Cold-resistant performance and the promoted development of functional community with flexible metabolic patterns in a Biofilm Bio-Nutrient Removal (BBNR) system amended with supplementary carbon source for phosphorus recovery.

The need for recovery of phosphorus (P) from wastewater has accelerated the retrofitting of existing bio-nutrient removal (BNR) processes into bio-nutrient removal-phosphorus recovery processes (BNR-PR). A periodical carbon source supplement is needed to facilitate the P-recovery. But the impact of this amendment on the cold resistances of the reactor and the functional microorganisms (for nitrogen and phosphorus (P) removal/recovery) are still unknown. This study presents the performances of a biofilm BNR process with a carbon source regulated the P recovery (BBNR-CPR) process operating at different temperatures. When the temperature was decreased from 25 ± 1 °C to 6 ± 1 °C, the system total nitrogen and total phosphorus removals and the corresponding kinetic coefficients decreased moderately. The indicative genes of the phosphorus-accumulating organisms (e.g., Thauera spp. and Candidatus Accumulibacter spp.) increased significantly. An increase of Nitrosomonas spp. genes aligned to polyhydroxyalkanoates (PHAs), glycine, and extracellular polymeric substance synthesis were observed, which was probably related to cold resistance. The results provide a new vision for understanding the advantages of P recovery-targeted carbon source supplementation for constructing a new type of cold-resistant BBNR-CPR processes.

Dissolved organic matter byproducts from combined low-level alkaline and mechanical treatment of sludge: species, and their bioavailability.

Low-level alkalinity (pH 9-10) coupled with ultrasonic or mechanical cutting with different energy input for obtaining carbon sources were tested for sludge pretreatment process before anaerobic sludge digestion. The differences between the primary sludge (PS) and waste activated sludge (WAS)-derived dissolved organic matter (DOM) species were evaluated for their bioavailability and affinity (in the form of amino acids) to the bio-nutrient removal (BNR) biomass. Soluble microbial by-product-like substances as the predominant DOM components in the raw PS and WAS increased by 23 and 22%, respectively, after low-level alkaline treatment (pH 9-10) and ultrasonication. In addition, the protein components were degraded further as free amino acids (FAAs). The sludge-derived aspartate, glutamate, followed by arginine were the most commonly used FAAs by the BNR biomass. The pattern of recovering this special sludge-derived carbon source to enhance P removal and recovery in the BNR process is depicted.

[Effect of Intracellular Carbon Source (PHA) Storage on the Mixed Growth Microbial Community Resistance to Low Temperature].

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.