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Analytical Modeling of Well Design in Riverbank Filtration Systems

Mustafa S, Darwish M, Bahar A, Aziz ZA

Ground Water, 2019 09;57(5):756-763.
PMID: 30740693 DOI: 10.1111/gwat.12868

Analytical studies for well design adjacent to river banks are the most significant practical task in cases involving the efficiency of riverbank filtration systems. In times when high pollution of river water is joined with increasing water demand, it is necessary to design pumping wells near the river that provide acceptable amounts of river water with minimum contaminant concentrations. This will guarantee the quality and safety of drinking water supplies. This article develops an analytical solution based on the Green's function approach to solve an inverse problem: based on the required level of contaminant concentration and planned pumping time period, the shortest distance to the riverbank that has the maximum percentage of river water is determined. This model is developed in a confined and homogenous aquifer that is partially penetrated by the stream due to the existence of clogging layers. Initially, the analytical results obtained at different pumping times, rates and with different values of initial concentration are checked numerically using the MODFLOW software. Generally, the distance results obtained from the proposed model are acceptable. Then, the model is validated by data related to two pumping wells located at the first riverbank filtration pilot project conducted in Malaysia.
Solute transport modelling to manage groundwater pollution from surface water resources

Mustafa S, Bahar A, Aziz ZA, Darwish M

J Contam Hydrol, 2020 Aug;233:103662.
PMID: 32569923 DOI: 10.1016/j.jconhyd.2020.103662

This article provides an analytical solute transport model to investigate the potential of groundwater contamination by polluted surface water in a two dimensional domain. The clogging of streambed which makes the aquifer partially penetrated by the stream, is considered in the model. The impacts of pumping process, hydraulic conductivity and clogging layer on the quality of water produced from nearby drinking water wells are evaluated. It is found that results are consistent with numerical simulation conducted by MODFLOW software. Moreover, the model is applied using data of contamination occurrence in Malaysia, where high contaminants concentrations are found close to streams. Results show that the pumping activities (rate and time period) are crucial factors when evaluating the risk of groundwater contamination from surface water. Additionally, this study illustrates that the increase in either hydraulic conductivity or leakance coefficient parameters due to the clogging layer will enlarge the area of contamination. The model is able to determine the suitable pumping rate and location of the well so that the contamination plume never reaches the extraction well, which is useful in constructing riverbank filtration sites.
Spectral estimation of nonstationary EEG using particle filtering with application to event-related desynchronization (ERD)

Ting CM, Salleh ShH, Zainuddin ZM, Bahar A

IEEE Trans Biomed Eng, 2011 Feb;58(2):321-31.
PMID: 21257361 DOI: 10.1109/TBME.2010.2088396

This paper proposes non-Gaussian models for parametric spectral estimation with application to event-related desynchronization (ERD) estimation of nonstationary EEG. Existing approaches for time-varying spectral estimation use time-varying autoregressive (TVAR) state-space models with Gaussian state noise. The parameter estimation is solved by a conventional Kalman filtering. This study uses non-Gaussian state noise to model autoregressive (AR) parameter variation with estimation by a Monte Carlo particle filter (PF). Use of non-Gaussian noise such as heavy-tailed distribution is motivated by its ability to track abrupt and smooth AR parameter changes, which are inadequately modeled by Gaussian models. Thus, more accurate spectral estimates and better ERD tracking can be obtained. This study further proposes a non-Gaussian state space formulation of time-varying autoregressive moving average (TVARMA) models to improve the spectral estimation. Simulation on TVAR process with abrupt parameter variation shows superior tracking performance of non-Gaussian models. Evaluation on motor-imagery EEG data shows that the non-Gaussian models provide more accurate detection of abrupt changes in alpha rhythm ERD. Among the proposed non-Gaussian models, TVARMA shows better spectral representations while maintaining reasonable good ERD tracking performance.
Modelling contaminant transport for pumping wells in riverbank filtration systems

Mustafa S, Bahar A, Aziz ZA, Suratman S

J Environ Manage, 2016 Jan 01;165:159-166.
PMID: 26433356 DOI: 10.1016/j.jenvman.2015.09.026

