# Detection and Treatment Methods for Perfluorinated Compounds in Wastewater Treatment Plants
## 4 Conclusions  
We surveyed the PFCs pollution sources, targeting the influent and effluent of wastewater treatment plants, and conducted a pilot test with influent to review whether PFCs could be removed using physiochemical methods. This study produced the following results. 1. The influent/effluent removal of the existing biological treatment process was able to remove some PFNA, PFPeA, and PFHxS, but most of the other compounds could not be removed through biological treatment. 2. The correlational analysis results showed that there was a high correlation in the wastewater among PFOA, PFHxA, and PFNA, which contain carboxyl groups. The PFCs correlational research did not produce data that could be representative. Thus, further research is required. 3. The pilot batch test with the influent to the treatment plant showed that about 10% of PFCs was removed by an injection of 40 to 50 mg/L of Alum in the coagulation-sedimentation test. For the pilot continuous test, the removal in the ozone test and chlorine injection test was negligible regardless of the oxidant dose. The activated carbon adsorption test showed that about 60% to 70% of PFCs was removed after EBCT 5 min, and removing over 90% of PFCs after 15 min EBCT was found to be possible. 4. The pilot test results showed that PFHxS removal in single ozone or activated carbon process was low. However, it improved in the continuous ozone process followed by the activated carbon process. This demonstrated that ozone oxidization would promote the removal during the next process. Therefore, the continuous oxidization process, such as the ozone process, followed by an adsorption process using activated carbon, would be a desirable process enabling high removal. \begin{table}
\begin{tabular}{c c c c c c c c c c c} \hline \hline \multirow{2}{*}{**Process**} & \multicolumn{8}{c}{**PFCs**} \\ \cline{2-10}  & \multicolumn{2}{c}{**PFOA**} & \multicolumn{2}{c}{**PFHxA**} & \multicolumn{2}{c}{**PFNA**} & \multicolumn{2}{c}{**PFPeA**} & \multicolumn{2}{c}{**PFHsS**} \\ \cline{2-10}  & \multicolumn{2}{c}{**Bat \({}^{*}\)**} & \multicolumn{2}{c}{**Conti**} & \multicolumn{2}{c}{**Bat**} & \multicolumn{2}{c}{**Conti**} & \multicolumn{2}{c}{**Bat**} & \multicolumn{2}{c}{**Conti**} & \multicolumn{2}{c}{**Bat**} & \multicolumn{2}{c}{**Conti**} & \multicolumn{2}{c}{**Bat**} & \multicolumn{2}{c}{**Conti**} \\ \hline Bioreactor & X & X & \(\triangle\) & \(\triangle\) & X & X & \(\triangle\) & \(\triangle\) & X & X & X \\ \hline Coagulation-Sedimentation & X & \(\triangle\) & X & \(\triangle\) & \(\triangle\) & \(\triangle\) & \(\triangle\) & \(\triangle\) & \(\triangle\) & \(\triangle\) & \(\triangle\) \\ \hline \multicolumn{10}{c}{Ozonation} & X & \(\triangle\) & X & \(\triangle\) & X & \(\triangle\) & X & \(\triangle\) & X & \(\triangle\) \\ \hline Activated carbon & EBCT 5 min & \(\oplus\) & \(\oplus\) & O & O & \(\oplus\) & \(\oplus\) & O & O & O & \(\oplus\) \\ \cline{2-10} treatment & EBCT 15 min & \(\oplus\) & \(\oplus\) & \(\oplus\) & \(\oplus\) & \(\oplus\) & \(\oplus\) & \(\oplus\) & \(\oplus\) & \(\oplus\) \\ \hline Chlorination & X & \(\oplus\) & X & \(\oplus\) & X & \(\oplus\) & X & \(\oplus\) & X & \(\oplus\) \\ \hline \multicolumn{10}{c}{Note: X: removal efficiency \(<\)10\%, \(\triangle\): removal efficiency 10–40\%, O: removal efficiency 40–70\%, \(\oplus\): removal efficiency \(>\)70\%, \(\diamondsuit\): Batch process; \({}^{**}\): Continuous process.} \\ \end{tabular}
\end{table} 
Table 3: Summary of PFCs applicability by various treatments. **Author Contributions:** Conceptualization, S.-h.L. ; Methodology, S.-h.L. ; Validation, S.-h.L. and Y.-j.C.; Formal analysis, Y.-j.C.; Investigation, S.-h.L. ; Writing--original draft preparation, B.-D.L. ; Writing--review and editing, B.-D.L. ; Visualization, M.L. ; Supervision, S.-h.L. ; Project administration, S.-h.L. ; Funding acquisition, M.L.