In comparison to other conventional microalgae process models, PM 2 has the distinct advantage of being able to account for changes in stored carbohydrate and lipid concentrations according to nutrient availability and diel light-dark cycles. Due to its application at treatment plants with stringent effluent phosphorus permits, the EcoRecover system tends to treat secondary effluents with <1 mg-P•L -1 of phosphorus, making it important to understand the storage and mobilization (consumption) of biopolymers that help microalgae balance growth across nutrient deplete and replete conditions. In addition, the EcoRecover system has different light availability in the mix tank and PBR and an internal recirculation between reactors, all of which will influence carbon storage dynamics and overall system performance. In this regard, PM 2 was particularly suited to elucidate a mechanistic understanding of the factors governing phosphorus recovery across unit operations and over 24-hour cycles, thereby supporting the optimization of system design and operational controls. In our previous study characterizing the performance of the EcoRecover system, we demonstrated the importance of biopolymer storage under light, nutrient-deplete conditions (in the PBR) to support phosphorus uptake under dark, nutrient-replete conditions (in the mix tank). Consistent with these experimental findings, the model results also predicted that the majority of orthophosphate would be removed from the mix tank (Figure ), and higher carbohydrate and lipid concentrations were consistently observed at the end of the PBR (Figure ). Moreover, the diel rhythms found in carbohydrate and lipid concentrations verified that the PM 2 can help predict microalgal response to the light availability (Figure ).