Simultaneous organic and strong nitrogen removal from sewage in a pilot-scale BNR process with food waste

As sewage showing low C/N ratio in Korea has a small, but considerable amount of easily biodegradable organics, it is difficult to remove nutrients effectively. Approximately 11,434 tons of daily food waste that contain a lot of organic materials has been produced. The applicability of food waste as an external carbon source was examined in a pilot-scale BNR (biological nutrients removal) process for about 180 days. As the supply of the external carbon increased, the average removal efficiencies of T-N and T-P increased from 53% and 55% to 97% and 93% respectively. VFAs (volatile fatty acids) concentration of the external carbon source strongly affects denitrification efficiency and EBPR activity. EBPR (enhanced biological phosphorus removal) activity increased when T-N removal efficiency increased from 78% to 97%. In this study, several kinds of intracellularly stored PHAs (poly-hydroxyalkanoates) were observed. These were composed of 31% of 3HB (poly-3-hydroxybutyrate), 47% of 3HV (poly-3-hydroxyvalerate), 9% of 3HH (poly-3-hydroxyhexanoate), 5% of 3HO (poly-3-hydroxyoctanoate), and 2% of 3HD (poly-3-hydroxydecanoate) in biomass.