[Influence of carbon source on biological nutrient removal in A2O process]

A 52.5 L pilot-scale biosystem, based on A2O configaration, was employed to investigate the effect of carbon source on biological nutrient removal and its metabolism process. Acetic acid and propionic acid were selected as the sole carbon source in different step. The COD was about 250 mg/L and NH4(+) -N was about 52 mg/L in the influent. The results showed that the removal efficiency of TN was about 65% and without any relationship to the carbon source. The TP viariation along the reactor, PHA formation and content were determined by different carbon source. When acetic acid was the sole carbon source, more phosphate was released in the anaerobic phase compared to propionic acid as the carbon source and the content of PHA was mainly PHB and PHV. The amount of PHB and PHV was almost equal. PHB was depleted in the following anoxic and aerobic phase for phosphorus removal but PHV was almost constant along the reactor. When propionic acid was the sole carbon source, less phosphate was released in the anaerobic phase and the content of PHA was mainly PHV. Almost no PHB and PH2MV were formed. PHV was depleted in the following anoxic and aerobic phase for phosphate uptake. Besides, the glycogen formation, variation and amount were different when different carbon source was dosed. More glycogen was depleted and formed in anaerobic and anoxic/aerobic phase when acetic acid was used as carbon source. Compared to acetic acid, propionic acid was more suitable for biological nutrient removal in wastewater treatment systems.