Contribution to the comparative study of treated and untreated wastewater: a case study (Wadi Fatima and Al Misk Lake) in Saudi Arabia

Abstract

Saudi Arabia is mainly characterized by desert landform with arid climate with severe scarcity of water. Groundwater is generally present within alluvial aquifers. In Saudi Arabia, treated and untreated sewage water is generally disposed of in the alluvial aquifers comprising of gravelly and sandy sediments. The disposal of treated and untreated water into alluvial aquifers is changing the groundwater quality of these aquifers to varying extent that rendered it unfit for drinking and irrigation purposes. It is not clear how much change in the groundwater quality takes place as a result of this disposal. This research compares the quality of treated and untreated sewage wastewater to determine its suitability for agriculture purpose. In total thirty three samples were collected from two different sites of Jeddah including 19 samples from Al Misk Lake (untreated sewage) and 14 samples from Wadi Fatima (treated sewage). T test indicates that the concentration of all major ions in treated and untreated sewage wastewater is significantly different (p < 0.05) except bicarbonate. Concentration of major ions in untreated sewage wastewater is much higher compared with treated sewage water except the bicarbonate. In Wadi Bani Malik area, Na and Cl are dominant cation and anion, respectively, in groundwater samples, whereas in Wadi Fatima area, Na is the most abundant cation like in Bani Malik area but in terms of anion CO3 and SO4 are most abundant anions followed by HCO3 and Cl. Cluster analysis results show that all treated wastewater samples are classified as one cluster, whereas the untreated wastewater samples are classified into three subgroups. Agricultural potential analysis results revealed that the untreated sewage wastewater is unsuitable for irrigation purpose, whereas the treated wastewater is suitable. This means that wastewater treatment plants can help to overcome the water shortage for agriculture purpose in the countries like Saudi Arabia.