## 3 Results and Discussion
### Effect of Different Carbon Sources on Microalgal Growth, Pigments, and Nutrient Removal
Meanwhile, other groups exhibited gradual increases in growth rate, yet their biomass production remained significantly lower than those of the glucose and sodium acetate groups. After 14 days of cultivation, the glucose group achieved the highest biomass (3.90 g/L), followed by the sodium acetate group (3.33 g/L), while the \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Carbon** & **Biomass** & **Biomass Productivity** & **Maximum Biomass** & **Specific Growth** & **Maximum Specific** \\
**Source** & **Production (g/L)** & **(mg/L/d)** & **Productivity (mg/L/d)** & **Rate (/d)** & **Growth Rate (/d)** \\ \hline CK & 0.92 \(\pm\) 0.09 \({}^{\text{e}}\) & 43.81 \(\pm\) 9.67 \({}^{\text{e}}\) & 166.67 \(\pm\) 16.27 \({}^{\text{e}}\) & 0.08 \(\pm\) 0.02 \({}^{\text{c}}\) & 0.31 \(\pm\) 0.02 \({}^{\text{b}}\) \\ NaHCO3 & 0.99 \(\pm\) 0.17 \({}^{\text{de}}\) & 50.95 \(\pm\) 15.68 \({}^{\text{de}}\) & 261.25 \(\pm\) 51.27 \({}^{\text{cd}}\) & 0.09 \(\pm\) 0.02 \({}^{\text{c}}\) & 0.27 \(\pm\) 0.11 \({}^{\text{b}}\) \\ Glucose & 3.90 \(\pm\) 0.15 \({}^{\text{a}}\) & 258.10 \(\pm\) 15.24 \({}^{\text{a}}\) & 830.00 \(\pm\) 45.89 \({}^{\text{a}}\) & 0.19 \(\pm\) 0.01 \({}^{\text{a}}\) & 0.86 \(\pm\) 0.04 \({}^{\text{a}}\) \\ Na2 CO3 & 0.88 \(\pm\) 0.12 \({}^{\text{e}}\) & 42.26 \(\pm\) 120 \({}^{\text{e}}\) & 185.00 \(\pm\) 45.21 \({}^{\text{ed}}\) & 0.08 \(\pm\) 0.02 \({}^{\text{e}}\) & 0.28 \(\pm\) 0.08 \({}^{\text{b}}\) \\ CH4 yCOONa & 3.33 \(\pm\) 0.23 \({}^{\text{b}}\) & 216.31 \(\pm\) 18.63 \({}^{\text{b}}\) & 542.50 \(\pm\) 4.33 \({}^{\text{b}}\) & 0.17 \(\pm\) 0.01 \({}^{\text{a}}\) & 0.70 \(\pm\) 0.01 \({}^{\text{a}}\) \\ Glycerol & 1.62 \(\pm\) 0.17 \({}^{\text{c}}\) & 94.52 \(\pm\) 10.82 \({}^{\text{c}}\) & 301.25 \(\pm\) 37.12 \({}^{\text{c}}\) & 0.12 \(\pm\) 0.01 \({}^{\text{b}}\) & 0.29 \(\pm\) 0.04 \({}^{\text{b}}\) \\ Sucrose & 1.31 \(\pm\) 0.10 \({}^{\text{cd}}\) & 70.83 \(\pm\) 3.93 \({}^{\text{cd}}\) & 235.83 \(\pm\) 46.46 \({}^{\text{de}}\) & 0.10 \(\pm\) 0.01 \({}^{\text{bc}}\) & 0.40 \(\pm\) 0.19 \({}^{\text{b}}\) \\ \hline \hline \end{tabular} Note: Values with different letters represent significant difference (\(p<0.05\)) between treatments.  
\end{table} 
Table 2: Biomass growth profiles of FACHB-8 cultivated in ADSW supplemented with different carbon sources. Figure 2: Biomass growth of FACHB-8 cultivated in ADSW supplemented with different carbon sources. remaining four groups showed a relatively lower biomass production (Figure 2). As shown in Table 2, the glucose group also demonstrated a superior biomass productivity (258.10 mg/L/d) and maximum biomass productivity (830.00 mg/L/d). Previous studies on carbon-supplemented mixotrophic cultivation in microalgae report biomass productivities often ranging from 200 to 500 mg/L/d [41; 42; 43], within which our glucose-supplemented group (258.10 mg/L/d) falls. Additionally, the specific growth rates in the glucose (0.19/d) and sodium acetate (0.17/d) groups significantly exceeded those of other treatment groups (\(p<0.05\), Table 2). These results suggest that, aside from glucose and sodium acetate, the other tested carbon sources, especially inorganic carbon sources, exhibited limited efficacy in enhancing the microalgal biomass production in ADSW under mixotrophic cultivation. Among all tested carbon sources, glucose exhibited a superior efficiency in enhancing biomass production for FACHB-8, a finding consistent with [PERSON] et al. 's report of glucose as the optimal carbon source for enhancing _Chlorella_ biomass in wastewater systems [18]. In previous studies, glucose was identified as the optimal carbon source for enhancing biomass production in microalgae [17; 44]. The rapid biomass accumulation in glucose-supplemented cultures is attributed to its efficient assimilation by most microorganisms. It has been recognized that carbon source utilization (e.g., glucose, acetate) through heterotrophic or mixotrophic pathways varies across species and depends on the presence of specific transporters.