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CONTENTS
Volume 10, Number 4, July 2019
 

Abstract
Fabricating hydrophobic porous membrane is important for exploring the applications of membrane distillation (MD). In the present paper, poly(vinylidene fluoride) (PVDF) hollow fiber membrane was modified by coating polydimethylsiloxane (PDMS) on its surface. The effects of PDMS concentration, cross-linking temperature and cross-linking time on the performance of the composite membranes in a vacuum membrane distillation (VMD) process were investigated. It was found that the hydrophobicity and the VMD performance of the PVDF hollow fiber membrane were obviously improved by coating PDMS. The optimal PDMS concentration, cross-linking temperature and cross-linking time were 0.5 wt%, 80 degree(c), and 9 hr, respectively.

Key Words
poly(vinylidene fluoride) membrane; polydimethylsiloxane; hydrophobic modification; vacuum membrane distillation

Address
State Key Laboratory of Materials-Oriented Chemical Engineering, College of Chemistry and Chemical Engineering,
Nanjing Tech University, Nanjing 210009, P.R. China

Abstract
Cost effective clay adsorptive microfiltration membranes were synthesized to remove Cr (III) from high polluted water. Raw and calcined bentonite were mixed in order to decrease the shrinkage and also increase the porosity; then, 20 wt% of carbonate was added and the samples, named B (without carbonate) and B-Ca20 (with 20 wt% calcium carbonate) were uniaxially pressed and after sufficient drying, fired at 1100 degree(C) for 3 hours. Then, physical and mechanical properties of the samples, their phase analyses and microstructure and also their ability for Cr(III) removal from high polluted water (including 1000 ppm Cr (III) ions) were studied. Results showed that the addition of calcium carbonate lead the porosity to increase to 33.5% while contrary to organic pore formers like starch, due to the formation of wollastonite, the mechanical strength not only didn\'t collapse but also improved to 36.77 MPa. Besides, sample B-Ca20, due to the presence of wollastonite and anorthite, could remove 99.97% of Cr (III) ions. Hence, a very economic and cost effective combination of membrane filtration and adsorption technology was achieved for water treatment which made microfiltration membranes act even better than nanofiltration ones without using any adsorptive nano particles.

Key Words
water treatment, Cr(III) removal, clay adsorptive membrane, microfiltration, wollastonite, anorthite, cost effective

Address
Department of Metallurgy and Materials Engineering ,Iran University of science and Technology, Narmak, Tehran, Islamic Republic of Iran

Abstract
This study aimed to develop a compact partial nitritation step by forming granules with high Ammonia-Oxidizing Bacteria (AOB) fraction using the Air-lift Granulation Reactor (AGR) and to evaluate the feasibility of treating reject water with high ammonium content by combination with the Anammox process. The partial nitritation using AGR was achieved at high nitrogen loading rate (2.25+/-0.05 kg N m-3 d-1). The important factors for successful partial nitritation at high nitrogen loading rate were relatively high pH (7.5~8), resulting in high free ammonia concentration (1~10 mg FA L-1) and highly enriched AOB granules accounting for 25% of the total bacteria population in the reactor. After the establishment of stable partial nitritation, an effluent NO2--N/NH4+-N ratio of 1.2+/-0.05 was achieved, which was then fed into the Anammox reactor. A high nitrogen removal rate of 2.0 kg N m-3 d-1 was successfully achieved in the Anammox reactor. By controlling the nitrogen loading rate at the partial nitritation using AGR, the influent concentration ratio (NO2--N/NH4+-N = 1.2+/-0.05) required for the Anammox was controlled, thereby minimizing the inhibition effect of residual nitrite.

