[Cultivation and nitrogen removal characteristics of ANAMMOX granules]

An SBR reactor seeded with anaerobic granular sludge was started-up to enrich ANAMMOX (anaerobic ammonia oxidation) bacteria and investigate its nitrogen removal characteristics. Research results showed that hydraulic retention time (HRT) was the most important factor to enrich ANAMMOX bacteria. When the HRT was controlled at 30 d during the initial cultivation, the SBR reactor presented ANAMMOX activity at t = 58 days. Simultaneously, the anaerobic granular sludge changed gradually from dust black to brownish color and its diameter became smaller. At t = 90 days, the ANAMMOX was obvious, and ANAMMOX granules was cultivated successfully. NH4(+) -N and NO2(-) -N were removed simultaneously with higher speed and maximum removal rate reached 14.6 g/(m3 x d) and 6.67 g/(m3 x d) respectively. Between t = 110 days and t = 156 days, the nitrogen load was increased gradually to a hydraulic retention time of 5 days. The removal rate of ammonium and nitrite were 60.6% and 62.5% respectively. The ratio of nitrite/ammonium was 1.12. The sludge changed to henna and formed ANAMMOX granulation with high nitrogen removal activity. The total nitrogen load was 34.3 g/(m3 x d).