Comparative Study between Two Substrates of Constructed Wetlands in the Treatment of Domestic Wastewater in Arid Regions

This work aims to conduct a comparative study between two natural substrates (clay and gravel) used in constructed wetlands to treat domestic wastewater effluent in arid regions. Experiments were carried out using four basins planted with phragmites australis, where two were filled with clay and two with gravel substrates. The efficiency of filtration systems has been studied by monitoring several physicochemical and organic parameters. This study is of great importance in determining the most effective type of local substrate in light of the lack of previous studies and the low spread of CWs in arid regions.Results showed that the clay filters clogged very fast, and the total Suspended Solids increased in the planted clay filter by 4 % and decreased in the planted gravel filter, where the removal efficiency was 73%. The pH was generally around neutral, with values between 6.8 and 7.2 regardless of the substrate, and the temperature was related solely to local weather conditions. The electrical conductivity was higher in the effluent from clay than the gravel filters, with 9.72 and 5.47 mS/cm, respectively. The nitrate concentration increased in all filters due to the complete transformation of ammonium to nitrate. After five days, nitrite and chemical oxygen demand removal efficiencies were 38.33%, 75% in the planted clay filter, and 60%, 88% in the planted gravel filter, respectively.