Key Words
reject water; AOB granules; partial nitritation; nitrogen removal; anammox

Address
Minki Jung and Sungpyo Kim: Department of Environmental System Engineering, Korea University, Sejong 30019, Korea
Minki Jung, Taeseok Oh, Kyungbong Jung, Jaemin Kim: BKT Co. Ltd., 25 Yuseong-daero 1184beon-gil, Yuseong-gu , Daejeon 34109, Korea

Abstract
In 2014, the first demineralization plant, using nanofiltration (NF) membrane coupled with renewable energies was realized at Al Annouar high school of Sidi Taibi, Kenitra, Morocco. This project has revealed difficulties related to the membrane performances loss (pressure increase, flux decline, poor water quality of the produced water and increase of energy consumption), as consequences of membrane fouling. To solve this problem, an autopsy of the membrane was done in order to determine the nature and origin of the fouling. The samples of membrane and fouling were then analyzed by scanning electron microscopy using a scanning electron microscope (SEM) connected with an energy dispersive X-ray (EDX) detection system and X-ray diffractometer (XRD). Moreover, three cleaning solutions (hydrochloric acid, nitric acid and sulfuric acid) were tested and assessed in a single cleaning step to find the suitable one for the fouled membrane to regain its initial permeability and performances. The analysis of the experimental results showed that the fouling layer is mainly composed of calcium carbonate (inorganic fouling). Results showed also that the permeability is improved by the hydrochloric acid cleaning (pH=3) with a cleaning efficiency of 93%. Cleaning efficiency did not exceed 75 % with nitric acid (pH=3) and 40 % with sulfuric acid (pH= 3).

Key Words
nanofiltration; desalination plant; fouling; autopsy; demineralization; membrane cleaning

Address
Soufian El-ghzizel, Hicham Jalté, Hajar Zeggar, Mohamed Zait, Sakina Belhamidi,
Fathallah Tiyal, Mohamed Taky and Azzedine Elmidaoui\" Laboratory of Separation Processes, Department of Chemistry, Faculty of Sciences, Ibn Tofail University, Kenitra 14000, Morocco
Mahmoud Hafsi: International Institute for Water and Sanitation, National Office of Electricity and potable Water ONEE-IEA, Rabat, Morocco

Abstract
Lotus leaf has a special dual micro and nano surface structure which gives its highly hydrophobic surface characteristics and so-called self cleaning effect. In order to endow PVDF hollow fiber membrane with this special structure and improve the hydrophobicity of membrane surface, PVDF hollow fiber composite membranes was obtained through the immersion coating of poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) dilute solution on the outside surface of PVDF support membrane. The prepared PVDF composite membranes were used in the vacuum membrane distillation (VMD) for the desalination. The effects of PVDF-HFP dilute solution concentration in the dope solution and coating time on VMD separation performance was studied. Membranes were characterized by SEM, WCA measurement, porosity, and liquid entry pressure of water. VMD test was carried out using 35 g.L-1 NaCl aqueous solution as the feed solution at feed temperature of 30 degree(C) and the permeate pressure of 31.3 kPa. The vapour flux reached a maximum when PVDF-HFP concentration in the dilute solution was 5 wt% and the coating time was kept in the range of 10-60 s. This was attributed to the well configuration of micro-nano rods which was similar with the dual micro-nano structure on the lotus leaf. Compared with the original PVDF membrane, the salt rejection can be well maintained which was greater than 99.99 % meanwhile permeation water conductivity was kept at a low value of 7-9 uS.cm-1 during the continuous testing for 360 h.

Key Words
hydrophobicity; PVDF; hollow fiber membrane; vacuum membrane distillation; desalination

Address
Hongbin Li, Xingchen Zi, Wenying Shi, Longwei Qin, Haixia Zhang and Xiaohong Qin: School of Textiles Engineering, Henan University of Engineering, 1 Xianghe Road, Zhengzhou 450007, P. R. China
Hongbin Li, Wenying Shi: Collaborative Innovation Center of Textile and Garment Industry of Henan Province, 41 Zhongyuan Road, Zhengzhou 450007, P. R. China
Xiaohong Qin: School of Textiles Science, Donghua University, 2999 North Renmin Road, Shanghai 201620, P. R. China

Abstract
Managed aquifer recharge (MAR) systems are gaining interest as an alternative to conventional water resources. However, when the water recovered in MAR systems, dissolved iron and manganese species may easily oxidize and they cause well screen clogging or require abandonment of extraction wells. In this study, both oxic and anoxic conditions were analyzed to verify the feasibility of the membrane filtration performance under various solution chemistries. The fouling mechanisms of the metal ions under anoxic conditions were also investigated by employing synthetic wastewater. The fouled membranes were then further analyzed to verify the major causes of inorganic fouling through SEM and XPS. The newly suggested anoxic process refining existing membrane process is expected to provide more precious information about nanofiltration (NF) membrane fouling, especially for demonstrating the potential advantages to chemical-free drinking water production for indirect potable reuse.

