Physicochemical characterization and Analysis of total metal concentration of grease and wastewater samples: Case study for two wastewater treatment plants in the North of Morocco: Tangier and Tetouan

In this paper, physicochemical characterization and analysis of total metal concentration of greases and wastewater samples from two wastewater treatment plants in the North of Morocco, Tangier and Tetouan, were carried out. The samples were taken in the winter period of the year 2011-2012. For two case studies of wastewater treatment plants in Tangier and Tetouan (WWTPTG and WWTP-TT), waste solid grease samples were collected from the degreasing tank belonging to the wastewater pre-treatment step. The physico-chemical parameters analyzed for the two stations were selected to determine biodegradable and non-biodegradable organic pollution such as Biochemical oxygen demand BOD5 (mg O2/L) chemical oxygen demand (COD g O2/Kg), and the dosage rate of nitrate [NO3 ] (mg/L), nitrite [NO2 ] (mg/L), phosphate [PO4 3] (mg/L) and organic matter. An analysis of total metal concentrations for Cu, Zn, Cr, Pb, Ni, Tl, Cd, Ba, As, Se, Ag, V, Co, Fe and Mn was performed by inductively coupled plasma mass spectroscopy (ICP-MS) and Inductively coupled plasma atomic emission spectroscopy (ICP-AES). The results indicated the presence of all of the studied heavy metals. In general, the metal pollution obtained in the Tetouan treatment plant (WWTP -TT) is double or higher than that obtained in the Tangier treatment plant (WWTP -TG) with few exceptions. Notably, in both types of samples analyzed for each treatment plant (greases and wastewater), the metal pollution is more concentrated in the solid fraction (grease) than in the liquid fraction (wastewater), with both samples containing a high concentration of similar metals (in mg/kg) Cu, Mn, Zn and Fe for the two wastewater treatment plants (WWTP-TT and WWTPTG). Grease, a by-product of wastewater treatment, is a hazardous waste, and thus a cause for serious consideration, especially in light of the 28-00 law enforced in Morocco in 2006.