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CONTENTS
Volume 14, Number 1, January 2023
 


Abstract
This study explored the feasibility of calcium-rich food waste, Mactra veneriformis shells (MVS), as an adsorbent for phosphate removal, and its removal efficiency was enhanced by the thermal activation process. The CaCO3 in MVS was converted to CaO by thermal activation (>800 °C), which is more favorable for adsorbing phosphate. Thermal activation did not noticeably influence the specific surface area of MVS. The MVS thermally activated at 800 °C (MVS-800), showed the highest phosphate adsorption capacity, was used for further adsorption experiments, including kinetics, equilibrium isotherms, and thermodynamic adsorption. The effects of environmental factors, including pH, competing anions, and adsorbent dosage, were also studied. Phosphate adsorption by MVS-800 reached equilibrium within 48h, and the kinetic adsorption data were well explained by the pseudo-first-order model. The Langmuir model was a better fit for phosphate adsorption by MVS-800 than the Freundlich model, and the maximum adsorption capacity of MVS-800 obtained via the Langmuir model was 188.86 mg/g. Phosphate adsorption is an endothermic and involuntary process. As the pH increased, the phosphate adsorption decreased, and a sharp decrease was observed between pH 7 and 9. The presence of anions had a negative impact on phosphate removal, and their impact followed the decreasing order CO32- > SO42- > NO3- > Cl-. The increase in adsorbent dosage increased phosphate removal percentage, and 6.67 g/L of MVS-800 dose achieved 99.9% of phosphate removal. It can be concluded that the thermally treated MVS-800 can be used as an effective adsorbent for removing phosphate.

Key Words
adsorption; calcination; phosphorus; seashell; thermal activation

Address
Yeon-Jin Lee: Department of Bioresources and Rural System Engineering, Hankyong National University, Anseong 17579, Republic of Korea

Jae-In Lee: Department of Integrated System Engineering, Hankyong National University, Anseong 17579, Republic of Korea

Chang-Gu Lee: Department of Environmental and Safety Engineering, Ajou University, Suwon 16499, Republic of Korea

Seong-Jik Park: Department of Bioresources and Rural System Engineering, Hankyong National University, Anseong 17579, Republic of Korea/ Department of Integrated System Engineering, Hankyong National University, Anseong 17579, Republic of Korea/ Institute of Agricultural Environmental Sciences, Hankyong National University, Anseong 17579, Republic of Korea

Abstract
This work addresses the development of microfiltration ceramic membrane from alumina using extrusion method. The membranes were sintered at different temperatures ranging between 1000 and 1300°C. The alumina was characterized with thermogravimetric analysis, particle size distribution, X-ray diffraction, Fourier transform infrared spectrometer and scanning electron microscope analysis. Subsequently, the effect of sintering temperature on the membrane properties such as porosity, flexural strength, and pure water permeability was investigated and optimized for the sintering temperature. It is observed that with increasing sintering temperature, the porosity of the membranes decreases and the flexural strength, and pure water permeability of the membranes increase. The uncoated and coated membranes were compared at constant flux mode of filtration. Under the turbidity solution recirculation alone at 100 NTU, trans-membrane pressure (TMP) of uncoated membrane remained constant when the filtration flux was below 121 Lm-2 h-1, while the coated membrane was 111 Lm-2 h-1. Although suction pressure increased more rapidly at higher turbidity, coated membrane filtration showed better removal efficiency of the turbidity.

Key Words
alumina; ceramic membrane; fouling; microfiltration; turbidity

Address
Hyunsoo Kim and Oyunbileg Purev: Department of Energy and Resource Engineering, Chosun University, Gwangju 61452, Korea

Eunji Myung: Green-bio Research Facility Center, Seoul National University, Gangwon-do 25354, Korea

Kanghee Cho and Nagchoul Choi: Research Institute of Agriculture and Life Sciences, Seoul National University, Seoul 08826, Korea

Abstract
The studies on the effect of different plastic properties (e.g., types, shapes, presence of additivies) on the sorption of contaminants in the agricultural environment are limited. In this study, Cu and Pb, the commonly found heavy metals in the environment, were used to investigate the sorption capacities of microplastics (MPs). The Pb sorption capacity increased in the order of polystyrene (PS)<polyethylene (PE)<polyvinyl chloride (PVC). The estimated Cu sorption capacity was greater for the PE films than the PE fragments, while the sorption strength was greater for the PE fragments. This suggests that the shapes of MPs can affect the contaminant sorption capacities. With the PE fragments, the Pb sorption capacity was greater than the Cu sorption capacity by 10-12 times. Also, the Pb and Cu sorption capacities were greater for the PE fragments with additives than the PE fragment without additives. After the sorption of Pb or Cu on MPs, the toxic effects of the Pb or Cu solutions were decreased, suggesting that the toxic effects of contaminants can be affected by the co-presence of MPs in the environment. Overall, the results show that different types and shapes of MPs and the presence of additives can affect the heavy metal sorption capacities of MPs.

