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Nanoemulsions play a crucial role in various industries. However, their application often results in hazardous waste, posing significant risks to human health and the environment. Effective management and separation of waste nanoemulsions requires special attention and effort. This review provides a comprehensive understanding of waste nanoemulsions, covering their sources, characteristics, and suitable treatment technologies, intending to mitigate their environmental impact. This study examines the evolution of nanoemulsions from beneficial products to hazardous wastes, provides an overview of the production processes, fate, and hazards of waste nanoemulsions, and highlights the critical characteristics that affect their stability. The latest advancements in separating waste nanoemulsions for recovering oil and reusable water resources are also presented, providing a comprehensive comparison and evaluation of the current treatment techniques. This review addresses the significant challenges in nanoemulsion treatment, provides insights into future research directions, and offers valuable implications for the development of more effective strategies to mitigate the hazards associated with waste nanoemulsions., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024. Published by Elsevier B.V.)

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 (A 2 /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 A 2 /O process. The energy footprint (ENF) and carbon footprint (CF) were approximately 2.1 times and 1.7 times higher than those of the A 2 /O process, respectively. The resistance to hydraulic shocks of the A 2 /O-MBR process is approximately 5.5 times higher than that of the A 2 /O process. In conclusion, the A 2 /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., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024. Published by Elsevier Ltd.)

The extensive use of antidiabetic drugs (ADDs) and their detection in high concentrations in the environment have been extensively documented. However, the mechanism of ADDs dissipation in aquatic environments is still not well understood. This study thoroughly investigates the dissipation behavior of ADDs and the underlying mechanisms in the aerobic activated sludge system. The results indicate that the removal efficiencies of ADDs range from 3.98% to 100% within 48 h, largely due to the biodegradation process. Additionally, the gene expression of cytochrome P450 (CYP450) is shown to be significantly upregulated in most ADDs-polluted samples (P < 0.05), indicating the vital role of CYP450 enzymes in the biodegradation of ADDs. Enzyme inhibition experiments validated this hypothesis. Moreover, molecular docking and simulation results indicate that a strong correlation between the biodegradation of ADDs and the interactions between ADDs and CYP450 (E binding ). The differences in dissipation behavior among the tested ADDs are possibly due to their electrophilic characteristics. Overall, this study makes the initial contribution to a more profound comprehension of the crucial function of CYP450 enzymes in the dissipation behavior of ADDs in a typical aquatic environment., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Mitigation of nitrous oxide (N 2 O) emissions in full-scale wastewater treatment plant (WWTP) has become an irreversible trend to adapt the climate change. Monitoring of N 2 O emissions plays a fundamental role in understanding and mitigating N 2 O emissions. This paper provides a comprehensive review of direct and indirect N 2 O monitoring methods. The techniques, strengths, limitations, and applicable scenarios of various methods are discussed. We conclude that the floating chamber technique is suitable for capturing and interpreting the spatiotemporal variability of real-time N 2 O emissions, due to its long-term in-situ monitoring capability and high data acquisition frequency. The monitoring duration, location, and frequency should be emphasized to guarantee the accuracy and comparability of acquired data. Calculation by default emission factors (EFs) is efficient when there is a need for ambiguous historical N 2 O emission accounts of national-scale or regional-scale WWTPs. Using process-specific EFs is beneficial in promoting mitigation pathways that are primarily focused on low-emission process upgrades. Machine learning models exhibit exemplary performance in the prediction of N 2 O emissions. Integrating mechanistic models with machine learning models can improve their explanatory power and sharpen their predictive precision. The implementation of the synergy of nutrient removal and N 2 O mitigation strategies necessitates the calibration and validation of multi-path mechanistic models, supported by long-term continuous direct monitoring campaigns., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

There is a lack of knowledge on the biodegradation mechanisms of benzene and benzo [a]pyrene (BaP), representative compounds of polycyclic aromatic hydrocarbons (PAHs), and benzene, toluene, ethylbenzene, and xylene (BTEX), under individually and mixed contaminated soils. Therefore, a set of microcosm experiments were conducted to explore the influence of benzene and BaP on biodegradation under individual and mixed contaminated condition, and their subsequent influence on native microbial consortium. The results revealed that the total mass loss of benzene was 56.0% under benzene and BaP mixed contamination, which was less than that of individual benzene contamination (78.3%). On the other hand, the mass loss of BaP was slightly boosted to 17.6% under the condition of benzene mixed contamination with BaP from that of individual BaP contamination (14.4%). The significant differences between the microbial and biocide treatments for both benzene and BaP removal demonstrated that microbial degradation played a crucial role in the mass loss for both contaminants. In addition, the microbial analyses revealed that the contamination of benzene played a major role in the fluctuations of microbial compositions under co-contaminated conditions. Rhodococcus, Nocardioides, Gailla, and norank&#95;c&#95;Gitt-GS-136 performed a major role in benzene biodegradation under individual and mixed contaminated conditions while Rhodococcus, Noviherbaspirillum, and Phenylobacterium were highly involved in BaP biodegradation. Moreover, binary benzene and BaP contamination highly reduced the Rhodococcus abundance, indicating the toxic influence of co-contamination on the functional key genus. Enzymatic activities revealed that catalase, lipase, and dehydrogenase activities proliferated while polyphenol oxidase was reduced with contamination compared to the control treatment. These results provided the fundamental information to facilitate the development of more efficient bioremediation strategies, which can be tailored to specific remediation of different contamination scenarios., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Thoroughly exploring carbon emissions within Urban Rail Transit (URT) systems is crucial for effectively reducing emissions while satisfying increasing energy demands. This study evaluated the spatiotemporal characteristics of carbon emissions in China's URT sector. Tapio decoupling and the Logarithmic Mean Divisia Index, used to scrutinize decoupling states and identify principal contributing factors, respectively, revealed the following: (1) Total emissions increased by 217 %, with significant spatiotemporal heterogeneity from 2015 to 2022. Type I and Type II cities accounted for >85 % of emissions but exhibited lower carbon intensity. (2) Most URT cities showed expansion-negative decoupling between economic growth and carbon emissions. Developed regions show strong decoupling, and the overall decoupling status improved in 2021-2022. (3) Emissions growth was influenced by energy intensity and economic activity, and transportation intensity was the main inhibitor for Type I cities and a driving force for other cities. Finally, recommendations for carbon emission reduction in the URT industry are proposed., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Polycyclic aromatic hydrocarbons (PAHs) and benzene, toluene, ethylbenzene, and xylene (BTEX) are the most persistent and toxic organic contaminants often found co-contaminated in anthropogenic and petrochemical industrial sites. Therefore, an experiment was performed for the safe biodegradation of benzene and benzo[a]pyrene (BaP) through thermally-enhanced biodegradation, and to explore the influence of elevated thermal treatments on microbial diversity and composition. The results revealed that elevated thermal treatments (15 to 45 °C) significantly enhanced the diversity of both bacteria and fungi. The composition analysis revealed that short-term and long-term elevated temperature conditions can directly enhance the specificity of microorganisms that play a crucial role in the biodegradation of benzene and BaP co-contaminated soil. Moreover, the indirect role of elevated temperature conditions on microbial compositions was through the fluctuations of soil properties, especially soil pH, moisture, TOC, potassium, phosphorous, total Fe, Fe(II), and Fe(III). In addition, the correlation analyses revealed that thermal exposure enhances the synergistic association (fungal-fungal, fungal-bacterial, bacterial-bacterial) of microbes to degrade the toxic contaminants and to cope with harsh environmental conditions. These results concluded that the biodegradation of benzene and BaP co-contamination was efficiently enhanced under the thermally-enhanced biodegradation approach and the elevation of temperature can affect the microbial compositions directly via microbial specificity or indirectly by influencing the soil properties., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier B.V. All rights reserved.)

