Techno Press
Tp_Editing System.E (TES.E)
Login Search


mwt
 
CONTENTS
Volume 10, Number 5, September 2019
 

Abstract
The objective of this study was to examine the recovery of the power plant cooling tower blowdown water (CTBD) by membrane distillation. The experiments were carried out using a flat plate poly vinylidene fluoride (PVDF) membrane with a pore diameter of 0.22 um by a direct contact membrane distillation unit (DCMD). The effects of operating parameters such as transmembrane temperature difference (delta-T), circulation rate and operating time on permeate flux and membrane fouling have been investigated. The results indicated that permeate flux increased with increasing delta-T and circulation rate. Whereas maximum permeate flux was determined as 47.4 L/m2.h at delta-T of 50 degree Celcius for all short term experiments, minimum permeate flux was determined as 7.7 L/m2.h at delta-T of 20 degree Celcius. While 40 degree Celcius was determined as the optimum delta-T in long term experiments. Inorganic and non-volatile substances caused fouling in the membranes.

Key Words
power plant; cooling tower blowdown water; membrane distillation; flux; circulation rate; transmembrane temperature difference

Address
Gebze Technical University, Department of Environmental Engineering, Kocaeli, Turkey

Abstract
This study aimed to investigate the membrane fouling and sludge characteristics in a pilot-scale submerged membrane bioreactor (MBR) operated under low temperature (7 degree Celcius) To elucidate the mechanisms of membrane fouling at low temperature, we studied the correlation between MBR performances and physicochemical properties of sludge including extracellular polymeric substance (EPS), relative hydrophobicity (RH) and floc size during long-term operation. The MBR was shown able to remove chemical oxygen demand (COD) stably and efficiently (>90 %) in the case of overgrowth of filamentous bacteria (bulking sludge) at low temperature. On the other hand, the occurrence of filamentous bulking greatly accelerated membrane fouling, as indicated by membrane filtration period of 14 days for filamentous bulking at 7 degree Celcius, in comparison with that of 27 days for non-bulking sludge at 24 degree Celcius. The overgrowth of filamentous bacteria resulting from low-temperature condition led to an increased release of EPS, higher RH, smaller floc size and lower fractal dimension of sludge. These factors accelerated the formation of compact cake layer on membrane surface in association with performance diminution in terms of increase in transmembrane pressure (TMP) of the membrane and thus the decrease in membrane permeability.

Key Words
membrane bioreactor; membrane fouling; sludge bulking; low temperature; extracellular polymeric substances; hydrophobicity

Address
Yuan Yuan: College of Bioengineering, Beijing Polytechnic, Beijing, China, 100176
Jianqiao Zhang: Environmental Protection and Water Affairs Bureau, Luohu District, Shenzhen, China, 518007

Abstract
Long term water quality change was analyzed to evaluate the effect of the Total Maximum Daily Load (TMDL) policy. A trend analysis was performed for biochemical oxygen demand (BOD) and total phosphorus (TP) concentrations data monitored at the outlets of the total 41 TMDL unit watersheds of the Nakdong River in the Republic of Korea. Because water quality data do not usually follow a normal distribution, a nonparametric statistical trend analysis method was used. The monthly mean values of BOD and TP for the period between 2004 and 2015 were analyzed by the seasonal Mann-Kendall test and the locally weighted scatterplot smoother (LOWESS). The TMDL policy effect on the water quality change of each unit watershed was analyzed together with the results of the trend analysis. From the seasonal Mann-Kendall test results, it was found that for BOD, 7.8 % of the 41 points showed downward trends, 26.8 % and the rest 65.9% showed upward and no trends. For TP, 51.2% showed no trends and the rest 48.8% showed downward trends. From the LOWESS analysis results, TP began to decrease in most of the unit watersheds from mid-2010s when intensive chemical treatment processes were introduced to existing wastewater treatment plants. Overall, for BOD, relatively more points were improved in the main stream compared to the points of the tributaries although overall trends were mostly no trend or upward. For TP, about half of the points were improved and the rest showed no trends.