Key Words
Cu; microplastics; Microtox; Pb; sorption

Address
Ruri Lee and Eun Hea Jho: Department of Agricultural and Biological Chemistry, Chonnam National University, 77 Yongbong-ro, Buk-gu, Gwnagju 61186, Republic of Korea

Jinsung An: Department of Civil & Environmental Engineering, Hanyang University, 55 Hanyangdaehak-ro, Sangrok-gu, Ansan 15588, Republic of Korea


Abstract
In previous studies, solely ferric (Fe3+) and calcium (Ca2+) ions were commonly used for removal of PO4-P (considered as T-P in this study) in wastewater via chemical precipitation. Herein, the removal of total phosphorus (T-P) in wastewater was performed using various mineral and lime dissolved solutions. The dissolution kinetics of different minerals (feldspar, olivine, elvan, illite, sericite, and zeolite) and lime was compared and used their solutions for T-P removal of real wastewater. The highest T-P removal (almost 90%) was obtained by the lime dissolved solution and followed by zeolite, illite, feldspar, and others. We observed a significant co-relationship (R of 0.96) between the amount of initial Ca2+ and T-P removal. This was induced by formation of hydroxyapatite-like mineral via Ca-P precipitation reaction at high pH solution. Furthermore, additional removal of suspended solid (SS) and chemical oxygen demand (COD) was achieved by only lime dissolved solution. Finally, the lime-feldspar dissolved solutions were prepared at different ratios (10-50%), which showed a successive T-P removal up to two times by samples of 40 and 50%.

Key Words
Ca dissolved solution; feldspar; lime; mineral; phosphorus

Address
Joohyun Kim: Department of Civil and Environmental Engineering, Konkuk University, 120 Neungdong-ro, Gwangjin-gu, Seoul 05029, Republic of Korea/ School of Chemical and Biological Engineering, Institute of Chemical Process (ICP), Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul, 08826, Republic of Korea

Sunho Yoon, Jueun Jung and Sungjun Bae: Department of Civil and Environmental Engineering, Konkuk University, 120 Neungdong-ro, Gwangjin-gu, Seoul 05029, Republic of Korea


Abstract
Biofilms significantly affect the performance of wastewater treatment processes in which biodegradability of numerous microorganisms are actively involved, and various technologies have been applied to secure microbial biofilms. Understanding changes in biofilm characteristics by regulating expression of signaling molecules is important to control and regulate biofilms in membrane bioreactor, i.e., biofouling. This study investigated effects of addition of acyl-homoserine lactones (AHL) as a controllable factor for the microbial signaling system on biofilm formation of Pseudomonas aeruginosa PAO1 and multiple strains in membrane bioreactor. The addition of three AHL, i.e., C4-, C6-, and C8-HSL, at a concentration of 200 μg/L, enhanced the formation of the PAO1 biofilm and the degree of increases in the biofilm formation of PAO1 were 70.2%, 76.6%, and 72.9%, respectively. The improvement of biofilm formation of individual strains by C4-HSL was an average of 68%, and the microbial consortia increased by approximately 52.1% in the presence of 200 μg/L C4-HSL. CLSM images showed that more bacterial cells were present on the membrane surface after the AHL application. In the COMSTAT results, biomass and thickness were increased up to 2.2 times (PAO1) and 1.6 times (multi-strains) by C4-HSL. This study clearly showed that biofilm formation was increased by the application of AHL to individual strain groups, including PAO1 and microbial consortia, and significant increases were observed when 50 or 100 μg/L AHL was administered. This suggests that AHL application can improve the biofilm formation of microorganisms, which could yield an enhancement in efficiency of biofilm control, such as in various biofilm reactors including membrane bioreactor and bioflocculent systems in water/wastewater treatment processes.

Key Words
acyl-homoserine lactones; biofilm formation; PVDF membrane; Quorum sensing

Address
Wonjung Song: The Academy of Applied Science and Technology, Konkuk University, 120 Neungdong-ro, Gwangjin-gu, Seoul 05029, Republic of Korea

Chehyeun Kim, Jiwon Han, Jihoon Lee, Zikang Jiang and Jihyang Kweon: Department of Environmental Engineering, Konkuk University, 120 Neungdong-ro, Gwangjin-gu, Seoul 05029, Republic of Korea

Abstract
In this study, high concentrations of cadmium-containing wastewater were treated by electrodialysis (ED) with a channel stack. The limiting current density (LCD), cadmium removal efficiency, and current efficiency were investigated under each experimental condition according to the Reynolds number (Re), membrane area, and pH. With the increase in the film area to 111, 333, 555, and 777 cm2 at Re (109.1), LCDs decreased to 408.11, 44.45, 35.32, and 13.64 A/m2, respectively. The highest cadmium removal efficiency (99.6%) and current efficiency were obtained for the membrane area of 111 and 777 cm2, respectively. Under changing Re in the pH range of 1 to 4, Re and LCD were proportional under the same pH condition, and pH and LCD tended to be inversely proportional under the same Re condition. Cadmium removal rate was the best at the pH range 3 - 4. It has been found that ED with channeled stacks can be successfully applied to treat wastewater containing high concentrations of cadmium.

Key Words
cadmium; channeled stack; electrodialysis; limiting current density; Reynolds number

Address
Kyung Jin Min, Hyo Jin An, Ah Hyun Lee and Ki Young Park: Department of Civil and Environmental Engineering, Konkuk University, 120 Neungdong-ro, Gwangjin-gu, Seoul 05029, Korea

Hyun-Gon Shin: Department of Energy and Environmental Engineering, Shinhan University, Gyeonggi-do 480-857, Korea


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