Le rôle des différents types de matériaux des filtres plantés à macrophytes sur l’élimination simultanée de la pollution phosphatée et azotée contenue dans les eaux usées.

Abstract

Constructed Wetlands systems provide an economical alternative to wastewater treatment in developing countries. Therefore, in order to achieve the objectives of the study related to the removal of nitrogen and phosphorus pollution in municipal wastewater from the city of Biskra using local substrates in arid conditions, we prepared an experimental vertical flow constructed wetland system. This study explores the efficiency of substrates such as gravel, sand, and clay planted with Phragmites australis to remove nitrogen and phosphorus. Also it emphasizes the combined use of sand, which showed promising results in initial trials, compared with other substrates, and commercial activated carbon to improve their performance. The plant grew well in all substrates, significantly increasing pollutant removal efficiency. The removal rates of NH4⁺, NO2 ⁻, and PO4³⁻ were 93.54%, 68.63%, and 80.59%, respectively, in the planted gravel filter, and 89.63%, 66.26%, and 72.56% in the planted clay filter. Finally, the planted sand filter demonstrated the best performance, with removal rates of 95.43% for NH4⁺, 74.45% for NO2 ⁻, and 77.64% for PO4³⁻. For nitrates, their concentration increased in all filters due to the complete conversion of ammonium into nitrates. The removal rates observed in the planted gravel filter were 84.38% for BOD5, 77.45% for COD, and 83.30% for TSS. The planted clay filter showed slightly lower performance, with removal rates of 75.22% for BOD5 and 71.14% for COD. In contrast, the planted sand filter achieved superior results, with removal rates of 89.59% for BOD5, 85.80% for COD, and 86.63% for TSS. The combination of sand with commercial activated carbon (10% carbon), improved efficiency through mechanisms such as adsorption and microbial degradation, achieving removal rates of up to 95.71% for NH4⁺ and 80.38% for PO4³⁻. While promising, this study is preliminary. The authors recommend further research to confirm that activated carbon is a sustainable and cost-effective solution for wastewater treatment.