Antibiotic resistance genes (ARGs) can be easily promoted by antibiotics, however, the structural effects of antibiotics on the proliferation of ARGs dynamic and the associated mechanisms remain obscure in, especially, activated sludge sequencing batch reactors. In the present study, the effects of 9 sulfonamides (SAs) with different structures on the proliferation dynamic of sulfonamide resistance genes (Suls) in the activated sludge sequencing batch reactors and the corresponding mechanisms were determined (30 days), and the results showed that the largest proliferation value (∆A R ) of Suls dynamic for SAs (sulfachloropyridazine) was approximately 2.9 times than that of the smallest one (sulfadiazine). The proliferation of Suls was significantly related to the structural features (minHBint6, SssNH, SHBd and SpMax2&#95;Bhm) that represent the biological activity of SAs. To interpret the phenomenon, a mechanistic model was developed and the results indicated that the biodegradation of SAs (T 1/2 ) rather than conjugative transfer frequency or mutation frequency tends to be the key process for affecting Suls proliferation. T 1/2 was proved to be dependent on the interactions between SAs and receptors (E binding ), the cleavage mode (bond dissociation energy), and the site of nucleophilic assault. Besides, the metagenomic analysis showed that SAs posed significant effect on antibiotic resistome and Tnp31 played a vital role in the proliferation of Suls. Overall, our findings provide important insight into a theoretical basis for understanding the structural effects of SAs on the proliferation of ARGs in SBR systems., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022. Published by Elsevier B.V.)

The effects of antibiotics on the proliferation of antibiotic resistant genes (ARGs) in WWTPs have drawn great attention in recent years. The effects of antibiotics on ARGs in the enhanced biological phosphorus removal (EBPR) system and its mechanisms, however, are still not well understood. In this study, EBPR systems were constructed using activated sludge to investigate the effects of ten commonly detected antibiotics in the environment on the proliferation of ARGs and the mechanisms involved. The results showed that the total abundance of ARGs increased to varying degrees with the addition of different antibiotics (0.05 mmol/L), and the top 30 ARGs increased by 271.1 % to 370.0 %. Mobile genetic elements (MGEs), functional modules, and the bacteria community were consistently related to the changes in ARGs. Refractory antibiotics, in particular, have a stronger promoting effect on transduction in the EBPR system. The insertion sequence common region (ISCR) and transposon (Tnp) were identified as crucial factors in the proliferation of ARGs. Moreover, the risk of polyphosphate accumulating organisms (PAOs) carrying ARGs in the presence of antibiotics should not be ignored. Our findings emphasize the potential efficacy of employing strategies that target the reduction of MGEs, regulation of cellular communication, and management of microbial communities to effectively mitigate the risks associated with ARGs., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023. Published by Elsevier B.V.)

Wastewater treatment plants (WWTPs) are a significant anthropogenic source of greenhouse gas (GHG), but the quantitative assessment of GHG emissions from WWTPs in vulnerable water areas under stricter discharge limits remains unclear. Herein, depending on a case WWTP in southern China, we investigated the impacts of discharge standard improvement and key drivers of GHG emissions using daily operating data. We demonstrated that the stricter discharge limits increased the total GHG emission intensity by 18.2 %, with direct emissions increasing more than indirect GHG emissions. The GHG emissions were negatively correlated with water quantity, showing the scale effect, which became more pronounced after the discharge standard improvement. Increasing influent chemical oxygen demand and total nitrogen concentrations significantly drove the variations in GHG emissions, which were accelerated under stricter discharge limits. This study provides insights into the evaluation of GHG emission from WWTPs in vulnerable water areas and carbon-neutral wastewater management policies., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier B.V. All rights reserved.)

Membrane separation technology has significant advantages for treating oil-in-water emulsions. Understanding the evolution of oil droplets could reveal the interfacial and colloidal interactions, facilitate the design of advanced membranes, and improve the separation performances. This review on the characteristic behavior and evolution of oil droplets focuses on the advanced analytical techniques, and the subsequent fouling as well as demulsification effects during membrane separation. A detailed introduction is provided on microscopic observations and numerical simulations of the dynamic evolution of oil droplets, featuring real-time in-situ visualization and accurate reconstruction, respectively. Characteristic behaviors of these oil droplets include attachment, pinning, wetting, spreading, blockage, intrusion, coalescence, and detachment, which have been quantified by specific proposed parameters and criteria. The fouling process can be evaluated using Hermia and resistance models. The related adhesion force and intrusion pressure as well as droplet-droplet/membrane interfacial interactions can be accurately quantified using various force analysis methods and advanced force measurement techniques. It is encouraging to note that oil coalescence has been achieved through various effects such as electrostatic interactions, mechanical actions, Laplace pressure/surface free energy gradients, and synergistic effects on functional membranes. When oil droplets become destabilized and coalesce into larger ones, the functional membranes can overcome the limitations of size-sieving effect to attain higher separation efficiency. This not only bypasses the trade-off between permeability and rejection, but also significantly reduces membrane fouling. Finally, the challenges and potential research directions in membrane separation are proposed. We hope this review will support the engineering of advanced materials for oil/water separation and research on interface science in general., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023. Published by Elsevier B.V.)

