The biological phosphorus removal by humus soil sequencing batch reactor process (HS-SBR) and a conventional sequencing batch reactor (cSBR) were compared using acetate as a sole carbon source. The HS-SBR was composed of a humus soil reactor (HSR) and a conventional SBR (designated as hsSBR). The HS-SBR showed a more stable and effective phosphorus removal with the efficiency of 97.3%. while as to the cSBR, it was 80%. However, in the HS-SBR for the removal of COD and nitrogen it was not improved. Moreover, in the anaerobic phase, the hsSBR had greater soluble orthophosphate (SOP) release and poly-beta-hydroxybutyrate (PHB) synthesis capacity, but lower poly-beta-hydroxyvalerate (PHV) synthesis and glycogen (Gly) degradation capacity than those in the cSBR. In addition, acetate (HAc) uptake rate and SOP release rate in the hsSBR were greater than those in the cSBR. In the aerobic phase, the PHA utilization efficiency for SOP uptake in the hsSBR was higher than the cSBR. All these observations suggested that adding the HSR improved the relative dominance of the phosphate accumulating organisms (PAOs) in the hsSBR. (C) 2010 Elsevier B.V. All rights reserved.