## 3 Results and Discussion
### Nutrient Removal Efficiency
For phosphate removal, Figure 3b shows that the PO\({}_{4}\)-P concentrations dropped and reached 23.26 mg L\({}^{-1}\)\(\pm\) 5.62 mg L\({}^{-1}\), 12.43 mg L\({}^{-1}\)\(\pm\) 1.88 mg L\({}^{-1}\), 6.80 mg L\({}^{-1}\)\(\pm\) 1.42 mg L\({}^{-1}\), and 12.88 mg L\({}^{-1}\)\(\pm\) 0.02 mg L\({}^{-1}\), respectively, in BBM medium and 10%, 20%, and 50% whey wastewater. The removal efficiencies of PO\({}_{4}\)-P were higher, about 77.08% \(\pm\) 3.98%, 65.40% \(\pm\) 8.02%, and 55.14% \(\pm\) 0.02%, respectively, in 10%, 20% and 50% whey wastewater compared to BBM medium (48.00 \(\pm\) 5.47%). The N/P ratio should have a significant impact on phosphorus removal [56]. Redfield's Ratio is widely recognized as a worldwide average \begin{table}
\begin{tabular}{c c c c c} \hline
**Parameters** & **BBM (\%)** & **10\% WW (\%)** & **20\% WW (\%)** & **50\% WW (\%)** \\ \hline TN & - & 92.69 \(\pm\) 0.29 \({}^{\text{a}}\) & 88.00 \(\pm\) 0.50 \({}^{\text{b}}\) & 44.78 \(\pm\) 0.50 \({}^{\text{c}}\) \\ NO\({}_{3}\)-N & 31.34 \(\pm\) 4.02 \({}^{\text{d}}\) & 98.19 \(\pm\) 0.06 \({}^{\text{a}}\) & 92.98 \(\pm\) 2.08 \({}^{\text{b}}\) & 34.58 \(\pm\) 1.69 \({}^{\text{c}}\) \\ NH\({}_{4}\)-N & - & 97.11 \(\pm\) 1.44 \({}^{\text{a}}\) & 91.92 \(\pm\) 1.50 \({}^{\text{b}}\) & 38.47 \(\pm\) 7.94 \({}^{\text{c}}\) \\ PO\({}_{4}\)-P & 48.00 \(\pm\) 5.47 \({}^{\text{d}}\) & 77.08 \(\pm\) 3.98 \({}^{\text{a}}\) & 65.40 \(\pm\) 8.02 \({}^{\text{b}}\) & 55.14 \(\pm\) 0.02 \({}^{\text{c}}\) \\ COD & - & 85.47 \(\pm\) 0.45 \({}^{\text{a}}\) & 86.27 \(\pm\) 0.85 \({}^{\text{a}}\) & 24.75 \(\pm\) 1.64 \({}^{\text{b}}\) \\ TC & - & 79.75 \(\pm\) 2.73 \({}^{\text{a}}\) & 77.84 \(\pm\) 0.93 \({}^{\text{b}}\) & 23.03 \(\pm\) 1.75 \({}^{\text{c}}\) \\ TOC & - & 92.78 \(\pm\) 3.21 \({}^{\text{a}}\) & 80.54 \(\pm\) 1.22 \({}^{\text{b}}\) & 21.96 \(\pm\) 1.76 \({}^{\text{c}}\) \\ Lactose & - & 99.90 \(\pm\) 0.10 \({}^{\text{a}}\) & 69.37 \(\pm\) 0.06 \({}^{\text{b}}\) & 27.03 \(\pm\) 0.05 \({}^{\text{c}}\) \\ Lactate & - & 99.35 \(\pm\) 0.70 \({}^{\text{a}}\) & 86.25 \(\pm\) 0.13 \({}^{\text{b}}\) & 33.24 \(\pm\) 0.45 \({}^{\text{c}}\) \\ Acetate & - & 99.81 \(\pm\) 0.23 \({}^{\text{a}}\) & 98.16 \(\pm\) 1.09 \({}^{\text{b}}\) & 38.29 \(\pm\) 1.96 \({}^{\text{c}}\) \\ \hline \end{tabular}
\begin{tabular}{c c c c} \hline
10  
\end{table} 
Table 2: Nutrient removal efficiency (%) of _C. zofingiensis_ cultivated in different concentrations of whey wastewater (WW) compared to BBM medium (mean \(\pm\) standard deviation of three different tests, n = 3). Letters indicate statistical order of differences after one way ANOVA and post hoc tests (\(p<0.05\)): a \(>\) b \(>\) c \(>\) d.  
that varies significantly between phytoplankton species [57]. Although there are clear taxon-specific variances, it is generally acknowledged that this ratio may represent the ideal nutrient ratio needed for growth. For example, the average optimum N/P ratio for eukaryotic algae is 16-23 N/1 P, but for cyanobacteria it can vary from 10 to 16 N to 1 P [58]. In this investigation, 10% whey wastewater diluted in BBM medium resulted in a higher N/P ratio of 25. Depending on the biological parameters in the wastewater, ref. [56] proposed that the ideal N/P ratio for phosphorus removal from municipal wastewater treatment utilizing microalgae ranges from 5 to 30. The total carbon (TC) and total organic carbon (TOC) levels were decreased with removal efficiencies of 79.75% \(\pm\) 2.73%, 77.84% \(\pm\) 0.93%, and 23.03% \(\pm\) 1.75% for TC and 92.78% \(\pm\) 3.21%, 80.54% \(\pm\) 1.22%, and 21.96% \(\pm\) 1.76% for TOC in 10%, 20%, and 50% whey wastewater, respectively. For chemical oxygen demand (COD), as observed in Table 2, the removal efficiency was higher using 10% and 20% whey wastewater (85.47% \(\pm\) 0.45% and 86.27% \(\pm\) 0.85%, respectively) compared to 50% effluent (24.75% \(\pm\) 1.64%). The concentrations of lactose, lactate, and acetate were reduced by _Chromochloris zofingiensis_ (Figure 4a-c).