Key Words
TMDLs; LOWESS; Seasonal Mann-Kendall test; Nonparametric statistical methods

Address
Kang Young Jung, Yeong Jae Lee, Kyunghyun Kim: National Institute of Environmental Research Yeongsan River Environment Research Center, 5, Cheomdangwagi-ro 208beon-gil,
Buk-gu, Gwangju 61011, Republic of Korea
Jung Min Ahn: National Institute of Environmental Research Water Quality Assessment Research Division, 42 Hwangyong-ro, Seo-gu, Incheon 22689, Republic of Korea
Kun Yeun Han: Department of Civil Engineering, Kyungpook National University, 80 Daehak-ro, Buk-gu, Daegu 41566, Republic of Korea
Dongseok Shin: National Institute of Environmental Research Watershed Pollution Load Management Research Division, 42 Hwangyong-ro, Seo-gu, Incheon 22689, Republic of Korea

Abstract
ZSM-5 membrane was prepared on tubular macroporous alpha-alumina support using a different synthesis route. The effects of organic template agent and Si/Al ratio of the synthesis gel on morphology, structure, and separation performance of the ZSM-5 membrane used for dehydration of isopropanol were investigated. High water perm-selectivity ZSM-5 membrane with a thickness of about 3.0 um and a low Si/Al ratio of 10.1 was successfully prepared from organotemplate-free synthesis gel with a molar composition of SiO2 : 0.050Al2O3 : 0.21Na2O : NaF : 51.6H2O at 175 degree Celcius for 24 h. The ZSM-5 membrane exhibited high pervaporation performance with a flux of 3.92 kg/(m2.h) and corresponding separation factor of higher than 10,000 for dehydration of 90 wt.% isopropanol/water mixture at 75 degree Celcius.

Key Words
Zeolite membrane; dehydration of isopropanol; pervaporation; organotemplate-free synthesis gel; hydrothermal synthesis

Address
Jiajia Li, Liangqing Li: Collaborative Innovation Center of Fine Chemical and Materials Technology, School of Chemistry and Chemical Engineering,
Huangshan University, No. 39 Xihai Road, Huangshan, China
Jianhua Yang, Jinming Lu and Jinqu Wang: Institute of Adsorption and Inorganic Membrane, State Key Laboratory of Fine Chemicals, Dalian University of Technology,
No. 2 Linggong Road, Dalian, China

Abstract
Effect of different alkane based solvents on the stability of emulsion liquid membrane was investigated using normal alkanes (n-hexane, n-heptane, n-octane and n-decane) under various operating parameters of surfactant concentration, emulsification time, internal phase concentration, volume ratio of internal phase to organic phase, volume ratio of emulsion phase to external phase and stirring speed. Results of stability revealed that emulsion liquid membrane containing n-octane as solvent and span-80 (5 % (w/w)) as emulsifying agent presented the highest amount of emulsion stability (the lowest breakage) compared with other solvents; however, operating parameters (surfactant concentration (5% (w/w)), emulsification time (6 min), internal phase concentration (0.05 M), volume ratio of internal phase to organic phase (1/1), volume ratio of emulsion phase to external phase (1/5) and stirring speed (300 rpm)) were also influential on improving the stability (about 0.2% breakage) and on achieving the most stable emulsion. The membrane with the highest stability was employed to extract acridine orange with various concentrations (10, 20 and 40 ppm) from water. The emulsion liquid membrane prepared with n-octane as the best solvent almost removed 99.5% of acridine orange from water. Also, the prepared liquid membrane eliminated completely (100%) other cationic dyes (methylene blue, methyl violet and crystal violet) from water demonstrating the efficacy of prepared emulsion liquid membrane in treatment of dye polluted waters.

