Recirculation and Aeration Effects on Deammonification Activity

Deammonification process has been studied as an alternative technology for nitrogen removal. This process consists of the association between nitrifying and anammox bacteria, in which the process success is related to aeration, recirculation, and reactor configuration. Considering this, the present study aimed to evaluate the performance of an expanded granular sludge bed (EGSB) reactor on nitrogen removal by deammonification process. Established in a single reactor, it considered the effects of recirculation rate and variation of dissolved oxygen (DO) concentration in microbial community and nitrogen removal efficiency. Thus, two independent tests were conducted: (T1) high recirculation flow rate, performed at 43 L d−1 (Qr/Qin = 16), aeration of 30 mLair min−1 L−1 reactor, and conducted during 16 days; (T2) low recirculation flow rate performed at 6.7 L d−1 (Qr/Qin = 2.5), operated for 55 days, divided into three aeration phases: (T2a) 30 mLair min−1 L−1 reactor, (T2b) 20 mLair min−1 L−1 reactor, and (T2c) 30 mLair min−1 L−1 reactor. Results showed that in T1 the high recirculation rate favored nitrifying bacteria prevalence, intensified by reactor turbulence and anammox granules disintegration, changing activity from deammonification to a nitrification process. In addition, T1 reached up to 350 ± 100 mgN L−1 d−1 nitrogen removal rate (NRR). For T2, at low recirculation rate, deammonification process was successfully established with a NRR of 490 mgN L−1 d−1 at Qr/Qin = 2.5 and air flow rate of 20 mLair min−1 L−1 reactor.