NOVELTY - Aerobic granular sludge preservation involves determining chemical oxygen demand of an aerobic granular sludge that is stored in a sequencing batch reactor. The aerobic granular sludge is added with sodium acetate or glucose as the only carbon source, where ammonia nitrogen concentration is 70-80 mg/l, concentration of phosphate is 10 mg/l, calcium ion concentration is 20 mg/l and the pH of aerobic granular sludge is 7.5. The obtained aerobic granular sludge is removed from the sequencing batch reactor and then added with distilled water to remove surface nutrient.    USE - Method for preserving aerobic granular sludge (claimed).    ADVANTAGE - The method enables to preserve aerobic granular sludge with improved durability.    DETAILED DESCRIPTION - Aerobic granular sludge preservation involves determining chemical oxygen demand of an aerobic granular sludge that is stored in a sequencing batch reactor. The aerobic granular sludge is added with sodium acetate or glucose as the only carbon source, where ammonia nitrogen concentration is 70-80 mg/l, concentration of phosphate is 10 mg/l, calcium ion concentration is 20 mg/l and the pH of aerobic granular sludge is 7.5. The obtained aerobic granular sludge is removed from the sequencing batch reactor and then added with distilled water to remove surface nutrient. The obtained removed nutrient is kept in a container and then dried in a freeze drier. The obtained dried nutrient is vacuumized for 1-3 hours. The product is cooled at 15-30 degrees C and then dried for 24 hours to obtain desired product. An INDEPENDENT CLAIM is included for a method for recovery of aerobic granular sludge, which involves:    (A) taking aerobic granular sludge;    (B) freezing the product at 20 degrees C;    (C) adding tap water in the product;    (D) putting the obtained product in sequencing batch reactor, where the concentration of mixed liquor suspended solids in aerobic granular sludge is 2000-3000 mg/l;    (E) dipping the product in an micro-organism quantity; and    (F) operating the cycle for 6 hours to obtain desired product.