The Effects of Substrate Type and Concentration on Filamentous Growth in Aerobic Granular Sludge SBR

The effects of substrate type and concentration on cultivation and stability of aerobic granular sludge are investigated.During start-up phase,sucrose is used as the sole substrate,compact aerobic granular sludge form in 10 days under influent COD concentration of 600-900 mg/L,the mean diameter of the granule is 1.15±0.14 mm,SVI is 90 mL/g.However,when the influent COD concentration is increased from 900 to 1 200 mg/L,outgrowth of filamentous bacteria in aerobic granular sludge occur,when SVI is increased to 175 mL/g and large amounts of aerobic granular sludge are washed out of the reactor.In order to control the filamentous growth in aerobic granular sludge,sucrose+peptone(1∶1) are used as the substrate under influent COD concentration of 600 mg/L,during 34 days,the filamentous bacteria gradually disappear,the filamentous growth aerobic granular sludge transits to stable smooth aerobic granular sludge again.When the influent COD concentration is increased from 600 mg/L to 1 200 mg/L,non-filamentous bacteria prevail and aerobic granular sludge are stable.This study shows that substrate diversity and increased substrate N/COD ratio leads to the control of filamentous growth in aerobic granular sludge.