Najla LASSOUED^1,2, Essaid BILAL³, Saloua REJEB², Issam GUENOLE-BILAL⁴, Mohamed Naceur KHELIL², Mohamed Nejib REJEB², & Frédéric GALLICE^3
1 National Agronomic Institute of Tunisia, 1082 Mahragène Tunis, Tunisia; lassoued_najla@yahoo.fr
² National Institute for Rural Engineering’ research, Water and Forestry, BP10, 2080 Ariana, Tunis
³ Ecole Nationale Supérieure des Mines de Saint Etienne, GSE, CNRS UMR 5600, F42023 Saint Etienne France; bilal@emse.fr
⁴ Physiology Department, Lausanne-CHUV University, Lausanne, Switzerland; bilal.issam.1698 @ gmail.com

BEHAVIOR CANOLA (BRASSICA NAPUS) FOLLOWING A SEWAGE SLUDGE TREATMENT

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In this study, two types of sludge were being used, while the first was with urban dominance, the second was with industrial dominance. The effects of sewage sludge had been studied in a Brassica Napus field. The  mineralogical, chemical and microscopic study of the sludge showed that industrial sludge had very high levels of Cr, Pb and Cd. These metals existed mainly under the form of daubreelita Cr₂FeS₄, brezininaite Cr₃S₄, wattersite Hg₅CrO₆, crocoite PbC₂O₄, pheonicochroite Pb₂O(CrO₄) and PboxalatePbC₂O₄. The results showed that sludge significantly improves the growth of the undergroundpart of the plant (root) and the upper part (stem, leaves etc…). This improvement is more important forurban sludge. However, this beneficial effect was accompanied by a change in the composition of theplant some trace element metals. An abnormal accumulation of Cr was found in the roots, stem, leaves,and siliques when the industrial sludge was brought which reflected the richness of the latest. The doseeffectsewage sludge was very clear at the levels of Pb in the roots especially for industrial sludge whichexceeded the threshold values of toxicity starting from the dose of 25t/ha of industrial sludge. Cd levelsonly increased with the addition of 100t/ha of industrial sludge. For Ni, Cu, Co and Zn, especially at rootslevel, the increase depends on mud’s dose and especially on its type. On the contrary, levels of iron, andto a less extent manganese levels, had been reduced due to sludge despite their richness with these elements. That was probably due to antagonism with one or more particular elements especially Zn.