Document Type
Thesis
Date of Award
9-30-1984
Degree Name
Master of Science in Environmental Engineering - (M.S.)
Department
Civil and Environmental Engineering
First Advisor
Paul C. Chan
Second Advisor
Su Ling Cheng
Third Advisor
Richard B. Trattner
Abstract
Leachate migration into groundwater from leaking lagoons, hazardous waste sites, solid waste disposal sites, etc. has recently become a major cause of groundwater pollution. A possible solution to prevent leachate migration into groundwater is to create a negative hydraulic gradient toward the site. This can be achieved by installing two parallel slurry trench cut-offs around the perimeter of a leaking lagoon and by filling it with water. The water und-er the influence of positive hydraulic gradient will move toward the site and will finally find its way on the surface of the lagoon. Along with the flow of water, the leachate will also move towards the lagoon, thereby reversing the flow direction of leachate.
The dispersion of contaminant, subject to such a situation can be two fold. The contaminant will disperse along the flow direction due to convection and molecular diffusion and for very low velocities, when molecular diffusivity becomes comparable to or larger than convection, the diffusion against the flow direction will occur. Longitudinal diffusion against the mean direction of flow, which makes up the body of this thesis, has been studied by performing a series of experiments.
Two columns were used to investigate the longitudinal dispersion of a soluble matter in slowly moving fluid. One was used as a reservoir to store water and the other to obtain a porous medium. Cupric sulfate mixed sand was used as a source of contaminant. For different hydraulic gradients i, longitudinal diffusivities (KL) were measured for diffusion against the flow direction. On the basis of Saffman's equation for longitudinal diffusivity, an equation has been proposed with the help of which hydraulic gradient i could be related to KL.
For four different values of i, KL against the flow direction were calculated. It was observed that for i>3.55x10-2, there was no transport of contaminant against the flow.
This method, which is being developed at the New Jersey Institute of Technology, will have therefore no adverse effect on groundwater pollution as long as the hydraulic gradient is large enough to prevent diffusion against the flow direction.
Recommended Citation
Shakya, Surya Man, "Contaminant transport against a slowly moving fluid : an experimental investigation" (1984). Theses. 3612.
https://digitalcommons.njit.edu/theses/3612
