This research for decolorization of monoazo dye by an anaerobic-aerobic SBBR. The cycle time was 24 hrs. in every part. (fill time and draw time were 1 hrs.) Hydraulic retention time was 1.1 day. The process of SBBR process is the same SBR process but in the SBBR process was filled with media in the reactor. In this study used hollow pellet poly propyrene media, used 1.5L per one reactor, and was fed with synthetic wastewater which was composed monoazo reactive dre and sugar. This research had 3 reactors and 3 experiments. The first experiment, to study effects of anaerobic retention time was 10, 14 and 18 hrs. (aerobic retention time were 13, 9 and 5 hrs.) The longer anaerobic retention time had the higher decolorization efficiency. The decolorization efficiencies were 49.90%, 58.55% and 68.65% in SU unit and 55.03%, 65.26% and 78.45% in ADMI unit. The COD removal efficiencies were 94.60%, 94.46% and 94.28% and the TKN removal efficiencies were 92.38%, 86.51% and 71.06%. The longer aerobic retention time than the high TKN removal efficiency. The second experiment, to study the effects of dye and sugar ratio were 1:0, 1:10, 1:15, 1:20 and 1:30. The higher quantity of sugar used had the higer decolorization efficiency. The decolorization effiencies were 0.44%, 37.51%, 60.14%, 68.65% and 74.29% in SU unit and 0.82%, 42.46%, 65.32%, 78.45% and 84.92% in ADMI unit. The COD removal efficiencies were 1.66%, 90.90%, 92.76%, 94.28% and 94.80% respectively. The TKN removal efficiencies were 3.55%, 83.05%, 79.65%, 71.06% and 67.98% respectively. Studying the effects of recirculation rate in the third experiment were 60, 100 and 140 time. The efficiencies of COD removal ; TKN removal and the efficiencies of the decolorization were the same value. The decolorization efficiencies were 73.09%, 74.66% and 74.29% in SU unit and 82.44%, 84.29% and 86.97% in ADMI unit. The COD removal and TKN removal efficiencies were 94.76%, 94.80% and 94.82 and 68.43%, 67.98% and 68.23%. In the profile study, appeared fastest decolotization rate in the initial 2 hours and when the sugar was out of in the process then it appeared slow decolorization rate. In calculation of decolorization rate and specific decolorization rate in half order it had the same trend of the efficiencies of decolorization. MLSS and MLVSS in the water above the media had less than the mass of bacteria which attached at the madia. The mass of bacteria which attached at media got more when more sugar was used.
