for the adsorption of hsDNA on biochar; this was well explained by the increase in E^* and F(E^*) with the adsorption temperature. These results are useful for evaluating the migration and transformation of eDNA in the presence of biochar.     

Methanation and chemolitrophic nitrogen removal by an anaerobic membrane bioreactor coupled partial nitrification and Anammox

● Efficient carbon methanation and nitrogen removal was achieved in AnMBR-PN/A system. ● AOB outcompeted NOB in PN section by limiting aeration and shortening SRT. ● The moderate residual organic matter of PN section triggered PD in anammox unit. ● AnAOB located at the bottom of UASB played an important role in nitrogen removal. An AnMBR-PN/A system was developed for mainstream sewage treatment. To verify the efficient methanation and subsequent chemolitrophic nitrogen removal, a long-term experiment and analysis of microbial activity were carried out. AnMBR performance was less affected by the change of hydraulic retention time (HRT), which could provide a stable influent for subsequent PN/A units. The COD removal efficiency of AnMBR was > 93% during the experiment, 85.5% of COD could be recovered in form of CH₄. With the HRT of PN/A being shortened from 10 to 6 h, nitrogen removal efficiency (NRE) of PN/A increased from 60.5% to 80.4%, but decreased to 68.8% when the HRT_PN/A further decreased to 4 h. Microbial analysis revealed that the highest specific ammonia oxidation activity (SAOA) and the ratio of SAOA to specific nitrate oxidation activity (SNOA) provide stable NO₂⁻-N/NH₄⁺-N for anammox, and anammox bacteria (mainly identified as Candidatus Brocadia) enriched at the bottom of Anammox-UASB might play an important role in nitrogen removal. In addition, the decrease of COD in Anammox-UASB indicated partial denitrification occurred, which jointly promoted nitrogen removal with anammox.     

Contributions of adsorption,bioreduction and desorption to uranium immobilization by extracellular polymeric substances

● EPS immobilizes U(VI) via adsorption, bioreduction and desorption. ● This work provides a framework to quantify the three immobilization processes. ● The non-equilibrium adsorption of U follows pseudo-second-order kinetics. ● The equilibrium adsorption of U followed Langmuir and Freundlich isotherms. Hexavalent uranium (U(VI)) can be immobilized by various microbes. The role of extracellular polymeric substances (EPS) in U(VI) immobilization has not been quantified. This work provides a model framework to quantify the contributions of three processes involved in EPS-mediated U(VI) immobilization: adsorption, bioreduction and desorption. Loosely associated EPS was extracted from a pure bacterial strain, Klebsiella sp. J1, and then exposed to H₂ and O₂ (no bioreduction control) to immobilize U(VI) in batch experiments. U(VI) immobilization was faster when exposed to H₂ than O₂ and stabilized at 94% for H₂ and 85% for O₂, respectively. The non-equilibrium data from the H₂ experiments were best simulated by a kinetic model consisting of pseudo-second-order adsorption (k_a = 2.87 × 10⁻³ g EPS·(mg U)⁻¹·min⁻¹), first-order bioreduction (k_b = 0.112 min⁻¹) and first-order desorption (k_d = 7.00 × 10⁻³ min⁻¹) and fitted the experimental data with R² of 0.999. While adsorption was dominant in the first minute of the experiments with H₂, bioreduction was dominant from the second minute to the 50^th min. After 50 min, adsorption was negligible, and bioreduction was balanced by desorption. This work also provides the first set of equilibrium data for U(VI) adsorption by EPS alone. The equilibrium experiments with O₂ were well simulated by both the Langmuir isotherm and the Freundlich isotherm, suggesting multiple mechanisms involved in the interactions between U(VI) and EPS. The thermodynamic study indicated that the adsorption of U(VI) onto EPS was endothermic, spontaneous and favorable at higher temperatures.     

Ozonation of aromatic monomer compounds in water: factors determining reaction outcomes

● p- CNB and IBP were selected, to explore factors determining ozonation outcomes. ● •OH contributed only 50 % to IBP removal, compared to the 90 % for p -CNB removal. ● IBP achieved fewer TOC removal and more by-product types and quantities. ● A longer ring-opening distance existed during the degradation of IBP. ● Multiple positions on both branches of IBP were attacked, consuming more oxidants. For aromatic monomer compounds (AMCs), ozonation outcomes were usually predicted by the substituents of the benzene ring based on the electron inductive effect. However, the predicted results were occasionally unreliable for complex substituents, and other factors caused concern. In this study, p-chloronitrobenzene (p-CNB) and ibuprofen (IBP) were selected for ozonation. According to the electron inductive theory, p-CNB should be less oxidizable, but the opposite was true. The higher rates of p-CNB were due to various sources of assistance. First, the hydroxyl radical (•OH) contributed 90 % to p-CNB removal at pH 7.0, while its contribution to IBP removal was 50 %. Other contributions came from molecular O₃ oxidation. Second, p-CNB achieved 40 % of the total organic carbon (TOC) removal and fewer by-product types and quantities, when compared to the results for IBP. Third, the oxidation of p-CNB started with hydroxyl substitution reactions on the benzene ring; then, the ring opened. However, IBP was initially oxidized mainly on the butane branched chain, with a chain-shortening process occurring before the ring opened. Finally, the degradation pathway of p-CNB was single and consumed fewer oxidants. However, both branches of IBP were attacked simultaneously, and three degradation pathways that relied on more oxidants were proposed. All of these factors were determinants of the rapid removal of p-CNB.     

