**9. Conclusions**

Perlite supplies the biofilter with support, aeration and allows to increase the availability of the pollutant due to its low adsorption capacity. While peat is a packing material that provides nutrients to the microorganisms in charge of the biodegradation process, it retains the direct blue 2 dye increasing the contact capacity between the pollutant and the microorganisms in charge of the degradation process. The perlite does not have a hysteresis process because the adsorption rate is the same as desorption. While the peat showed hysteresis, obtaining a value less than 1, which indicates that the adsorption rate is higher than the desorption rate, which favors the retention of the direct blue 2 dye. Due to the specific adsorption capacity of each material: perlite and peat, the mixture of the materials complements the properties of the packed material and improves the performance of the biofilter itself and consequently the removal capacity of the organic matter and the direct blue dye pollution of the wastewater fed into the biofilter. No reports have been found using this mixture (peat and perlite) as a packing material either in lab or pilot scale, and consequently, there are no full-scale experiences including industrial or municipal wastewater treatment reports using this nonconventional technology and packing material. This is an important opportunity to continue this research line to use this kind of nonconventional packing materials and biomasses to be used for biofilters, due to its ease of operation and economical benefits that allows us to implement them in small communities and/or for industrial wastewater treatment in small installations. Some other scale-up experiences with peat and other waste biomass indicate that it is necessary to pretreat the wastewater to be fed to eliminate solids that could clog the biofilter; therefore, the treatment train is easy to implement (septic tank or a primary settler and the biofilter packed with this mixture, and if needed a disinfection method).

### **Acknowledgements**

The authors thanked UPEMOR for the support of chemicals and materials received to implement this research and Environmental Engineer Briseida Emilia Velázquez Vázquez for her contribution to this research.

*Biomass, Biorefineries and Bioeconomy*
