Environmental genome-wide association studies across precipitation regimens reveal that the E3 ubiquitin ligase MBR1 regulates plant adaptation to rainy environments.

In an era characterized by rapidly changing and less-predictable weather conditions fueled by the climate crisis, understanding the mechanisms underlying local adaptation in plants is of paramount importance for the conservation of species. As the frequency and intensity of extreme precipitation events increase, so are the flooding events resulting from soil water saturation. The deriving onset of hypoxic stress is one of the leading causes of crop damage and yield loss. By combining genomics and remote sensing data, today it is possible to probe natural plant populations that have evolved in different rainfall regimes and look for molecular adaptation to hypoxia. Here, using an environmental genome-wide association study (eGWAS) on 934 non-redundant georeferenced Arabidopsis ecotypes, we have identified functional variants for the gene MED25 BINDING RING-H2 PROTEIN 1 (MBR1). This is a ubiquitin-protein ligase that regulates MEDIATOR25 (MED25), part of a multiprotein complex that interacts with transcription factors which act as key drivers of the hypoxic response in Arabidopsis, namely the RELATED TO AP2 proteins, RAP2.2 and RAP2.12. Through experimental validation, we show that natural variants of MBR1 have a differential impact on the stability of MED25 and, in turn, on hypoxia tolerance. This study also highlights the pivotal role of the MBR1/MED25 module in establishing a comprehensive hypoxic response. Our findings show that molecular candidates for plant environmental adaptation can be effectively mined from large datasets. This thus supports the need for the integration of forward and reverse genetics with robust molecular physiology validation of the outcomes.

A comparison study on membrane fouling in A/O-MBR and A/A-MBR at different mixed liquor-suspended solids concentrations.

Membrane fouling leads to decreased membrane flux, increases the frequency of membrane tissue replacement and membrane cleaning, and increases the operating cost of membrane bioreactor. In this study, the pollutant removal effects, membrane fouling differences and microbial characteristics of anaerobic/aerobic MBR (A/O-MBR) and anaerobic/anoxic MBR (A/A-MBR) were investigated at different mixed liquor suspended solids (MLSS) concentrations. The results showed that the chemical cleaning cycle of membrane contamination was 12, 28, 44 h and 24, 40, 104 h, respectively, and the cycle was prolonged with the increase of MLSS concentration (from 6000 to 9000 mg L-1). A/O-MBR was 1.4-2.4 times the rate of membrane fouling of A/A-MBR. In irreversible resistance, extracellular polymer substances (EPS) were the most significant contributors to membrane fouling. EPS concentration in A/A-MBR (118.33, 73.75, 54.26 mg/gMLSS) was lower than that in A/O-MBR (171.68, 91.92, 62.33 mg/gMLSS). Therefore, increasing MLSS concentration could mitigate membrane fouling. 16S rRNA high-throughput sequencing demonstrated that filamentous bacteria was the primary reason for the membrane fouling difference. Filamentous bacteria were more likely to be attached to the surface of the membrane, causing membrane fouling. The abundance percentage of filamentous bacteria in A/A-MBR was smaller than that in A/O-MBR. In summary, The excellent performance of A/A-MBR in membrane fouling behaviour, resistance analysis, EPS and microorganisms proved that A/A-MBR is more promising than A/O-MBR in wastewater nitrogen and phosphorus removal. This study can provide a theoretical basis for the application of MBR in the field of sewage treatment.

Stratified structure of membrane clogs observed in full scale cross-flow tubular ultrafiltration (UF) system: Fouling characterization and a proposed two-stage formation mechanism.

Membrane fouling remains a significant challenge in wastewater treatment, hindering both efficiency and lifespan. This study reports a distinct phenomenon of stratified membrane clogging observed in a full-scale cross-flow tubular ultrafiltration (UF) system treating sludge anaerobic digestion (AD) reject water. The distinct stratified structure, comprising inner and outer layers within the cake layer, has not been previously described. This research involved characterizing the filtration performance, analyzing membrane clog composition, and proposing a two-stage formation mechanism for the stratified clogs. It was revealed that higher inorganic and lower organic content in the outer layer compared to the inner layer. Acid and alkali treatments demonstrated the effectiveness of combined cleaning strategies. A mathematical model was developed to determine the critical conditions for stratified clog formation, influenced by membrane flux and cross-flow velocity (CFV). It is proposed that outer layer forms through long-term selective deposition, while the inner layer results from short-term dewatering within limited tubular space. High CFV (>2.5 m/s) prevents inner layer formation. Critical conditions for stratification occur at a flux of 18 L/m2/h with a CFV of 0.1 m/s or 65 L/m2/h with a CFV of 0.35 m/s. This study contributes a novel understanding of stratified membrane clogging, proposing a two-stage formation mechanism and identifying critical conditions, which provides insights for effective fouling control strategies and maintenance of operational efficiency for membrane systems.

