Browsing by Autor "Chihiro Yoshimura"

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Application of WetSpass model to estimate groundwater recharge variability in the Nile Delta aquifer
(Springer Science+Business Media, 2016) Asaad M. Armanuos; Abdelazim M. Negm; Chihiro Yoshimura; Oliver Saavedra
Erratum to: Application of WetSpass model to estimate groundwater recharge variability in the Nile Delta aquifer
(Springer Science+Business Media, 2016) Asaad M. Armanuos; Abdelazim M. Negm; Chihiro Yoshimura; Oliver Saavedra
Modeling the impact of nitrate fertilizers on groundwater quality in the southern part of the Nile Delta, Egypt
(IWA Publishing, 2016) Mohamed Galal Eltarabily; Abdelazim M. Negm; Chihiro Yoshimura; Oliver Saavedra
The use of fertilizers in agriculture in Egypt, especially nitrogen, has increased significantly in the last decade, resulting in nonpoint contamination of the groundwater resources. This study investigated the effect of using nitrogen fertilizer on groundwater contamination with nitrate in the central southern part of the Nile Delta. NO3− concentrations in shallow groundwater were assessed based on the applied urea dose (the common nitrogen fertilizer used) in year 2014. A groundwater modeling system (GMS) comprising MODFLOW and MT3D was used to simulate the three-dimensional groundwater flow and NO3− transportation processes in El-Menoufia Governorate, located in the central region of the Nile Delta aquifer. Calibration for MODFLOW was conducted to match known head configurations to minimize the water balance differences. Calibration of MT3D was accomplished by fitting the model to the measured NO3− concentrations during the year 2014. The results highlighted areas of groundwater contamination by NO3−, which occurred at shallow depths (40 m) due to the significant loads of nitrogen fertilizer application and the flood irrigation method. While the results suggested one approach was to avoid using contaminated shallow groundwater as a water source, a more sustainable approach would be to implement best management practices to reduce and control the amount of nitrate leaching into the shallow groundwater system in the future.
Quality Assessment of Southeast Nile Delta Groundwater for Irrigation
(Pleiades Publishing, 2018) Mohamed Galal Eltarabily; Abdelazim M. Negm; Chihiro Yoshimura; Sommer Abdel-Abdel-Fattah; Oliver Saavedra
The Nile Delta aquifer has deteriorated in the quality of the groundwater due to domestic, agricultural and industrial activities. In order to examine this, a dataset of thirty-one shallow groundwater samples and four surface water samples were collected in May 2014. The objective of our study is to investigate the hydrochemical characteristics of the groundwater at El-Khanka region in El-Qalubia governorate, southern Nile Delta to discuss the possibility of groundwater use for agricultural purpose. Groundwater types were defined, and the suitability for use in irrigation was evaluated. The factor analysis was conducted to investigate the relationship between the thirteen variables for exploring the loading of them in the model. Then, the principal component analysis was performed to identify the linear combination of variables that account for the greatest amount of common variance. Results showed that groundwater samples are mainly alkaline with an average pH value of 8.60. The total dissolved solids (TDS) range from 350 to 1456 mg/L. The highest concentrations of the anions and cations are sulfate ( $$\rm{SO}_4^{2-}$$ ) and sodium (Na+) respectively. The residual sodium carbonate (RSC) is less than 1.25 meq/L. Also, all groundwater samples are located in good and permissible salinity with TDS < 1500 mg/L. In addition, all samples are located in the low sodium hazard zone where sodium adsorption ratio (SAR) is less than 10. Therefore, it is concluded that, the groundwater is suitable for irrigation use in El-Qalubia Governorate. Four factors with Eigenvalues above 1.0 which correlated to each other contributed to the model with 81% of the total variance and governed the spatial variability of the aquifer.
Small-Scale Operation of an Integrated Anaerobic Baffled Reactor and Biofilter: Factors Affecting Its Performance
(American Society of Civil Engineers, 2022) Ivette Echeverría; Oliver Saavedra; Ramiro Escalera; Gustavo Heredia; Chihiro Yoshimura; Renato Montoya
This study aims to evaluate the effect of factors influencing the performance of a small-scale operating wastewater treatment plant (WWTP) integrating anaerobic baffled reactor (ABR) and biofilters with temperature fluctuations in the psychrophilic–mesophilic range. Over nine months of monitoring, the overall removal efficiencies for total chemical oxygen demand (TCOD), soluble chemical oxygen demand, particulate chemical oxygen demand, total suspended solids, ammonia nitrogen (NH3–N), and phosphorus (P) were 92%, 82%, 98%, 98%, 49%, and 31%, respectively, on average. The ABR’s TCOD removal efficiency (57%) was about 20% lower than the simulated efficiency using the Bremen Overseas Research and Development Association (BORDA)’s ABR design model, implying that temperature fluctuation and intermittent wastewater flow are possibly the factors that most affect performance. Although it was lower than the expected efficiency, the global performance of the system is supported by the significant contribution of horizontal and vertical gravel biofilters. The effluent quality complies with the local standard for wastewater discharge, except for the high content of nitrogen and phosphorus concentrations, which can be used for crop irrigation. To improve the WWTP performance, we recommend using a primary settler considering the use of a chemically enhanced solid separation process to avoid overloading organic solids in the ABR operation.