Agricultural biochar and arbuscular mycorrhizal fungi were used to promote the growth of Phragmites in the structural damaged and nutritional imbalanced littoral zone soils. Wheat straw biochar played a significant role in improving soil porosity and supplementing available phosphorus to 79.20 ± 3.20 mg/kg, compared with CK at 17.50 ± 0.88 mg/kg. The addition of Diversispora versiformis improved the plant net photosynthetic rate reaching up to 25.66 ± 0.65 μmol·m -2 ·s -1 , which was 36.60 % higher than CK. The combination of biochar and fungi contributed to the whole plant dry weight biomass of 32.30 % and 234.00 % higher than the single biochar or AMF amendment groups, respectively. Meanwhile, the analysis of microbial co-occurrence networks showed the most relevant networks node species were mainly Talaromyces, Chaetomiacea and Gemmatimonadetes etc. Root lipid metabolite of Glycerophospholines further proved that phosphorus utilization was also enhanced endogenously in the rhizosphere soil. These results indicate that the combination of biochar and arbuscular mycorrhizal fungi play synergic role in enhancing phosphorus utilization endogenously and exogenously., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier B.V. All rights reserved.)

Centralized sludge treatment plants (CSTPs) are implicated as strong hotspots of antibiotic resistance genes (ARGs). However, the knowledge gap on the fate of intracellular and extracellular ARGs (iARGs and eARGs), and the functionality of resistant hosts limit risk assessment and management of CSTP resistome. Here, the flow of iARGs and eARGs across treatment units and analyses of ARG hosts were systematically explored in three full-scale CSTPs using quantitative metagenomic approaches. We found that 29% of sludge ARGs could be removed, with iARGs being dominant in the produced biosolids. The treatment process significantly affected the variations of iARG and eARG abundance while no significant difference in composition between iARGs and eARGs was observed in CSTPs. 15% of 295 recovered genomes were identified as antibiotic-resistant hosts, among which Actinobacteriota tended to encode multiple resistance. The key functions of ARG hosts were relative to the biological organic removal (e.g., carbohydrates). There also existed relationships between certain resistance mechanisms and functional traits, indicating that ARGs might take part in the physiological process of microorganisms in the sludge treatment. These findings provide important insight into the differential resistome variations and host functionality, which would be crucial in the management of antibiotic resistance in CSTPs., (Copyright © 2022. Published by Elsevier Ltd.)

The separation of ultrafine oil droplets from wasted nanoemulsions stabilized with high concentration of surfactants is precondition for oil reuse and the safe discharge of effluent. However, the double barriers of the interfacial film and network structures formed by surfactants in nanoemulsions significantly impede the oil-water separation. To destroy these surfactant protective layers, we proposed a newly-developed polyethyleneimine micelle template approach to achieve simultaneous surface charge manipulation and morphology transformation of magnetic nanospheres to magnetic nanorods. The results revealed that positively charged magnetic nanospheres exhibited limited separation performance of nanoemulsions, with a maximum chemical oxygen demand (COD) removal of 50%, whereas magnetic nanorods achieved more than 95% COD removal in less than 30 s. The magnetic nanorods were also applicable to wasted nanoemulsions from different sources and exhibited excellent resistance to wide pH changes. Owing to their unique one-dimensional structure, the interfacial dispersion of magnetic nanorods was significantly promoted, leading to the efficient capture of surfactants and widespread destruction of both the interfacial film and network structure, which facilitated droplet merging into the oil phase. The easy-to-prepare and easy-to-tune strategy in this study paves a feasible avenue to simultaneously tailor surface charge and morphology of magnetic nanoparticles, and reveals the huge potential of morphology manipulation for producing high-performance nanomaterials to be applied in complex interfacial interaction process. We believe that the newly-developed magnetic-nanorods significantly contribute to hazardous oily waste remediation and advances technology evolution toward problematic oil-pollution control., (Copyright © 2021. Published by Elsevier B.V.)

Nitrogen pollution in water bodies is a serious environmental issue which is commonly treated by various methods such as heterotrophic denitrification. In particular, solid carbon source (SCS)-based denitrification has attracted widespread research interest due to its gradual carbon release, ease of management, and long-term operation. This paper reviews the types and properties of SCSs for different target water bodies. While both natural (wheat straw, wood chips, and fruit shells) and synthetic (polybutylene succinate, polycaprolactone, polylactic acid, and polyhydroxyalkanoates) SCSs are commonly used, it is observed that the denitrification performance of the synthetic sources is generally superior. SCSs have been used in the treatment of wastewater (including aquaculture wastewater), agricultural subsurface drainage, surface water, and groundwater; however, the key research aspects related to SCSs differ markedly based on the target waterbody. These key research aspects include nitrogen pollutant removal rate and byproduct accumulation (ordinary wastewater); water quality parameters and aquatic product yield (recirculating aquaculture systems); temperature and hydraulic retention time (agricultural subsurface drainage); the influence of dissolved oxygen (surface waters); and nitrate-nitrogen load, HRT, and carbon source dosage on denitrification rate (groundwater). It is concluded that SCS-based denitrification is a promising technique for the effective elimination of nitrate-nitrogen pollution in water bodies., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2021 Elsevier B.V. All rights reserved.)

Oily sludge is widely produced in the processes of petroleum exploitation, storage, transportation, and refining, and becomes more stable during aging. The interfacial stability of aging oily sludge hinders the recovery and disposal of oil resources. This review summarizes the interfacial film stability of aging oily sludge, which occurs through the formation of viscoelastic and rigid bilayer interfacial films between heavy components (asphaltenes and resins) and inorganic particles. The bilayer interfacial films enhance interfacial film strength and hinder the aggregation of droplets, contributing to the formation of a stable and high-viscosity oil-water-solid three-phase mixture. Recent demulsification technologies for reducing the stability of interfacial films have been classified as follows: removing heavy components, changing asphaltene aggregate structure, and reducing inorganic particle content. More efficient demulsification technologies are expected to be developed by deeply analyzing the microstructure and interfacial properties of asphaltenes and resins, as well as comprehensively studying the complex interactions among various components. This review constructs a bridge between the stability mechanism and the corresponding destabilization methods, which would promote future studies in aging oily sludge treatment., (Copyright © 2021. Published by Elsevier B.V.)

