# Exploring an Integrated Manure-Sewater System for Sustainable Cyanobacterial Biomass Production
## 3 Results  
### Effect of NaCl Concentration on Growth of Cyanobacterial Strain HSaC  
The biomass of cyanobacterial strain HSaC was significantly (\(p<0.05\)) influenced by the NaCl concentration. The biomass of HSaC increased as the NaCl salt concentration increased up to 120 mM, but further increases in salt concentration resulted in a decrease in biomass production. Accordingly, the highest (30.52 mg/mL) biomass yield was obtained at 120 mM NaCl concentration, while the lowest (10.60 mg/mL) amount was obtained at 0 mM (Figure 1).  
\begin{table}
\begin{tabular}{c c c c} \hline
**Nutrient Constituent** & **Cow Manure** & **Pig Manure** & **Chicken Manure** \\ \hline N (\%) & 1.56 & 2.28 & 2.08 \\ P\({}_{2}\)O\({}_{5}\) (\%) & 1.49 & 3.97 & 3.53 \\ K\({}_{2}\)O (\%) & 1.96 & 2.09 & 2.38 \\ Zn (mg kg\({}^{-1}\)) & 138.6 & 663.3 & 306.6 \\ Cu (mg kg\({}^{-1}\)) & 48.5 & 488.1 & 78.2 \\ \hline \end{tabular}
\end{table}
Table 1: The nutrient contents of cow manure, pig manure and chicken manure in China (Source: Nutrient Contents in Main Animal Manures in China. J. Agro-Environ. Sci. [33]).  
\begin{table}
\begin{tabular}{c c c c} \hline
**Element** & \begin{tabular}{c} **Cow (Dairy) Manure** \\ **(mg L\({}^{-1}\))** \\ \end{tabular} & \
\begin{tabular}{c} **Pig (Swing) Manure** \\ **(mg L\({}^{-1}\))** \\ \end{tabular} &
\begin{tabular}{c} **Chicken (Poultry)** \\ **Manure (mg L\({}^{-1}\))** \\ \end{tabular} \\ \hline Ca & 860 & 170 & 173 \\ Mg & 260 & 100 & 21.5 \\ Si & 115 & - & 25.7 \\ Fe & 20.6 & 16.5 & 22.4 \\ Al & 20.6 & 7.3 & 6.92 \\ Mn & 9.2 & 2.7 & 4.57 \\ B & 1.6 & - & 2.87 \\ Cd & 0.08 & 0.009 & 0.989 \\ Pb & 0.05 & 0.036 & 2.76 \\ Ni & 0.09 & - & 1.33 \\ Mo & 0.06 & 0.11 & 1.76 \\ \hline \end{tabular}
\end{table}
Table 2: Elemental composition of cow (dairy) manure, pig (swine) manure and chicken (poultry) manure presented in different reports (source: for dairy manure, [23]; for swine manure, [9]; and for poultry manure [11]).  
The exo-polysaccharide (EPS) content of the HSaC culture showed a significant (\(p<0.05\)) difference among the NaCl salt concentrations. Unlike biomass and photosynthetic pigment content, the highest (0.84 mg/g) EPS content was obtained at 180 mM NaCl salt concentration, while the lowest content (0.22 mg/g) was at 0 mM (Figure 2).  
Figure 1: Cyanobacterial strain HSaC biomass (mg/mL) in different NaCl salt concentrations (0 mM, 60 mM, 120 mM, 180 mM, 240 mM and 300 mM). The error bars represent standard deviation (SD). The data are the mean of the three replicates. Differing letters indicate significant differences in the means of HSaC cyanobacterial biomass in pair-wise comparisons (Tukey’s test \(p<0.05\)) for each treatment by LSD.  
Figure 2: HSaC cyanobacterial exo-polysaccharide (EPS) content as influenced by different NaCl salt concentration (0 mM, 60 mM, 120 mM, 180 mM, 240 mM and 300 mM). The error bars represent standard deviation (SD). The data are the mean of the three replicates. Differing letters indicate significant differences in the means of HSaC cyanobacterial exo-polysaccharide content pairwise comparisons ([PERSON]’s test \(p<0.05\)) for each treatment by LSD.  
The photosynthetic pigment (chlorophyll a and carotenoid) content showed a significant (\(p<0.05\)) difference among the NaCl salt concentrations. Accordingly, the highest chlorophyll a and carotenoid contents (1.23 mg/g and 0.33 mg/g, respectively) were obtained at 120 mM NaCl, while the lowest chlorophyll a and carotenoid contents (0.53 mg/g and 0.13 mg/g, respectively) were obtained at 0 mM (Figure 3 and Figure S1, respectively).