The Phototrophic Process Model (PPM) is one example of a lumped pathway metabolic model previously developed for mixed microalgal communities. The PPM used metabolic pathways of Chlamydomonas reinhardtii for its metabolic reactions and stoichiometry, and its kinetic expressions were determined by observing mixed microalgal communities. In this model, the microalgae were assumed to grow on light energy and internally stored carbohydrates and lipids, without allowing for the consumption of extracellular organic carbon. To date, the PPM has only been calibrated and validated for laboratory-scale applications under highly controlled environments using sterilized culture media, heat-controlling fans, and artificial light sources (LEDs) without natural variability. To improve model accuracy under fluctuations in wastewater composition and environmental conditions, the development of a model considering the various carbon and energy sources used during different types of microalgal growth (photoautotrophy or heterotrophy) is required. There is also a need to demonstrate whether the core metabolic pathways embedded in the PPM are shared across a broader set of microalgal species (i.e., beyond C. reinhardtii). Furthermore, calibration and validation of the model using a robust dataset that represents real-world dynamics at full-scale is required to properly assess the accuracy and fidelity of the model for real-world applications.