# Bioremediation of Hydrocarbon-Polluted Soil: Evaluation of Different Operative Parameters
## 3 Results
### Statistical Analysis
#### 3.1.2 Test B  
Table 4 reports the ANOVA for test B.  
Since the \(p\)-values of all the sources are lower than 0.05, the main effects have a statistically significant influence on TPH concentration with a 95.0% of confidence level. Furthermore, the interaction between Treatments and Time is also statistically significant.  
The multiple comparisons procedure was developed to determine which levels of each factor are different from the others. Table 5 presents the result of the multiple ranks for the factor Treatments, where all TPH values of four replicas at all times of test B were averaged.  
We identified four homogenous groups by X columns. The results show that adding organic waste to the biopsies can significative influence the removal of the sludge hydrocarbons.  
Due to the considerable amount of data overlapped in test B, the means graph with the range of TPH concentrations for each level of the factor Time was plotted. Figure 5 represents this relationship.  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Source** & \
\begin{tabular}{c} **Sum of** \\ **Squares** \\ \end{tabular} & **Df** &
\begin{tabular}{c} **Mean** \\ **Square** \\ \end{tabular} & **F-Ratio** & \(p\)**-Value** \\ \hline
**Main Effects** & & & & \\ Treatments & 23.77 & 5 & 4.75 & 11.54 & 0.000 \\ Time & 315.93 & 4 & 78.98 & 191.81 & 0.000 \\
**Interactions** & & & & \\ Treatments-Time & 17.09 & 20 & 0.85 & 2.08 & 0.012 \\ Residual & 31.71 & 77 & 0.41 & & \\ Total (corrected) & 389.30 & 106 & & & \\ \hline \hline \end{tabular}
\end{table}
Table 4: ANOVA for test B.  
Figure 5: Overall TPH concentration by levels of the factor Time.  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Treatments** & **Mean (g-kg\({}^{-1}\))** & \begin{tabular}{c} **Standard** \\ **Deviation** \\ \end{tabular} & \begin{tabular}{c} **Lower Limit** \\ **(g-kg\({}^{-1}\))** \\ \end{tabular} & \
\begin{tabular}{c} **Upper Limit** \\ **(g-kg\({}^{-1}\))** \\ \end{tabular} &
\begin{tabular}{c} **Homogeneous** \\ **Groups** \\ \end{tabular} \\ \hline Beef manure & 7.07 & 0.148 & 6.78 & 7.37 & X \\ _Thalassia testabilityimum_ & 7.53 & 0.153 & 7.23 & 7.88 & X \\ Sugarcane filter cake & 7.73 & 0.148 & 7.44 & 8.03 & X X \\ Sugarcane bagasse & 7.80 & 0.157 & 7.49 & 8.12 & X X \\ Coffee PulP & 8.13 & 0.157 & 7.81 & 8.44 & X \\ Sawdust & 8.65 & 0.166 & 8.32 & 8.98 & X \\ \hline \hline \end{tabular}
\end{table}
Table 5: Multiple rank tests for the levels of the factor Treatment in test B.  
The data show a quite constant decrement of the TPH concentration for all the treatments, except at Tb3 (90 days) and Tb4 (150 days) days, when the TPH concentration values are similar.  
The \(p\)-values in Table 3 prove existing interaction effects among the different kinds of organic waste used as a bulking agent, the identification of which treatment ensures better removal of hydrocarbons, and when it is relevant. Figure 6 reports the interactions of both factors.  
The lines which represent the levels of treatments were crossed by each other repeatedly within the levels of time. This confirms the aforesaid interaction reported in the ANOVA table. These results invite to the later discussion about the comparison among the treatments. The model assumptions are verified in Appendix B.