Property-performance relationship of core-shell structured black TiO2 photocatalyst for environmental remediation

● Properties and performance relationship of CSBT photocatalyst were investigated. ● Properties of CSBT were controlled by simply manipulating glycerol content. ● Performance was linked to semiconducting and physicochemical properties. ● CSBT (W:G ratio 9:1) had better performance with lower energy consumption. ● Phenols were reduced by 48.30% at a cost of $2.4127 per unit volume of effluent. Understanding the relationship between the properties and performance of black titanium dioxide with core-shell structure (CSBT) for environmental remediation is crucial for improving its prospects in practical applications. In this study, CSBT was synthesized using a glycerol-assisted sol-gel approach. The effect of different water-to-glycerol ratios (W:G = 1:0, 9:1, 2:1, and 1:1) on the semiconducting and physicochemical properties of CSBT was investigated. The effectiveness of CSBT in removing phenolic compounds (PHCs) from real agro-industrial wastewater was studied. The CSBT synthesized with a W:G ratio of 9:1 has optimized properties for enhanced removal of PHCs. It has a distinct core-shell structure and an appropriate amount of Ti³⁺ cations (11.18%), which play a crucial role in enhancing the performance of CSBT. When exposed to visible light, the CSBT performed better: 48.30% of PHCs were removed after 180 min, compared to only 21.95% for TiO₂ without core-shell structure. The CSBT consumed only 45.5235 kWh/m³ of electrical energy per order of magnitude and cost $2.4127 per unit volume of treated agro-industrial wastewater. Under the conditions tested, the CSBT demonstrated exceptional stability and reusability. The CSBT showed promising results in the treatment of phenols-containing agro-industrial wastewater.     

Highly efficient and selective removal of phosphate from wastewater of sea cucumber aquaculture for microalgae culture using a new adsorption-membrane separation-coordinated strategy

● A new adsorption-membrane separation strategy is used for phosphate removal. ● PVC/Zr-BT shows a selective adsorption ability to low-concentration phosphate. ● Low concentration of P below 0.05 mg/L was achieved in actual wastewater treatment. ● Algal biomass production served as a demonstration of phosphorus recycling. Enhanced phosphorus treatment and recovery has been continuously pursued due to the stringent wastewater discharge regulations and a phosphate supply shortage. Here, a new adsorption-membrane separation strategy was developed for rational reutilization of phosphate from sea cucumber aquaculture wastewater using a Zr-modified-bentonite filled polyvinyl chloride membrane. The as-obtained polyvinyl chloride/Zr-modified-bentonite membrane was highly permeability (940 L/(m²·h)), 1–2 times higher than those reported in other studies, and its adsorption capacity was high (20.6 mg/g) when the phosphate concentration in water was low (5 mg/L). It remained stable under various conditions, such as different pH, initial phosphate concentrations, and the presence of different ions after 24 h of adsorption in a cross-flow filtration system. The total phosphorus and phosphate removal rate reached 91.5% and 95.9%, respectively, after the membrane was used to treat sea cucumber aquaculture wastewater for 24 h and no other water quality parameters had been changed. After the purification process, the utilization of the membrane as a new source of phosphorus in the phosphorus-free f/2 medium experiments indicated the high cultivability of economic microalgae Phaeodactylum tricornutum FACHB-863 and 1.2 times more chlorophyll a was present than in f/2 medium. The biomass and lipid content of the microalgae in the two different media were similar. The innovative polyvinyl chloride/Zr-modified-bentonite membrane used for phosphorus removal and recovery is an important instrument to establish the groundwork for both the treatment of low concentration phosphate from wastewater as well as the reuse of enriched phosphorus in required fields.     

