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CONTENTS
Volume 13, Number 1, January 2022
 


Abstract
The regulations of the International Maritime Organization (IMO) have been steadily strengthened in ship emissions. Accordingly, there is a growing need for development of related technologies for the removal of contaminants that may occur during the treatment of SOx and NOx using a wet scrubber. However, this system also leads to wastewater production when the exhaust gas is scrubbed. In this research, we evaluated the performance of an ion selective resin process in accordance with scrubber wastewater discharge regulations, specifically nitrate discharge, by the IMO. Accelerated real and synthetic wastewater of wet scrubbers, contained high amounts of TDS with high nitrate, is used as feed water in lab scale systems. Furthermore, a pilot scale dissolved air flotation (DAF) using microbubble generator with ion exchange resin process was combined and developed in order to apply for the treatment of wet scrubber wastewater. The results of the present study revealed that operating conditions, such as resin property, bed volume (BV), and inlet wastewater flow rate, significantly affect the removal performance. Finally, through a pilot test, DAF with ion exchange resin process showed a noticeable improvement of the nitrate removal rate compared to the single DAF process.

Key Words
dissolved air flotation (DAF); international maritime organization (IMO) regulation; ion exchange resin; nitrate removal; wet scrubber wastewater treatment

Address
Bongchul Kim, Inseol Yeo and Chan-gyu Park: Water Environment Center, Environmental Technology Division, Korea Testing Laboratory (KTL), 87, Disital-ro 26-gil, Guro-gu, Seoul, Republic of Korea


Abstract
Using the SWOT-AHP method, this study identifies the priorities in the development of floating solar photovoltaics (PV) and suggests possible strategies. Our study analyzed the priorities in planning future solar PV strategies based on the opinions of 27 experts. Our results indicate that the government should expand support while emphasizing the benefit of floating solar PV in that it causes less environmental damage compared to onshore solar PV. In addition, the government should properly deal with the public-private conflict regarding the installation of floating solar PV. Floating solar PV itself has not reached a mature technological and institutional stage, but could be an option or alternative for saturated onshore solar PV facilities in Korea.

Key Words
floating solar PV; floating photovoltaic (FPV); Korean energy policy; SWOT-AHP

Address
Youhyun Lee: Ajou University, Department of Public Administration, 206, Worldcup-ro, Yeongtong-gu, Suwon-si, Gyeonggi-do, 16499, Republic of Korea

Kyoungmin Kim: National Assembly Research Service, 1 Uisadang-ro, Yeongdeungpo-gu Seoul, 07233, Republic of Korea


Abstract
The continuous industrial growth increases the volume of pollutants discharged into the water, which induces Cyanobacteria in the receiving bodies. The removal of various cyanobacteria such as Microcystis, Anabaena, and Oscillatoria was explored to analyze their removal characteristics using different chemical and mineral coagulants. The chemical coagulants, including poly aluminium chloride (PACl), Alum, and mineral coagulants such as Loess and Illite, were tested to remove selected cyanobacteria. Results indicated that the removal rate increased with coagulant dosage regardless of the type of coagulant. The removal of selected cyanobacteria using chemical coagulant was found in the order: Microcystis > Anabaena > Oscillatoria. The PACl coagulant showed the most efficient removal rate for Microcystis, Anabaena, Oscillatoria. Removal rate of Microcystis conducted by PACl showed 92% at 100,000 cells/mL and 98.4% at 1,000,000 cells/mL whereas Illite showed lower 70% and Loess showed lower 50% in both 100,000 cells/mL and 1,000,000 cells/mL. The removal rate of Anabaena and Oscillatoria by PACl and Alum was higher 80%, while the other coagulants exhibited lower than 75% at 1,000,000 cells/mL. The removal rate of Oscillatoria by PACl was 80.1%, while the other coagulants exhibited lower than 70% at 1,000,000 cells/mL. Moreover, the mineral coagulants showed better removal efficiency at a higher concentration than low concentration during experiments. Therefore, removing cyanobacteria from water streams can be improved through coagulation by selecting a specific coagulant for a particular type of algae.

Key Words
algae; anabaena; coagulation; cyanobacteria; microcystis; oscillatoria

Address
Joo Eun Han, Soo Hyung Park, Muhammad Yaqub and Wontae Lee: Department of Environmental Engineering, Kumoh National Institute of Technology, Gumi 39177, Republic of Korea

Sang Leen Yun and Seog-ku Kim: Korea Institute of Civil Engineering and Building Technology, Goyang-si 10223, Republic of Korea

Abstract
The use of plastics in our everyday lives have been drastically increased during the last few decades. However with the usage of commercial plastic products there is a possibility of microplastic consumption, due to the fragmentation of the products. Additionally, the potential for microplastic ingestion may also be increased by using damaged products. Hence, the current study was conducted to understand the potential release of micro/nano plastics and organic matter from damaged teabags. To check the leakage tendency, the amount of damage to the tea bags from 1-10 cm were tested along with temperatures of 25-70

Key Words
microplastic; microplastic release; organic leachate; SEM analysis; teabags

Address
Sion Kim and Eun Ha Jo: Department of Environmental & IT Engineering, Chungnam University, 99 Daehak-ro, Yuseong-gu, Daejeon 34134, Korea

Soohoon Choi: Department of Environmental Engineering, Chungnam University, 99 Daehak-ro, Yuseong-gu, Daejeon 34134, Korea