Magnetic particles were coupled with a flocculant to enhance the demulsification and separation of waste cutting emulsions. The optimal magnetic particle size and critical magnetic field conditions were investigated to achieve large-scale engineering application of magnetic demulsification separation for waste cutting emulsion treatment. The micro-scale magnetic particles were found to show comparable effects to nano-scale magnetic particles on enhancing the demulsification and separation of cutting emulsions, which are beneficial for broadening the selectivity of low-cost magnetic particles. The critical magnetic separation region was determined to be an area 40 mm from the magnetic field source. Compared to the flocculant demulsification, the magnetic demulsification separation exhibited a significant advantage in accelerating flocs-water separation by decreasing the separation time of flocs from 180-240 min to less than 15 min, compressing the flocs by reducing the floc volume ratio from 60%-90% to lower than 20%, and showing excellent adaptability to the variable properties of waste cutting emulsions. Coupled with the design of the magnetic disk separator, continuous demulsification separation of the waste cutting emulsion was achieved at 1.0 t/hr for at least 10 hr to obtain clear effluent with 81% chemical oxygen demand removal and 89% turbidity reduction. This study demonstrates the feasibility of applying magnetic demulsification separation to large-scale continuous treatment of waste emulsion. Moreover, it addresses the flocs-water separation problems that occur in practical flocculant demulsification engineering applications., (Copyright © 2021. Published by Elsevier B.V.)

Many kinds of antibiotics are continuously discharged into wastewater and typically cause a great decrease in sewage treatment performance, whereas mechanisms of differences in the impacts of commonly used antibiotics on phosphate removal are still elusive. Thus, an enhanced biological phosphorus removal (EBPR) system, as an effective method of phosphate removal, was developed, and its performance in the treatment of artificial wastewater containing antibiotics at short- (8 h) and long-term (15 days) exposure was investigated. The results show that phosphorus removal was consistently inhibited by the addition of antibiotics with a significant difference (P < 0.05). To interpret the phenomena, mechanistic equations were developed, and the results indicate that for short-term tests, the difference was mainly caused by the suppression of polyhydroxyalkanoate (PHA) degradation and the activity of polyphosphate kinase (PPK), resulting in the different inhibition of the soluble orthophosphorus (SOP) uptake process. For long-term tests, the difference in SOP uptake was principally caused by the inhibition of PHA degradation and the activity of PPK, whereas the difference in SOP release resulted from the inhibition of activities of exopolyphosphatase (PPX) and adenylate kinase (ADK). Moreover, micro-mechanisms of such inhibition were identified from molecular docking and electrostatic potential., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2021 Elsevier B.V. All rights reserved.)

An automatic calibration framework of water quality parameters for surface runoff during modeling with InfoWorks ICM was constructed. The framework is based on a genetic algorithm (GA) and fully considers the calibration sequence for multiple water pollutants, namely, total suspended solids (TSS), chemical oxygen demand (COD), total nitrogen (TN), and total phosphorous (TP). Meanwhile, four different objective functions including the Nash-Sutcliff efficiency coefficient (NSE), coefficient of determination (R 2 ), percentage error in the peak (PEP), and percentage bias (PBIAS) were selected as fitness evaluators for the GA. The framework was applied successfully to a specific area of Fuzhou in China, and the multi-objective results were compared with the single-objective results. The comprehensive indexes of TSS, COD, TN, and TP by multi-objective calibration were lower than that of the single-objective calibration in both scenarios. Compared with single-objective calibration, the iterations to reach the optimal value were shortened 9, 5, 13, and 15 iterations by multi-objective calibration. Therefore, the findings showed that the multi-objective function GA was more balanced and more efficient than the single-objective function GA. Then, the uncertainty of the model was evaluated by using the samples generated by automatic calibration, which provided a reliable basis for the subsequent application of the model. This framework can be applied to other programs through adjustments of the number and weight of objective functions according to the specific situation, which will make the modeling more efficient and accurate.

Woodchip bioreactors can effectively remove waterborne nitrates from subsurface agricultural drainage and prevent the eutrophication of receiving water, but rapid biofilm growth can severely reduce water flux and denitrification efficiency of this practice within a few years. Tourmaline minerals with thermal excitation could generate reactive oxygen species which would inhibit bacterial growth. In this study, laboratory scale woodchip bioreactors were set up to test the anti-clogging and denitrification efficiency of heated woodchips with tourmaline, heated woodchips without tourmaline, and unheated woodchips. The results showed that the heated tourmaline treatment could reduce the clogging and optimize the nitrate removal rate (47.6 g N/m 3 /day) under all three hydrologic retention times tested (1, 4, and 8 h). Dissolved oxygen and pH values fluctuated with the removal rate and temperature change, while temperature was identified as the key factor impacting the tourmaline treatment. The heated tourmaline treatment had the lowest biofilm growth (lowest DNA concentration), while the 16S rRNA and a higher abundance of nirS-, nirK-, and nosZ-encoding denitrifying bacteria (based on qPCR) confirmed the higher denitrification efficiency of the heated tourmaline treatment., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Water reclamation and ecological reuse is gradually becoming a popular solution to address the high pollutant loads and insufficient ecological flow of many urban rivers. However, emerging contaminants in water reuse system and associated human health and ecological risks need to be assessed. This study determined the occurrence and human health and ecological risk assessments of 35 emerging contaminants during one year, including 5 types of persistent organic pollutants (POPs), 5 pharmaceutical and personal care products (PPCPs), 7 endocrine disrupting chemicals (EDCs) and 18 disinfection by-products (DBPs), in a wastewater treatment plant (WWTP) and receiving rivers, as well as an unimpacted river for comparison. Results showed that most of PPCPs and EDCs, especially antibiotics, triclosan, estrogens and bisphenol A, occurred frequently at relatively high concentrations, and they were removed from 20.5% to 88.7% with a mean of 58.9% via WWTP. The highest potential noncarcinogenic and carcinogenic risks in different reuse scenarios were assessed using maximal detected concentrations, all below the acceptable risk limits, with the highest total combined risk value of 9.21 × 10 -9 and 9.98 × 10 -7 , respectively. Ecological risk assessment was conducted using risk quotient (RQ) method and indicated that several PPCPs, EDCs and haloacetonitriles (HANs) pose high risk (RQ > 1) to aquatic ecology in the rivers, with the highest RQ up to 83.8. The study suggested that ecological risks need to be urgently addressed by updating and optimizing the process in WWTPs to strengthen the removal efficiencies of emerging contaminants. The study can serve as a reference for safer water reuse in the future, while further studies could be conducted on the health risk of specific groups of people, exposure parameters in water reuse, as well as more emerging contaminants., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020. Published by Elsevier B.V.)

