Stability of Aerobic Granular Sludge Stored in Solutions Containing Fe(Ⅲ)and Pb(Ⅱ)
This study investigated the preservation of aerobic granular sludge(AGS)in Fe(Ⅲ)and Pb(Ⅱ)solutions.Mature AGS were stored in clean water,Fe(Ⅲ)solution with concentration of 20 mg/L,and Pb(Ⅱ)solution with concentration of 20 mg/L for 60 days to explore changes in AGS stability.The shape of AGS remained largely unchanged during wet storage.However,algae growth was observed on the surface of the granules stored in clean water and Fe(Ⅲ)solution.Wet storage had minimal impact on the structural stability of the granules.After 60 days,SVI ranged from 37.91 to 40.55 mL/g,average particle size ranged from 1.02 mm to 1.15 mm,and granulation rate was between 89.15％and 93.48％.Nevertheless,both bioactivity and extracellular polymeric substances content were reduced by more than half in AGS after storage.Significant migration between AGS and the liquid phase was observed during storage,resulting in an increase in chemical oxygen demand,ammonia nitrogen,and total phosphorus to 102.72 mg/L-142.22 mg/L,24.69 mg/L-32.59 mg/L,and 4.11 mg/L-7.44 mg/L on Day 60 respectively.In contrast,Fe(Ⅲ)and Pb(Ⅱ)concentrations almost dropped to zero in the liquid phase on Day 60.The XPS analysis results confirmed that the interaction mechanism of AGS with Fe(Ⅲ)and Pb(Ⅱ)involved chemisorption and ion exchange.
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