How would you design a biological phosphorus removal system?

Enhanced Biological Phosphorus Removal (EBPR) uses polyphosphate accumulating organisms (PAOs) in alternating anaerobic-aerobic conditions. In anaerobic zone (1-2 hr HRT), PAOs release phosphate while storing VFAs. In aerobic zone, PAOs uptake excess phosphorus for polyphosphate synthesis. Design parameters: rbCOD/P ratio >20, NO3-N in anaerobic zone <1 mg/L, minimum SRT 3-5 days, and MLSS 3-4 g/L. Process configurations: A2O (anaerobic-anoxic-oxic), UCT, or Johannesburg. Phosphorus removed in waste sludge (5-7% P content). Chemical backup (alum/ferric) for reliability.