The increasing availability of water quality datasets has led to a greater focus on hydrologic and water quality analysis, thus requiring more efficient and accurate modelling methods. Data mining techniques have been increasingly used for water quality analysis and prediction of the concentration and load of nitrogen pollutants instead of more traditional simulation methods. In this study, we tested the multilayer perceptron (MLP), k-nearest neighbor (k-NN), random forest, and reduced error pruning tree (REPTree) methods, along with the traditional linear regression, to predict nitrate levels based on long-term data from six watersheds with different land-use practices in the midwestern United States. Both the concentration and load results indicated that REPTree had the best performance, with an R 2 of 0.61-0.85 and a relative absolute error of <75.8%. The different watershed types, however, influenced the performance of the data mining methods, where all four methods showed a higher accuracy for urban dominant watershed and lower accuracy for agricultural and forest watersheds. Out of these four methods, classification tree methods (REPTree and RF) performed better than cluster methods (MLP and k-NN) for agricultural and forested watersheds. Our results indicated that both the data structure based on the dominant land use and type of algorithmic method should be carefully considered for selecting a data mining method to predict nitrate concentration and load for a watershed., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

Nitrate reduction by zero-valent iron-based materials has been extensively studied. However, the aggregation of nanoparticles and the preference for unfavored ammonia products limit the application of this technology. To overcome this issue, this study introduced a novel synthesized nanoscale palladized zero-valent iron graphene composite (nZVI-Pd/NG) and explored its nitrate reduction efficiency. A nitrate removal rate of 97.0% was achieved after 120 min of reaction for an initial nitrate concentration of 100 mg N/L. The nitrogen gas selectivity was enhanced from 0.4% to 15.6% at the end point compared to nanoscale zero-valent iron (nZVI) particles under the same conditions. Further analyses revealed that zero-valent metal nanoparticles spread uniformly on the graphene surface, with a thin layer of iron (hydr)oxides dominated by magnetite. The nZVI-Pd/NG exhibited good catalytic activity with the associated activation energy of 17.6 kJ/mol being significantly lower than that with nZVI (42.8 kJ/mol). The acidic condition promoted a higher nZVI utilization rate, with the excess dosage of nZVI-Pd/NG ensuring a high nitrate removal rate for a wide pH range. This study demonstrates an improvement in nitrate reduction efficiency in a nZVI system by combining the exceptional properties of graphene and palladium.

Waste cutting emulsions are difficult to treat efficiently owing to their complex composition and stable emulsified structure. As an important treatment method for emulsions, chemical demulsification is faced with challenges such as low flocs-water separation rates and high sludge production. Hence, in this study, Fe 3 O 4 magnetic nanoparticles (MNPs) were used to enhance chemical demulsification performance for treating waste cutting emulsions under a magnetic field. The addition of MNPs significantly decreased the time required to attain sludge-water separation and sludge compression equilibrium, from 210 to 20 min. In addition, the volume percentage of sludge produced at the equilibrium state was reduced from 45% to 10%. This excellent flocculation-separation performance was stable over a pH range of 3-11. The magnetization of the flocculants and oil droplets to form a flocculant-MNP-oil droplet composite, and the magnetic transfer of the composite were two key processes that enhanced the separation of cutting emulsions. Specifically, the interactions among MNPs, flocculants, and oil droplets were important in the magnetization process, which was controlled by the structures and properties of the three components. Under the magnetic field, the magnetized flocculant-MNP-oil droplet composites were considerably accelerated and separated from water, and the sludge was simultaneously compressed. Thus, this study expands the applicability of magnetic separation techniques in the treatment of complex waste cutting emulsions., (Copyright © 2019. Published by Elsevier B.V.)

Phosphorus (P) is a limiting element causing eutrophication, and thus, its removal has elicited significant attention in recent years. In this study, a La(OH) 3 embedded nanorod loaded PVA/PEI crosslinked nanofiber membrane (LNPPM) was synthesized for phosphorus removal at a low concentration and under high flux conditions. Comparative tests demonstrated that an LNPPM exhibited a high phosphate adsorption capacity (165.9 mg P/g La) and performed well even under interference with the pH and coexisting ions (Cl - , SO 4 2- , NO 3 - , and F - ). Through a continuous adsorption test, LNPPM also showed a fast adsorption efficiency with a 73.7% capacity used for C/C 0  = 0.5 under a low concentration and high flux phosphate solution. Fourier transform infrared, X-ray diffraction, X-ray photoelectron spectroscopy, SEM-EDS, and high-resolution transmission electron microscopy analyses indicated that the La(OH) 3 nanorod intensively and uniformly embedded into the nanofibers, providing an ideal condition for phosphate adsorption. A mechanistic analysis showed that the ligand exchange played a vital role in the phosphate adsorption of LNPPM. A cost index (capacity/synthesis cost) comparison with typical super phosphate adsorbents also indicated that LNPPM (795 mg P/USD) could be a viable option owing to its simple synthesis procedure, low synthesis cost, and considerable capacity. This technique shows promise for use in most dephosphorization applications., (Copyright © 2019. Published by Elsevier B.V.)

Two de-lignified cellulose of loofah sponge and sawdust were applied in two ways to enhance the lipid production from oleaginous yeast using acetic acid. When 30 g/L of acetic acid was used as a carbon source, direct addition of de-lignified loofah sponge or sawdust increased the extracellular lipid content to 33.94% and 53.25%, respectively. The latter reduced the energy input of lipid extraction process from 0.86 to 0.57 GJ per ton of biodiesel production. To relieve the inhibition caused by 40 g/L acetic acid, immobilization of oleaginous yeast on de-lignified sawdust increased the lipid concentration and yield from 3.83 g/L, 0.18 g/g C to 7.15 g/L, 0.20 g/g C, respectively. These improvements occurred due to the cell-immobilized sawdust which play an important role in the loading of cells and adsorption of acetic acid. Immobilized cultivation also increased the fatty acid proportion of C18:1, thereby improving biodiesel performance., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

Organophosphorus pesticides (OPs) have been widely used to control agricultural insects. Soil acidification is a major problem in soil of intensive agricultural systems, especially in red soil with a low pH buffer capacity. However, the effects of soil acidification on the toxicity of pesticides are still unclear. In the present study, the toxicity of three OPs on E. fetida was determined at individual (14-day lethal test) and biochemical levels (antioxidative defence enzymes) by using acidified soils (pH = 5.5, 4.3 and 3.1). The results showed that the toxicity of tested OPs was slightly increased with the decrease of soil pH. To interpret the phenomena, an optimum Quantitative Structure Activity Relationship (QSAR) model was developed based on the toxicity mechanism and the partial least squares regression (PLS) method. The model indicated bioavailability and toxicodynamics are key factors of soil acidification affecting the toxicity of the OPs. Further results revealed the bioavailability of the OPs was strongly related to their hydrolysis and biodegradation character, whereas the effects of soil acidification on toxicodynamics were mainly caused by the interaction between the acetylcholinesterase (AchE) and the OPs. Results will increase understanding of the effects of soil acidification on the toxicity of pesticides and its mechanism., (Copyright © 2018. Published by Elsevier B.V.)

