Abstract
Both of methanogenic reaction and denitrification were observed at an anaerobic digester fed with synthetic substrate which contained glucose and nitrate. The anaerobic digester to which nitrate was not fed converted 64.2% of influent COD to methane. On the other hand, the COD conversion efficiency decreased to 21.8% when the COD/NO3-N ratio of the substrate decreased to 6. The highest conversion ratio of nitrate to nitrogen gas was observed at the COD/NO3-N of 9. ORP of the digester contents were maintained between -376 and -330mV if the COD/NO3-N were higher than 6, While on the other hand, the ORP level reached extremely high value of +68mV and the number of methanogenic bacteria decreased dramaticaly when the COD/NO3-N ratio of the substrate decreased to 3.
