Municipal wastewater treatment plants (WWTPs) are recognized as key recipients of microplastics (MPs), with polyethylene terephthalate (PET) being among the most prevalent types in sewage. However, the systemic impact of PET MPs on integrated biological-membrane systems-especially their role in microbial ecology and membrane fouling-remains poorly understood. Therefore, the influence of PET MPs on the performance, microbial community and membrane fouling in a sequencing-batch membrane bioreactor (SMBR) was evaluated in this study. Based on the results, adding PET MPs decreased the MLSS from around 5000 mg/L to 4500 mg/L whereas the MLVSS/MLSS remain basically consistent. The SV30 and SVI increased rapidly to 76 % and 173.2 mL/g on the 3rd day (from 64 % and 128.3 mL/g on the 1st day) of adding PET MPs, however, they could be restored in the following days. For pollutants removal, the COD and NH4+-N removal were initially negatively affected but gradually recovered after several days of operation. The addition of PET MPs enhanced denitrification, resulting in a decrease in the effluent TN concentration from 15.1 ± 4.9 mg/L to 10.4 ± 4.4 mg/L. PET MPs changed microbial community structure and decreased the abundance of dominant bacteria and species diversity in activated sludge. Arenimonas and Sphingopyxis had strong relationships with PET MPs addition. PET MPs addition exacerbated membrane biofouling, and the microbial diversity on membrane at was basically consistent with activated sludge whereas the abundance changed significantly. This research provides a comprehensive understanding of how PET MPs affect the performance of integrated biological-membrane systems.

An improved wave-plate demister equipped with vortex generators (VGs) has been proposed for wet flue gas desulfurization systems (WFGD) in this work. Numerical and experimental methods were used to evaluate the effect of VGs on the separation of small droplets. Five types of wave-plate demister with different VGs were analyzed. The vortex generators in question included rectangular plates, semi-elliptical plates, square tubes, round tubes, and triangular tubes, respectively. In order to explain the strengthening mechanism, the distribution of flow field, secondary flow, and droplet trajectory were shown, and the effect of VGs on the flow field in the demister was discussed in depth. The simulation results show that the separation performances of the demisters with VGs were significantly improved over that of the initial demister, and the accompanying pressure drop was small. For the vortex generators studied, the rectangular plate fully demonstrated its superior separation performance, followed by semi-elliptical plate. The strengthening effect of VGs was tested through experiments. Experimental data reveal that the average droplet diameter (D50) at the outlet of the demister with a vortex generator can be reduced to 23.13 μm, whereas this value for the initial demister can be maintained at 32.07 μm. Moreover, compared with the original demister 0.81, the overall separation efficiency of the improved demister was improved to 0.92.

In controlled ecological life support system (CELSS), the water, oxygen, food and other life-support materials should be provided through material closure and circulation. Monovalent mineral salts were one kind of essential life-support substances for astronaut. However, few studies were focus on their recovery in CELSS. In this study, nanofiltration (NF) was used to investigate the feasibility of separating and recovering monovalent mineral salts from urine in CELSS by two membranes of DL and NF3. Results showed that the DL had higher flux and better monovalent ion separation efficiency (both the S-cation and S-anion were lower) than the NF3. The organics in NF permeate was mainly urea which could be hydrolyzed into NH4+-N in natural. Under operation pressure of 8 bar, cross-flow velocity of 0.8 m/s, pH of 6.0, volume reduction factor (VRF) of 4.0 and through storing for 72 h, the monovalent ions could be separated effectively with multivalent ions and organics. The main component of the solid part in the product solution were Na+, K+, and Cl-, which accounted for 26.32%, 18.00% and 49.96%, respectively. The results of this study suggested that recovery of mineral salt of NaCl and KCl from urine in CELSS by nanofiltration was feasible.

Spiral separator with punched holes was numerically analyzed and the correlation between structural variables and performance index was obtained based on the response surface method. Pitch, diameter, pipe length, and inlet velocity were selected as investigated variables, and the separation efficiency and pressure drop were chosen as objective functions. The results demonstrated that increasing the pitch or reducing the diameter results in greater separation efficiency. Pressure drop factor rises with the increase of vane diameter and the decrease of the pitch. Pitch, pipe length, and inlet velocity all have positive correlations with the separation efficiency. The optimization results were obtained by the Non-dominated Sorting Genetic Algorithm-II. These optimal points achieve greater separation efficiency and less pressure drop. Compared with original design, the separation efficiency of optimal point is enhanced by 1.92%–6.46%, while EU is reduced by 41.83%–58.18%. The maximal separation efficiency of optimal points achieves 0.99 with EU of 4.

