초록
<P>The reactor was started up under the neutral condition. The pH value in the reactor was gradually lowered down. At pH 7.0, the average COD removal efficiency the biogas yield and the methane content of the UASB reactor were steady at 93% above, 25L·d<SUP>-1</SUP>and 54%, respectively. During the period of the pH value lowered from 7.0 to 5.5, the average of the COD removal efficiency, the biogas yield and the methane content of the UASB reactor were 83.1%, 19.6L/d and 47.7%, respectively. At pH 5.5, the operating condition of UASB reactor began to recover from the 76<SUP>th</SUP>day, and on the 84<SUP>th</SUP>day, the COD removal efficiency, biogas yield and the methane content recovered to 80.5%, 17.1L/d and 47.9%, respectively.</P>