Structural stability of aerobic granules is generally poor during long-term operation. This study precipitated seven salts inside aerobic granules using supersaturated solutions of (NH4)(3)PO4, CaCO3, CaSO4, MgCO3, Mg-3(PO4)(2), Ca-3(PO4)(2) or SiO2 to enhance their structural stability. All precipitated granules have higher interior strength at ultrasonic field and reveal minimal loss in organic matter degradation capability at 160-d sequential batch reactor tests. The strength enhancement followed: Mg-3(PO4)(2) = CaSO4 > SiO2 > (NH4)(3)PO4 > MgCO3 > CaCO3 = Ca-3(PO4)(2) > original. Also, the intra-granular solution environment can be buffered by the precipitate MgCO3 to make the aerobic granules capable of degradation of organic matters at pH 3. Salt precipitation is confirmed a simple and cost-effective modification method to extend the applicability of aerobic granules for wastewater treatments. (C) 2016 Elsevier Ltd. All rights reserved.