Phosphorus removal and simultaneous sludge reduction in humus soil sequencing batch reactor treating domestic wastewater

The potential for enhanced biological phosphorus removal (EBPR) and simultaneous sludge reduction in humus soil sequencing batch reactor (HS-SBR) was investigated. The HS-SBR was composed of a humus soil reactor (HSR) and a conventional SBR (designated as hsSBR to differentiate from the conventional SBR used as a control). The observed sludge yield in the HS-SBR process was estimated to be 0.18 mg MLVSS (mixed liquor volatile suspended solid)/mg SCOD (soluble chemical oxygen demand), which represented a 24% reduction of solids production compared to a conventional SBR (cSBR) process. Meanwhile, the phosphorus removal in the HS-SBR remains unchanged compared with that in the cSBR. Intensive monitoring of SBR performance showed that polyhydroxy-alkanoates synthesis in the hsSBR was lower than in the cSBR. FISH analysis showed that the percentage of polyphosphate accumulating organisms (PAOs) in the hsSBR was much higher than that in the cSBR. These observations revealed the mechanism of phosphorus removal and simultaneous sludge reduction in the HS-SBR process. The role played by HSR in this process, especially on the reduction of glycogen-accumulating organisms (GAOs), was also explored and discussed.

• The HS-SBR process achieved phosphate removal and simultaneous sludge reduction.
• The percentage of PAOs in the HS-SBR was much higher than that in the cSBR.
• The growth of GAOs was repressed in the HSR.
• The PHAs synthesis in the hsSBR was much lower than that in the cSBR.