Low concentrations of acetic acid were used as carbon source to cultivate Cryptococcus curvatus MUCL 29819 for lipid production under high content of ammonia. Phosphorus limitation combined with initial pH regulation (pH = 6) weakened inhibition of free ammonia and promoted lipid accumulation. In batch cultivation, the produced lipid content and yield was 30.3% and 0.92 g/L, higher than those under unlimited condition (18.3% and 0.64 g/L). The content of monounsaturated fatty acid also increased from 37.3% (unlimited condition) to 45.8% (phosphorus-limited condition). During sequencing batch cultivation (SBC), the lipid content reached up to 51.02% under phosphorus-limited condition while only 31.88% under unlimited condition, which can be explained by the higher conversion efficiency of the carbon source to lipid. The total energy consumption including lipid extraction, transesterification and purification was 7.47 and 8.33 GJ under phosphorus-limited and unlimited condition, respectively., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

Nitrate and orthophosphate from agricultural activities contribute significantly to nutrient loading in surface water bodies around the world. This study evaluated the efficacy of woodchips and fly ash pellets in tandem to remove nitrate and orthophosphate from simulated agricultural runoff in flow-through tests. The fly ash pellets had previously been developed specifically for orthophosphate removal for this type of application, and the sorption bench testing showed a good promise for flow-through testing. The lab-scale horizontal-flow bioreactor used in this study consisted of an upstream column filled with woodchips followed by a downstream column filled with fly ash pellets (3 and 1 m lengths, respectively; both 0.15 m diameter). Using influent concentrations of 12 mg/L nitrate and 5 mg/L orthophosphate, the woodchip bioreactor section was able to remove 49-85% of the nitrate concentration at three hydraulic retention times ranging from 0.67 to 4.0 h. The nitrate removal rate for woodchips ranged from 40 to 49 g N/m 3 /d. Higher hydraulic retention times (i.e., smaller flow rates) corresponded with greater nitrate load reduction. The fly ash pellets showed relatively stable removal efficiency of 68-75% across all retention times. Total orthophosphate adsorption by the pellets was 0.059-0.114 mg P/g which was far less than the saturated capacity (1.69 mg/g; based on previous work). The fly ash pellets also removed some nitrate and the woodchips also removed some orthophosphate, but these reductions were not significant. Overall, woodchip denitrification followed by fly ash pellet P-sorption can be an effective treatment technology for nitrate and phosphate removal in subsurface drainage., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

Co-processing lime-dried sludge (LDS) in cement kilns is an appropriate technique to solve the problem of LDS disposal and promote the sustainable development for cement industry. However, there were limited studies that investigated the effects of feeding points on product quality and cement kiln emissions. In this study, simulated experiments were conducted by dividing the feeding points into high-temperature zones (HTZs) and raw mill (RM). Cement quality and major cement kiln emission characteristics were comprehensively investigated. The results showed that in terms of burnability, compressive strength and microstructure, the optimum co-processing amount of LDS were 9 wt% when feeding at RM, while 6% when feeding at HTZs. Meanwhile, the organic emissions of RM samples were mainly low environmental risk compounds of amides and nitrogenous heterocyclic compounds. Inorganic gaseous pollutions of NO X and SO 2 , respectively, were 8.11 mg/g DS and 12.89 mg/g DS, compared with 7.61 mg/g DS and 4.44 mg/g DS for HTZs. However, all the cement kiln emissions concentration were still much lower than standard requirements. Overall, RM had a bigger LDS co-processing capacity and higher, but acceptable, cement kiln emissions. Feeding LDS via RM could dispose larger amounts of sludge and provide more alternative materials for cement manufacturing.

The lower utilization ratios of high-content VFAs resulted in less lipid yield by the oleaginous yeast Cryptococcus curvatus ATCC 20509. In this work, increasing the inoculation concentration to OD600=5.1 improved the acetic acid utilization ratio (99.8%) and lipids production (4.63g/L) in mediums with 30g/L of acetic acid. For the higher acetic acid concentration (40g/L), increasing the nitrogen to carbon ratio (0.033) and raising the initial pH (pH=8) was superior over improvement in the inoculate, with the lipid production increased from 1.08g/L to 6.49g/L. Subsequently, mixed VFAs at concentrations of 30g/L and 40g/L were used as the carbon source to simulate waste-derived VFAs. High lipid production (4.82 and 7.45g/L, respectively) was correspondingly achieved with similar high lipid yield (0.187g/g). This study provides an effective strategy to enhance the bioconversion of high-content VFAs into microbial lipids., (Copyright © 2017. Published by Elsevier Ltd.)

Cell-surface functional groups (amino, carboxyl, hydroxyl, as well as phosphate) were chemically modified in various ways to enhance the demulsification capability of the demulsifying bacteria Alcaligenes sp. S-XJ-1. Results demonstrated that the demulsifying activity was significantly inhibited by amino enrichment with cetyl trimethyl ammonium bromide, amino methylation, hydroxyl acetylation, and phosphate esterification, but was gradually promoted by carboxyl blocking with increasing the extents of esterification. Compared with the raw biomass, an optimal esterification of carboxyl moieties enhanced the demulsification ratio by 26.5% and shortened the emulsion half-life from 24 to 8.8 h. The demulsification boost was found to be dominated by strengthened hydrophobicity (from 53° to 74°) and weakened electronegativity (from -34.6 to -4.3 mV at pH 7.0) of the cell surface, allowing the rapid dispersion and adsorption of cells onto the oil-water interface. The chemical modification of the functional groups on the biomass surface is a promising tool for the creation of a high-performance bacterial demulsifier.

According to the characteristics of the reverse osmosis concentrate (ROC) generated from iron and steel company, we used three sets of parallel horizontal subsurface flow (HSF) constructed wetlands (CWs) with different plants and substrate layouts to treat the high-salinity wastewater. The plant growth and removal efficiencies under saline condition were evaluated. The evaluation was based entirely on routinely collected water quality data and the physical and chemical characteristics of the plants (Phragmites australis, Typha latifolia, Iris wilsonii, and Scirpus planiculmis). The principal parameters of concern in the effluent were chemical oxygen demand (COD), total nitrogen (TN), and total phosphorus (TP). The results showed that the CWs were able to remove COD, TN, and TP from ROC. S. planiculmis was not suitable for the treatment of high-saline wastewater. The sequence of metals accumulated in CW plants was K>Ca>Na>Mg>Zn>Cu. More than 70% of metals were accumulated in the aboveground of P. australis. The CW filled with gravel and manganese ore and planted with P. australis and T. latifolia had the best performance of pollutant removal, with average removal of 49.96%, 39.45%, and 72.01% for COD, TN, and TP, respectively. The effluent water quality met the regulation in China. These results suggested that HSF CW planted with P. australis and T. latifolia can be applied for ROC pollutants removal.

