Abstract
Biological nutrient removal is gaining increasing attention in wastewater treatment plants; however, it is adversely affected by low temperatures. This study examined temperature effects on nutrient removal and morphological stability of the granular and denitrifying phosphorus accumulating organisms (PAO and DPAO, respectively) using sequencing batch reactors (SBRs) at 5, 10, and 20
Key Words
biological nutrient removal; granular sludge DPAO; granular sludge PAO; morphological characteristics; temperature dependency
Address
Geumhee Yun AND Young Kim: Department of Environmental Engineering, Korea University, Sejong, 30019, Republic of Korea
Jongbeom Kwon and Sunhwa Park: National Institute of Environmental Research, Incheon 22689, Republic of Korea
Kyungjin Han: Department of Environmental Engineering, Korea National University of Transportation, Chungju, 27469, Republic of Korea
Abstract
This study presents the characteristics of growth and morphology of Anabaena sp., a representative filamentous cyanobacterium, depending on temperature variation from 10 to 30 °C. Both the filament density (or number) and its length of Anabaena were highly affected by temperature, as well as growth stage. Rapid growth at a higher temperature led to an increase in Anabaena filament density, as well as optical density at 680 nm (OD680). However, the number of vegetative cells within a single filament of Anabaena grown at 30 °C was smaller than those grown at lower temperatures, due to the intercalary division of the filament. Of the three different cells comprising a single Anabaena filament, the vegetative cell marginally affects the growth of Anabaena. The main dimensions of the vegetative cell, i.e., length and width, depend on the temperature and growth stage. The length-to-width (L/W) ratios of vegetative cells and akinetes were relatively consistent regardless of the temperature. However, in vegetative cells with dichotomous growth, the L/W ratio shows clear differences depending on their growth stage. It has been demonstrated that the L/W ratio could be used as an indicator to indirectly predict the growth stage of on-sit Anabaena samples.
Key Words
Anabaena sp.; cyanobacteria; growth; length; morphology; temperature
Address
Oh Kyung Choi: Bio Resource Center, Institute for Advanced Engineering, 17180, Republic of Korea
Dong Hyuk Shin, Dandan Dong,and Jae Woo Lee: Department of Environmental Engineering, Korea University, 30019, Republic of Korea
Sung Kyu Maeng: Department of Civil and Environmental Engineering, Sejong University, 05006, Republic of Korea
Jungsu Park: Department of Civil and Environmental Engineering, Hanbat National University, 34158, Republic of Korea
Abstract
1H,1H,2H,2H-perfluorodecytriethoxysilane (C16H19F17O3Si) be successfully applied to the hydrophobic modification of Al2O3 tubular ceramic membrane. Taking the concentration of modification solution, modification time, and modification temperature as factors, orthogonal experiments were designed to study the hydrophobicity of the composite membranes. The experiments showed that the modification time had the greatest impact on the experimental results, followed by the modification temperature, and the modification solution concentration had the smallest impact. Concentration of the modified solution 0.012 mol·L-1, modification temperature 30°C and modification time 24 h were considered optimal hydrophobic modification conditions. And the pure water flux reached 274.80 kg·m-2·h-1 at 0.1MPa before hydrophobic modification, whereas the modified membrane completely blocked liquid water permeation at pressures less than 0.1MPa. Air gap membrane distillation experiments were conducted for NaCl (2wt%) solution, and the maximum flux reached 4.20 kg·m-2·h-1, while the retention rate remained above 99.8%. Given the scarcity of freshwater resources in coastal areas, the article proposed a system for seawater desalination using air conditioning waste heat, and conducted preliminary research on its freshwater production performance using Aspen Plus. Finally, the proposed system achieved a freshwater production capacity of 0.61 kg·m-2·h-1.
Abstract
The flow in a nanopore of filtration membrane is often multiscale and consists of both the adsorbed layer flow and the intermediate continuum fluid flow. There is a controversy on which interface the slippage should occur in the nanopore filtration: On the adsorbed layer-pore wall interface or on the adsorbed layer-continuum fluid interface? What is the difference between these two slippage effects? We address these subjects in the present study by using the multiscale flow equations incorporating the slippage on different interfaces. Based on the limiting shear strength model for the slippage, it was found from the calculation results that for the hydrophobic pore wall the slippage surely occurs on the adsorbed layer-pore wall interface, however for the hydrophilic pore wall, the slippage can occur on either of the two interfaces, dependent on the competition between the interfacial shear strength on the adsorbed layer-pore wall interface and that on the adsorbed layer-continuum fluid interface. Since the slippage on the adsorbed layer-pore wall interface can be designed while that on the adsorbed layer-continuum fluid interface can not, the former slippage can result in the flux through the nanopore much higher than the latter slippage by designing a highly hydrophobic pore wall surface. The obtained results are of significant interest to the design and application of the interfacial slippage in nanoporous filtration membranes for both improving the flux and conserving the energy cost.
Key Words
adsorbed layer; fluid; mass transport; multiscale; nanopore; slippage
Address
Xiaoxu Huang and Wei Li: School of Mechanical Technology, Wuxi Institute of Technology, Gaolang Xilu 1600, 214121, Wuxi, Jiangsu Province, China
Yongbin Zhang: College of Mechanical Engineering, Changzhou University, Gehu Lu 21, Wujin, 213164, Changzhou, Jiangsu Province, China
Abstract
Presence of hazardous dyes in water cause considerable risks to the human health and environment due to their potential toxicity and ecological disruptions. Therefore, in the present research, to suggest an alternative method for the retention of toxic Azocarmine G (ACG) dye from aqueous media, natural and H2SO4-modified acacia sawdust were performed for the first time as low-cost and efficient adsorbents. Based on batch experiments, it was determined that the best conditions for the developed dye retention process were an initial pH of 2.0 and an equilibrium time of 240 min. Analysis of the data using both pseudo-first order and pseudo-second order kinetic models showed that the retention of ACG onto the adsorbents predominantly occurred through chemical adsorption. Langmuir, Freundlich, and Dubinin-Radushkevich isotherm models were employed to provide insights into the interaction between the adsorbate and adsorbent and the mechanism of the adsorption process. Maximum monolayer adsorption capacities of natural and H2SO4-modified acacia sawdust were determined as 28.01 and 64.90 mg g-1, respectively by Langmuir isotherm model. Results of the study clearly indicated that the modification of acacia sawdust with H2SO4 leads to a substantial increase in the adsorption performance of anionic dyes.
Key Words
acacia sawdust; adsorption; Azocarmine G; isotherm; kinetics; modification
Address
Celal Duran, Sengul Tugba Ozeken and Aslihan Yilmaz Camoglu: Karadeniz Technical University, Faculty of Sciences, Department of Chemistry, Trabzon, Turkey
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