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• Positively charged magnetic nanorod was synthesized by PEI micelle induction. • Transformation of nanosphere to nanorod improved separation of nanoemulsion by 45%. • Nanorod enhanced destruction of surfactant interfacial-film and network structure. 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. [Display omitted] [ABSTRACT FROM AUTHOR]

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 (R2), 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. [ABSTRACT FROM AUTHOR]

Abstract Waste cutting emulsions have high oil concentration, complex components, and strong stability, making them extremely difficult to dispose of. Efficient separation of oil and water is key to disposing of such emulsions. In this study, magnetic nanoparticles (MNPs) were applied in different ways to the membrane separation process to form four coupling processes for emulsion treatment. Compared to direct ultrafiltration, the four coupling processes showed improved performance in chemical oxygen demand (COD) rejection and flux for sample waste cutting emulsions. In particular, the flux of the optimal process was 83 LMH, which was 41.5 times greater than the control process. The interactions between MNPs and emulsions, such as coalescence, coating, and migration under a magnetic field, were also studied. We believe that the introduction of MNPs actively affected the membranes; the MNPs avoided direct oil-membrane contact via the coating of oil drops and a cake layer that formed on the membrane surface, which then enhanced ultrafiltration and improved flux significantly. Highlights • Various ultrafiltration processes coupled with MNPs for treating emulsions. • The effects of MNPs on oil droplets included coating, coalescence and migration. • Coupling process significantly improved the flux for waste cutting emulsions. • Coat of oil drops and cake layer formed by MNPs helped to reduce membrane fouling. [ABSTRACT FROM AUTHOR]

The water quality of Yapu River flowing into Lake Taihu was monitored for one year and the effects of substrate, configuration, hydraulic retention time (HRT) and temperature on nitrogen removal were evaluated in five pilot-scale horizontal subsurface-flow-constructed wetlands (CWs). Additionally, the impact of adding external carbon on nitrogen removal was investigated. Yapu River was shown to be eutrophic, with a low C/N ratio (COD/TN ≤ 1.5) and the main pollutant was total nitrogen (TN ≥ 2 mg/L). CWs with substrates of combined gravel-zeolite and gravel-ceramsite showed higher ammonium nitrogen (-N) and chemical oxygen demand (COD) removal efficiencies than the CWs with gravel substrates. Trapezoidal CWs showed improved dissolved oxygen in the front when compared with the rectangular CWs, enabling complete nitrification. A longer HRT (four days) improved the removal efficiencies of organics, nitrogen, and phosphorus. CWs performed better during the warm period. Moreover, addition of 400 g cattail litter during winter led to increased influent of COD. The average removal efficiencies of-N and TN were increasing up to 90.5 and 85.3%, respectively. [ABSTRACT FROM AUTHOR]

The combined sewer overflows (CSO) pollution has caused many serious environmental problems, which has aroused a worldwide concern. Traditional interception-storage measures, which exhibit the disadvantages of the larger storage tank volume and the low concentration, cannot efficiently control the CSO pollution. To solve this problem, a water quality-based double-gate control strategy based on the pollution based real-time control (PBRTC) rule was proposed, and the chemical oxygen demand (COD) concentration was taken as the control index. A case study was carried out in Fuzhou, China as an example, in which the hydraulic and water quality model were constructed to evaluate two schemes. According to the results, compared to the traditional scheme, the double-gate scheme can not only reduce the storage tank volume by 1515 m3, but also increase the average COD interception rate by 1.84 times, thus ensuring the effective and stable operation of the facility. Furthermore, the traditional scheme and the double-gate scheme were evaluated under design rainfall beyond the design return period, which confirmed the high performance of the double-gate scheme in controlling CSO pollution. [ABSTRACT FROM AUTHOR]

In view of problems such as the poor control effect of combined sewage pollution caused by traditional intercepting weir and the limited extension of the urban drainage model, which needs a large amount of basic data, this paper not only studied the characteristics of mixed-flow pollution via the urban drainage model but also simulated and optimized 6 interception control strategies and proposed a water quality interception strategy based on the pollution concentration of combined sewage. The results showed that, compared with the traditional interception weir, the interception control strategy of rainwater discharge based on the mixed pipe network model can obviously improve the control rate of various pollutants and reduce the interception amount required for pollution control. Through optimization of the interception based on water quality control by the combination of chemical oxygen demand (COD) and NH4-N, the interception rate was improved by 10.9% to 56.1% in contrast to the traditional interception weir and the closure water volume was reduced by 1432–6154 m3, which effectively improved the reliability and economy of the interception. [ABSTRACT FROM AUTHOR]