Application of Recycled Ultrafiltration Membranes in an Aerobic Membrane Bioreactor (aMBR): A Validation Study.

A validation study using recycled ultrafiltration membranes (r-UF) on an aerobic membrane bioreactor (aMBR) was conducted for the first time. Four different polyethersulfone (PES) membranes were tested using synthetic urban wastewater (COD 0.4-0.5 g/L) during two experimental periods: (i) recycled ultrafiltration membrane (r-UF) and commercial UF membrane (molecular weight cut-off (MWCO) 150 kDa) (c-150 kDa); (ii) r-UF membrane modified by dip-coating using catechol (CA) and polyethyleneimine (PEI) (mr-UF) and c-20 kDa membrane. Permeability, fouling behavior, and permeate quality were evaluated. Extensive membrane characterization was conducted using scanning electron microscopy (SEM), atomic force microscopy (AFM), energy-dispersive X-ray (EDX), and confocal laser scanning microscopy (CLSM). Permeate quality for r-UF and mr-UF membranes was excellent and comparable to that obtained using commercial membranes under similar conditions. Additionally, r-UF and mr-UF membranes presented a steadier performance time. Additionally, r-UF membrane demonstrated less tendency to be fouled (Rf, m-1) r-UF 7.92 ± 0.57 × 1012; mr-UF 9.90 ± 0.14 × 1012, c-150 kDa 1.56 ± 0.07 × 1013 and c-20 kDa 1.25 ± 0.50 × 1013. The r-UF membrane showed an excellent antibiofouling character. Therefore, r-UF membranes can be successfully implemented for wastewater treatment in aMBR, being a sustainable and cost-effective alternative to commercial membranes that can contribute to overcome membrane fouling and membrane replacement issues.

Genome-wide identification of the MED25 BINDING RING-H2 PROTEIN gene family in foxtail millet (Setaria italica L.) and the role of SiMBR2 in resistance to abiotic stress in Arabidopsis.

MAIN CONCLUSION: The SiMBR genes in foxtail millet were identified and studied. Heterologous expression of SiMBR2 in Arabidopsis can improve plant tolerance to drought stress by decreasing the level of reactive oxygen species. Foxtail millet (Setaria italica L.), a C4 crop recognized for its exceptional resistance to drought stress, presents an opportunity to improve the genetic resilience of other crops by examining its unique stress response genes and understanding the underlying molecular mechanisms of drought tolerance. In our previous study, we identified several genes linked to drought stress by transcriptome analysis, including SiMBR2 (Seita.7G226600), a member of the MED25 BINDING RING-H2 PROTEIN (MBR) gene family, which is related to protein ubiquitination. Here, we have identified ten SiMBR genes in foxtail millet and conducted analyses of their structural characteristics, chromosomal locations, cis-acting regulatory elements within their promoters, and predicted transcription patterns specific to various tissues or developmental stages using bioinformatic approaches. Further investigation of the stress response of SiMBR2 revealed that its transcription is induced by treatments with salicylic acid and gibberellic acid, as well as by salt and osmotic stresses, while exposure to high or low temperatures led to a decrease in its transcription levels. Heterologous expression of SiMBR2 in Arabidopsis thaliana enhanced the plant's tolerance to water deficit by reducing the accumulation of reactive oxygen species under drought stress. In summary, this study provides support for exploring the molecular mechanisms associated with drought resistance of SiMBR genes in foxtail millet and contributing to genetic improvement and molecular breeding in other crops.

Predicting thermodynamic adhesion energies of membrane fouling in planktonic anammox MBR via backpropagation neural network model.

