This study investigated the removal of nitrogen and phosphorous by a biological bio-nutrient removal-carbon regulation and phosphorus recovery (BBNR-CPR) reactor at low temperature. The operating temperature of the BBNR-CPR reactor was continuously reduced, and it was found that the BBNR-CPR reactor could operate steadily at low temperature (<15℃) and low C/N ratio (<4.16). The average removal rates of total phosphorus, ammonia, and total nitrogen were 91.20%, 81.10%, and 58.62%, respectively. With increasing running time and decreasing temperature, the relative abundance of Candidatus_Competibacter, Candidatus_Accumulibacter, Run-SP 154, Thauera, and Candidatus_Nitrotoga increased. These bacteria had the functions of nitrogen and phosphorus removal and the storage of polyhydroxyalkanoate (PHA) in the biofilm of the BBNR-CPR reactor and became the dominant species to tolerate low temperature. It was found that low temperatures reduced the amount of PHA synthesized for a given equal carbon source concentration and reaction time. The amounts of PHA synthesized at 25℃, 15℃, and 8℃ accounted for 16.24%, 11.49%, and 9.01% of the dry weight of the biofilm, respectively. The pre-stored PHA biofilm has the capacity to resist low temperature. At high PHA levels, the phosphorus removal efficiencies at 8℃ and 15℃ were 97.46% and 100%, respectively, and the denitrification efficiencies were 55.15% and 82.55%. At low PHA levels, the phosphorus removal efficiencies at 8℃ and 15℃ were 11.39% and 35.02%, respectively, and the denitrification efficiencies were 0% and 12.10%, respectively.
Keywords: low C/N; low temperature; mixed growth microbial community; nitrogen and phosphorus removal; polyhydroxyalkanoate (PHA).