A dynamic modelling of nutrient metabolism in a cyclic activated sludge technology (CAST) for treating low carbon source wastewater.

A new mathematical model incorporating biopolymer kinetics and the process of the simultaneous storage and growth are established for the treatment of low carbon source wastewater with a high effluent quality and energy efficiency. A set of initial parameter values was assigned as a combination of estimated values, literature-based values, and fitted values to simulate a cyclic activated sludge technology (CAST) system effectively. Compared with experimental data from the CAST system, the calibrated model demonstrated a good performance. Model simulations indicated that the recommended condition for a CAST fed with low carbon source wastewater was a volume ratio of the anoxic zone to the aerobic zone of 7/28. Moreover, using high-throughput 16S rRNA gene sequencing not only characterised the microbial communities in the CAST reactors operated under two feeding ratios but also indirectly validated the model predictions.