In 1991, Koreans produced 92,000 ton/d of MSW(municipal solid waste) of which 90 % was disposed by landfilling. The landfills generate leachate when water from precipitation, surface run-off, and groundwater contacts the landfilled refuse. The quality and quantity of leachate depend on the refuse characteristics, age of landfill, climate, geology, moisture content of the refuse, type of landfill, and operational methods such as compacting, and backfilling.
Leachate often contains high concentrations of organic matters as well as inorganic ions including ammonia and heavy metals. Leachate could be detrimental to environment as it pollutes groundwater, soil, and water resources if it is not properly collected, treated, and disposed. Therefore, landfill leachate has to be treated by physical, chemical or biological methods before released into receiving environment. Physical-chemical treatments are inefficient in organic removal, while efficient in metals. But these cost high and produce large quantites of chemical sludge. The aerobic treatments of leachate are effective in organic removal but require high dilution of raw waste. Leachate produced from young landfills is generally characterized by the presence of substantial amount of volatile fatty acids(VFAs), that are the products of anaerobic fermentation of the landfilled matters. These acids account for the most degradable chemical oxygen demand(COD) of young leachate, making them amenable to anaerobic treatment.
In this respect, this work aimed to investigate the anaerobic treatability of landfill leachate and the effect of material addition including granular activated carbon(GAC) and sludge granules on UASB reactors. This study includes not only biodegradability of different leachate but the inhibition by sodium and ammoina nitrogen.
The results of this study were as follows :
1. Leachate composition varied widely depending on the refuse characteristics and type of landfill. Leachate from young MSW landfills contains high concentrations of dissolved organic substances and ammonia nitrogen while phosphorus was low.
2. Results from the biodegradability test indicated that biochemical methane potential of A, B, C and D landill leachates were 0.12, 0.038, 0.012, and 0.020 ml CH$_4$/mg COD, respectively.
3. Initial acclimation period was reduced by the addition of granular sludge, while the treatment efficiency was enhanced by the addition of GAC.
4. The three UASB reactors operating at 35℃ with flocculent rather than granular sludge could treat leachate effectively at OLR up to 8.2 kg COD/㎥.d. At HRT of one day, COD removal rates in three reactors were over 90%, and SMA increased about ten times during 130 days of operation.
5. When treating leachate using an UASB reactor, over 80 % of COD removal in all reactors was achieved during in this experiment. For the floating problems of the granular sludge due to metal precipitates, it was necessary to pretreat the metal.
