Cultivation And Characteristics Study Of Aerobic Granular Sludge With Municipal Wastewater

It should be noticed that most of studies concerning aerobic granule in both domestic and abroad have been focused on well-controlled lab-scale reactors with high strength synthetic wastewaters. In this study, taking aerobic flocculent activated sludge as seed sludge, aerobic granular sludge was successfully cultivated using low-strength organic municipal wastewater in the lab-scale(Q=12 L/d) and the pilot-scale (Q= 180 m3/d) sequencing batch reactors (SBR), respectively. The characteristics of the granular sludge were investigated. Main contents and results are as follows:1. Taking aerobic flocculent activated sludge as seed sludge, aerobic granular sludge was successfully cultivated using low-strength organic municipal wastewater in three sequencing batch reactors (SBR) under different operating conditions. The degradation characteristics of the granular sludge were investigated. The results indicated that, under proper shear force, settling time conditions, small granules were observed in the 14th, 16th and 14th days in the three reactors (R1-R3), respectively. The average size of the granule reached 1.0 mm after getting mature. No significant difference was observed in the granular size of R1 and R2, while that of R3 is slightly larger. The Sludge Volumetric Index (SVI) of granular sludge in the three SBRs ranged from 27 mg/L to 40 mg/L and the granules showed good settling ability. The mature granular sludge has strong absorption and degradation performance for organic carbon and nitrogen is removed via simultaneous nitrification and denitrification. The effluent COD and NH4+-N concentrations were about 30 mg/L and below 1.0 mg/L, respectively, indicating high contaminant removal efficiency of the aerobic granular sludge.2. Taking aerobic activated sludge as seed sludge, aerobic granular sludge was successfully cultivated using low-strength organic municipal wastewater in pilot-scale sequencing batch reactors (SBR). During granulation process the performances of sludge and optimized operation parameters were investigated. The results indicated that, by adjusting and optimizing settling time, volume exchange ratio conditions constantly, aerobic granulation of activated sludge was achieved in a pilot-scale sequencing batch reactor (SBR). The small granules were observed about three months in the reactor, and the granules were mature after 170 days. The Sludge Volumetric Index (SVI) decreased from 120 mL/g to 50 mL/g. During the stage of stable operation, the effluent COD and NH 4+ -N were about 50 mg/L and 8 mg/L, respectively, indicating high contaminant removal efficiency of the aerobic granular sludge. The size of the granule reached 1.5 mm after getting mature and a high level of protozoa was observed on the granules surface.