Behaviour of physicochemical and microbiological characteristics of vertical flow constructed wetland substrate after treating a mixture of urban and Olive Mill Wastewaters

Abstract The aim of the current work is to evaluate the effect of a mixture of olive mill wastewater (OMWW) and urban wastewater (UW) on constructed wetland (CW) substrate physicochemical parameters and to study the abundance and behaviour of microbial community at different depths. In this regard, substrate samples were investigated at tree depth levels (0-10cm, 10-20cm and 20-30cm) inside a pilot scale CW treating the mixture. In order to compare the obtained results treating the mixture with the conventional case, a control (CW pilot plant treating only UW) was implemented. Result shows that an increase in electrical conductivity (from 134.78 to 222.33µS/cm in 0-10cm and from 131.25 to 283.33 µS/cm in 10-20cm), total dissolved salts (from 65.45 to 108.67 mg/kg in 0-10cm and from 64.33 to 135.3 mg/kg in 10–20 cm), total organic carbon (from 0.86 to 6.84%), total nitrogen (from 0.1 mg/kg to 0.45, 0.43 and 0.41 mg/kg, in 0-10cm, 10-20cm and 20-30cm respectively), and C/N ratio occurred in the substrate after the treatment of the mixture. As for the microbiological parameters, treating the mixture by CW results in the increasing of yeast and fungi concentration in the substrate which contributes probably to optimize the biodegradation of non-easily degraded organic compound such as polyphenol.