# Effect of Temperature, pH, and Reaction Duration on Microbially Induced Calcite Precipitation
## 3 Test Results  
Sixty different combinations of pH, temperature, and reaction duration were used for each microbial species, and the amount of calcite precipitation was measured for each combination. The test results are tabulated in Table 1. Figure 3 shows the effect of temperature on the amount of calcite precipitates for _S. saprophyticus_ and _S. pasteurii_. It is clear that under all the different testing conditions, the _S. saprophyticus_ precipitates considerably more than _S. pasteurii_. The amount of precipitation is approximately five times more in the majority of conditions used for testing in _S. saprophyticus_. Although the amount of precipitation significantly differs between the two microbes, the optimal condition for maximum precipitation was identical. Maximum precipitation was observed at a temperature of 30 \({}^{\circ}\)C and a pH 7 of the urea-CaCl\({}_{2}\) medium. At higher temperatures, the precipitation significantly dropped for both microbes. Figure 4 shows calcite precipitation at a specific condition relative to that of the optimal condition at reaction duration of 3 days. Both _S. saprophyticus_ and _S. pasteurii_ were found to be very sensitive to the change in temperature during precipitation, showing a considerable drop of approximately 60%. On the other hand, the effect of pH was found to be different between the microbes. The productivity of _S. saprophyticus_ is less influenced by a change in pH, while that of _S. pasteurii_ is strongly influenced. The difference in the precipitation was at the most around 25% for _S. saprophyticus_ (see Figure 4c) while it was around 60% for _S. pasteurii_ (see Figure 4d). It should be noted that the measurement tolerance is 0.0018 g, which is about 1.2% and 4.5% of the maximum calcite precipitation of 3 days for _S. saprophyticus_ and _S. pasteurii_, respectively. \begin{table}
\begin{tabular}{c c c c c c c c c c c} \hline \hline \multirow{2}{*}{
\begin{tabular}{c} **Reaction** \\ **Duration** \\ **(Day)** \\ \end{tabular} } & \multicolumn{8}{c}{**Amount of Calcite Precipitation (g)**} \\  & \multicolumn{8}{c}{_Staphylococcus saprophyticus_} & \multicolumn{8}{c}{_Sporosarcina pasteurii_} \\  & **PH** & **6** & **7** & **8** & **9** & **10** & **6** & **7** & **8** & **9** & **10** \\ \hline \multirow{4}{*}{2} & 20 & 0.1102 & 0.1193 & 0.1065 & 0.1010 & 0.0991 & 0.0184 & 0.0220 & 0.0147 & 0.0147 & 0.0147 \\  & 30 & 0.1193 & 0.1285 & 0.1230 & 0.1157 & 0.1120 & 0.0220 & 0.0330 & 0.0220 & 0.0165 & 0.0165 \\  & 40 & 0.0918 & 0.0101 & 0.0918 & 0.0863 & 0.0826 & 0.0129 & 0.0202 & 0.0147 & 0.0092 & 0.0092 \\  & 50 & 0.0551 & 0.0661 & 0.0569 & 0.0496 & 0.0477 & 0.0110 & 0.0165 & 0.0129 & 0.0092 & 0.0055 \\ \hline \multirow{4}{*}{3} & 20 & 0.1138 & 0.1230 & 0.1120 & 0.1065 & 0.1010 & 0.0220 & 0.0275 & 0.0239 & 0.0184 & 0.0184 \\  & 30 & 0.1432 & 0.1469 & 0.1285 & 0.1285 & 0.1249 & 0.0330 & 0.0404 & 0.0312 & 0.0220 & 0.0220 \\  & 40 & 0.1010 & 0.1138 & 0.1010 & 0.0955 & 0.0918 & 0.0202 & 0.0294 & 0.0184 & 0.0147 & 0.0129 \\  & 50 & 0.0643 & 0.0734 & 0.0606 & 0.0551 & 0.0551 & 0.0165 & 0.0239 & 0.0147 & 0.0092 & 0.0092 \\ \hline \multirow{4}{*}{4} & 20 & 0.1120 & 0.1249 & 0.1102 & 0.1065 & 0.1065 & 0.0239 & 0.0294 & 0.0239 & 0.0184 & 0.0184 \\  & 30 & 0.1322 & 0.1432 & 0.1285 & 0.1230 & 0.1193 & 0.0312 & 0.0422 & 0.0294 & 0.0239 & 0.0220 \\  & 40 & 0.1047 & 0.1102 & 0.1010 & 0.0955 & 0.0973 & 0.0184 & 0.0312 & 0.0202 & 0.0147 & 0.0147 \\  & 50 & 0.0643 & 0.0753 & 0.0588 & 0.0569 & 0.0551 & 0.0165 & 0.0220 & 0.0129 & 0.0092 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: The estimated calcite precipitation at different pHs, temperatures, and reaction durations. Figure 2: Testing procedure: (**a**) insert strain into 35 mL TSB; (**b**) urea-CaCl\({}_{2}\) medium and microbes; and (**c**) oven-dried sample. The calcite precipitations for both the species appear to reach a maximum value at a reaction duration of 3 days under most of the tested conditions. An average increase of about 10% was observed in _S.