Geochemical and thermodynamic study about the transport pipes clogging of treated wastewater and sprinklers of Agadir Golf Ocean, Southern Morocco

Abstract

In order to reduce the water deficit in the Moroccan Souss-Massa region, the region's master development plan recommends the use of unconventional resources. The reuse of treated wastewater represents a significant contribution to reduce water deficiency, and it is becoming unavoidable today. The treated wastewater is currently used to water the green space of Agadir's Golf. This water is conveyed, from the L'Mzar wastewater treatment plant to the Golf Ocean, in 60 cm diameter transport pipes over a length of 3 km. During one month of flow of treated wastewater through these pipes, the phenomenon of scaling of the latter is observed and has led to the formation of solid and adherent deposits on the sidewalls of these pipes and on the golf sprinklers (Due to high values of HCO 3 − ̴ 712 °F, Ca 2+ ̴ 288 °F and Mg 2+ ̴ 13 °F). Consequently, this causes several technical, economic and environmental problems. The objective of this work is the study of the scaling phenomenon observed in the purified wastewater transport pipes of L'Mzar treatment plant. Thus, in the first step, the purified wastewater was collected and analyzed. In this study, we used the representations of Piper and Schoeller-Berkaloff of purified wastewater of L'Mzar treatment plant in the second step. The predominant facies are calcium and magnesium hyperchloride and hypersulfate calcic with a slight tendency toward sodium hyperchloride. Then we presented, in a last step, the results of thermodynamic predictions of scaling phenomenon of treated water from the treatment plant of L'Mzar using the method of Legrand-Poirier-Leroy (LPL) with respect to the calco-carbonic equilibrium and to conclude that this water is a calcifying type (the ionic balance is less than 5% for all samples, and the supersaturation coefficient is largely exceeded 1 (β > 1)). The highlighting of new scale inhibitors to prevent the formation of scale in the pipelines of purified water transport pipes will also be discussed.