Laboratory　batch　experiments　were　conducted　to　investigate　pH　profiles　during　partial　and　complete　denitrification　with　sufficient　organic　carbon　source.　Five　stirred　tank-type　glass　vessels,　with　a　7　L　working　volume　for　each,　were　used　as　SBR　reactors　that　were　all　operated　in　denitrification　mode.　Five　levels　of　initial　proportion　of　nitrogen　substances,　i.e.　nitrate　and　nitrite,　were　used　in　five　reactors,　respectively.　Results　showed　that,　at　given　temperature　and　mixed　liquor　suspended　solids　(MLSS),　partial　denitrification　could　attain　a　higher　pH　value　than　complete　denitrification　at　the　end　of　denitrification　with　the　same　initial　NO　x　concentration.　The　larger　proportion　the　nitrite　took　in　initial　NOx-　concentration,　the　higher　pH　peak　would　be　obtained　on　pH　profiles　during　denitrification　despite　the　same　total　alkalinity　produced.　It　was　found　that　different　types　of　alkalinity　were　produced　during　biological　denitrification　with　different　nitrogen　substances.　Partial　denitrification　could　more　carbonate　alkalinity　produce　than　complete　denitrification.　Furthermore,　some　characteristic　points　were　identified　on　pH　profiles　which　could　indicate　the　disappearance　of　not　only　nitrate,　but　also　nitrite　in　system.　When　computers　are　used　to　detect　these　features,　they　can　provide　rapid,　real-time　information,　regarding　the　biological　state　of　the　system.