Predicting thermodynamic adhesion energies was a critical strategy for mitigating membrane fouling. This study utilized a backpropagation (BP) neural network model to predict the thermodynamic adhesion energies associated with membrane fouling in a planktonic anammox MBR. Acid-base (ΔGAB), electrostatic double layer (ΔGEL), and Lifshitz-van der Waals (ΔGLW) energies were selected as output variables, the training dataset was collected by the advanced Derjaguin-Landau-Verwey-Overbeek (XDLVO) method. Optimization results identified "7-10-3″ as the optimal network structure for the BP model. The prediction results demonstrated a high degree of fit between the predicted and experimental values of thermodynamic adhesion energy (R2 ≥ 0.9278), indicating a robust predictive capability of the model in this study. Overall, the study presented a practical BP neural network model for predicting thermodynamic adhesion energies, significantly enhancing the prediction tool for adhesive fouling behavior in anammox MBRs.

A practical study on the near-zero discharge of rainwater and the collaborative treatment and regeneration of rainwater and sewage.

Non-conventional water recovery, recycling, and reuse have been considered imperative approaches to addressing water scarcity in China. The objective of this study was to evaluate the technical and economic feasibility of Water Reclamation Plants (WRP) based on an anaerobic-anoxic-oxic membrane bioreactor (A2O-MBR) system for unconventional water resource treatment and reuse in towns (domestic sewage and rainwater). Rainwater is collected and stored in the rainwater reservoir through the rainwater pipe network, and then transported to the WRP for treatment and reuse through the rainwater reuse pumping station during the peak water demand period. During a year of operation and evaluation process, a total of 610,000 cubic meters of rainwater were reused, accounting for 10.4 % of the treated wastewater. In the A2O-MBR operation, the average effluent concentrations for COD (chemical oxygen demand), NH4+-N (ammonium), TN (total nitrogen), and TP (total phosphorus) were 14.23 ± 4.07 mg/L, 0.22 ± 0.26 mg/L, 11.97 ± 1.54 mg/L, and 0.13 ± 0.09 mg/L, respectively. The effluent quality met standards suitable for reuse in industrial cooling water or for direct discharge. The WRP demonstrates a positive financial outlook, with total capital and operating costs totaling 0.16 $/m3. A comprehensive cost-benefit analysis indicates a positive net present value for the WRP, and the estimated annualized net profit is 0.024 $/m3. This research has achieved near-zero discharge of wastewater and effective allocation of rainwater resources across time and space.

Revamping of a Full-Scale Membrane Plant for Landfill Leachate Pretreatment Using Partial Nitritation.

This paper describes a case study involving a revamping of a full-scale membrane bioreactor that treats landfill leachate and other liquid wastes. The main change was the introduction of nitritation/denitritation in alternating cycles instead of the classic denitrification/nitrification process, together with the installation of fine bubble diffusers, a reduction in the volume of the biological compartment, and an increase in the equalization volume. The most significant results were obtained for the biological compartment, with a decrease in the specific energy consumption of 46.6%. At the same time, the removal efficiency of COD, BOD, and TN substantially remained the same before and after plant revamping, while the removal efficiency of TP increased over the years, reaching an average value of almost 71%. Regarding the ultrafiltration unit, the specific flux (or permeability) was characterized by an increasing trend. At the same time, the specific energy consumption of this section decreased by 9.4%. These results led to the conclusion that the changes introduced with the revamp led to a more stable process, a reduction in membrane fouling, and important energy savings.

Study on efficiency and mechanism of ultrasonic controlling membrane fouling in ceramic membrane bioreactors.

In recent years, ceramic membranes have been increasingly used in membrane bioreactors (MBRs). However, membrane fouling was still the core issue restricting the large-scale engineering application of ceramic MBRs. As a novel and alternative technology, ultrasonic could be used to control membrane fouling. This research focused on the efficiency and mechanism of ultrasonic controlling membrane fouling in ceramic MBRs. The results showed that ultrasonic reduced the sludge concentration in MBR, and the average particle size of sludge was always in a high range. The sludge activity of the system was stable at 6-9 (mg O2·(g MLSS·h)-1), indicating that ultrasonic did not destroy the activity of microorganisms in the system. The extracellular polymer substance (EPS) of the ultrasonic group was slightly higher than that of the control group, while the soluble microbial product (SMP) content was relatively stable. The ceramic membrane of the ultrasonic group has a partial retention effect on the organic components. The application of ultrasonic slowed down the decrease of the hydrophilicity of the ceramic membrane. The main pollutants on the membrane surface exist in the form of aromatic and heteroaromatic rings, alkynes, and so forth. Ultrasonic removes the amide substances from the membrane surface. Membrane fouling resistance is mainly due to membrane pore blockage, accounting for 75.53%. PRACTITIONER POINTS: Enrich the research on the mechanism of ultrasonic technology in membrane fouling control. The MBR can still operate normally with ultrasonic applied. The time for the ceramic membrane to reach the fouling end point is 2.4 times that without ultrasonic. The main cause of membrane fouling was pore blocking, accounting for 75.53%.