In this study, numerical simulations were carried out to examine the performance of the cyclone separator with different fin diameter ratios (FDRs) and porosities on the fins. As three key indicators, removal efficiency, pressure drop and dimensionless factor (Eu) were investigated and then corresponding mechanisms of flow and separation were analyzed by discussing velocity, turbulent kinetic energy and pressure distribution. The results showed that separation and flow performances of separators kept stable for FDR less than (or equal to) 7/10. On the other hand, with the increase of the porosity, the separation efficiency and pressure drop suffered drastic losses. Compared with FDR = 1, the removal efficiency of FDR= 2/5 decreased by 6.7 percentage points (Eu was reduced by 23.5%). In addition, the removal efficiency of porosity = 0.2 was 9.2 percentage points less than that of porosity = 0 (Eu was reduced by 22.2%). Therefore, cyclone separator with FDR= 2/5 or porosity =0.2 was recommended for low flow resistance requirements. Flow field analysis found that the weakening of the flow of the spiral fins leads to the attenuation of the tangential velocity values in the flow field downstream of the fins. Furthermore, the change of the local velocity distribution in the flow field, such as the increase of the tangential velocity, is beneficial to the increase of the demisting efficiency of the spiral mist eliminator. At the same time, it also leads to greater flow resistance. (C) 2018 Published by Elsevier B.V. on behalf of Taiwan Institute of Chemical Engineers.

Solar‐aided coal‐fired power generation (SAPG) has been attracting more and more attentions in recent years. However, the multi‐objective optimization of SAPG system considering off‐design work conditions has not been fully studied. In this paper, a general system integration optimization method (GIOM) has been developed for integration schemes optimization, and Nondominated Sorting Genetic Algorithm‐II (NSGA‐II) algorithm is used for multi‐objective optimization of SAPG system. As a case study, a SAPG system that refers to a real 600 MWe supercritical coal‐fired power plant is optimized based on a typical day. By simultaneous optimization of both initial investment (P) and solar net electric generation (Esolar), the solar subsystem design schemes are optimized as Pareto optimal set. At last, to maximum Esolar/P, the final design scheme is selected from the Pareto optimal set, whose Esolar and P are 237.6 MWh and 113.5 M$, respectively. The results show that, the final design scheme is a heliostat field with instantaneous optical efficiency of 63.24% at the design point, the receiver power rating is 133 MWt, the tower height is 136.6 m, and distances of successive rows of the three zones are 13.6, 17.7, and 24.5 m, respectively. A larger or smaller size of solar subsystem is considered to be uneconomical.

Many procedures have been developed to design and optimize a heliostat field, however it is a rather challenging work partly because many influencing factors of a heliostat optical efficiency, especially the shading and blocking efficiency, are computationally intensive. And it's difficult to judge whether a heliostat field layout is an ideal design intuitively and reliable. In this paper, two concise and accurate analytic geometry methods (AGM-I and AGM-II) are developed to identify the heliostats with the possibilities of shadowing or blocking a given heliostat firstly. The results compared with the Sassi method and bounding sphere & Sassi method show that the same accurate results are obtained while the computational time is significantly reduced by 32% and 23%, respectively. Then an intuitive approach is proposed to optimize and evaluate the rationality of a heliostat field layout by applying the maximum optical efficiency map (MOEM). Finally, a heliostat field based on the Gemasolar plant is studied, whose optical efficiency is optimized and evaluated by the proposed methods. Compared with the un-optimized result and the result optimized by using the reference method, the MOEM optimization result of the heliostat field with higher instantaneous optical efficiency and annual optical efficiency is more reasonable.

