Nitrogen and carbon removal from synthetic wastewater in a vertical structured-bed reactor under intermittent aeration

The removal of nitrogen and organic matter using a single reactor has been a common focus of investigation, and reactors operated in batch mode and under intermittent aeration have attracted special attention. This study aimed to evaluate the application of a new reactor configuration consisting of a fixed-bed reactor that was operated under conditions of continuous feeding and intermittent aeration. The reactor was built using acrylic, with a working volume of 6.1 L. The fixed bed used for biomass support was composed of polyurethane foam cylinders vertically oriented inside the reaction zone. The reactor was operated under intermittent aeration (2 h aerated and 1 h non-aerated) and a recirculation ratio Qr/Q = 5. Three different operating conditions (Phase I, Phase II, and Phase III) corresponding to hydraulic retention times (HRT) of 12 h, 8 h, and 10 h, respectively, were tested. In Phase I, the system achieved total nitrogen (TN) and chemical oxygen demand (COD) removal efficiencies of 82% and 89%, respectively. At HRTs of 8 h and 10 h, the reactor was unstable with respect to TN removal, and the average resultant removal efficiencies were 49% and 45%, respectively. However, COD removal efficiencies remained high with mean values of 85% and 88% for Phases II and III, respectively. Based on these results, it can be concluded that this new reactor configuration constitutes an alternative method for effective removal of organic matter and nitrogen from wastewater.

► We studied a new biological reactor to promote nitrogen and carbon removal.
► Polyurethane foam cylinders were vertically placed in the reactor for biomass growth.
► Decrease the hydraulic detention time decrease the efficiency of nitrogen removal.
► The best result was with hydraulic detention time of 12 h.
► The higher efficiency removal of nitrogen and carbon was 82% and 89% respectively.