Predatory Bdellovibrio-and-like organism mixtures on efficient MBR in-situ membrane fouling diminishment and mechanisms.

Membrane fouling is a major hindrance that restricts the application of membrane bioreactors (MBRs). Bdellovibrio-and-like organisms (BALOs), as obligatory parasitic bacteria, prey upon various bacteria. In this study, the BALO mixtures were screened and found more effective in membrane fouling mitigation compared to the single BALO species and extended the membrane filtration period by as long as 33.3%. The higher BALO diversity reduced the potential foulants generation in the activated sludge by decreasing the sludge viscosity as high as 13.8 ± 0.6% than the pure culture of BALO. Meanwhile, the mixed BALOs demonstrated superior biofilm predation capabilities, with the content of soluble microbial products and extracellular polymeric substances on the biofilm decreasing by 26.1 ± 0.5% and 38.3 ± 0.2% as the most compared to the single BALO species involved system. Additionally, the BALO mixtures expanded the single strains' host lysis spectrum of both the activated sludge and biofilm. The abundance of membrane-fouling-related bacteria such as Flavobacterium, Rhodobacter, and Labilithrix and pioneer bacteria such as Sphingorhabdus and Pseudomonas was significantly reduced. In summary, this study disclosed the significantly better membrane fouling mitigation effects of the BALOs with higher diversity, suggesting that the expansion of the host range is crucial for the further application of BALOs to enhance the anti-fouling performance of the MBR system.

Unveiling the influence of microaeration and sludge recirculation on enhancement of pharmaceutical removal and microbial community change of the novel anaerobic baffled biofilm - membrane bioreactor in treating building wastewater.

This research aims to conduct a comparative investigation of the role played by microaeration and sludge recirculation in the novel anaerobic baffled biofilm-membrane bioreactor (AnBB-MBR) for enhancing pharmaceutical removal from building wastewater. Three AnBB-MBRs - R1: AnBB-MBR, R2: AnBB-MBR with microaeration and R3: AnBB-MBR with microaeration and sludge recirculation - were operated simultaneously to remove Ciprofloxacin (CIP), Caffeine (CAF), Sulfamethoxazole (SMX) and Diclofenac (DCF) from real building wastewater at the hydraulic retention time (HRT) of 30 h for 115 days. From the removal profiles of the targeted pharmaceuticals in the AnBB-MBRs, it was found that the fixed-film compartment (C1) could significantly reduce the targeted pharmaceuticals. The remaining pharmaceuticals were further removed with the microaeration compartment. R2 exhibited the utmost removal efficiency for CIP (78.0 %) and DCF (40.8 %), while SMX was removed most successfully by R3 (microaeration with sludge recirculation) at 91.3 %, followed by microaeration in R2 (88.5 %). For CAF, it was easily removed by all AnBB-MBR systems (>90 %). The removal mechanisms indicate that the microaeration in R2 facilitated the adsorption of CIP onto microaerobic biomass, while the enhanced biodegradation of CAF, SMX and DCF was confirmed by batch biotransformation kinetics and the adsorption isotherms of the targeted pharmaceuticals. The microbial groups involved in biodegradation of the targeted compounds under microaeration were identified as nitrogen removal microbials (Nitrosomonas, Nitrospira, Thiobacillus, and Denitratisoma) and methanotrophs (Methylosarcina, Methylocaldum, and Methylocystis). Overall, explication of the integration of AnBB-MBR with microaeration (R2) confirmed it as a prospective technology for pharmaceutical removal from building wastewater due to its energy-efficient approach characterized by minimal aeration supply.

Evaluation of autotrophic process influencing extracellular polymeric substances in aerobic membrane bioreactor with expanded ASM model.