通过数值模拟研究了平板、椭圆板、圆管、方管和三角管5种涡发生器分别安装于湿法烟气脱硫系统折流板除雾器中的除雾效率与压降.采用欧拉-拉格朗日方法分别求解气相-液相运动状态,入口流速Uin为3～6m/s,液滴直径范围2～80μm.结果表明,平板的除雾效率与压降增大最多,Uin=3m/s时,除雾效率相比无涡发生器高31.98％,压降高30Pa.平板对2μm液滴具有较高的除雾效率,最大为34.88％,比无涡发生器高20.81％.椭圆板Uin=3m/s时除雾效率比无涡发生器增加29.14％,压降升高20.47Pa.圆管、方管和三角管的总除雾效率分别高达95.05％、97.49％和96.48％.压降方面,方管为无涡发生器的4.18倍,圆管和三角管分别为2.05倍和2.79倍.另外,考察了椭圆板攻角的影响.在相同Uin下,除雾效率随着攻角的增加而增大,50°的椭圆板除雾效率为97.09％～99.15％.攻角对2μm液滴的分级除雾效率影响不大.压降随着攻角的增大而增加,Uin=4m/s时,攻角从0°增加到50°,压降从25.3Pa增加到92.78Pa.椭圆板因其迎流面积与长宽比的匹配以及流线型产生了较多涡流,具有良好的强化除雾效率效果以及较小的压降.

Solar aided coal-fired power generation (SAPG) has been attracted more and more attentions in recent years. However, its integration and optimization is a rather challenging work. Most of the studies are based on the researches of one or several certain schemes, and no general system integration optimization method (GIOM) considering all possibilities has been proposed. In this paper, a general system integration optimization model is developed, which is configured with 8 virtual molten salt heat exchangers (FHms) and used to simulate any scheme of different integration locations and heat distributions. A SAPG system based on Solar Two plant and a 600 MWe supercritical coal-fired plant is studied. The results show that at the relatively higher heliostat field power (HFP) work conditions, the heat energy should be injected into the highest pressure feedwater heater (FHs) as a priority. While at the relatively lower HFP and higher turbine power work conditions, the heat should be distributed to the two highest pressure FHs in a certain proportion instead of fully distributed to the highest pressure FHs. The performances of both the receiver and the power block are improved. The solar-electric conversion efficiency of SAPG system is obviously higher than that of Solar Two.

以抗生素制药废水的二级生化出水为研究对象,采用DK纳滤膜对其进行深度处理.优化了操作压力、pH值、进水流量、温度等操作参数,并考察了增加活性炭预处理对产水水质及膜污染的影响.结果表明,操作压力为1 000 kPa、pH值为6.0、进水流量为8.0 L/min是纳滤的最佳操作条件,在此操作条件下,采用纳滤膜深度处理经活性炭预处理后的抗生素制药废水的二级生化出水,TOC基本降至零左右,色度降至零,脱盐率达到31.51％,产水可回用于原厂生产过程.活性炭预处理可提高膜通量,改善产水水质,有效降低膜污染,运行216 h后,膜通量衰减率可由14.87％降至10.30％.

The heliostat field of solar power tower (SPT) system occupies a large proportion of both the total investment and total energy losses of a plant. However, the optimization design of a heliostat field is a challenging work, because there are too many parameters to be optimized. In this paper, a new high-dimensional genetic algorithm toolbox (HDGA) is developed in Visual Studio Community 2015 for the heliostat field design, in which a new crossover strategy is employed for the high-dimensional optimization. The algorithm is verified by both mathematical models and engineering cases, the results show that HDGA is more effective for the high-dimensional problem, and its convergence speed is much faster than that of the genetic algorithm toolbox developed by the University of Sheffield (Sheffield GA). The new algorithm is explained in detail and the optimal field layout is presented. With the new algorithm, a heliostat field referencing to the Gemasolar plant is optimized in this paper. The results show that the optical performance of the heliostat field is improved significantly than that of the un-optimized case, and the optical efficiency of 63.7% is reachable at the design point. At the same time, the annual insolation weighted efficiency is 56.9%.

Nanofiltration (NF) is considered to be a promising alternative process for the reuse of wastewater recently. However, membrane fouling is one of the major obstacles for the practical application of NF in the treatment of wastewater. The purpose of this paper is to summarize status of NF membrane fouling in the treatment of wastewater, to thoroughly review the analyze methods and control strategies of membrane fouling, and to propose the future research direction.

The nanofiltration (NF) membrane fouling characteristics and cleaning strategies were investigated and compared for treating membrane bioreactor (MBR) effluent and MBR-granular activated carbon (GAC) effluent of an antibiotic production wastewater by DK membrane. Results showed that the fouling of treating MBR effluent was more severe than that of treating MBR-GAC effluent. After filtering for 216 h, the difference of membrane flux decline was obvious between MBR effluent and MBR-GAC effluent, with 14.9% and 10.3% flux decline, respectively. Further study showed that organic fouling is the main NF membrane fouling in the advanced treatment of antibiotic production wastewater for both of the two different effluents. Soluble microbial by-product like and tyrosine-like substances were the dominant components in the foulants, whereas humic-like substances existing in the effluents had little contribution to the NF membrane fouling. A satisfactory efficiency of NF chemical cleaning could be obtained using combination of acid (HCl, pH 2.0-2.5) and alkali (NaOH + 0.3 wt% NaDS, pH 10.0-10.5). The favorable cleaning strategy is acid-alkali for treating the MBR-GAC effluent, while it is alkali-acid for treating the MBR effluent.

