Sangchul Park*, Tetsuya Kusuda*, Takayuki Shimaoka**, Yasushi Matsufuji** and Masataka Hanashima**

*Faculty of Engineering, Kyushu University
**Faculty of Engineering, Fukuoka University

+ Correspondence should be addressed to Takayuki Shimaoka:
Faculty of Engineering, Fukuoka University
(8-19-1, Nanakuma, Jonan-ku, Fukuoka 814-01 JAPAN)

Abstract

Gas concentration profiles in landfill layers, behavior of organic and inorganic contents in leachate and self-purification capacity in the bottom landfill layers were investigated. Three large scale lysimeters simulating semi-aerobic landfill were used in this study. Lysimeter "A" has only one leachate drain pipe, and lysimeter "B" has a vertical gas venting facility and a leachate drain pipe. Lysimeter "C" has a largely air permeable layer consisting of 60-80mm[phi] converter slag in the middle of the landfill layer together with a leachate drain pipe and gas venting facility. An area of more than 10% of oxygen concentration was enlarged by 2 times in "B" and 3 times in "C" , compared to lysimeter "A" . Simultaneously, it was observed that the decomposition of organic matters, e.g., TOC and T-N was accelerated, and a smaller amount of leachate was produced in lysimeter "C" , with higher air permeability. Behavior of inorganic contents, such as Fe, Mn, Ca, Cu, Zn, and Pb in landfill layers were found to have a tendency similar to those of the organic contents, which differ largely in concentration with depth. All heavy metals contained in the leachate were found not to exceed the effluent standards of Water Pollution Control Law. The leaching amounts of Mn, Ca, Cu, Zn, and Pb were also less than 1% of leachable amounts in the original adjusted solid waste over a period of 600 days after landfilling. Self-purification capacity in the bottom landfill layer was evaluated as BOD5 of 0.23kg/m3 d.

Key words: solid waste, semi-aerobic landfill, gas composition, organic and inorganic contents, self-purification