Correlation Between Polyhydroxyalkanoates And Extracellular Polymeric Substances In The Activated Sludge Biosystems With Different Carbon To Nitrogen Ratio

Within a wide range of carbon to nitrogen (C/N) ratio, the correlation model between polyhydroxyalkanoates (PHA) and extracellular polymeric substances (EPS) remains unclear during treating industrial wastewater. The correlation between PHA and EPS in the activated sludge biosystems with different C/N ratio (20-95) for treating the effluent of oilfield wastewater fermentation was explored in this research. PHA concentration rose first and then dropped with time (0-23 h) under different C/N ratio. The highest PHA storage (402-2130 mg.L-1) appeared gradually, and kept a quadratic upward tendency with time (R-2 = 0.991). Protein concentration declined linearly from 714 to 205 mg.L-1 (R-2 = 0.967), and polysaccharide concentration descend linearly from 409 to 117 mg.L-1 with C/N ratio (R-2 = 0.980). The fluorescence intensity (R-2 =0.973) and the concentration of proteins (R-2 = 0.965) and polysaccharides (R-2 = 0.970) displayed a cubic negative correlation with the highest PHA storage. The change trend first fell down sharply and then slowly, and the inflection point occurred in the range of 923-1486 mg.L-1 of PHA storage. Carbon transformation related to PHA and EPS through balance calculation revealed the carbon delivery flowing to EPS occupied a dominant position under normal C/N ratio, and the carbon transformation flowing to PHA played a leading role under high C/N ratio. These findings are expected to provide a "win-win" for pollutant removal and valuable bio-product production in the process of wastewater treatment.