This review discusses microalgae assimilation of C, N and P as affected by pH-dependent factors (solubility, ionization state and bioavailability) and CO 2 enrichment in tertiary water treatment during microalgae biomass production. This study indicates the importance of monitoring critical conditions such as: 1) pH and inorganic carbon species interaction; 2) P bioavailability; 3) nitrogen removal through NH3 volatilization and 4) NH3 toxicity. Also, optimal CO2 enriched air considerations, such as: 1) combining intermittent and variable CO2 enrichment to avoid losses into the atmosphere; 2) preventing microalgae growth inhibition due to H2CO3 formation and pH acidification at early stages of the culture and 3) maintenance of optimal pH (approximate to 8.5) through the buffer system (CO2 / HCO3-). Finally, we suggest that biological technologies based on microalgae culture to remove excessive nutrient loads and compliance with environmental laws from water, represent a viable alternative attached to recycling and revaluation of resources through the generation and potential uses of biomass (e.g., fertilizer, pigments and antioxidants).