Key Words
Emulsion liquid membrane (ELM); alkane based solvents; stability; extraction; dye removal

Address
Negin Ghaemi, Farzaneh Darabi : Department of Chemical Engineering, Kermanshah University of Technology,67178 Kermanshah, Iran
Monireh Falsafi: Department of Inorganic Chemistry, Faculty of Chemistry, Razi University, Kermanshah, Iran

Abstract
One of the real issues of the recent years is water contamination because of harmful synthetic dyes. Liquid Membranes (LM) resemble a promising alternative to the current separation processes, demonstrating various points of interest as far as effectiveness, selectivity, and operational expenses. The improvement of various Liquid Membranes designs has been a matter of examination by few researchers, particularly for the expulsion of dyes from aqueous solutions. The choice of organic surfactants plays an essential role in the efficiency of the dye removal. In LM design, the most significant step towards productivity is the decision of the surfactant type and its concentration. Liquid emulsion membrane (LEM) was used to remove safranin from aqueous solutions in which the emulsion was made with the help of D2EHPA as carrier, kerosene was used as a diluent and Span 80 (Sorbiton monooleate) was used as an emulsifying agent or surfactant. Various sorts of internal stages were utilized, to be specific sulphuric acid and sodium hydroxide. The impact of parameters influencing extraction efficiency such as pH of feed solution, concentrations of surfactant and emulsifying agent in membrane phase, volume ratio of internal phase to membrane phase, internal phase concentration, agitation speed and time of extraction were analyzed.

Key Words
liquid membrane, synthetic dyes, surfactant, safranin, D2EHPA

Address
Department of Chemical Engineering, Malaviya National Institute of Technology, Jaipur-302017, India

Abstract
Surface modification is very efficient and scalable approach to achieve improved membrane performance. We treated Reverse Osmosis Thin Film Composite (TFC RO) membrane with various concentrations of Polyethylene Glycol (PEG), a hydrophilic polymer after activation with sodium hypochlorite. This treatment resulted in an increment of the water flux by 43% and the salt rejection by 2.36% for the 3000 mg/l PEG-treated membrane. Further, these PEG-treated membranes were exposed to a mixture of 3000 mg/l PEG and 1000 mg/l sodium hypochlorite for 1 hour. Further modification of this membrane by PEG and sodium hypochlorite mixture increased the water permeance up to 133% when compared with the virgin TFC RO membrane. We characterized the treated membranes to understand the changes in wettability by contact angle analysis, changes in surface morphology and roughness by scanning electron microscope (SEM) and atomic force microscope (AFM) analysis.

Key Words
antifouling; desalination; membrane; thin film composite; sustainability

Address
Membrane Science and Separation Technology Division, CSIR-Central Salt and Marine Chemicals Research Institute (CSIR-CSMCRI),
Council of Scientific & Industrial Research (CSIR), Gijubhai Badheka Marg, Bhavnagar- 364002, Gujarat, India

Abstract
Membrane distillation (MD) is one of the water treatment processes which involves the momentum, heat and mass transfer through channels and membrane. In this study, CFD modeling has been used to simulate the heat and mass transfer in the direct contact membrane distillation (DCMD). Also, the effect of operating parameters on the water flux is investigated. The result shows a good agreement with the experimental result. Results indicated that, while feed temperature is increasing in the feed side, water flux improves in the permeate side. Since higher velocity leads to the higher mixing and turbulence in the feed channel, water flux rises due to this increase in the feed velocity. Moreover, results revealed that temperature polarization coefficient is rising as flow rate (velocity) increases and it is decreasing while the feed temperature increases. Lastly, the thermal efficiency of direct contact membrane distillation is defined, and results confirm that thermal efficiency improves while feed temperature increases. Also, flow rate increment results in enhancement of thermal efficiency.

Key Words
computational fluid dynamic (CFD); heat transfer; water flux; temperature polarization coefficient (TPC); thermal efficiency; membrane distillation

Address
Department of Mechanical Engineering, College of Engineering, Shahid Chamran University of Ahvaz, Ahvaz, Iran


Techno-Press: Publishers of international journals and conference proceedings.       Copyright © 2020 Techno-Press
P.O. Box 33, Yuseong, Daejeon 34186 Korea, Tel: +82-42-828-7996, Fax : +82-2-736-6801, Email: info@techno-press.com