A mathematical model was developed to predict the formation of both the autotrophic and heterotrophic extracellular polymeric substances (EPS) in the aerobic membrane bioreactor (MBR). Batch experimental results and 45-day operation data on a pilot MBR at a sludge retention time (SRT) of 20 d were used to calibrate and validate the model. Simulated MBR setup results demonstrated the key role of the influent COD and NH4+-N in governing the composition of heterotrophic and autotrophic EPS in the MBR. These results also revealed that the autotrophic EPS process was non-ignorable in the system. According to the autotrophic EPS simulation in the MBR, the EPS yield increased with increasing influent COD/NH4+-N ratio towards a constant level. The EPS yield was significantly influenced by the SRT, attributed to the autotrophic process's impact on EPS. Simulation results revealed a slight increase in EPS yield with an SRT of up to 5 days, followed by a rapid decrease beyond that threshold.

Removal efficiency of antibiotic residues, antibiotic resistant bacteria, and genes across parallel secondary settling tank and membrane bioreactor treatment trains in a water reclamation plant.

Antimicrobial resistance is recognized as a potent threat to human health. Wastewater treatment facilities are viewed as hotspots for the spread of antimicrobial resistance. This study provides comprehensive data on the occurrences of 3 different antibiotic resistant opportunistic pathogens (with resistance to up to 5 antibiotics), 13 antibiotic resistant genes and intI1, and 22 different antimicrobial residues in a large water reclamation plant (176 million gallons per day) that runs a conventional Modified Ludzack-Ettinger (MLE) reactor followed by a secondary settling tank (SST) and membrane bioreactor (MBR) in parallel. All the antibiotic resistant bacteria and most of the antibiotic resistance genes were present in the raw influent, ranging from 2.5 × 102-3.7 × 106 CFU/mL and 1.2× 10-1-6.5 × 1010 GCN/mL, respectively. MBR outperformed the SST system in terms of ARB removal as the ARB targets were largely undetected in MBR effluent, with log removals ranging from 2.7 to 6.8, while SST only had log removals ranging from 0.27 to 4.6. Most of the ARG concentrations were found to have significantly higher in SST effluent than MBR permeate, and MBR had significantly higher removal efficiency for most targets (p < 0.05) except for sul1, sul2, blaOXA48, intI1 and 16S rRNA genes (p > 0.05). As for the antibiotic residues (AR), there was no significant removal from the start to the end of the treatment process, although MBR had higher removal efficiencies for azithromycin, chloramphenicol, erythromycin, erythromycin-H2O, lincomycin, sulfamethoxazole and triclosan, compared to the SST system. In conclusion, MBR outperformed SST in terms of ARB and ARGs removal. However low removal efficiencies of most AR targets were apparent.

Coupling a Simple and Generic Membrane Fouling Model with Biological Dynamics: Application to the Modeling of an Anaerobic Membrane BioReactor (AnMBR).

A simple model is developed for membrane fouling, taking into account two main fouling phenomena: cake formation, due to attached solids on the membrane surface, and pore clogging, due to retained compounds inside the pores. The model is coupled with a simple anaerobic digestion model for describing the dynamics of an anaerobic membrane bioreactor (AnMBR). In simulations, we investigate its qualitative behavior: it is shown that the model exhibits satisfying properties in terms of a flux decrease due to membrane fouling. Comparing simulation and experimental data, the model is shown to predict quite well the dynamics of an AnMBR. The simulated flux best fits the experimental flux with a correlation coefficient r2=0.968 for the calibration data set and r2=0.938 for the validation data set. General discussions are given on possible control strategies to limit fouling and optimize the flux production. We show in simulations that these strategies allow one to increase the mean production flux to 33 L/(h·m2),whereas without control, it was 18 L/(h·m2).

Application of a water-energy-carbon coupling index to evaluate the long-term operational stability of the anaerobic-anoxic-oxic-membrane bioreactor (A2/O-MBR) process under the influence of rainstorms.

In the context of global climate change, sudden rainstorms and typhoons induce fluctuations in hydraulic shocks to wastewater treatment plants (WWTPs) in coastal areas, causing two challenges of stable effluent quality and low-carbon operation. We established a quantitative evaluation method for resistance of wastewater treatment processes to hydraulic shocks based on the water-energy-carbon nexus using operational data from a WWTP in southeast coastal China from July 2018 to December 2022. The effects of hydraulic shocks on the operational stability of the anaerobic-anoxic-oxic-membrane bioreactor (A2/O-MBR) process were analyzed following five steps. The results showed that the gray water footprint (GWF) of the process was 9.3% lower than that of the A2/O process. The energy footprint (ENF) and carbon footprint (CF) were approximately 2.1 times and 1.7 times higher than those of the A2/O process, respectively. The resistance to hydraulic shocks of the A2/O-MBR process is approximately 5.5 times higher than that of the A2/O process. In conclusion, the A2/O-MBR process exhibits higher process operational stability when subjected to hydraulic shocks, which is more conducive to the efficient and stable operation of WWTPs in rainstorm and typhoon-prone areas. The evaluation methodology provides qualitative technical support for selecting upgrading processes for WWTPs in different regions.

