Abstract

The macromolecular composition of activated sludge (lipids, intracellular proteins and intracellular polysaccharides) was studied together with its capacity to store macromolecules such as polyhydroxybutyrate (PHB) in a conventional activated sludge system fed with synthetic sewage water at an organic load rate of 1.0kg COD/(m(3)center dot d), varying the dissolved oxygen (DO) and temperature. Six DO concentrations (0.8, 1.0, 1.5, 2.0, 2.5 and 8mg/L) were studied at 20 degrees C with a sludge retention time (SRT) of 6days. In addition, four temperatures (10oC, 15oC, 20oC and 30oC) were assessed at constant DO (2mg/L) with 2days SRT in a second experimental run. The highest lipid content in the activated sludge was 95.6mg/g VSS, obtained at 30 degrees C, 2mg/L of DO and a SRT of 2days. The highest content of intracellular proteins in the activated sludge was 87.8mg/g VSS, obtained at 20 degrees C, 8mg/L of DO and a SRT of 6days. The highest content of intracellular polysaccharides in the activated sludge was 76.6mg/g VSS, which was achieved at 20 degrees C, a SRT of 6days and a wide range of DO. The activated sludge PHB storage was very low for all the conditions studied.