Desalination of brackish groundwater by solar-powered membrane distillation

Freshwater scarcity has become one of the major challenges humans are faced with in this century. Natural freshwater is becoming scarce while water demand is continuously rising with the rapid population and economic growth in many regions of the world. Desalination of brackish water and seawater is more and more considered as an alternative way of freshwater supply. The utilization of solar energy to drive desalination processes is a potential sustainable solution to the world’s water scarcity issue. This study comprehensively reviewed recent development and applications of seven major solar desalination technologies, including solar still, solar humidification-dehumidification process, solar powered multi-stage flash (MSF), multi-effect distillation (MED), membrane distillation (MD), reverse osmosis (RO) and electrodialysis (ED). Potential integration of solar technologies and desalination processes are summarized. By collecting and analyzing performance data from recent studies, the status of productivity, energy production costs of different technologies are critically reviewed. The real-world applicability, as well as the technical and economic feasibility of these technologies, is also evaluated.Brackish groundwater treatment by solar-powered membrane distillation is a potential sustainable alternative for drinking water supply in many arid, semi-arid regions that lack freshwater resources. In this research, a three-loop solar-powered vacuum membrane distillation (SVMD) has been developed, which was designed to be operated autonomously with abundant solar radiation. Evacuated tube solar collectors and PV panels are utilized to supply thermal and electrical energy, respectively. A commercial polypropylene capillary membrane module with 0.1 m2 effective surface area is adopted in the VMD process. In order to improve the system efficiency, the SVMD setup is continuously optimized during the implementation of the experimental studies. Major modifications include the installation of a new shell-and-tube condenser, higher capacity pumps in the membrane feeding and cooling loops, and the optimization of the permeate side pipelines. The effect of these modifications on the SVMD performance is investigated and discussed.Brackish groundwater (BGW) has a TDS range of 600~30,000 mg/L. Besides the high salinity, BGW often contains some naturally occurring inorganic contaminants, such as fluoride, nitrate, iron, and manganese. The removal of these contaminants from brackish groundwater by the SVMD system was investigated under real weather conditions. High quality permeate water with TDS of less than 12 mg/L was produced and more than 99.7% salt rejection rate was achieved in the tests. Fluoride was not detected in any of the permeate water samples while nitrate, iron and manganese concentrations were all below the Australian Drinking Water Guideline. Modifications of the SVMD system were done between the three experimental phases of this study. Significant improvement of permeate flux and overall thermal efficiency was obtained after the modification.Membrane scaling and wetting is one of the major problems in the application of membrane distillation technology. The scaling and wetting of the membrane during brackish groundwater treatment were investigated in this study using the SVMD system with the commercial PP capillary membrane module as well as using a DCMD system with commercial flat sheet PTFE membrane. The SVMD experiment was conducted under real weather conditions for 10 days while the DCMD experiment was operated for 188 h intermittently. Significant permeate flux decline and severe membrane wetting were observed in both cases. A dramatic decline of salt rejection rate, i.e. from almost 100% to 60%, was observed on the last day of SVMD operation. The exceedance of LEP during the SVMD operation was supposed to be the major reason for the membrane wetting. Acid cleaning and membrane drying were able to effectively recover the permeate flux and temporarily mitigate membrane wetting. However, the hydrophobicity of the membrane was not fully recovered. Membrane wetting occurred gradually in the DCMD experiment, resulting in an increase of daily average permeate conductivity, i.e. from less than 3.0 μS/cm to 160 μS/cm. A 57% reduction of water contact angle was observed for the fouled PTFE flat sheet membrane after the DCMD experiment. The feed side of the PP capillary membrane in the SVMD system also showed 19% lower contact angle than the relatively unaffected permeate side PP membrane after the cleaning and drying procedure. SEM/EDS results revealed that the fouled PTFE membrane surface was almost covered by CaCO3 salt crystals. While in the PP capillary membrane examined after acid cleaning, only a small amount of deposit was detected on the feed side membrane surface. Cu, Zn and Fe oxides were found to be the major components of the remaining foulants.A few scaling mitigation approaches were examined for brackish groundwater (BGW) treatment with direct contact membrane distillation, including regular distilled water flushing, pre-acidification and degassing, and addition of a polyacrylic acid based antiscalant X1030A into the feed water. During the 200 h DCMD operation, all three approaches have reduced the permeate flux decline to some degree. Among them, the antiscalant addition group achieved the most stable permeate flux performance. However, membrane wetting occurred during the operation. The daily average permeate water conductivity gradually increased from less than 4.0 μS/cm to 52.4 μS/cm. Membrane wetting did not occur in DCMD experiments without or with the other two scaling mitigation approaches. Less permeate flux reduction at low conductivity levels, less deposits in the SEM images and higher water contact angles on the fouled membrane were observed in the pre-acidification + degassing group than the regular distilled water flushing group.Chemical cleaning of the fouled and wetted PTFE membrane after 100 h DCMD BGW treatment was conducted using five different cleaning agents (i.e. deionized water, 3 wt.% HCl solution, 5 wt.% citric acid, 0.2 wt.% EDTA solution and 0.1 wt.% oxalic acid + 0.8 wt.% citric acid). 3 wt.% HCl showed the best performance in terms of scale removal and membrane feed side contact angle recovery, followed by 0.2 wt.% EDTA solution and 5 wt.% citric acid. However, long-term or frequent 3 wt.% HCl cleaning may potentially have a negative impact on the hydrophobicity of the membrane.</p