Adsorption behavior of imidacloprid pesticide on polar microplastics under environmental conditions: critical role of photo-aging

● Small molecular chains formed on photo-aged polylactic acid microplastics (MPs). ● Oxygen-containing functional groups generated on photo-aged polyamide MPs. ● Photo-aging has the opposite influence on the imidacloprid adsorption on two MPs. ● Electrostatic interactions and hydrogen bonds were the main mechanisms. ● High pH value and low ionic strength increase the adsorption capacity. The photo-aging behavior of microplastics (MPs) in natural environment has become a global concern. The ultraviolet radiation has enough energy to change the polymer structure and physical-chemical properties of MPs. Less attention has focused on the interactions of the photo-aged polar and biodegradable MPs with organic pollutants. This work investigated the structural properties of aged polar polyamide (PA) MPs and biodegradable polylactic acid (PLA) MPs exposed to ultraviolet irradiation and their adsorption behavior and mechanism for neonicotinoid insecticide imidacloprid (IMI). The results showed that the MPs had extensive changes in surface morphology and chemical properties after photo-aging. The C–N bond of PA MPs was disrupted to form more carbonyl groups. The oxygen-containing functional groups on the surface of aged PLA MPs were broken and generated relatively smaller molecules. The adsorption capacity of IMI on PA MPs decreased by 19.2 %, while the adsorption capacity of IMI on PLA MPs increased by 41.2 % after photo-aging. This depended on the natural structure of the MPs and their ability to absorb ultraviolet light. The electrostatic interactions, hydrogen bonds, van der Waals interactions, and polar-polar interactions were the main adsorption mechanisms of IMI on MPs. High initial solution pH and low ionic strength favored the adsorption of IMI by altering charge distribution on the MPs surface. The formation of the humic acid-IMI complexes decreased the concentration of IMI in the water phase and further decreased the adsorption on MPs. These results are enlightening for a scientific comprehension of the environmental behavior of the polar MPs.     

Water quality soft-sensor prediction in anaerobic process using deep neural network optimized by Tree-structured Parzen Estimator

● Hybrid deep-learning model is proposed for water quality prediction. ● Tree-structured Parzen Estimator is employed to optimize the neural network. ● Developed model performs well in accuracy and uncertainty. ● Usage of the proposed model can reduce carbon emission and energy consumption. Anaerobic process is regarded as a green and sustainable process due to low carbon emission and minimal energy consumption in wastewater treatment plants (WWTPs). However, some water quality metrics are not measurable in real time, thus influencing the judgment of the operators and may increase energy consumption and carbon emission. One of the solutions is using a soft-sensor prediction technique. This article introduces a water quality soft-sensor prediction method based on Bidirectional Gated Recurrent Unit (BiGRU) combined with Gaussian Progress Regression (GPR) optimized by Tree-structured Parzen Estimator (TPE). TPE automatically optimizes the hyperparameters of BiGRU, and BiGRU is trained to obtain the point prediction with GPR for the interval prediction. Then, a case study applying this prediction method for an actual anaerobic process (2500 m³/d) is carried out. Results show that TPE effectively optimizes the hyperparameters of BiGRU. For point prediction of COD_eff and biogas yield, R² values of BiGRU, which are 0.973 and 0.939, respectively, are increased by 1.03%–7.61% and 1.28%–10.33%, compared with those of other models, and the valid prediction interval can be obtained. Besides, the proposed model is assessed as a reliable model for anaerobic process through the probability prediction and reliable evaluation. It is expected to provide high accuracy and reliable water quality prediction to offer basis for operators in WWTPs to control the reactor and minimize carbon emission and energy consumption.     

Prediction and cause investigation of ozone based on a double-stage attention mechanism recurrent neural network

● Used a double-stage attention mechanism model to predict ozone. ● The model can autonomously select the appropriate time series for forecasting. ● The model outperforms other machine learning models and WRF-CMAQ. ● We used the model to analyze the driving factors of VOCs that cause ozone pollution. Ozone is becoming a significant air pollutant in some regions, and VOCs are essential for ozone prediction as necessary ozone precursors. In this study, we proposed a recurrent neural network based on a double-stage attention mechanism model to predict ozone, selected an appropriate time series for prediction through the input attention and temporal attention mechanisms, and analyzed the cause of ozone generation according to the contribution of feature parameters. The experimental data show that our model had an RMSE of 7.71 μg/m³ and a mean absolute error of 5.97 μg/m³ for 1-h predictions. The DA-RNN model predicted ozone closer to observations than the other models. Based on the importance of the characteristics, we found that the ozone pollution in the Jinshan Industrial Zone mainly comes from the emissions of petrochemical enterprises, and the good generalization performance of the model is proved through testing multiple stations. Our experimental results demonstrate the validity and promising application of the DA-RNN model in predicting atmospheric pollutants and investigating their causes.     