Abstract
To verify the fate and transport of engineered nanoparticles (ENP), it is essential to understand its interactions with organic matter. Previous research has shown that dissolved organic matter (DOM) can increase particle stability through steric repulsion. However, the majority of the research has been focused on model organic matter such as humic or fulvic acids, lacking the understanding of organic matter found in field conditions. In the current study, organic matter was sampled from wastewater treatment plants to verify the stability of engineered nanoparticles (ENP) under field conditions. To understand how different types of organic matter may affect the fate of ENP, wastewater was sampled and separated based on their size; as small organic particular matter (SOPM) and large organic particular matter (LOPM), and dissolved organic matter (DOM). Each size fraction of organic matter was tested to verify their effects on nano-zinc oxide (nZnO) and nano-titanium oxide (nTiO2) stability. For DOM, critical coagulation concentration (CCC) experiments were conducted, while sorption experiments were conducted for organic particulates. Results showed that under field conditions, the surface charge of the particles did not influence the stability. On the contrary, surface charge of the particles influenced the amount of sorption onto particulate forms of organic matter. Results of the current research show how the size of organic matter influences the fate and transport of different ENPs under field conditions.

Key Words
attachment; critical coagulation concentration; dissolved organic matter; fate and transport; TiO2 and ZnO nanoparticles

Address
Soohoon Choi: Department of Civil and Environmental engineering, University of Delaware, Newark, DE 19711, USA/ Department of Environmental Engineering, Chungnam University, 99 Daehak-ro, Yuseong-gu, Daejeon 34134, Korea

Ching-Lung Chen:Department of Civil and Environmental engineering, University of Delaware, Newark, DE 19711, USA/ Department of Safety, Health and Environmental Engineering, Ming Chi University of Technology, New Taipei City, 24301, Taiwan/ Center for Environmental Sustainability and Human Health, Ming Chi University of Technology, New Taipei City, 24301, Taiwan

Murray V. Johnston: Department of Chemistry and Biochemistry, University of Delaware, Newark, DE 19711, United States

Gen Suh Wang: Institute of Environmental Health, National Taiwan University, Taipei 100, Taiwan

Chin-Pao Huang: Department of Civil and Environmental engineering, University of Delaware, Newark, DE 19711, USA

Abstract
Seawater desalination is doubtlessly a viable option to supply fresh drinking water. Nevertheless, RO (reverse osmosis) desalination plants in specific areas may be intermittently operated to match the imbalance between water demand and supply. Although a handful of works have been done on other membrane systems, few studies have attempted to mitigate fouling in intermittent RO systems. Accordingly, the objectives of this paper were to examine the effect of the intermittent operation on RO fouling; and to compare four intermittent operation modes including feed solution recirculation, membrane storage in the feed solution, deionized water (DI) recirculation, and membrane storage in DI water. Results showed that intermittent operation reduced RO fouling under several conditions. However, the extents of fouling mitigation were different depending on the feed conditions, foulant types, and membrane lay-up methods. When the feed solution was recirculated during the lay-up, the restoration of the flux was less significant than that by the feed solution feed-up. The use of deionized water during the lay-up was effective to restore flux, especially when the feed solution contains scale-forming salts (CaSO4) and/or colloidal silica.

Key Words
cleaning; flux; fouling; intermittent operation; reverse osmosis; scale formation

Address
Heungsik Yang, Jihyeok Choi and Yongjun Choi: School of Civil and Environmental Engineering, Kookmin University, 77 Jeongneung-Ro, Seongbuk-Gu, Seoul, 02707, Republic of Korea

Sangho Lee: School of Civil and Environmental Engineering, Kookmin University, 77 Jeongneung-Ro, Seongbuk-Gu, Seoul, 02707, Republic of Korea/ Desalination Technologies Research Institute (DTRI), Saline Water Conversion Corporation (SWCC), WQ36+XJP, Al Jubayl 35417, Kingdom of Saudi Arabia


Abstract
Vacuum-assisted air gap membrane distillation (V-AGMD) has the potential to achieve higher flux and productivity than conventional air gap membrane distillation (AGMD). Nevertheless, there is not much information on technical aspects of V-AGMD operation. Accordingly, this study aims to analyze the effect of membrane deformation on flux in V-AGMD operation. Experiments were carried out using a bench-scale V-AGMD system. Statistical models were applied to understand the flux behaviors. Statistical models based on MLR, GNN, and MLFNN techniques were developed to describe the experimental data. Results showed that the flux increased by up to 4 times with the application of vacuum in V-AGMD compared with conventional AGMD. The flux in both AGMD and V-AGMD is affected by the difference between the air gap pressure and the saturation pressure of water vapor, but their dependences were different. In V-AGMD, the membranes were found to be deformed due to the vacuum pressure because they were not fully supported by the spacer. As a result, the deformation reduced the effective air gap width. Nevertheless, the rejection and LEP were not changed even if the deformation occurred. The flux behaviors in V-AGMD were successfully interpreted by the GNN and MLFNN models. According to the model calculations, the relative impact of the membrane deformation ranges from 10.3% to 16.1%.

Key Words
air gap membrane distillation (AGMD); artificial neural network; flux; membrane deformation; vacuum; vacuum-assisted AGMD (V-AGMD)

Address
Yusik Kim, Jihyeok Choi and Yongjun Choi: School of Civil and Environmental Engineering, Kookmin University, 77 Jeongneung-ro, Seongbuk-Gu, Seoul, 02707, Republic of Korea

Sangho Lee: School of Civil and Environmental Engineering, Kookmin University, 77 Jeongneung-ro, Seongbuk-Gu, Seoul, 02707, Republic of Korea/ Desalination Technologies Research Institute (DTRI), Saline Water Conversion Corporation (SWCC), WQ36+XJP, Al Jubayl 35417, Kingdom of Saudi Arabia



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