[Effect of gas-lift device on the morphology and performance of ANAMMOX sludge].

ABSTRACT

The upflow reactor with gas-lift device was started up by inoculating ANAMMOX sludge granules of less than 0.9 mm. The effects of gas lift device system on the morphology and performance of ANAMMOX sludge were studied by using the nitrogen gas produced in ANAMMOX to drive the effluent circulation in the reactor. The results showed that, the airlift circulation function was not clear in the startup stage of the reactor, because the nitrogen gas production was very low. At the same time, the ANAMMOX granular sludge was easy to condensate. When the load rate of nitrogen removal reached 3.4 kg x (m3 x d)(-1), the function of gas lift was significant, resulting in gradually increased effluent self-circulation, and the granules were dispersed and grew gradually. After 183d of operation, the granular sludge was dominated by the granules with sizes of 1.6-2.5 mm, which accounted for 53.2% of the total sludge volume. The MLVSS content increased with the increase of sludge particle size. The gas lift device had the same function as the external reflux pump, and was helpful for sludge granulation in the ANAMMOX reactor, while reducing power consumption and the cost of the equipment.