Etsuko FUKUDA Evaluation of Methane Production Activity of Digested Sludge Based on Methanogens Quantified by Real-time PCR Akiyoshi OHASHI, Hideki HARADA Batch test as methanogenic activity test is one of the indicators for operation and maintenance in anaerobic digestion system. Although methane production usually increase in proportion to time, in order to estimate the biological activities of sludge with a very low substrate degradability, to which batch experimental data couldnot be applied. Firstly, we developed a new analytical method combined with a mathematical model and could evaluate the low activity. The specific growth rates of methanogenic bacteria in the sludge, which were obtained by the mathematical model and the methane production data of batch tests, lie in the general range. However, so this evaluation is based on usual activity test, it needs long time and hard works. Then we proposed a new evaluation based on 16S rDNA copies of methanogens quantified by real-time PCR. We measured methanogenic activity of Methanosaeta concilii in batch test and quantified 16S rDNA of them. And we could indicate the proportional relation of methanogenic activity and 16S rDNA copies and suggest to be able to evalumate the activity from 16S rDNA copies by real-time PCR.