Stabilization And Application Of Aerobic Granular Sludge In SBR For Domestic Sewage Treatment

Aerobic granular sludge has been one of focuses in the biological wastewater treatment area. To study the possibility of aerobic granular sludge SBR applying in domestic sewage treatment and find the optimal operational parameters, An anaerobic/aerobic SBR was used to treat domestic sewage. The characteristics and stabilization of granular sludge was investigated, as well as the efficiency and mechanism of organic pollutants, nitrogen and phosphorus removal.The granular sludge cultivated with synthetic wastewater grew and existed stably when it was applied to treat domestic sewage. The granules are tawny, looks like fine sand. The morphology of granules is nearly spherical or elliptical with dense structure and clear outline. It is mainly composed of cocci and bacillus. The concentration and percentage of granular sludge increased first and then decreased with the same change of influent COD volume loading. At steady state, the granules had an average diameter of 948.36μm and SVI of 20~35. As the diameter of granules increased, the settling velocity, wet density and MLVSS/MLSS increased. However, SVI and water content decreased.When the granular sludge SBR was applied to treat synthetic wastewater, the average removal efficiencies of TOC, phosphate, NH4+-N, TN were 85.03%, 92.33%, 95.21% and 72.80%, respectively. Then it turned to treat domestic sewage for 6 months. Although the influent concentration varied a lot, the granular sludge SBR still had good removal performance. The average removal efficiencies of COD, TOC, phosphate, ammonium nitrogen, total nitrogen, SS were 80.54%, 70.27%, 70.98%, 92.29%, 47.47% and 82.46%, respectively. The granular sludge SBR had a certain ability to adapt shock loadings. Analysis of typical cycle showed that the granular sludge has good simultaneous phosphorus and nitrogen removal performance. Most of the organics was uptaked in anaerobic stage with the release of phosphate. The phosphorus uptake and simultaneous nitrification and denitrification (SND) occurred during aerobic period.The influent COD volume loading of 2.0~3.5 kg/(m3·d) is good for maintain sludge stabilization and the increase of sludge concentration and diameter. High organic loading is also benefit for SND. The granular sludge SBR is more suitable to operate under high organic loading. Increasing the C/N of influent and the proportion of granules in reactor is benefit for improving the SND performance. Decreasing the sludge phosphate content will improve the phosphate removal efficiency in a certain degree.