## 3 Results and Discussion
### Nutrient Removal Efficiency
The removal efficiencies of lactose, lactate, and acetate were more than 99% in 10% whey wastewater compared to 20% (69.37% \(\pm\) 0.06%, 86.25% \(\pm\) 0.13%, and 98.16% \(\pm\) 1.09%, respectively) and 50% whey wastewater (27.03% \(\pm\) 0.05%, 33.24% \(\pm\) 0.45%, and 38.29% \(\pm\) 1.96%, respectively). The observed reductions in COD, TC, TOC, lactose, lactate, and acetate contents in this research indicated that _Chromochloris zofingiensis_ has the ability to use the organic matter found in whey wastewater as an energy source and substrate for its development, in addition to CO\({}_{2}\). _Chromochloris zofingiensis_ achieved the highest removal efficiencies of NO\({}_{3}\)-N, NH\({}_{4}\)-N, TN, PO\({}_{4}\)-P, COD, TC, TOC, lactose, lactate, and acetate using 10% whey wastewater, at about 98.19%, 97.11%, 92.69%, 77.08%, 85.47%, 79.75%, 92.78%, 99.90%, 99.35%, and 99.81%, respectively. Presumably, under these conditions, algal cells exhibited enhanced metabolic (catabolism) efficiency due to the low concentration of total solids in the medium [9]. There is a scarcity of research that has assessed the efficacy of nutrient removal (such as NO\({}_{3}\)-N, NH\({}_{4}\)-N, TN, PO\({}_{4}\)-P, COD, TC, TOC, lactose, lactate, and acetate) from whey wastewater using microalgae. [PERSON] et al. [9] cultivated _Chlorella vulgaris_ in 10% cheese whey wastewater diluted in BBM medium to evaluate the potential of this species for wastewater treatment. They observed removal efficiencies for TC, TN, and COD of approximately 46%, 59%, and 17%, respectively, which were lower than the results of this current study using the microalgae _Chromochloris zofingiensis_. Similarly, [PERSON] et al. [4] reported lower COD removal (60%) using _Galdieria sulphuraria_ grown in 20% whey permeate. _Chromochloris zofingiensis_ has been used to treat various types of wastewaters [15; 20; 27; 28]. For example, [PERSON] et al. [20] found approximately (93%) the same removal efficiency of TN using _Chromochloris zofingiensis_ cultivated in 8% pig biogas slurry diluted in municipal wastewater. In another study, _C. zofingiensis_ cultivated using 10% dairy wastewater diluted in municipal wastewater achieved a lower removal of TN at approximately 90% [15]. [PERSON] et al. [27] explored six microalgal species, including _Chromochloris zofingiensis_, for the potential generation of lipids and the removal of nutrients from anaerobically digested swine effluent. Their findings showed that the TN and NH\({}_{4}\)-N removal efficiencies (74.87% and 64.71%, respectively) were higher in 20% anaerobically digested swine wastewater as opposed to TP removal (62.05%); it was higher in 100% anaerobically digested swine effluent. _Chromochloris zofingiensis_ was grown by [PERSON] et al. [28] in dairy wastewater with _Scenedesmus_ spp. and _Chlorella_ sp. to determine the consortium's potential for treating dairy wastewater. They found that the microalgal consortia achieved the maximum removal efficiencies of chemical oxygen demand and total phosphorus (57.01-62.86% and 91.16-95.96%, respectively) compared to the _Chlorella_ sp. monoalgal cultivation system (44.76% and 86.74%, respectively). These investigations demonstrated that different wastewater types, pretreatment setups, and _Chromochloris zofingiensis_ culture types resulted in different levels of nutrient removal.