Key Words
anoxic; managed aquifer recharge; nanofiltration; iron; indirect potable reuse

Address
Yongxun Jin, Yeseul Choi, Kyung Guen Song: Water Cycle Research Center, Korea Institute of Science and Technology, Seoul 02792, South Korea
Yeseul Choi: School of Civil, Environmental and Architectural Engineering, Korea University, Seoul 02841, South Korea
Soyoun Kim and Chanhyuk Park: Department of Environmental Science and Engineering, Ewha Womans University, Seoul 03760, South Korea

Abstract
The ejector type microbubble generator, which is the method to supply air to water by using cavitation in the nozzle, does not require any air supplier so it is an effective and economical. Also, the distribution of the size of bubbles is diverse. Especially, the size of bubbles is smaller than the bubbles from a conventional air diffuser and bigger than the bubbles from a pressurized dissolution type microbubble generator so it could be applied to the aeration tank for wastewater treatment. However, the performance of the ejector type microbubble generator was affected by hydraulic pressure and MLSS(Mixed Liquor Suspended Solid) concentration so many factors should be considered to apply the generator to aeration tank. Therefore, this study was performed to verify effects of hydraulic pressure and MLSS concentration on oxygen transfer of the ejector type microbubble generator. In the tests, the quantity of sucked air in the nozzle, dissolved oxygen(DO) concentration, oxygen uptake rate(OUR), oxygen transfer coefficient were measured and calculated by using experimental results. In case of the MLSS, the experiments were performed in the condition of MLSS concentration of 0, 2,000, 4,000, 8,000 mg/L. The hydraulic pressure was considered up to 2.0 mH2O. In the results of experiments, oxygen transfer coefficient was decreased with the increase of MLSS concentration and hydraulic pressure due to the increased viscosity and density of wastewater and decreased air flow rate. Also, by using statistical analysis, when the ejector type microbubble generator was used to supply air to wasterwater, the model equation of DO concentration was suggested to predict DO concentration in wastewater.

Key Words
ejector type microbubble generator; hydraulic pressure; oxygen transfer coefficient (KLa); oxygen uptake rate (OUR); mixed liquor suspended solid (MLSS)

Address
Dept. of Civil & Environmental Engineering, Incheon National University, Incheon, 22012, South Korea

Abstract
Increasing the concentration of nitrate ions in the soil solution and then leaching it to underground aquifers increases the concentration of nitrate in the water, and can cause many health and ecological problems. This study was conducted to evaluate the vulnerability of Meymeh aquifer to nitrate pollution. In this research, sampling of 10 wells was performed according to standard sampling principles and analyzed in the laboratory by spectrophotometric method, then; the nitrate concentration zonation map was drawn by using intermediate models. In the drastic model, the effective parameters for assessing the vulnerability of groundwater aquifers, including the depth of ground water, pure feeding, aquifer environment, soil type, topography slope, non-saturated area and hydraulic conductivity. Which were prepared in the form of seven layers in the ARC GIS software, and by weighting and ranking and integrating these seven layers, the final map of groundwater vulnerability to contamination was prepared. Drastic index estimated for the region between 75-128. For verification of the model, nitrate concentration data in groundwater of the region were used, which showed a relative correlation between the concentration of nitrate and the prepared version of the model. A combination of two vulnerability map and nitrate concentration zonation was provided a qualitative aquifer classification map. According to this map, most of the study areas are within safe and low risk, and only a small portion of the Meymeh Aquifer, which has a nitrate concentration of more than 50 mg / L in groundwater, is classified in a hazardous area.

Key Words
nitrate contamination; GIS; Meymeh aquifer; drastic model

Address
Javad Tabatabaei: Department of petroleum engineering and geology, Meymeh branch, Islamic Azad University, Meymeh, Iran
Leila Gorji: Department of Geology, Meymeh branch, Islamic Azad University, Meymeh, Iran


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