Effect of temperature on storage polymers and settleability of activated sludge

This paper describes the effect of tropical temperatures on substrate storage and settleability in an activated sludge sequencing batch reactor (SBR). Substrate uptake, ammonium consumption, oxygen uptake, CO2 production and poly-β-hydroxyalkanoate formation and consumption were measured at different temperatures (15, 20, 25, 30 and 35°C). Kinetics of the processes were strongly influenced by temperature. All the observable rates except the PHB and NH4 consumption increased with an increase in temperature. The accumulation of storage polymers strongly depended on temperature. The role of substrate storage for microbial population dynamics and resulting SVI is discussed. The SVI strongly increased with an increased temperature. The results are discussed in the context of the kinetic selection theory of Chudoba et al. [Chudoba, J., Grau, P. and Ottavá, V. (1973) Control of activated sludge filamentous bulking. II. Selection of microorganism by means of a selector. Water Res. 7, 1389-1406.]. From this it becomes evident that the formation of storage polymers should be considered as equally important as the direct competition for substrate based on affinity constants.