Analytical study of the influence of both the pumping well discharge rate and pumping time on contaminant transport and attenuation is significant for hydrological and environmental science applications. This article provides an analytical solution for investigating the influence of both pumping time and travelling time together for one-dimensional contaminant transport in riverbank filtration systems by using the Green's function approach. The basic aim of the model is to understand how the pumping time and pumping rate, which control the travelling time, can affect the contaminant concentration in riverbank filtration systems. Results of analytical solutions are compared with the results obtained using a MODFLOW numerical model. Graphically, it is found that both analytical and numerical solutions have almost the same behaviour. Additionally, the graphs indicate that any increase in the pumping rate or simulation pumping time should increase the contamination in groundwater. The results from the proposed analytical model are well matched with the data collected from a riverbank filtration site in France. After this validation, the model is then applied to the first pilot project of a riverbank filtration system conducted in Malaysia. Sensitivity analysis results highlight the importance of degradation rates of contaminants on groundwater quality, for which higher utilization rates lead to the faster consumption of pollutants.
Analytical solutions of contaminant transport in homogeneous and isotropic aquifer in three-dimensional groundwater flow

Mustafa S, Bahar A, Aziz ZA, Darwish M

Environ Sci Pollut Res Int, 2022 Dec;29(58):87114-87131.
PMID: 35802329 DOI: 10.1007/s11356-022-21402-8

Modeling three-dimensional contaminant transport released from arbitrary shape source geometries is useful in hydrological and environmental sciences. This article produces several analytical solutions for three-dimensional contaminant transport in a homogeneous and isotropic aquifer by using Green's function with the groundwater flow which is assumed to be in three directions. The solutions are obtained for both finite depth aquifer and semi-infinite depth aquifer. Various types of sources are discussed: point, line, plane, or cuboid sources. The continuous and instantaneous sources are also investigated. A MATLAB coding is developed to calculate the numerical integrals which occur at the solutions. Some solutions are verified with the solutions obtained in the literature. This study confirms the effect of groundwater velocities in all directions on the degree and the directions of contaminant spreading. Additionally, the results highlight the significant effect of the geometrical shape of the contaminant sources on contaminant concentrations for instantaneous and continuous sources. In particular, the cuboid source and the horizontal rectangular source provide the highest concentrations. The analytical solutions developed in this article can be applied for a wide range of contaminant transport.
Trauma outcomes differences in females: a prospective analysis of 76 000 trauma patients in the Asia-Pacific region and the contributing factors

Bin Kunji Mohamad MI, Jamaluddin SF, Ahmad N, Bahar A, Khalid ZM, Binti Mohd Zaki NA, et al.

Scand J Trauma Resusc Emerg Med, 2025 Feb 24;33(1):34.
PMID: 39994732 DOI: 10.1186/s13049-025-01342-1

BACKGROUND: Trauma is a leading cause of mortality, particularly in low and middle-income countries. While extensively studied in North America and Europe, data from the Asia-Pacific are limited. An important area of research is the difference in trauma outcomes, which are theoretically noted to be better among females. However, the clinical findings are inconclusive among Asians. This study examines sex-based differences in trauma outcomes in Asia Pacific, focusing on in-hospital mortality and functional recovery at discharge.
METHODS: This observational study, from the Pan-Asia Trauma Outcomes Study (PATOS), included 76,645 trauma patients from 12 Asian Pacific countries. We analysed in-hospital mortality and functionality at discharge using the Glasgow Outcome Scale (GOS) and the modified Rankin Scale (mRS). Logistic regression models were built to test the association of sex on the outcomes.
RESULTS: Males exhibited higher in-hospital mortality (1.6%) compared to females (1.06%) ( p 50 years and ISS > 15.
CONCLUSION: This study indicates no difference in the general trauma outcomes in the Asia Pacific between females and males. Although younger females with less severe injuries had better functional outcomes, this advantage disappeared in severe injuries and those over 50 years. These results align with some previous studies, and understanding the nuances may lead to more tailored trauma care, potentially improving patient outcomes.
A global assessment of microplastic abundance and characteristics on marine turtle nesting beaches

Botterell ZLR, Ardren J, Dove E, McArthur E, Addison DS, Adegbile OM, et al.

Mar Pollut Bull, 2025 Mar 20;215:117768.
PMID: 40117935 DOI: 10.1016/j.marpolbul.2025.117768

Sandy coastal beaches are an important nesting habitat for marine turtles and a known sink for plastic pollution. Existing methodologies for monitoring the spatiotemporal patterns of abundance and composition of plastic are, however, disparate. We engaged a global network of marine turtle scientists to implement a large-scale sampling effort to assess microplastic abundance in beach sediments on marine turtle nesting beaches. Sand samples were collected from 209 sites spanning six oceans, microplastics (1-5 mm) were extracted through stacked sieves, visually identified, and a sub-sample verified via Fourier-transform infrared spectroscopy. Microplastics were detected in 45 % (n = 94) of beaches and within five ocean basins. Microplastic presence and abundance was found to vary markedly within and among ocean basins, with the highest proportion of contaminated beaches found in the Mediterranean (80 %). We present all data in an accessible, open access format to facilitate the extension of monitoring efforts and empower novel analytical approaches.