Response and recovery of mature algal-bacterial aerobic granular sludge to sudden salinity disturbance in influent wastewater: Granule characteristics and nutrients removal/accumulation

The impact of sudden salinity (1–3%) disturbance in influent wastewater on mature algal-bacterial aerobic granular sludge (AGS) was investigated, in addition to its recovery possibility when salinity disturbance was removed. Results show that the mature algal-bacterial AGS with less filamentous could maintain its good settleability with sludge volume index below 41 mL/g when wastewater salinity was increased to 3%, in which loosely bound extracellular polymeric substances might play an important role. Under this condition, the granule system achieved slightly lower dissolved organic carbon removal (from 97% to 94%), while the removals of ammonia nitrogen, total nitrogen and total phosphorus were remarkably decreased from ~100%, 66% and 70% to 23%, 16% and 38%, respectively. However, the organics and nutrients removals could be recovered immediately when the salinity disturbance was removed from the influent. P bioavailability, on the other hand, kept almost stable (93–97%) in the AGS during the examination period.