The characteristics and kinetic behaviors of steady-state aerobic gra- nules under different aerobic starvation

Abstract

A brief review of aerobic granulation shows that the longer aerobic starvation was an important factor in the formation of aerobic granules,but little information could be found currently available on the essential role of aerobic starvation at steady-state aerobic granules.Thus,this study investigated the characteristics and kinetics of mature aerobic granules in SBR,which performed visible differences at aerobic starvation of 1 h,2 h,3 h and 4 h(R1-R4) respectively.Results indicated that the longer starvation was not a key factor on steady-state granular system.All reactors could keep sludge granulation and stable operating,and the COD removal rate of four reactors was above 98%.However,different aerobic starvation showed an obviously effect on the characteristics of aerobic granules.In 35 days,due to the lower starvation,the production yield of extracellular polymeric substance was reduced,but the ratio of polysaccharides to proteins of granules was increased by 6%,and the size granules still increased.Meanwhile,the longer starvation(2 h) would cause overgrowth of filamentous bacteria,thereby weak the physical characteristics and increase the SVI30 value of granules.In addition,kinetic behaviors of mature aerobic granules showed that the maximum specific COD removal rates(qmax) was 0.25-0.29 h?1(R1-R4),those of four reactors kept the similar level.The apparent half rate constant(K) and biomass yield(Y) of granules were 5.39-8.45 mg/L and 0.391-0.746 kgMLVSS/kgCOD in R1-R4,the reactor had a higher COD effluent and biomass yield under the lower starvation.Thus,the steady-state aerobic granules with low aerobic starvation could successfully apply in SBR,thereby save the energy consumption and keep the stability of granular system.