## 3 Results and Discussion
### Effect of Different Glucose Concentration on Microalgal Growth, Pigments, and Nutrient Removal
These findings confirm the efficacy of glucose supplementation in enhancing the FACHB-8 growth and wastewater treatment efficiency, while enabling the co-production of high-value products like lipids. To further evaluate the nutrient removal trends of FACHB-8 under an optimal glucose supplementation (20 g/L), the time course changes in TN and TP concentrations in ADSW were measured. As shown in Figure 7a, the TN was rapidly removed within the first 8 days and stabilized afterward. The TN assimilation by _Chlorella_ cells primarily occurred through chemical synthesis and enzymatic reactions within cells. Ammonium (NH4\({}^{+}\)-N) and nitrate (NO3\({}^{-}\)-N) served as the main nitrogen sources. These were converted into ammonia and nitrate through ammonification and nitrite reduction, followed by the nitrification and enzymatic synthesis of amino acids [15; 57]. Consequently, TN concentrations decreased steadily as microalgae grew. The TN removal reached 62.68% by day 6 and 88.70% at the end of cultivation, indicating a robust TN removal performance. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{
\begin{tabular}{c} **Glucose** \\ **Concentration** \\ **(g/L)** \\ \end{tabular} } & \multicolumn{3}{c}{**TN**} & \multicolumn{3}{c}{**TP**} \\ \cline{2-7}  & **Initial** & **Final** & **Removal** & **Initial** & **Final** & **Removal** \\  & **Concentration** & **Concentration** & **Efficiency** & **Concentration** & **Concentration** & **Emerg/L** & **Efficiency (\%)** \\ \hline
0 & 329.50 \(\pm\) 50.77 & 27.03 \(\pm\) 0.96 & 91.60 \(\pm\) 1.00 \({}^{\mathrm{ab}}\) & 19.21 \(\pm\) 0.86 & 13.87 \(\pm\) 3.36 & 37.38 \(\pm\) 9.56 \({}^{\mathrm{e}}\) \\
2 & 349.90 \(\pm\) 13.71 & 27.90 \(\pm\) 2.41 & 92.15 \(\pm\) 0.63 \({}^{\mathrm{a}}\) & 21.53 \(\pm\) 1.97 & 12.82 \(\pm\) 1.99 & 40.58 \(\pm\) 5.73 \({}^{\mathrm{de}}\) \\
5 & 347.93 \(\pm\) 14.01 & 41.95 \(\pm\) 4.85 & 87.97 \(\pm\) 0.93 \({}^{\mathrm{a}}\) & 18.80 \(\pm\) 1.00 & 4.13 \(\pm\) 0.60 & 78.03 \(\pm\) 2.86 \({}^{\mathrm{a}}\) \\
8 & 312.33 \(\pm\) 12.99 & 49.25 \(\pm\) 2.17 & 84.76 \(\pm\) 0.62 \({}^{\mathrm{d}}\) & 19.95 \(\pm\) 0.93 & 9.32 \(\pm\) 0.49 & 53.21 \(\pm\) 3.63 \({}^{\mathrm{d}}\) \\
10 & 347.47 \(\pm\) 29.22 & 47.42 \(\pm\) 3.89 & 86.22 \(\pm\) 2.34 \({}^{\mathrm{cd}}\) & 22.18 \(\pm\) 0.88 & 8.95 \(\pm\) 1.04 & 59.65 \(\pm\) 4.52 \({}^{\mathrm{bc}}\) \\
20 & 329.80 \(\pm\) 23.55 & 37.23 \(\pm\) 4.44 & 88.70 \(\pm\) 1.17 \({}^{\mathrm{bc}}\) & 19.73 \(\pm\) 2.54 & 3.32 \(\pm\) 0.56 & 82.93 \(\pm\) 4.18 \({}^{\mathrm{a}}\) \\
30 & 297.40 \(\pm\) 34.47 & 46.33 \(\pm\) 0.74 & 84.27 \(\pm\) 1.96 \({}^{\mathrm{d}}\) & 22.25 \(\pm\) 1.26 & 6.55 \(\pm\) 1.28 & 70.70 \(\pm\) 4.23 \({}^{\mathrm{ab}}\) \\ \hline \hline \end{tabular} Note: Values with different letters represent significant difference (\(p<0.05\)) between treatments.  
\end{table} 
Table 5: Nutrient removal of FACHB-8 cultivated in ADSW supplemented with varying glucose concentrations. For the TP removal (Figure 7b), TP concentrations increased during days 0-2 but declined rapidly in the subsequent 12 days. Reports have shown that microalgae possess a unique phosphorus storage mechanism that enables them to absorb excess phosphorus beyond immediate growth requirements, storing it as phosphate within intracellular polymeric substances [58]. During the initial 0-2 days, low metabolic activity might trigger phosphate release from the intracellular region into the medium, probably explaining the observed TP concentration increase in ADSW (Figure 7b). After day 4, cells entered the exponential growth phase. The elevated phosphorus levels and restored photosynthetic efficiency might promote excessive phosphorus uptake [59], driving a sharp TP decline (about 17 mg/L reduction from days 4 to 8, Figure 7b). After day 10, TP concentrations stabilized at a low level of approximately 4 mg/L (Figure 7b). Most of the phosphorus was consumed (-80%). This suggests that phosphorus might be the limiting factor in this study.