# Sustainable Treatment Techniques for Emerging Pollutants--The Case of Personal Hygiene Products
## 4 Discussion  
Table 2 indicates the weights obtained by the four criteria evaluated, with maintenance costs having the highest weight with 0.38, followed by construction cost with 0.29, efficiency with 0.21 and the development stage with 0.13, with the latter being the lower weight. The weight of each criterion allowed the generation of priority scales based on the authors' judgments made with comparisons using a preference scale. When applying modified Satty for each of the four criteria and normalizing the values obtained, from the three techniques individually, the maintenance cost (MC) was 1 for both the co-composing technique and the CNT absorption technique, while that for the anaerobic-aerobic technique was 0.293. In the construction cost criterion (CC), the technique of combined anaerobic-aerobic reactors and CNT absorption obtained a value of 0. On the other hand, the co-composing technique had a value of 1. For the efficiency factor, the co-composing and anaerobic-aerobic techniques obtained a value of 0.924, and the CNT adsorption method obtained a value 1, as evidenced in Table 3.  
Regarding the development stage criterion, the three techniques had a zero rating, as the three experiments were conducted in the laboratory; thus, its value is negligible. However, it is fundamental to mention that the co-composing technique in other studies is already in the operation phase and has been marketed for several years [90]. In Table 4, the results determined that the most profitable technique was co-composing with a score of 0.86/1; therefore, it can be interpreted that it is the most sustainable technique that maintains an optimal balance between the criteria considered in the comparison of techniques for the reduction in PCPs. It is a technique with great potential to reduce the concentration of multiple contaminants such as triclosan, a compound commonly used in PCPs (soaps, creams, toothpastes and detergents) [96]. However, in several case studies, it has been shown that the co-composing technique does not help in completely degrading the concentration of TCS, since it occurs only partially during the composting period of one month, indicating that longer periods are needed for the most complete removal of these compounds [96]. In the same manner, there are cases in the co-composing process where the transformation of triclosan into methyltriclosan is promoted, a compound that is extremely persistent to greater biodegradation and is strongly absorbed in solids that have a potential for accumulation in the soil [97]. Most of the PCPs residues are in a liquid state, forming what is known as leachate; thus, the co-composting method is not very suitable for the elimination of these contaminants, since it has a greater efficiency of treatment of solid waste. Despite this, the co-composting method has been well received by the reuse that can be given in the elimination of contaminants due to its sustainable viability and its easy accessibility. On the other hand, \begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline
**Technique** & **=** & **0.375 \(\times\) CM** & **+** & **0.292 \(\times\) CC** & **+** & **0.208 \(\times\) Eff** & **+** & **0.125 \(\times\) ED** & **=** & **Results** \\ \hline Co-composting & = & 0.3750 & + & 0.2917 & + & 0.1925 & + & 0.000 & = & 0.86 \\ Anaerobic-Aerobic & = & 0.0855 & + & 0.0000 & + & 0.1155 & + & 0.000 & = & 0.20 \\ CNT & = & 0.2083 & + & 0.0000 & + & 0.0000 & + & 0.000 & = & 0.21 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Comparison of the viability percentages of the techniques studied.