Most microalgae are photoautotrophic, meaning that their growth requirements are: illumination, inorganic carbon and minerals dissolved in the culture medium [35]. However, some microalgae are capable of growing under heterotrophic or mixotrophic conditions [36]. For instance, in heterotrophic conditions, the growth occurs in the absence of light and microalgae uses organic carbon through aerobic respiration [37]. While under mixotrophic conditions, microalgae assimilate organic carbon (i.e., glucose or glycerol) through aerobic respiration [38]. Thus, the microalgal species must be wisely selected according to the wastewater type and the final metabolic product targeted. _Chlorella vulgaris_ is commonly found in municipal wastewaters [18; 39; 40; 41], as a unicellular, eukaryotic and green microalgae (Chlorophyta). This is a resilient and freshwater species, characterized for having a coccoid shape, often exhibiting a diameter of 2 to 10 \(\upmu\)m [25; 42]. This microalgae species holds an important economic value, thus several studies were conducted to optimize the microalgal growth [25; 43; 44; 45; 46]. Previous research showed that the optimal conditions for _C. vulgaris_ growth is observed under mixotrophic conditions [45], within a temperature range of 25 to 35 \({}^{\circ}\)C [44], an alkaline pH (9-10) [47], a 16 h (day): 8 h (night) photoperiod, with a light intensity of 5-7 klux [44] and an aeration rate of 200 mL/ min [25]. Moreover, all the aforementioned abiotic parameters will affect the capability of _C. vulgaris_ for nutrient uptake, impacting the growth efficiency. The microalgae _C. vulgaris_ is one of the species that, according to the carbon source and concentration, can change their metabolism [48; 49]. According to the abiotic parameters, particularly the carbon source, _C. vulgaris_ can exhibit a photoautotrophic, heterotrophic or mixotrophic metabolism [45; 50; 51; 52]. Microalgae growth optimization is pivotal for the research of their biotechnological applications. Furthermore, the application of wastewater as a culture medium is an important tool to reduce the costs associated with microalgae growth, as well as, to promote Circular Economy and develop innovative products and techniques. For instance, microalgal biomass can be used for pharmaceutical, agricultural or energy purposes. _Chlorella_ pigments, such as chlorophyll and carotenoids, have also been researched for use as a natural colorant that can be employed as antioxidants in the biomedical industry [53; 54], and as a dye in textile industry [55; 56]. Microalgal biostimulants include macro and micronutrients, phytohormones, carotenoids, amino acids, antifungal agents, hormones, polyamines, carbohydrates, proteins and vitamins essential to improve plant growth, nitrogen fixation and solubilize phosphate solubilization, important for plant health [57; 58]. _Chlorella_ is also considered a potential resource for biofuel production due to its high lipid content (ranging from 14 to 63% of dry weight). Following lipid transesterification for biodiesel, the residual biomass can be used to generate other biofuels such as methane, bio-oil and ethanol [46; 59; 60]. Nevertheless, the high costs associated with microalgae culture medium hamper microalgal production. For this reason, this work aims to assess the growth of _C. vulgaris_ in different effluents from a municipal WWTP, namely secondary effluent (SE) and sludge run-off (SR), as possible substitutes of synthetic growth media, and evaluate the chlorophyll synthesis, as well as the nutrient removal.