جستجوی مقالات مرتبط با کلیدواژه « تصفیه درجا » در نشریات گروه « مهندسی آب »

Groundwater nitrate pollution is nowadays one of the most important environmental issues with significant effect on human and environment health. Due to the importance of this vital water source, methods have been developed for purifying the groundwater contaminated with nitrate. One of the effective and long-lasting purification methods for groundwater contaminated with agricultural drains is the in-situ method of denitrification wall. The general concept of this technology is placing a denitrification wall with carbon material across the nitrate-contaminated groundwater pathway so that it can block the nitrate pollution as nitrate masses pass through the wall due to the groundwater natural hydraulic gradient. Despite widespread acceptance, there are still many unresolved issues regarding the long-term performance of denitrification walls which requires more understanding on the behavior, principles of design and construction methods of such walls. Accordingly the aim of this study was to fully investigate the technology and implementation of denitrification walls in all aspects. The method of this study was library type and the content, explored in simple expressions in different sections, is based on a descriptive-analytical approach to experimental and scientific experiences of this method on contaminated sites. Results showed that denitrification wall can be drilled underground either in form of funnel and gate or continuous configuration and the choice depends on the hydrological characteristics of the site and the cost of materials used in the wall. Also, when water flow contaminated with nitrate passes through the denitrification wall, nitrate pollution is treated with either adsorption or biological removal mechanisms or a combination of them. The right application of the denitrification wall can be economically efficient and the success of the system depends on the use of appropriate tools and solutions for accurate formulation of the problem in the real aquifer environment with its large dimensions and complexity. In this regard, numerical modeling and laboratory studies can help to achieve a detailed understanding of the problem in a real environment.

Determination of the extent and growth rate of contamination zones in water resources is a crucial stage in remediation studies. The process is especially complicated due to the multiplicity of the variables involved and the limited access to groundwater aquifers. The present study uses the image processing technique to define the contaminant plume and to analyze diffusivity coefficients for seepage flows in porous media. The image processing algorithm was developed in MATLAB software and the least squares method was used to solve the diffusion equation. Thus, the hydrodynamic dispersion coefficients in porous media were calculated without any turbulence over wide ranges of time and place with an acceptable accuracy. Analysis and verification of the data thus obtained confirmed the accuracy of the proposed model and revealed a limited error range of less than 11%. It may, therefore, be claimed that the proposed method is an effective means for studying diffusivity. The equations for estimating diffusivity coefficients were developed as a function of both the porous media characteristics and the Péclet number.Using the equations, diffusivity coefficients in the range of 0.002 to 0.0028 m were obtained for a porous medium with a grain size varying from 0.5 to 3 mm.

This study investigates the potential of nano-zero-valent iron particles coated with nickel in the removal of lead (Pb2+) from porous media. For this purpose, the nano-particles were initially synthesized and later stablilized using the strach biopolymer prior to conducting batch and continuous experiments. The results of the batch experiments revealed that the reaction kinetics fitted well with the pseudo-first-order adsorption model and that the reaction rate ranged from 0.001 to 0.035 g/mg/min depending on solution pH and the molar ratio of Fe/Pb. Continuous experiments showed that lead remediation was mostly influenced not only by seepage velocity but also by the quantity and freshness of nZVI as well as the grain type of the porous media. Maximum Pb2+ removal rates obtained in the batch and lab models were 95% and 80%, respectively. Based on the present study, S-nZVI may be suggested as an efficient agent for in-situ remediation of groundwater contaminated with lead.