Characterization Of Metallic Trace Elements In The Products Of Composting And Co-Composting Coming From The Sludge Of The WWTP Of Fez And The Pomace From The Region Of Ain Taoujdate (Morocco)

摘要

Sludge disposal is a major challenge for sewage treatment plant managers given their reputation as a high-risk source of environmental pollution. The objective of this study is to propose a way to eliminate and recover sludge from Fez wastewater treatment plant (WWTP), Morocco through its co-composting with pomace from Ain Taoujdate region (Morocco). The study focused on the production of three composts (C1, C2 and C3) from sludge and pomace, which differ in terms of their proportions of these two components (C1 = 1/1, C2= 1/2 and C3= 1/4). Composting is carried out in greenhouses using the method of turned over Andean trees for 105 days. The characterization analyses of the final product focused on the determination of the contents of the three composts, such as total chromium, lead, nickel, mercury and cadmium. This was necessary in order to evaluate the fate of the initial levels present in the starting sludge and to judge the quality of the composts through the standards provided. The co-composting thus carried out made it possible to significantly reduce all levels of the trace metal elements studied in the three composts. The reductions recorded for total chromium were significant as 81.9%, 88.9% and 93.7%, respectively in C1, C2 and C3; whereas they were 72.9%, 82.2% and 89.4%, respectively for lead in C1, C2 and C3. Nickel, mercury and cadmium levels also declined with relatively lower than initial levels. In general, all grades have declined and are believed to be due to leaching from watering applied during rollovers. The study of quality of the three composts (according to standard NF U 44-051) showed that compost C3 is the only compost that complies with the standards applied to the metallic trace elements studied. The total chromium content exceeding the applied standard will exclude C2 and C3 composts from the NF U 44-051 standard. Thus, the initial total chromium content, which averaged 1900 mg/kg, had a negative influence on the classification of these two composts.