Removal of polycyclic aromatic hydrocarbons from offshore produced water by advanced oxidation technologies

As the largest waste stream from offshore oil and gas industry, offshore produced water contains dissolved toxic organic pollutants that are hard to be removed by conventional wastewater treatment technologies. Among those pollutants, polycyclic aromatic hydrocarbons (PAHs) are of growing concern due to their high toxicity and persistence in the marine and coastal environments. Removal of PAHs from produced water before disposal is thus essential for offshore oil and gas production. However, the offshore operation and facilities (e.g., platforms and ships) usually have many special technical and economic constraints that limit the applications of many treatment technologies. Since advanced oxidation processes (AOPs) are featured with high cost-efficiency, small footprints, and eco-friendliness which well match with the requirements of offshore operation and present a promising treatment option for offshore wastewater (e.g., produced water). However, limited research efforts have been reported in investigating AOPs’ mechanisms, performance and applicability in treating offshore produced water. In order to help fill the knowledge and technical gaps, this research aimed at development of advanced oxidation technologies for removal of PAHs from offshore produced water treatment and examination of the oxidation processes and kinetics, and effluent toxicity and biodegradability. To ensure efficient, reliable, and acurate analysis results, a refined analytical method, Vortex and Shaker Assisted Liquid-liquid Microextraction (VSA-LLME), was first developed, tested and adopted in the analysis of 16 priority PAHs recommended by U.S. Environmental Protection Agency. Under the optimized condition, the enrichment factors ranged from 68 to 78. The recoveries of the method were 74 to 85%, and the limits of detection were as low as 2 to 5 ng/L. The linearity results (R² values) for 16 PAHs were all above 0.99 with the relative standard deviations (RSD%) of 6 to 11%. This method also creatively utilized the organic constitutes in produced water as dispersive solvents to reduce the solvent consumption. Its straightforward procedure and excellent performance showed a strong potential for application in research and regulatory and industrial practice. The photolysis of 16 PAHs in offshore produced water was then thoroughly investigated in this research. The results indicated much more complex kinetics in the removal of PAHs from produced water than those in stilled water, mianly due to the complex chemical constitutions of the substrate. The experiment disclosed the unique mechanisms including direct photolysis, dynamic light screening, and radical induced organic synthesis. A novel kinetic model involving dynamic light screening was developed and approved to support the mechanism analysis, and a semi-empirical model was also established to simulate the photolysis process. The proposed mechanisms and kinetics not only helped answered some scientific questions but also showed strong practical significance for further AOP development and applications. The performance of ozonation in removing polycyclic aromatic hydrocarbons (PAHs) from offshore produced water (OPW) was studied. The experimental results showed that ozone dose had positive effect due to enhancement in ozone decomposition, and radical yield. On the other hand, the removal was suppressed at increased bubble size and pH, which may be attributed to the reduction of interfacial area as well as stronger radical scavenging effect, respectively. Microtox tests showed that the acute toxicity of OPW was reduced after ozonation, which was highly correlated with the removal of PAHs. Such reduction was inhibited at high ozone doses, possibly due to the formation of disinfection by-products via reactions with halogens. As compared to control, ozonated OPW had higher oxygen uptake and less organic residual after biodegradation, indicating more bioavailable organics were formed after ozonation. Results from this study can be used as good references for designing new or upgrading existing OPW treatment systems using ozonation. Based on the experimental results, the three major mechanisms affecting the PAHs removal through AOP treatment were proposed in the first time. Novel kinetic models based on the dynamic oxidant competitiveness was developed and validated. The model was able to simulate the oxidation processes, quantify the effects of different operational parameters. The testing result also indicated that insufficient treatment could lead to carcinogenetic by-products. On the other hand, proper advanced oxidation technologies could significantly increase biodegradability, showing strong potential of combining with conventional biological treatment in practice

A Multiple-stage Simulation-Based Mixed Integer Nonlinear Programming Approach for Supporting Offshore Oil Spill Recovery with Weathering Processess

As one of the most commonly used technologies in offshore oil spill response, skimming is facing challenges in recovering the spilled oil in the north region due to cold weather and harsh marine conditions. It is valuable to simulate and optimize the skimming process to improve efficiency of oil skimming during emergency response especially in harsh offshore environments. However, no studies have reported on integrating optimization and simulation approaches to support the offshore oil spill recovery by skimmers. This study developed a multiple-stage simulation based mixed integer nonlinear programming (MSINP) approach to provide sound decisions for skimming spilled oil in a fast, dynamic and cost-efficient manner, which is especially helpful to harsh environments. In the case study, regression models were developed to simulate the efficiencies of two drum skimmers based on the referenced performance tests. The models were further integrated with the optimization methods to determine the optimal strategy to achieve the maximum oil recovery with constraints of time and resources. The results indicated a 96% recovery efficiency based on the optimal settings. Furthermore, the approach was also tested with the integration of the oil weathering processes (e.g., evaporation, emulsification, and dispersion). The results indicated that with the consideration of evaporation and dispersion, in order to achieve the maximum oil recovery, the optimal setting for the oil recovery would be 5 sets of SK1 and 15 sets of SK2, yielding an oil recovery efficiency of 91.5%. The proposed approach was able to efficiently incorporate the regression models and optimization into the same framework and to support efficient skimming for offshore oil spills. The MSINP approach can timely and effectively support offshore oil recovery operations under dynamic conditions and therefore provide expeditious decision-making support during offshore oil spill response in harsh environments

