Removal of nitrate ions by adsorption onto micro-particles of shrimp-shells waste: Application to wastewater of infiltration-percolation process of the city of Agadir (Morocco)

The infiltration-percolation process adopted at the M'zar wastewater treatment plant (WWTP) is a widely used treatment process capable of depolluting and decontaminating the effluent. The first objective of this study was to evaluate the purification performance of this treatment process with regard to the elimination of carbonaceous pollution and nitrate ions. The obtained results confirmed that infiltration-percolation is an advanced treatment technique for the treatment of organic pollution parameters such as: chemical oxygen demand (COD), biochemical oxygen demand measured after five days (BOD5) and total suspended solids (TSS). Nevertheless, this process contributes to the increase of nitrate ions by oxidation of nitrogen pollution at the sand filter level; consequently, this pollutant causes serious ecological problems, such as the eutrophication phenomenon. Therefore, it is therefore essential to reasonably control nitrates before they are released into the environment. The second objective of this work was to develop and valorize new low-cost, widely available and environmentally friendly adsorbents of animal origin. Raw shrimp shell (RSS), a biomaterial of animal origin, is abundant, available, renewable and non-toxic. It has physicochemical properties that can induce a significant adsorptive activity. The surface micro-morphology of the biomaterial was investigated using scanning electron microscope; while the qualitative element composition was analyzed using energy dispersive X-ray and infrared spectroscopies. For this reason, our research team proceeded to evaluate the effectiveness of crushed shrimp shell particles in order to remove nitrate ions from municipal wastewater effluents. The founded results of raw wastewater decanted (RWWD) and purified wastewater (PWW) are encouraging and show significant purification yields: 68% (RWWD) and 79% (PWW) for nitrate ions.