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51.
Kei Nakagawa Kazuro Momii Ronny Berndtsson 《Environmental Modeling and Assessment》2005,10(4):323-329
Proper management and evaluation of environmental effects for coastal groundwater aquifers require accurate estimation of
salt and fresh water movement. For this we compare two numerical methods to study saltwater intrusion. The two numerical methods
are the CIP (constrained interpolation profile) and the MOC (method of characteristics). The two numerical methods are used
to solve the salt transport equation. The two methods are applied and compared to saltwater intrusion experiments for confined
and unconfined aquifer case studies. It is found that for both cases, the CIP-method is superior in terms of calculation time
while keeping an acceptable numerical accuracy. 相似文献
52.
Kei Nakagawa Shin-Ichiro Wada Kazuro Momii Ronny Berndtsson 《Environmental Modeling and Assessment》2008,13(1):121-134
A compact model for evaluation of acid flushing of heavy-metal-contaminated soil in a small-scale on-site treatment plant
is proposed. The model assumes that the soil was re-packed in a container after excavation resulting in a soil structure with
heterogeneous and random physical and chemical properties. To evaluate the effects of heterogeneity on the efficiency of contaminant
removal by acid flushing, a numerical analysis of lead transport in the heterogeneous soil medium was performed. The model
examines cation exchange and surface complexation reactions involving three cations (Ca, Pb, and H) and one anion (Cl) in
both dissolved and exchangeable forms, two Pb surface complexes (SOPbCl and SOPbOH), and one Cl surface complex (SOH2Cl). The transport of these species during flushing with acid in a synthetically generated two-dimensional heterogeneous soil
was simulated in the model. Results indicated that the flushing fluid preferentially followed pathways with large permeability.
The heterogeneous cation exchange capacity (CEC) distribution and surface complexation sites had a significant effect on the
transport of dissolved species. Because the CEC was set to a relatively low value, Pb was adsorbed mainly as surface complexes
(SOPbCl and SOPbOH). Simulation results suggest that blocks of low hydraulic conductivity located in the upper part of the
model domain greatly impede solute transport. Ponding conditions did not significantly affect the efficiency of decontamination.
The model and its results are useful in the design of small-scale treatment plants for acid flushing. 相似文献
53.
Greywater reuse is becoming an increasingly important factor for potable water saving in many countries. Syria is one of the most water scarce countries in the Middle East. However, greywater reuse is still not common in the country. Regulations and standards for greywater reuse are not available. Recently, however, several stakeholders have started to plan for greywater reuse. The main objective of this paper is to evaluate the potential for potable water saving by using greywater for toilet flushing in a typical Syrian city. The Sweida city in the southern part of Syria was chosen for this purpose. Interviews were made in order to reflect the social acceptance, water consumption, and the percentage of different indoor water uses. An artificial wetland (AW) and a commercial bio filter (CBF) were proposed to treat the greywater, and an economic analysis was performed for the treatment system. Results show that using treated greywater for toilet flushing would save about 35% of the drinking water. The economic analyses of the two proposed systems showed that, in the current water tariff, the payback period for AW and CBF in block systems is 7 and 52 years, respectively. However, this period will reduce to 3 and 21 years, respectively, if full water costs are paid by beneficiaries. Hence, introducing artificial wetlands in order to make greywater use efficient appears to be a viable alternative to save potable water. 相似文献