Contribution of organic composition and loading to enhance nutrient removal in biological spatial-temporal phase separation

A biological spatial-temporal phase separation system without an additional anaerobic reactor was devised for simultaneous removal of nitrogen and phosphorus. The process was operated at hydraulic retention time (HRT) of 8 h, solids retention time (SRT) of 10 days, and cycle time of 4 h (Anoxic/Anaerobic periods : Aerobic period = 1.5 : 2.5). Three types of influents were examined, namely glucose, glucose/acetate/propionate, and domestic wastewater. They were used to evaluate the contribution of organic composition and loading on the system performance. Nitrogen removal was strongly affected by the organic composition upon low influent C/N ratio. However, for influent C/N of 9.2–11.7 and C/P of 53.0–88.1, nitrogen and phosphorus removal noticeably improved regardless of the organic composition. Biological reactions including nitrification, denitrification, phosphate release and uptake, and PHA synthesis and utilization were clearly observed during the cycle with high organic loading, without any decline on organics removal. Furthermore, significant phosphate release and uptake were successfully accomplished without any nitrate interference and carbon competition under high organic loading. Therefore, organic loading is essential for the simultaneous removal of nitrogen and phosphorus in biological spatial-temporal phase separation.