Start-up of a High Performance Nitrosation Reactor Through Continuous Growth of Aerobic Granular Sludge

Abstract

In order to examine the continuous growth capacity of the nitrosation granular sludge (NGS), the sludge was inoculated to start up the columnar sequencing batch reactor (SBR). During 130 d, the concentration of mixed liquor suspended solids (MLSS) in SBR increased from 0.1 g·L-1 to 11.8 g·L-1, corresponding to the nitrite-nitrogen accumulation rate of 0.4-4.9 kg·(m3·d)-1, promoted by a higher ammonia-nitrogen loading rate (NLR) from 0.74 kg·(m3·d)-1 to 6.66 kg·(m3·d)-1in the influent. Because of the obvious increase in small granules (size<200 μm), the mean average diameter of NGS decreased significantly at NLR<4.44 kg·(m3·d)-1. At higher NLR values, the growth of the mean average diameter of NGS could be fitted well using a modified logistic model. The specific growth rate of the k value was 0.0229 d-1. In addition, the combined inhibition of nitrite oxidizing bacteria (NOB) was expected at relatively high concentrations of both free ammonia (FA) and free nitrite acid (FNA); thus, the nitrite accumulation ratio (NAR) in the effluent was always higher than 80%. These results provide a feasible approach to start up a high-performance NGS reactor at the industrial-scale.