Formation of aerobic granules by Mg2+ and Al3+ augmentation in sequencing batch airlift reactor at low temperature

Aerobic granules technology (AGS) was difficult to cultivate at low temperature, and the treatment efficiency of domestic sewage was remarkably low because of low temperature, which greatly limits its development and application. AGS formation time significantly decreased for 43 days by adding 19.0 mg/L Mg(2+) and 21.0 mg/L Al(3+), moreover, AGS possessed better simultaneously chemical oxygen demand, NH(4) (+)-N, TP removal efficiencies at low temperature, which the respective removal efficiencies were 85.6, 88.8, and 91.9%. The content of total polysaccharides was 8.23 mg/gMLSS as well as the content of total protein was 8.52 mg/gMLSS, consequently, the total proteins/total polysaccharides ratio was 1.04, which the relatively high protein content induced by Mg(2+) and Al(3+) presented an essential feature for AGS formation. In addition, the affinity among Mg(2+), Al(3+) and -OH may drive the stretching vibration of -OH band which led to the infrared motion of functional groups in AGS and accelerate AGS formation as well.