The optimization of the nanofiltration (NF) concentrate backflow ratio ( R cb ) and the influence of the NF concentrate on the performance of membrane bioreactor-nanofiltration (MBR-NF) process treating antibiotic production wastewater were investigated on a laboratory scale. The R cb was optimized at 60 % based on the removal rates of chemical oxygen demand (COD) and NH 4 + -N by MBR. Data analyses indicated that salinity brought by NF concentrate is the major driver leading to the decrease of sludge activity, especially at a high R cb . EPS analysis showed that electric conductivity (EC), proteins in soluble microbial products (SMP), and SMP brought by NF concentrate are the dominant factors causing the severe membrane fouling in MBR. Furthermore, undegradable substances including fulvic acid-like and humic acid-like compounds accumulated in NF concentrate showed significant influence on fouling of NF. MBR could well degrade small MW compounds in NF concentrate, which confirmed the enhancement of organic removal efficiency by recycling the NF concentrate to MBR. The MBR-NF process showed a relatively stable performance at the R cb of 60 % (volume reduction factor (VRF) = 5), and the NF permeate could satisfy the water quality standard for fermentation process with a water recovery rate of 90.9 %.

The nanofiltration (NF) membrane fouling characteristics and cleaning strategies were investigated through a laboratory-scale NF fouling test treating membrane bioreactor (MBR) effluent and MBR-granular activated carbon (GAC) effluent of an antibiotic production wastewater by DK and NF90 membranes, respectively. Results showed that organic fouling is the main NF membrane fouling for treating both the MBR effluent and MBR-GAC effluent. Soluble microbial by-product (SMP)-like and aromatic protein-like substances were the dominant components in the foulants, whereas humic-like substances had little contribution to the NF fouling. The fouling of DK was more severe than that of NF90. However, foulants respond by UV254 were more easily to foul NF90 membrane. It could get satisfactory effect using combined cleaning of acid (HCl, pH 2.0∼2.5) and alkali (NaOH + 0.3 wt% NaDS, pH 10.0∼10.5). The favorable cleaning strategy is “acid + alkali” for treating MBR-GAC effluent, while it is “alkali + acid” for treating MBR effluent.

纳滤(nanofiltration,NF)作为一种分离效果介于超滤和反渗透之间的膜过滤技术,在过滤过程中同时兼具物理孔隙产生的筛分效应和膜面电荷产生的道南效应作用.纳滤对水中的大多数有机物和多价盐离子具有很高的截留率,而对单价离子截留率较低,因而对单价多价盐具有良好的选择分离特性,近年来在饮用水软化、污水深度处理与回用、工业过程浓缩分离等方面得到了较为广泛的应用.据估计,到2019年纳滤膜的全球市场份额将达到4.451亿美元,同时在2015-2019年间将保持高达15.6％的年复合增长率(compound annual growth rate,CAGR).本文总结了目前市场上的纳滤膜品种、产品性能以及纳滤膜在水处理与回用中应用情况,并针对纳滤膜在应用中存在的问题提出了可行的方法和建议,最后对纳滤膜未来的发展方向提出了展望.

Municipal sewage from an oxidation ditch was treated for reuse by nanofiltration (NF) in this study. The NF performance was optimized, and its fouling characteristics after different operational durations (i.e., 48 and 169hr) were analyzed to investigate the applicability of nanofiltration for water reuse. The optimum performance was achieved when transmembrane pressure=12bar, pH=4 and flow rate=8L/min using a GE membrane. The permeate water quality could satisfy the requirements of water reclamation for different uses and local standards for water reuse in Beijing. Flux decline in the fouling experiments could be divided into a rapid flux decline and a quasi-steady state. The boundary flux theory was used to predict the evolution of permeate flux. The expected operational duration based on the 169-hr experiment was 392.6hr which is 175% longer than that of the 48-hr one. High molecular weight (MW) protein-like substances were suggested to be the dominant foulants after an extended period based on the MW distribution and the fluorescence characteristics. The analyses of infrared spectra and extracellular polymeric substances revealed that the roles of both humic- and polysaccharide-like substances were diminished, while that of protein-like substances were strengthened in the contribution of membrane fouling with time prolonged. Inorganic salts were found to have marginally influence on membrane fouling. Additionally, alkali washing was more efficient at removing organic foulants in the long term, and a combination of water flushing and alkali washing was appropriate for NF fouling control in municipal sewage treatment.

