Specific gravity of activated sludge was increased by proliferation of phosphorus accumulating organisms (PAOs), which helped to resume state of limited sludge bulking after excessive sludge bulking.

聚磷菌的增殖使活性污泥比重增大，有助于发生恶性膨胀的污泥逐渐恢复沉降性能，维持活性污泥微膨胀。