Hormesis is an intriguing phenomenon that is characterized by low dose stimulation and high dose inhibition. Several traditional parameters, such as the concentration of the zero equivalent point (ZEP) and the maximal stimulatory effect (Y max ), have been used to characterize the zone of hormesis or the extent of the stimulatory effect. However, the characteristics of hormesis for chemicals cannot be quantified completely by one parameter, which is important to accurately compare the hormetic effects of chemicals and to describe the combined effects of chemical mixtures at low doses. In the present study, a novel parameter, termed the relative standard area of hormetic zone (Hor Area R ), was developed and proposed to quantify the hormetic effects (24h exposure) of nine metal ions (Cr 3+ , Cu 2+ , Mg 2+ , Cd 2+ , Fe 3+ , Ni 2+ , Zn 2+ , Co 2+ , Cs + ) towards Vibrio fischeri, both individually and as binary mixtures. The results indicate that Hor Area R can be used not only to accurately assess the hormetic effects and its relationship with structural characteristics but also to conveniently describe the combined effects of interactive mixtures at low dose. Thus, the Hor Area R parameter can quantitatively assess the hormetic effects and can offer a useful approach to perform environmental risk assessments of chemicals at low doses., (Copyright © 2016 Elsevier B.V. All rights reserved.)

Volatile fatty acid (VFA) production stimulated by saponin (SP), an environmentally friendly bio-surfactant, was investigated during sludge alkaline fermentation in laboratory studies and pilot applications. The combined use of SP and pH 9 condition significantly enhanced VFA production to approximately 425 mg COD/g VSS, which was 4.7-fold of raw sludge and 1.5-fold of sole pH 10 adjustment (the optimum pH for alkaline fermentation). Further results indicated that SP & pH 9 condition provided sufficient substrates for acidification and decreased the consumption of VFAs through methanogenesis. Moreover, SP accompanied by moderate alkaline condition (i.e. pH 9) showed weaker inhibitory effects on key enzyme activities and metabolic potential of acidification microorganisms than sole pH 10 adjustment. On this basis, a pilot-scale system involving anaerobic fermentation and anaerobic-anoxic-aerobic step-feed bioreaction tanks was established to study the potential of VFAs as supplementary carbon sources for wastewater treatment. The influent of the pilot system was sanitary wastewater characterized by low C/N ratios from a scenic rural area. After flocculation and nutrient precipitation, the fermentation supernatant was mixed with the influent at a volume ratio of 1:30. With this approach, nitrogen and phosphorus concentrations in effluent fulfilled the first-A wastewater discharge standard in China.

Antibiotics are categorized as pseudopersistent compounds because of their widespread use and continuous emission into the environment. Biological systems such as active sludge and biofilms are still the principal tools used to remove antibiotics in wastewater treatment plants (WWTPs). Consequently, it is important to determine the relationship between toxic effects in biological WWTPs and the structural characteristics of antibiotics. In the present study, toxic effects of 10 sulfonamides (SAs) on nitrification in an active sludge system were studied. The toxicity results (half-effective concentrations, EC50) indicated that the toxicity of sulfadimethoxine (SDM) is approximately 4 times as large as that of sulfadiazine (SD). Based on the toxicity mechanism and the partial least squares regression (PLS) method, an optimum quantitative structure-activity relationship (QSAR) model was developed for the test system. The mechanistic model showed that the pKa, the binding energies between SAs with dihydropteroate synthetase ( [Formula: see text] ) and the binding energies between SAs with ammonia monooxygenase ( [Formula: see text] ) are the key factors affecting the toxic effects of SAs on nitration process in active sludge system, following an order of importance of [Formula: see text] > [Formula: see text] >pKa., (Copyright © 2015 Elsevier B.V. All rights reserved.)

Photocatalysis is one of the most effective methods for treating antibiotic wastewater. Thus, it is of great significance to determine the relationship between degradation rates and structural characteristics of antibiotics in photocatalysis processes. In the present study, the photocatalytic degradation characteristics of 10 sulfonamides (SAs) were studied using two photocatalytic systems composed of nanophase titanium dioxide (nTiO2) plus ultraviolet (UV) and nTiO2/activated carbon fiber (ACF) plus UV. The results indicated that the largest apparent SA degradation rate constant (Kapp) is approximately 5 times as large as that of the smallest one. Based on the degradation mechanism and the partial least squares regression (PLS) method, optimum Quantitative Structure Activity Relationship (QSAR) models were developed for the two systems. Mechanistic models indicated that the degradation rule of SAs in the TiO2 systems strongly relates to their highest occupied molecular orbital (Ehomo), the maximum values of nucleophilic attack (f(+)x), and the minimum values of the most negative partial charge on a main-chain atom (q(C)min), whereas the maximum values of OH radical attack (f(0)x) and the apparent adsorption rate constant values (kad) are key factors affecting the degradation rule of SAs in the TiO2/ACF system., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

Surfactin, one of the most effective biosurfactants, has great potential in commercial applications. Studies on effective methods to reduce surfactin's production cost are always a hotspot in the research field of biosurfactants. The aim of this study was to reveal the role of Mn 2+ in promoting the biosynthesis of surfactin by Bacillus subtilis ATCC 21332, which could arise more targeted suggestions on surfactin yield promotion. In this study, B. subtilis was cultivated in media containing different Mn 2+ concentrations. The obtained results showed that the yield of surfactin gradually increased upon Mn 2+ addition (0.001 to 0.1 mmol/L) and achieved the maximal production of 1500 mg/L, which reached 6.2-fold of the yield obtained in media without Mn 2+ addition. Correspondingly, the usage ratios of ammonium nitrate were improved. When the Mn 2+ concentration was higher than 0.05 mmol/L, nitrate became the main nitrogen source, instead of ammonium, indicating that the nitrogen utilization pattern was also changed. An increase in nitrate reductase activity was observed and the increase upon Mn 2+ dosage had a positive correlate with nitrate use, and then stimulated secondary metabolic activity and surfactin synthesis. On the other hand, Mn 2+ enhanced the glutamate synthase activity, which increased nitrogen absorption and transformation and provided more free amino acids for surfactin synthesis.