A combination of membrane bioreactor (MBR) and nanofiltration (NF) was tested at pilot-scale treating textile wastewater from the wastewater treatment station of a textile mill in Wuqing District of Tianjin (China). The MBR-NF process showed a much better treatment efficiency on the removal of the chemical oxygen demand, total organic carbon, color and turbidity in comparison with the conventional processes. The water recovery rate was enhanced to over 90% through the recycling of NF concentrate to the MBR, while the MBR-NF showed a stable permeate water quality that met with standards and could be directly discharged or further reused. The recycled NF concentrate caused an accumulation of refractory compounds in the MBR, which significantly influenced the treatment efficiency of the MBR. However, the sludge characteristics showed that the activated sludge activity was not obviously inhibited. The results of fluorescence spectra and molecular weight distribution indicated that those recalcitrant pollutants were mostly protein-like substances and a small amount of humic acid-like substances (650-6,000 Da), which contributed to membrane fouling of NF. Although the penetrated protein-like substances caused the residual color in NF permeate, the MBR-NF process was suitable for the advanced treatment and reclamation of textile wastewater under high water yield.

Membrane fouling, including foulants and factors, was investigated during hydraulic retention time (HRT) optimization of a membrane bioreactor (MBR) that treated wastewater from the production of antibiotics. The results showed that HRT played an important role in membrane fouling. Trans-membrane pressure (TMP), membrane flux, and resistance were stable at −6 kPa, 76 L m−2 h−1 bar−1, and 4.5 × 1012 m−1 when HRT was at 60, 48, and 36 h, respectively. Using Fourier transform infrared spectroscopy, foulants were identified as carbohydrates and proteins, which correlated with effluent organic matter and effluent chemical oxygen demand (COD) compounds. Therefore, membrane fouling trends would benefit from low supernatant COD (378 mg L−1) and a low membrane removal rate (26 %) at a HRT of 36 h. Serious membrane fouling at 72 and 24 h was related to soluble microbial products and extracellular polymeric substances in mixed liquor, respectively. Based on the TMP decrease and flux recovery after physical and chemical cleaning, irremovable fouling aggravation was related to extracellular polymeric substances’ increase and soluble microbial products’ decrease. According to changes in the specific oxygen uptake rate (SOUR) and mixed liquor suspended solids (MLSSs) during HRT optimization in this study, antibiotic production wastewater largely inhibited MLSS growth, which only increased from 4.5 to 5.0 g L−1 when HRT was decreased from 72 to 24 h, but did not limit sludge activity. The results of a principal component analysis highlighted both proteins and carbohydrates in extracellular polymeric substances as the primary foulants. Membrane fouling associated with the first principal component was positively related to extracellular polymeric substances and negatively related to soluble microbial products. Principal component 2 was primarily related to proteins in the influent. Additional membrane fouling factors included biomass characteristics, operational conditions, and feed characteristics.

A double membrane system comprising a membrane bioreactor (MBR) combined with a nanofiltration (NF) membrane was investigated on a pilot scale for the treatment of antibiotic production wastewater over a three-month period at a pharmaceutical company in Wuxi, China. By recycling the NF concentrate, the combined MBR–NF process was shown to be effective for the treatment of antibiotic production wastewater, resulting in excellent water quality and a high water yield of 92±5.6%. The water quality of the pilot-scale MBR–NF process was excellent; e.g., the concentrations of TOC, NH4+-N, TP were stable at 5.52, 0.68, 0.34mgL−1, respectively, and the values of turbidity and conductivity of the NF permeate were 0.15 NTU and 2.5mScm−1, respectively; these values meet China’s water quality standard requirements for industrial use (GB21903-2008). Not only were the antibiotic removal rates of spiramycin (SPM) and new spiramycin (NSPM) over 95%, the acute toxicity was also drastically reduced by the MBR–NF pilot system. The main organics in the MBR effluent were proteins, polysaccharides, and humic-like substances; they were almost completely retained by the NF membrane and further biodegraded in the MBR because the NF concentrate was recycled. The microbial community of the MBR did not significantly change with the recycling of the NF concentrate.