Non-filamentousactivated sludge bulking in SBR treating the domestic wastewater

The effects of sludge loads under low DO condition and temperatures on activated sludge settle ability in a Sequencing Batch Reactor (SBR) fed with domestic wastewater were investigated. Though the system was kept in low DO levels, the sludge settled properly at sludge load of 0.20kg·(kg·d)~(-1) and 0.26(kg·(kg·d)~(-1)), respectively. Deterioration of SVIs was observed after increasing sludge load to 0.57kg·(kg·d)~(-1), which was related to the excessive growth of Zoogloea colonies. Through increasing DO and decreasing sludge load, the zoogloea flocs gradually changed to the well-settling sludge. The non-filamentous activated sludge bulking also occurred when the temperature was decreased sharply. After increasing the temperature to the original level, the sludge bulking was controlled effectively and the low SVI was recovered. When the non-filamentous activated sludge bulking occurred, the sludge had a jelly-like viscous consistency and became hard to filter.