Waste sludge is the main waste produced by a wastewater treatment plant. It contains a wide variety of biological organisms, of which a tiny part is pathogenic for humans. It consists of a complex mixture of mineral and organic matter. Metallic trace elements and organic micro pollutants are also found. Rich in fertilizers, sludge can be used as a substitute for chemical fertilizers. Solar drying is an ecological and economical solution for the treatment of these sludges before their recovery. The objective of this study is the experimentation of two drying processes of urban sludge from the urban sewage treatment plant of Touggourt, intended for agricultural application. The agri-environmental quality of dried sludge is estimated by the determination of physico-chemical parameters (dryness, organic material OM, pH, electrical conductivity EC, major elements, metallic trace elements MTE ...). The maximum temperatures obtained experimentally by the two solar dryers are considerable (70° C and 80° C, respectively), resulting in the minimum water content of the sludge after 12 hours of continuous drying by the first mode, a time reduced to 7 hours in the second drying mode. The results obtained after drying show that sludge from Touggourt contains on average more than 50% organic matter (dry matter basis) and is rich in nitrogen, which is a significant contribution especially to Saharan soils. Moreover, the trace metal content was below the threshold set by the regulations thus eliminating the risk of contamination.

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