Start-up of anammox ASBR inoculated with different kinds of sludge

This paper is aimed at introducing the authors' study of the start-up feasibility of the two anammox ASBRs with different kinds of sludge as inoculum. Through monitoring and analyzing the data of NH~+_4-N and NO~-_2-N, as well as observing the sludge color change, we have found that, with the aerobic nitrifying sludge taken as inoculum, the anammox ASBR can be started up within 142 d. In this situation, the volumetric loading rate can reach 0.43 kg(TN)/(m~3·d) and the maximal removing efficiency of the nitrogen is likely to reach 93.3% if the anammox ASBR runs at a steady-fast state. However, the process of anammox is likely to get inhibited on the condition that the concentration of nitrite nitrogen is over 20 mmol/L. With little change of the sludge color in the process of start-up, it implies that the sludge is lacking in cytochrome C. But anammox ASBR can start up when the anaerobic granular sludge is used as inoculum within 249 d with the volumetric load rate being over 0.23 kg(TN)/(m~3·d) and the maximal removing efficiency of the total nitrogen being 99.3% under stable state of the anammox ASBR. Anammox is also likely to get inhibited on the condition that the concentration of nitrite nitrogen is over 13.4 mmol/L, and the macroscopic property of the sludge changes noticeably in the process of start-up. During the start-up process, the sludge would experience a gradual color change from black to brick-red, which indicates the increase of cytochrome C content and the enhancement of anammox activity, with the granular diameter of the sludge gradually turning from 1.5～2.5 mm to 0.5～1.0 mm. In addition, the anammox bacteria cultivated may also be different if the aerobic nitrifying sludge and anaerobic granular sludge can be taken as inoculum, respectively.