Abstract
Nitrification and denitrification in the semi-aerobic landfill of the circulatory type are experimentally studied. This landfill method is characterized by the circulation of leachate and has the advantage of the rapid decrease in the concentrations of organic matter and total-nitrogen with time.
Two dimensional model reactors of the semi-aerobic landfill were constructed, and experiments with incinerator residus as contents had been continued for about 3 years. Mass balance in the reactors based on the chemical analysis of leachate, supplied substrates, and the remaining materials in the reactors was discussed. As a result, it was found that both nitrification and denitrification are caused in the reactors and that 0.95g of organic carbon was consumed for the denitrification of 1g of nitrogen. From the counted numbers of microorganisms in the contents and leachate, the biological ecosystem in the landfill is expected to be as follows : First, oligotrophic bacteria are dominant species, and the denitrification observed in this study is caused by oligotrophic denitrifying bacteria ; Second, denitrifiers utilize the organic-carbon produced by proteolytic bacteria decomposing autotrophic organisms such as nitrifying bacteria.
