Air-water partitioning equilibrium of tetrahydrofuran in an activated sludge system.

This study evaluate the effect of liquid tetrahydrofuran (THF) concentration and biomass content on the THF air-water partitioning equilibrium for a simulated activated sludge system. The equilibrium of the partition at the air-water interface is given by a partitioning coefficient (pc) = Cg*/CL, where Cg* denotes the gaseous concentration in equilibrium with the aqueous THF concentration (CL). Variations of pc with CL in static pure water are evaluated, and high solubility of THF in water caused pc values to drop as the CL increased from 29.81 +/- 0.16 to 297.75 +/- 2.28 mg/L at a constant temperature of 27 degrees C. Meanwhile, the hydrophilicity of THF in water induced a biomass effect, causing pc to increase in the activated sludge liquor. Due to the co-effect of liquid THF concentration and biomass content, the pc values of THF for the liquor of mixed liquid suspended solid (MLSS) concentration = 1220 +/- 86 mg/L and THF CL = 242.91 +/- 69.09 mg/L increased 22.5% compared to those in the pure agitated water. The biomass effect on pc of hydrophilic VOC increases the gaseous VOC emission rate from the activated sludge facilities.

Denitrifying characteristics of the multiple stages enhanced biological nutrient removal process with external carbon sources.

This research investigated denitrifying activity of activated sludge with three external carbon sources (sodium acetate, methanol and glucose) via a series of batch experiments. Activated sludge used was cultivated in a multiple stages enhanced biological nutrient removal (EBNR) process that exhibited high removal efficiency of effective carbon, nitrogen, and phosphorus. Results showed type of external carbon source had a significant influence on specific nitrate utilization rate, nitrite accumulation, adaptive time of microorganisms, and nitrate removal efficiency. Sodium acetate addition resulted in high phosphate concentration in effluent; meanwhile methanol caused increasing turbidity and carbon breakthrough problem. When glucose was fed to be the external carbon source, accumulative nitrite concentration was higher than that with sodium acetate or methanol addition. When sodium acetate, methanol and glucose were used to be the electron donor, average dosages for nitrate elimination were 6.97, 5.85, and 5.65 mg-COD/mg-N, respectively. Because the final polyhydroxyalkanoates (PHAs) concentrations contained within the biomass were more than the original level and no phosphate re-release was observed, glycogen-accumulating organisms (GAOs) might exist in the multiple stages EBNR process and increased carbon dosage for further nitrate removal.