Site Evaluation for Waste Disposal Site in Eastern Cairo using Hydrogeochemical Techniques
Kamilia Hamed Hagagg Hamed;
Abstract
The present work introduces a hydrogeochemical indicator for surveying the area to the northeastern Cairo, to select potential sites for radioactive waste disposal facility. The index and overlay methodology exemplified by DUPIT index, has been applied to determine the susceptibility of groundwater contamination through unsaturated zone reach. This provides a basis for classifying the study area into subareas and mapping them according to their suitability for hosting radioactive waste disposal facility, from hydrogeochemical point of view. The environmental isotopes (18O, 2H, 3H and 14C) have been used for verifying the results of waste disposal siting survey. The transit time of chosen six radionuclides (3H, 14 C, 60Co, 99Tc, 59Ni and 90Sr) through the unsaturated zone reach, has been calculated, based on simple hydrological / pollutant retardation model. A considerable consistency exists between the calculated radioisotopes transit times and the corresponding waste disposal suitability index. A high adoptability has been proven for using the employed indicator methodology for siting survey of radioactive waste disposal facility.
A detailed hydrochemical characterization (ion dominance and distribution, water types, and chemical faces) and salinization processes identification (leaching and dissolution, ion exchange…..etc.) have been conducted on the collected groundwater samples of the preferred potential sites.
The groundwater quality in north east of Cairo has been evaluated for its suitability for different purposes. And for human drinking and domestic purposes a newly developed Canadian Council of Ministers of the Environment Water Quality Index (CCME WQI) has been calculated and mapped using GIS techniques. Based on this index the area under study have been classifying in to two categories : “Fair” water quality of CCME WQI values 65-79, for all Miocene aquifer and some localities in Quaternary aquifer (over pumping localities and mixing localities with Miocene aquifer). And “Good” water quality of CCME WQI values 80-94, was noticed for the Quaternary groundwater samples adjacent to Ismailia Canal.
A probabilistic safety assessment model has been applied on existing waste disposal site to investigate the risk that might arise from a near surface disposal facility for low level radioactive waste. The model is composed of three components: source term and repository failure through different engineering barriers and unsaturated zone, geosphere transport in the groundwater and radiological risk assessment.
The retention time of the radioisotopes of the source term inventory has been determined based on the work of Mercado 1992; the radioisotopes of high retention times (more than 10 years) have been used for the analysis. The analytical advection/dispersion/adsorption model is used to analyze the migration of the radioisotopes in the groundwater. The safety distance, beyond which the radioactive level reach minimum acceptable value has been determined, the mutual relationships between inventory, downstream distance, contaminated area, time, and dose have been calculated.
Sensitivity analysis of some model parameters (seepage velocity and dispersion coefficient) on the radionuclides downstream distribution. Revealing that; the most sensitive parameter is the seepage velocity followed by dispersion parameters and finally the initial mass in the inventory. This information is important for management of remediation systems, where concern should be directed to the higher weighable factor (which is the seepage velocity) for optimizing treatment.
Pump and treat systems has been proposed for remediation in the current investigation. This techniques use one or more recovery wells to hydraulically control the contaminant plume. An analytical model for calculating the capture zone has been used oppositely, to estimate the optimum discharge rate that can remove amount of water contained in a capture zone, delimited by the boundaries of the contaminated area at the given distance. The analysis has been conducted for the worst scenario, (4th scenario).
A detailed hydrochemical characterization (ion dominance and distribution, water types, and chemical faces) and salinization processes identification (leaching and dissolution, ion exchange…..etc.) have been conducted on the collected groundwater samples of the preferred potential sites.
The groundwater quality in north east of Cairo has been evaluated for its suitability for different purposes. And for human drinking and domestic purposes a newly developed Canadian Council of Ministers of the Environment Water Quality Index (CCME WQI) has been calculated and mapped using GIS techniques. Based on this index the area under study have been classifying in to two categories : “Fair” water quality of CCME WQI values 65-79, for all Miocene aquifer and some localities in Quaternary aquifer (over pumping localities and mixing localities with Miocene aquifer). And “Good” water quality of CCME WQI values 80-94, was noticed for the Quaternary groundwater samples adjacent to Ismailia Canal.
A probabilistic safety assessment model has been applied on existing waste disposal site to investigate the risk that might arise from a near surface disposal facility for low level radioactive waste. The model is composed of three components: source term and repository failure through different engineering barriers and unsaturated zone, geosphere transport in the groundwater and radiological risk assessment.
The retention time of the radioisotopes of the source term inventory has been determined based on the work of Mercado 1992; the radioisotopes of high retention times (more than 10 years) have been used for the analysis. The analytical advection/dispersion/adsorption model is used to analyze the migration of the radioisotopes in the groundwater. The safety distance, beyond which the radioactive level reach minimum acceptable value has been determined, the mutual relationships between inventory, downstream distance, contaminated area, time, and dose have been calculated.
Sensitivity analysis of some model parameters (seepage velocity and dispersion coefficient) on the radionuclides downstream distribution. Revealing that; the most sensitive parameter is the seepage velocity followed by dispersion parameters and finally the initial mass in the inventory. This information is important for management of remediation systems, where concern should be directed to the higher weighable factor (which is the seepage velocity) for optimizing treatment.
Pump and treat systems has been proposed for remediation in the current investigation. This techniques use one or more recovery wells to hydraulically control the contaminant plume. An analytical model for calculating the capture zone has been used oppositely, to estimate the optimum discharge rate that can remove amount of water contained in a capture zone, delimited by the boundaries of the contaminated area at the given distance. The analysis has been conducted for the worst scenario, (4th scenario).
Other data
| Title | Site Evaluation for Waste Disposal Site in Eastern Cairo using Hydrogeochemical Techniques | Authors | Kamilia Hamed Hagagg Hamed | Issue Date | 2015 |
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