Transcutaneous injection of triamcinolone acetonide for persistent glottic granulation after laser microsurgery

Abstract Objective The aim of study was to demonstrate that transcutaneous intralesional injection of Triamcinolone Acetonide (TA) under fibrolaryngoscopy could be an option for persistent granulation after Transoral Laser Microsurgery (TLM) in glottic cancer patients. Methods We recruited 32 patients, who had conservative treatment but failed. 20 patients accepted TA injection monthly until the granulation disappeared or did not shrink further. 12 patients chose to closely monitor. Results For the 20 patients, 17 (85.0%) patients’ granulations completely disappeared. 3 (15.0%) patients’ granulations had reduced 80%. For the 12 patients, 3 (25.0%) patients’ granulations disappeared but 9 (75%) patients’ granulations did not have an obvious change. Recurrence was not observed. Conclusion Our experience showed that transcutaneous intralesional TA injection for persistent granulation after TLM through cricothyroid membrane is an efficient, security, harmless and low recurrence method. Especially suitable for huge granulation which blocks the glottis and recur after a second operation.</div

Financial pre-factors for post-performance of cross-border mergers & acquisitions

We study mergers and acquisitions (M&A) when one company is Chinese and another company is outside China. Previous studies are still much lacking considerations on financial factors affecting subsequent performance of such multinational (or ‘cross-border’) M&A. Here, a few (5) influencing factors are tested through a multiple linear regression model for 100 listed companies over [2016–2018]. We examine the role of (i) the mode of payment, (ii) cultural differences, (iii) industry differences, (iv) company scale and (v) the shareholding ratio. The research denotes that the payment method and the shareholding ratio of the largest shareholder have both a positive correlation with the performance in the year of the M&A and in the following one,–whatever the industries differences and companies sizes

Corn 3D point clouds

This data are corn point clouds collected by Terrestrial laser scanning. They contain a total of 48 individual corn point clouds in three different growing seasons. The data format is pcd, and each point cloud data contains the (x,y,z) coordinates of the points.</p

The macroscopic ESL model illustrates a similar qualitative effect of spatial variation.

(A and C) Time and initial condition averaged drag and lift force versus layer spatial frequency. (B and D) Time and initial condition averaged fraction of drag (|〈Drag〉|/(|〈Drag〉| + |〈Lift〉|)) and lift force (|〈Lift〉|/(|〈Drag〉| + |〈Lift〉|)) versus spatial frequency over all values of permeability. In all simulations, the thickness is fixed to be (A + h) = 1.4839μm. In panel A and C 95% confidence intervals are plotted at each data point. Parameters are summarized in Table 2.</p

RBC-only simulation with extracted geometry in a healthy condition.

RBC-only simulation with extracted geometry in a healthy condition.</p

The effect of changes in the density of bundles using the microscopic ESL model.

(A and C) Time and initial condition averaged drag and lift force versus density of bundles for different values of permeability. (B and D) Time and initial condition averaged fraction of drag (|〈Drag〉|/(|〈Drag〉| + |〈Lift〉|)) and lift force (|〈Lift〉|/(|〈Drag〉| + |〈Lift〉|)) versus density of bundles. In all simulations, the thickness is fixed to be h = 1.4839μm. In panel A and C a 95% confidence intervals are plotted at each data point. Parameters are summarized in Table 1.</p

An illustration of the vessel wall layout with a RBC at its initial position.

(A) the macroscopic ESL model and (B) the microscopic ESL model. In both panels the vessel wall layout is labeled in red and the RBC is labeled in black. The no-slip boundary on the top and the bottom of the channel, representing the vessel wall, is labeled using a blue dotted line. Arrows at the inlet indicate the direction of flow.</p

Schematic of the vessel wall layout and the initial positions of the RBC.

(A) the microscopic ESL model and (B) the macroscopic ESL model. In both cases, the vessel wall layout is plotted in red.</p

The distance of the RBC’s center of mass to the wall for different thickness using the microscopic ESL model.

(A) The RBC’s center of mass in the y direction versus time for an impermeable wall. (B) The RBC’s center of mass in the y direction versus time for a highly permeable wall. In both panels, the black curve corresponds to a thinner wall of thickness 1.0811μm and the red curve corresponds to a thicker wall of thickness 1.7256μm. In both panels, 95% confidence intervals are plotted at each data point. In all simulations, we assume the ESL is in a healthy condition corresponding to a density of bundles of 5. Parameters are summarized in Table 1.</p