RESUMO
The present study evaluated the efficiency of a structured-bed reactor subjected to recirculation and intermittent aeration (SBRRIA) to promote nitrogen and carbon removal from domestic sewage. The intermittent aeration and the recycling rate of 3 keeps the desired mixing degree inside the SBRRIA. Four different operational conditions were tested by varying the hydraulic retention time (HRT) from 12 to 8â¯h and aerated and non-aerated periods (A/NA) from 2â¯h/1â¯h and 3â¯h/1â¯h. At the THD of 8â¯h and A/NA of 2â¯h/1â¯h there was a decrease in the nitrification process (77.5%) due to the increase of organic matter availability, affecting the total-N removal performance. However, by increasing the aerated period from 2â¯h to 3â¯h, the nitrification efficiency rose to 91.1%, reaching a total-N removal efficiency of 79%. The system reached a maximum total-N loading removed of 0.117â¯kgN.m-3.d-1 by applying an HRT of 8â¯h and an intermittent aeration cycle of 3â¯h, aerated and 1â¯h non-aerated. The simultaneous nitrification and denitrification (SND) process was related to a complex interplay among microorganisms affiliated mostly to Acidovorax sp., Comamonas sp., Dechloromonas sp., Hydrogenophaga sp., Mycobacterium sp., Rhodobacter sp., and Steroidobacter sp.