Electrocoagulation enhanced gravity driven membrane bioreactor for advanced treatment of rural sewage.

The daily discharge of rural sewage in China occupies 30 % of the national wastewater discharge, and developing an energy-efficient, easy to operate, and decentralized rural sewage treatment technology becomes an important task. In this work, a novel rural sewage treatment technology, Electrocoagulation enhanced Gravity-Driven Membrane Bioreactor (EC-GDMBR) was exploited for the rural sewage treatment under long-term operation (160 days). Two EC-GDMBRs with various module structures of ceramic membrane (horizontal module and side module) not only displayed the desirable effluent quality, but also sustained the stable flux (8-13 LMH). The electrocoagulation, electrooxidation, biodegradation, and separation in EC-GDMBRs were able to synergistically remove the particle matter, organic (CODCr effluent <11.6 ± 1.2 mg/L) and nutrients (NH3-N effluent <0.1 mg/L, TN effluent <8.5 mg/L, TP effluent <0.05 mg/L). Besides, the high permeability of ceramic membrane and large porosity of biofilm on its surface improved the sustainability of stable flux during the long-term operation. Moreover, by analyzing bacterial abundance, Extracellular Polymeric Substances, Adenosine Tri-Phosphate and Confocal Laser Scanning Microscopy, a large number of microorganisms grew and accumulated on the carrier, as well as formed the biofilm (23.46-659.9 µm), while Nitrobacteria (1.6-4.1 %) and Nitrate (0.01-0.06 %) exited in the carrier biofilms, promoting the nitrogen removal. Compared with EC-GDMBR with side module of ceramic membrane, EC-GDMBR with horizontal module of ceramic membrane has advantages in flux behavior, organic/nutrient removal, microbial abundance/activity, abundance of nitrogen removal functional bacteria and water permeability of biofilm, because the ceramic membrane of horizontal module can promote the uniform growth of biofilm and improve the uniformity of flow penetration distribution. In general, the findings of this work verify the reliability of EC-GDMBR for the sustainable operation of wastewater treatment and improve its application value of rural sewage treatment.

Modification of PAN electrospun nanofiber membranes with g-C3N4 nanotubes/carbon dots to enhance MBR performance.

This study is dedicated to the enhancement of electrospun polyacrylonitrile (PAN) nanofiber membranes for their application in membrane bioreactor (MBR) processes. The improvement is achieved through the incorporation of graphitic carbon nitride nanotubes/carbon dots (g-C3N4 NT/CDs) and subsequent heat post-treatments at varying temperatures. Notably, the hot-pressing methodology effectively mitigates surface roughness and significantly reduces issues related to peeling during nanofiber experimentation. Our results demonstrate that the introduction of 0.5 wt% of g-C3N4 NT/CDs leads to a substantial enhancement in water flux. In particular, nanocomposite membranes subjected to hot-pressing at 90 °C for 10 min exhibited an impressive flux recovery ratio (FRR) of 70%. Furthermore, the heat-treated nanocomposite membranes exhibited remarkable antifouling properties and significantly reduced fouling rates when compared to their heat-treated bare counterparts. This study underscores the noteworthy potential of g-C3N4 NT/CDs-modified PAN nanofiber membranes to substantially elevate MBR performance, firmly positioning them as highly promising candidates for critical applications in the domains of water and wastewater treatment. However, it is imperative to underscore that the existing written material necessitates a comprehensive overhaul to align with the provided structural framework.

Investigation on molecular characteristics of organic compounds during a full-scale landfill leachate treatment process based on non-targeted analysis.

