## 1 Introduction  
The dairy industry encompasses various processes that transform raw milk into a range of products for consumption, such as pasteurized and sour milk, yogurt, different types of cheese, cream and butter products, ice cream, milk and whey powders, lactose, condensed milk, and various desserts [1, 2]. In 2022, 160.0 million tons of raw milk were produced in Europe, with 149.9 million tons sent to dairies for processing into various fresh and manufactured dairy products [3]. Whey, or milk permeate, is the leftover liquid produced in the making of cheese and makes up around 85% (\(v/v\)) of the milk used. Based on the manufacture of cheese, about 8.7 L of whey are produced from 10 L of milk, with a total production of 145 million tons of whey each year [4; 5]. Around 42% of whey is thrown away, fed to animals, or used as fertilizer [5]. Milk permeate is acknowledged as the primary wastewater source, posing a significant problem for the dairy sector in terms of efficient treatment. Releasing it into natural habitats may have major environmental impacts due to its high nitrogen and organic matter concentrations [6]. Consequently, whey wastewater treatment using physical-chemical-biological process combinations is essential prior to discharge into the environment according to ref. [7]. These authors effectively used the chemical-based coagulation approach, followed by aerobic microbial degradation, to efficiently remove pollutants from cheese whey effluent [7]. Ref. [8] found that physicochemical treatments (such as coagulation-floculation) using iron salts, chitosan, and alginate may decrease indicators of contamination such as suspended particles, turbidity, and organic matter. Whey ultrafiltration is an industrial procedure utilized to extract whey protein, which is a dietary supplement with significant added value. However, this process additionally produces a byproduct known as whey permeate. The purification of these newly generated effluents is necessary due to their lactose content, which comprises 70% of the total particles [4]. Currently, various biological treatment techniques are under evaluation, and these methods are frequently recognized for their simplicity, low operational costs, and versatile applications [9]. Within the realm of biological treatments, there is rising interest in the utilization of microalgae. Algal microorganisms, when employed in wastewater treatment, contribute to a reduction in the need for chemical agents. This is attributed to the adaptability and thriving capability of efficient microalgae, which can easily acclimate to diverse wastewater environments owing to their high photosynthetic efficiency [10; 11]. Microalgae cultivated in wastewater have the potential to be used in the synthesis of many products, such as lipids, proteins, carbohydrates, and carotenoids [10]. _Chlorella_ and _Scenedesmus_ genera are the predominant microalgal species used for cultivation because of their accelerated cell proliferation in comparison to other microalgae [12]. Additionally, under conditions with high carbon dioxide levels, they can eliminate ammonia, total nitrogen, total phosphate, and generate a significant quantity of biomass [13]. _Chlorella zofingiensis_, also named _Chromochloris zofingiensis_, has been used to treat various types of wastewaters, among them dairy wastewater [14; 15; 16; 17; 18; 19; 20; 21; 22; 23; 24; 25; 26; 27; 28; 29; 30]. This species can remove 65-93% of TN (total nitrogen), 62-100% of TP (total phosphate), and 28-80% of COD (chemical oxygen demand) from wastewater and produce between 0.47 g L\({}^{-1}\) and 3.8 g L\({}^{-1}\) of biomass as well as a total lipid content between 19% and 44% under different culture conditions [14; 15; 16; 17; 18; 19; 20; 21; 22; 23; 24; 25; 26; 27; 28; 29; 30]. _Chromochloris zofingiensis_ has the potential for dual lipid-astaxanthin biosynthesis [21; 29].