Mechanism of ball milled activated carbon in improving the desalination performance of flow- and fixed-electrode in capacitive deionization desalination

● BACs were used in electrode material for both fixed and flowing electrodes. ● ASAR of FCDI and MCDI was improved by 134% and 17%, respectively. ● ENRS of FCDI and MCDI was improved by 21% and 53%. ● The mechanism of improving desalination performance was analyzed in detail. Capacitive deionization (CDI) is a novel electrochemical water-treatment technology. The electrode material is an important factor in determining the ion separation efficiency. Activated carbon (AC) is extensively used as an electrode material; however, there are still many deficiencies in commercial AC. We adopted a simple processing method, ball milling, to produce ball milled AC (BAC) to improve the physical and electrochemical properties of the original AC and desalination efficiency. The BAC was characterized in detail and used for membrane capacitive deionization (MCDI) and flow-electrode capacitive deionization (FCDI) electrode materials. After ball milling, the BAC obtained excellent pore structures and favorable surfaces for ion adsorption, which reduced electron transfer resistance and ion migration resistance in the electrodes. The optimal ball-milling time was 10 h. However, the improved effects of BAC as fixed electrodes and flow electrodes are different and the related mechanisms are discussed in detail. The average salt adsorption rates (ASAR) of FCDI and MCDI were improved by 134% and 17%, respectively, and the energy-normalized removal salt (ENRS) were enhanced by 21% and 53%, respectively. We believe that simple, low-cost, and environmentally friendly BAC has great potential for practical engineering applications of FCDI and MCDI.     

Electrocatalytic biofilm reactor for effective and energy-efficient azo dye degradation: the synergistic effect of MnOx/Ti flow-through anode and biofilm on the cathode

● MnO _x /Ti flow-through anode was coupled with the biofilm-attached cathode in ECBR. ● ECBR was able to enhance the azo dye removal and reduce the energy consumption. ● Mn^IV=O generated on the electrified MnO _x /Ti anode catalyzed the azo dye oxidation. ● Aerobic heterotrophic bacteria on the cathode degraded azo dye intermediate products. ● Biodegradation of intermediate products was stimulated under the electric field. Dyeing wastewater treatment remains a challenge. Although effective, the in-series process using electrochemical oxidation as the pre- or post-treatment of biodegradation is long. This study proposes a compact dual-chamber electrocatalytic biofilm reactor (ECBR) to complete azo dye decolorization and mineralization in a single unit via anodic oxidation on a MnO_x/Ti flow-through anode followed by cathodic biodegradation on carbon felts. Compared with the electrocatalytic reactor with a stainless-steel cathode (ECR-SS) and the biofilm reactor (BR), the ECBR increased the chemical oxygen demand (COD) removal efficiency by 24 % and 31 % (600 mg/L Acid Orange 7 as the feed, current of 6 mA), respectively. The COD removal efficiency of the ECBR was even higher than the sum of those of ECR-SS and BR. The ECBR also reduced the energy consumption (3.07 kWh/kg COD) by approximately half compared with ECR-SS. The advantages of the ECBR in azo dye removal were attributed to the synergistic effect of the MnO_x/Ti flow-through anode and cathodic biofilms. Catalyzed by Mn^IV=O generated on the MnO_x/Ti anode under a low applied current, azo dyes were oxidized and decolored. The intermediate products with improved biodegradability were further mineralized by the cathodic aerobic heterotrophic bacteria (non-electrochemically active) under the stimulation of the applied current. Taking advantage of the mutual interactions among the electricity, anode, and bacteria, this study provides a novel and compact process for the effective and energy-efficient treatment of azo dye wastewater.     

Penicillin fermentation residue biochar as a high-performance electrode for membrane capacitive deionization

● We have provided an activated method to remove the toxicity of antibiotic residue. ● PFRB can greatly improve the salt adsorption capacity of MCDI. ● The hierarchical porous and abundant O/N-doped played the key role for the high-capacity desalination. ● A new field of reuse of penicillin fermentation residue has been developed. Membrane capacitive deionization (MCDI) is an efficient desalination technology for brine. Penicillin fermentation residue biochar (PFRB) possesses a hierarchical porous and O/N-doped structure which could serve as a high-capacity desalination electrode in the MCDI system. Under optimal conditions (electrode weight, voltage, and concentration) and a carbonization temperature of 700 °C, the maximum salt adsorption capacity of the electrode can reach 26.4 mg/g, which is higher than that of most carbon electrodes. Furthermore, the electrochemical properties of the PFRB electrode were characterized through cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) with a maximum specific capacitance of 212.18 F/g. Finally, biotoxicity tests have showed that PFRB was non-biotoxin against luminescent bacteria and the MCDI system with the PFRB electrode remained stable even after 27 adsorption–desorption cycles. This study provides a novel way to recycle penicillin residue and an electrode that can achieve excellent desalination.