Characterization of sewage sludge generated from wastewater treatment plant in relation to agricultural use

Résumé

During wastewater treatment, precisely at wastewater treatment plant (WWTP), a big quantity of sewage sludge is produced resulting from the sedimentation of the suspended solids. This sludge can be incinerated, evacuated to landfills, or applied in agriculture as soil amendment. Compared to the first two options, land application is the most efficient and has the lowest cost. However, before being applied, there are regulations that must be respected. This study aims at characterizing the quality of treated sludge from wastewater treatment plant of Nador city; first in terms of some micropollutants, such as Heavy Metals (HMs), Polycyclic Aromatic Hydrocarbons (PAHs), and second in terms of fertilizing elements to assess their potential for land application. GC-MS and AAS were used to measure these contents in sludge. Analysis showed that concentrations of heavy metals such as Zinc, Copper, Lead, Chromium, Mercury and Nickel were below the regulatory limits for sludge to be used in agriculture. The same case for the 7 main PCBs and 4 PAHs. Moreover, from the point of view of nutrients, it has been proved that the sludge contains a high amount of nutrients. The results obtained show that the sludge of the WWTP of Nador city can be applied in agriculture to increase soil fertility.