Three conventional coalescence filters including walnut shells (WS), polystyrene resin particles (PR), and quartz sand (QS) were compared with bamboo charcoal (BC) to treat oily wastewater in a coalescence system process. The results showed the order of oil removal efficiency was QS>BC>WS>PR. To improve the oil removal efficiency of BC further, six types of modified BC were prepared. The results showed that the modified BC using silane coupling agent (SCA) significantly increased oil removal efficiency, but the other types (including the use of NaOH, HNO3, H2O2, FeCl3 and ultrasound) of modified BC exhibited nearly the same level of efficiency as that of pure BC. Infra-red, X-ray diffraction, scanning electron microscopy, and the contact angle for modified BC were measured to reveal the modified mechanism. It was found that the higher oil removal efficiency of the SCA-modified BC occurred due to the changed crystal structure of the BC and the increase in its surface hydrophobicity, which resulted in higher oil removal efficiency. Therefore, modified bamboo charcoal is an attractive filter candidate for oil removal in a coalescence system process.

Eutrophication of raw water results in outbreaks of algae, which hinders conventional water treatment. In this study, high density microbubble layers combined with micro-flocculation was adopted to remove algae from urban landscape water, and the effects of pressure, hydraulic loading, microbubble layer height and flocculation dosage on the removal efficiency for algae were studied. The greatest removal efficiency for algae, chemical oxygen demand, nitrogen and phosphorus was obtained at 0.42 MPa with hydraulic loading at 5 m/h and a flocculation dosage of 4 mg/L using a microbubble layer with a height of 130 cm. Moreover, the size, clearance distance and concentration of microbubbles were found to be affected by pressure and the height of the microbubble layer. Based on the study, this method was an alternative for algae separation from urban landscape water and water purification.

Generally, biofilm-supporting carriers in biological contact oxidation processes are made from thermoplastic polymers, which cause potential ecological damage because of the low biodegradation and high accumulation in organisms. Thus, four bamboo-based fibers, bamboo primitive fiber, bamboo fiber, bamboo charcoal fiber (BBF) and bamboo charcoal-cotton blending fiber (BCBF), were used as carriers and compared with two commercial carriers (vinylon (VY) and polypropylene (PP)) in a biological contact oxidation process system with the goal to develop a biodegradable and sustainable biofilm medium. Under steady state conditions, pollutants (chemical oxygen demand and NH4(+)-N) in stage 1 (days 1-29, hydraulic retention time (HRT) = 12 h) were efficiently removed with a removal efficiency ranging from 85 to 95%. In stage 2 (days 30-53, HRT = 4-12 h), the pollutant-removal efficiency of four reactors (BBF, BCBF, VY and PP) were nearly indistinguishable and were higher than the two other reactors, especially when the HRT was set at 4 h (days 46-53). Consequently, two optimized bamboo-based fibers (BBF and BCBF) can be developed as biofilm carriers for wastewater treatment in the future. Furthermore, studies demonstrated that the biofilm development difference showed good correlation with their specific area and relative oxygen content but not with their tenacity and antimicrobial activity.

Biodemulsifiers are environmentally friendly agents used in recycling oil or purifying water from emulsion, yet the demulsifying feature of cell-surface composition remains unclear. In this study, potentiometric titration, attenuated total reflectance-Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and matrix-assisted laser desorption/ionization-time-of-flight mass spectrometry were combined to characterize cell-surface chemical composition of demulsifying strain Alcaligenes sp. S-XJ-1 cultivated with different carbon sources. Cells cultivated with alkane contained abundant elemental nitrogen and basic functional groups, indicating that their surface was rich in proteins or peptides, which contributed to their highest demulsifying efficiency. For cells cultivated with fatty acid ester, the relatively abundant surface lipid contributed to a 50% demulsification ratio owing to the presence of more acidic functional group. The cells cultivated with glucose exhibited a high oxygen concentration (O/C ∼0.28), which indicated the presence of more polysaccharides on the cell surface. This induced the lowest demulsification ratio of 30%. It can be concluded that cell surface-associated proteins or lipids other than the polysaccharide of the demulsifying strain played a positive role in the demulsification activity. In addition, the cell-surface oligoglutamate compounds identified in situ were crucial to the demulsifying capability.

The main goal of this work was to analyze the effect of surface substances on demulsifying capability of the demulsifying strain Alcaligenes sp. S-XJ-1. The demulsifying substances were successfully separated from the cell surface with dichloromethane-alkali treatment, and exhibited 67.5% of the demulsification ratio for water-in-kerosene emulsions at a dosage of 356mg/L. FT-IR, TLC and ESI-MS analysis confirmed the presence of a carbohydrate-protein-lipid complex in the demulsifying substances with the major molecular ions from mass-to-charge ratio (m/z) 165 to 814. After the substances separated, the cell morphology changed from aggregated to dispersed, and the concentration of cell surface functional groups decreased. Cell surface hydrophobicity and the ability of cell adhesion to hydrophobic surface of the treated cells was also reduced compared with original cell. It was proved that the demulsifying substances had a significant effect on cell surface properties and accordingly with demulsifying capability of Alcaligenes sp. S-XJ-1., (Copyright © 2013 Elsevier Ltd. All rights reserved.)

Exploration of biodemulsifiers has become a new research aspect. Using waste frying oils (WFOs) as carbon source to synthesize biodemulsifiers has a potential prospect to decrease production cost and to improve the application of biodemulsifiers in the oilfield. In this study, a demulsifying strain, Alcaligenes sp. S-XJ-1, was investigated to synthesize a biodemulsifier using waste frying oils as carbon source. It was found that the increase of initial pH of culture medium could increase the biodemulsifier yield but decrease the demulsification ratio compared to that using paraffin as carbon source. In addition, a biodemulsifier produced by waste frying oils and paraffin as mixed carbon source had a lower demulsification capability compared with that produced by paraffin or waste frying oil as sole carbon source. Fed-batch fermentation of biodemulsifier using waste frying oils as supplementary carbon source was found to be a suitable method. Mechanism of waste frying oils utilization was studied by using tripalmitin, olein and tristearin as sole carbon sources to synthesize biodemulsifier. The results showed saturated long-chain fatty acid was difficult for S-XJ-1 to utilize but could effectively enhance the demulsification ability of the produced biodemulsifier. Moreover, FT-IR result showed that the demulsification capability of biodemulsifiers was associated with the content of C=O group and nitrogen element.