3.1. Physical profile of the reactor system
Fig. 1 shows the profile of biomass concentration in the reactor system at different HRT (Phase I–III). In Phase I, both MLSS and MLVSS was increased slightly but with occasional sporadic decrease. At high HRT (e.g. 24 h), the microorganisms undergo a long period of aerobic starvation which could reduce their growth rate. When the HRT was reduced from 24 to 12 h (Phase II), it is distinct that the biomass concentration (MLSS) in the reactor increased from 3.9 to 6.1 g L−1. The increment of biomass concentration is due to high OLR applied in the reactor system (0.9–1.8 kg COD m−3 d−1) as a result of HRT reduction. In general, during high substrate loading, additional carbon and nutrient is provided to microorganisms, and hence, a high growth rate takes place in the reactor system. When the OLR was increased again to 3.6 kg COD m−3 d−1 (Phase III), the MLSS concentration increased rapidly from 6.1 to 9.8 g L−1. At low HRT (6 h) bacteria grows faster due to high reproduction capacity which causes the biomass concentration to increase quickly in the granular sludge reactor. As reported by Wang et al. (2005), in terms of specific growth rate analysis, under the condition of high nutrient concentration, bacteria synthesize new cells at a fast growth rate and the biomass increases quickly in the granules. The MLVSS content demonstrated similar trend to MLSS (increased from Phase I to III), mainly due to high OLR when the HRT was reduced from 24 to 6 h. The ratio of volatile biomass (MLVSS) to total biomass (MLSS) was around 0.73 and an increased in reactor biomass concentrations indicated good biomass accumulation which substantially promoted good maturation of aerobic granular sludge in the SBR system.
3.1 โพรไฟล์ทางกายภาพของระบบเครื่องปฏิกรณ์Fig. 1 shows the profile of biomass concentration in the reactor system at different HRT (Phase I–III). In Phase I, both MLSS and MLVSS was increased slightly but with occasional sporadic decrease. At high HRT (e.g. 24 h), the microorganisms undergo a long period of aerobic starvation which could reduce their growth rate. When the HRT was reduced from 24 to 12 h (Phase II), it is distinct that the biomass concentration (MLSS) in the reactor increased from 3.9 to 6.1 g L−1. The increment of biomass concentration is due to high OLR applied in the reactor system (0.9–1.8 kg COD m−3 d−1) as a result of HRT reduction. In general, during high substrate loading, additional carbon and nutrient is provided to microorganisms, and hence, a high growth rate takes place in the reactor system. When the OLR was increased again to 3.6 kg COD m−3 d−1 (Phase III), the MLSS concentration increased rapidly from 6.1 to 9.8 g L−1. At low HRT (6 h) bacteria grows faster due to high reproduction capacity which causes the biomass concentration to increase quickly in the granular sludge reactor. As reported by Wang et al. (2005), in terms of specific growth rate analysis, under the condition of high nutrient concentration, bacteria synthesize new cells at a fast growth rate and the biomass increases quickly in the granules. The MLVSS content demonstrated similar trend to MLSS (increased from Phase I to III), mainly due to high OLR when the HRT was reduced from 24 to 6 h. The ratio of volatile biomass (MLVSS) to total biomass (MLSS) was around 0.73 and an increased in reactor biomass concentrations indicated good biomass accumulation which substantially promoted good maturation of aerobic granular sludge in the SBR system.
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