In this study, a new methodology for evaluating full-scale landfill leachate treatment processes by non-targeted analysis using comprehensive two-dimensional gas chromatography quadrupole time-of-flight mass spectrometry (GC × GC-QTOF-MS) was proposed. The method revealed the chemical complexity of organic compounds in landfill leachate samples at the molecular level and evaluated the removal efficiency of the anaerobic-anoxic-oxic (A2O) - membrane bioreactor (MBR) - nanofiltration (NF) treatment process in conjunction with multi-level classification of organic compounds. Results showed that the results of non-targeted analysis combined with multi-level classification of organic compounds had a significant correlation with the conventional water quality parameters and can be used to evaluate the treatment process. A total of 2508 organic compounds were detected in 6 samples. 17 emerging contaminants (ECs) with known potentially hazards were detected, including Diisobutyl Phthalate (DIBP), which is toxic to male reproduction and development, and 4-Tert-Butylphenol, which causes endocrine disruption in animals. The removal rate of organic compounds by this full-scale landfill leachate treatment processes reached 79.14%. The anaerobic tank played a crucial role with 64.98% contribution. For compounds, the removal rate of heterocyclics was as high as 94.67%, and the removal rate of aliphatics was poor, only 63.49%. This treatment process had almost perfect removal effect on the steroids in alicyclics and phenols in aromatics, but poor treatment effect on saturated alkanes in aliphatics and naphthenes in alicyclics. This study provides a methodology for accurate assessment of the molecular level of treatment processes, new insights for process optimization in waste treatment plants, and data support for the detection of emerging contaminants. The environmental hazards of landfill leachate can be further evaluated in the future in conjunction with ecotoxicity assessment studies.

Effects of microaeration and sludge recirculation on VFA and nitrogen removal, membrane fouling reduction and microbial community of the anaerobic baffled biofilm-membrane bioreactor in treating building wastewater.

A novel anaerobic baffled biofilm-membrane bioreactor (AnBB-MBR) with microaeration of 0.62 LO2/LFeed was developed to improve VFA and nitrogen removal from building wastewater. Three different membrane bioreactor systems - R1: AnBB-MBR (without microaeration); R2: AnBB-MBR with microaeration; and R3: AnBB-MBR with integrated microaeration and sludge recirculation - were operated in parallel at the same hydraulic retention time of 20 h and sludge retention time of 100 d. The microaeration promoted greater microbial richness and diversity, which could significantly enhance the removal of acetic acid and dissolved methane in the R2 and R3 systems. Moreover, the partial nitrification and the ability of anammox (Candidatus Brocadia) to thrive in R2 enabled NH4+-N removal to be enhanced by up to 57.8 %. The worst membrane fouling was found in R1 due to high amount of protein as well as fine particles (0.5-5.0 µm) acting as foulants that contributed to pore blocking. While the integration of sludge recirculation with microaeration in R3 was able to improve the membrane permeate flux slightly as compared to R2. Therefore, the AnBB-MBR integrated with a microaeration system (R2) can be considered as promising technology for building wastewater treatment when considering VFA and nutrient removal and an energy-saving approach with low aeration intensity.

Enhanced treatment of sludge drying condensate by A/O-MBR process: Microbial activity and community structure.

With the rapid increase of sludge production from sewage treatment plants, the treatment of sludge drying condensate rich in a large amount of pollutants urgently needs to be addressed. Due to the unique characteristics of sludge drying condensate (high ammonia nitrogen and COD concentration), there are almost no reports on biological treatment methods specifically targeting sludge drying condensate. In this study, A/O-MBR process was proposed for sludge drying condensate treatment and the effects of ammonia nitrogen loads, alkalinity and aeration intensity were explored. Experimental results show that under the ammonia nitrogen load of 0.35 kg NH4+-N/(m3·d) and the aeration intensity of 0.5 m3/(m2·min), the removal rate of COD and NH4+-N could reach 94% and 99.86% with the addition of alkalinity (m(NaHCO3): m(NH4+-N) = 7:1), respectively. The distribution of living and dead microbial cells in the activated sludge of three reactors also proved that the supplement of alkalinity in the influent can ensure the feasible living conditions for microorganisms. In addition to traditional nitrifying bacteria, through the supplementation of alkalinity and the reduction of aeration intensity, the system had also domesticated high abundance heterogeneous nitrification aerobic denitrification (HN-AD) and aerobic denitrification bacteria (both more than 10% of the total bacterial count). The denitrification process of sludge drying condensate was simplified and the denitrification efficiency was greatly improved. The findings of this study could provide important theoretical guidance for the biological treatment process of sludge drying condensate.