EVALUATION OF THE PHYSICO-CHEMICAL QUALITY OF WATERS USED IN IRRIGATION IN THE PERIMETER OF THE WASTEWATER TREATMENT PLANT OF DAR EL GUEDDARI

The present study concerns the evaluation of the quality of the water used in irrigation in the perimeter of the DAR EL GUEDDARI wastewater treatment plant, these waters are often purified water coming from the WWTP and sometimes water pumped into the canal. rejection from the Sebou wadi. For this, we realized a set of measures such as: the temperature, the pH, the electrical conductivity, the biochemical demand in oxygen BOD5, the chemical demand in oxygen COD, the suspended matter MES, the total nitrogen (N ( tot), ammonium NH4 +, nitrates NO3-, total phosphorus P (tot), ortho-phosphate PO43-, sulphates SO42-, sodium Na +, chlorides Cl-, potassium K +, metals such as: Cr, Cd, Pb, Hg, Cu, Mn, Fe and Zn The results obtained during this study indicate that the physicochemical quality of the WWTP water used for crop irrigation does not always meet the irrigation water criteria in agriculture (Moroccan standard for irrigation water). They are characterized by low levels of dissolved oxygen, high levels of TSS, BOD5, COD and sodium and low levels of heavy metals such as Cd, Pb, Hg, Cu, Mn. The combination of the electrical conductivity CE and the SAR sodium absorption coefficient according to the irrigation water classification diagram of RISVERD allows to classify these waters in the box of poor quality water. However, the water pumped into the sewage disposal canal from Oued Sebou is likely to meet the criteria set by the Moroccan standard for irrigation. On average, they are less rich in nutrients (NPK) with moderately lower values than wastewater from the WWTP and they are characterized by low levels of sodium, conductivity, SAR and pose no risk of salinization or alkalization; with the exception of nitrates, which have an average value of 4.2 mg / l.