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Watershed-scale modeling on the fate and transport of polycyclic aromatic hydrocarbons (PAHs)
Ligaray, M.,Baek, S.S.,Kwon, H.O.,Choi, S.D.,Cho, K.H. Elsevier Scientific Pub. Co 2016 Journal of hazardous materials Vol.320 No.-
PAHs are potentially carcinogenic substances that are persistent in the environment. Increasing concentrations of PAHs were observed due to rapid urbanization, thus; monitoring PAHs concentrations is necessary. However, it is expensive to conduct intensive monitoring activities of a large number of PAHs. This study addressed this issue by developing a multimedia model coupled with a hydrological model (i.e., Soil and Water Assessment Tool (SWAT)) for Taehwa River (TR) watershed in Ulsan, the industrial capital of South Korea. The hydrologic module of the SWAT was calibrated, and further used to simulate the fate and transport of PAHs in soil and waterbody. The model demonstrated that the temporal or seasonal variation of PAHs in soil and waterbody can be well reproduced. Meanwhile, the spatial distribution of PAHs showed that urban areas in TR watershed have the highest PAH loadings compared to rural areas. Sensitivity analyses of the PAH soil and PAH water parameters were also able to determine the critical processes in TR watershed: degradation, deposition, volatilization, and wash off mechanism. We hope that this model will be able to aid the stakeholders in: regulating PAH concentrations emitted by various sources; and also apply the model to other Persistent Organic Pollutants (POPs).
Ligaray, Mayzonee,Futalan, Cybelle M.,de Luna, Mark Daniel,Wan, Meng-Wei Elsevier 2018 Journal of cleaner production Vol.175 No.-
<P><B>Abstract</B></P> <P>In this study, real thin-film transistor liquid-crystal display wastewater with an initial chemical oxygen demand (COD) concentration of 1348.00 ppm was treated using chitosan-coated bentonite (CCB). Characterization analysis of the CCB adsorbent was performed using Brunauer-Emmett-Teller surface area analysis, scanning electron microscopy, and Fourier-transform infrared spectrometer. The effect of parameters such as contact time, CCB dosage, pH and temperature on the COD removal was examined. Results show that increasing the contact time and CCB dosage increases COD removal efficiency while no considerable change was observed in removal efficiency with varying temperature and pH. Adsorption experiments showed that the removal of COD using CCB best fits the Langmuir isotherm (<I>R</I> <SUP> <I>2</I> </SUP> ≥ 0.9821) while kinetic data was best described by the pseudo-second order equation (<I>R</I> <SUP> <I>2</I> </SUP> ≥ 0.9980), which implies that chemisorption is the rate-determining step. Thermodynamic studies revealed that adsorption of COD onto CCB was spontaneous, exothermic (ΔH° = 5.95 kJ/mol) and decreased randomness in the system (ΔS° = -0.88 J/mol·K). Optimization studies using response surface methodology with central composite design was performed to determine the operating parameters that would yield the maximum COD removal. It was determined that the optimum conditions of 20.32 h, 0.8 g CCB, pH 4.0, and 30 °C would yield a maximum removal of COD of 73.34%.</P> <P><B>Highlights</B></P> <P> <UL> <LI> COD removal using CCB is spontaneous, exothermic and results to low disorder. </LI> <LI> Maximum COD removal of 73.34% from TFT-LCD wastewater using CCB is attained. </LI> <LI> CCB mass is the most significant factor affecting COD removal from wastewater. </LI> </UL> </P>
Park, Yongeun,Ligaray, Mayzonee,Kim, Young Mo,Kim, Joon Ha,Cho, Kyung Hwa,Sthiannopkao, Suthipong Informa UK (Taylor Francis) 2016 Desalination and Water Treatment Vol.57 No.26
<P>Groundwater contamination with arsenic (As) is one of the major issues in the world, especially for Southeast Asian (SEA) countries where groundwater is the major drinking water source, especially in rural areas. Unfortunately, quantification of groundwater As contamination is another burden for those countries because it requires sophisticated equipment, expensive analysis, and well-trained technicians. Here, we collected approximately 350 groundwater samples from three different SEA countries, including Cambodia, Lao PDR, and Thailand, in an attempt to quantify total As concentrations and conventional water quality variables. After that, two machine learning models (i.e. artificial neural network (ANN) and support vector machine (SVM)) were applied to predict groundwater As contamination using conventional water quality parameters. Prior to modeling approaches, the pattern search algorithm in MATLAB software was used to optimize the ANN and SVM model parameters, attempting to find the best parameters set for modeling groundwater As concentrations. Overall, the SVM showed the superior prediction performance, giving higher Nash-Sutcliffe coefficients than ANN in both the training and validation periods. We hope that the model developed by this study could be a suitable quantification tool for groundwater As contamination in SEA countries.</P>
Jeon, Dong Jin,Ligaray, Mayzonee,Kim, Minjeong,Kim, Gayoung,Lee, Gil,Pachepsky, Yakov A.,Cha, Dong-Hyun,Cho, Kyung Hwa Elsevier 2019 Science of the Total Environment Vol.658 No.-
<P><B>Abstract</B></P> <P>Fecal coliform bacteria (FCB) contamination of natural waters is a serious public health issue. Therefore, understanding and anticipating the fate and transport of FCB are important for reducing the risk of contracting diseases. The objective of this study was to analyze the impacts of climate change on the fate and transport of FCB. We modified both the soil and the in-stream bacteria modules in the soil and water assessment tool (SWAT) model and verified the prediction accuracy of seasonal variability of FCB loads using observations. Forty bias-correcting GCM-RCM projections were applied in the modified SWAT model to examine various future climate conditions at the end of this century (2076–2100). Lastly, we also compared the variability of FCB loads under current and future weather conditions using multi-model ensemble simulations (MMES). The modified SWAT model yielded a satisfactory performance with regard to the seasonal variability of FCB amounts in the soil and FCB loading to water bodies. The modified SWAT model presented substantial proliferation of FCB in the soil (30.1%–147.5%) due to an increase in temperature (25.1%). Also, increase in precipitation (53.3%) led to an increase in FCB loads (96.0%–115.5%) from the soil to water body. In the in-stream environment, resuspension from the stream bed was the dominant process affecting the amount of FCB in stream. Therefore, the final FCB loads increased by 71.2% because of the growing peak channel velocity and volume of water used due to an increase in precipitation. Based on the results of MMES, we concluded that the level of FCB would increase simultaneously in the soil as well as in stream by the end of this century. This study will aid in understanding the future variability of FCB loads as well as in preparing an effective management plan for FCB levels in natural waters.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The modified bacteria module successfully predicted fecal coliform bacteria in water. </LI> <LI> Temperature was the dominant control for the fecal coliform population in soil. </LI> <LI> Precipitation was the dominant control for the fecal coliform transport to water bodies. </LI> <LI> Monitoring streambed bacteria is critical for the water quality projections. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>