An innovative total temporomandibular joint prosthesis with customized design and 3D printing additive fabrication: a prospective clinical study

Abstract Background Total temporomandibular joint (TMJ) prosthesis is an effective and reliable method of joint reconstruction. However, there is still an urgent need to design a new TMJ prosthesis because of no commercially available TMJ prosthesis appropriate for the clinical application on the Chinese population. This study was introduced to prospectively confirm the safety and effectiveness of a new TMJ prosthesis with customized design and 3D printing additive fabrication in clinical application. Methods Patients with unilateral end-stage TMJ osteoarthrosis were recruited in this study from Nov 2016 to Mar 2017. Computed tomography scans for all patients were obtained and transformed into three-dimensional (3D) reconstruction models. The customized TMJ prosthesis consisted of three components including the fossa, condylar head, and mandibular handle units, which were designed based on the anatomy of the TMJ and were fabricated using the 3D printing technology. The prominent characters of the prosthesis were the customized design of the fossa component with a single ultra-high-molecular-weight polyethylene and the connection mechanism between the condylar head (Co–Cr–Mo alloy) and mandibular handle components (Ti6Al4 V alloy). The clinical follow-up, radiographic evaluation and laboratory indices were all done to analyze the prosthesis’ outcomes in the clinical application. Results 12 consecutive patients were included in the study. There were no complications (infection of the surgical wound, damage of liver and kidney, displacement, breakage, or loosening of the prosthesis) found after surgery. Pain, diet, mandibular function, and maximal interincisal opening showed significant improvements after surgery. But the lateral movement was limited to the non-operated side and the mandible deviated towards the operated side on opening mouth following surgery. Conclusions The presented TMJ prosthesis is considered an innovative product in TMJ Yang’s system, which is unique compared to other prostheses for the special design and 3D printing additive manufacture. Moreover, the prosthesis is very safe and efficient for clinical use. Trial registration Prospective reports on Chinese customized total temporomandibular joint prosthesis reconstruction cases, ChiCTR-ONC-16009712. Registered 22 Nov 2016, http://www.chictr.org.cn/showproj.aspx?proj=1609

Development and validation of a nomogram for predicting severe respiratory syncytial virus-associated bronchiolitis

Abstract Background Respiratory syncytial virus (RSV) is the most common cause of bronchiolitis and is related to the severity of the disease. This study aimed to develop and validate a nomogram for predicting severe bronchiolitis in infants and young children with RSV infection. Methods A total of 325 children with RSV-associated bronchiolitis were enrolled, including 125 severe cases and 200 mild cases. A prediction model was built on 227 cases and validated on 98 cases, which were divided by random sampling in R software. Relevant clinical, laboratory and imaging data were collected. Multivariate logistic regression models were used to determine optimal predictors and to construct nomograms. The performance of the nomogram was evaluated by the area under the characteristic curve (AUC), calibration ability and decision curve analysis (DCA). Results There were 137 (60.4%) mild and 90 (39.6%) severe RSV-associated bronchiolitis cases in the training group (n = 227) and 63 (64.3%) mild and 35 (35.7%) severe cases in the validation group (n = 98). Multivariate logistic regression analysis identified 5 variables as significant predictive factors to construct the nomogram for predicting severe RSV-associated bronchiolitis, including preterm birth (OR = 3.80; 95% CI, 1.39–10.39; P = 0.009), weight at admission (OR = 0.76; 95% CI, 0.63–0.91; P = 0.003), breathing rate (OR = 1.11; 95% CI, 1.05–1.18; P = 0.001), lymphocyte percentage (OR = 0.97; 95% CI, 0.95–0.99; P = 0.001) and outpatient use of glucocorticoids (OR = 2.27; 95% CI, 1.05–4.9; P = 0.038). The AUC value of the nomogram was 0.784 (95% CI, 0.722–0.846) in the training set and 0.832 (95% CI, 0.741–0.923) in the validation set, which showed a good fit. The calibration plot and Hosmer‒Lemeshow test indicated that the predicted probability had good consistency with the actual probability both in the training group (P = 0.817) and validation group (P = 0.290). The DCA curve shows that the nomogram has good clinical value. Conclusion A nomogram for predicting severe RSV-associated bronchiolitis in the early clinical stage was established and validated, which can help physicians identify severe RSV-associated bronchiolitis and then choose reasonable treatment