Storage and degradation of poly-beta-hydroxybutyrate in activated sludge under aerobic conditions

This research analyses the accumulation and degradation of poly-beta -hydro xybutyrate (PHB) in experiments with pulse addition of acetate to samples o f activated sludge from pilot-plant and full-scale wastewater treatment pla nts. The experiments are divided into two periods: a feast period defined a s the time when acetate is consumed and a famine period when the added acet ate has been exhausted. In the feast period the significant process occurri ng is the production of PHB from acetate. The produced PHB is utilised in t he famine period for production of glycogen and biomass. According to model ling results approximately 90% of the total potential growth occurs in the famine period utilising the stored PHB. The degradation rate for PHB in the famine period is found to be dependent on the level of PHB obtained at the end of the feast period. It was found that multiple order kinetics gives a goad description of the rate of PHB degradation. The examined sludge of lo w SRT origin is found to degrade PHB faster than long SRT sludge at high fr actions of PHB. The observed yield of glycogen on PHB in the famine period is in the range of 0.22-0.33 g COD/g COD depending on the SRT. The storage pool of glycogen in the examined sludge is mon slowly degraded than PHB (CO D/COD/h). (C) 2001 Elsevier Science Ltd. All rights reserved.