Numerical Simulation of Leachate Flow into Landfill's Wells; Case Study of Kahrizak Landfill of Tehran

Pumping (extraction, purge) wells in the waste may be proposed as part of the design of new landfills to backup the leachate underdrain system. Wells are frequently used as a means of controlling leachate levels in landfills. These wells are intended to dewatering leachate mound in the landfill media after there has been a failure of the leachate collecting system or in landfills without any engineering design that is common in developing country like Iran. For an example Kahrizak Landfill which has commonly 8000 ton incoming waste per day, has no engineering design in liner at the bottom surface and there is no appropriate leachate collecting system for this volume of daily waste. Therefore infiltration of leachate to the underground water reservoir is predictable. Different kind of well piping use with variation in diameter, depth and spacing in landfills. A two phase flow in a porous media model considered for simulating flow into the wells. Hydraulic conductivity assumed to be reduced with depth. Percolation through the cover is calculated according to precipitation of the site. Model runs with time steps variation one day to 250 days. Leachate head on the liner and the flow rate into the screen faces have been determined for specific condition of Kahrizak Landfill. A deep well with 25 m depth, 15 m well screen and 15 m well spacing can reduce the leachate head below the standard criterion after 200 days.

کلیدواژه ها:

pumping wells ، landfills ، leachate control ، porous media ، dewatering