In the present study, vermicomposting of sewage sludges and their application in agriculture have been investigated. The impact of Eisenia fetida earthworms on the stabilization of these sludges during 7, 14 and 21 days was assessed. The final product was applied as soil amendment (set-1) to evaluate the effects on vegetative parameters (Chlorophyll, carotenoid, number of nodules, leaf weight, and plant height) of Phaseolus vulgaris.L bean. In the second test (set-2), the amendment was made with raw sludge. In the third test (set-3), the worms were added to the raw sludge at the time of spreading and left during the whole period of beans growth. In order to identify and better understand the behavior and role of worms with regard to sludge, their growth (weight and length), some pathogens and physico-chemical parameters were assessed during the vermicomposting. Results showed significant increase of earthworm weight of 10.62, 23.89 and 35.72 % after 7, 14 and 21 days of sludge vermicomposting, respectively, which explain their acclimatization . The vermicomposting caused a decrease of feacal coliforms number and organic matter (OM), an increase in electrical conductivity (EC) and stabilization in pH. Furthermore, significant differences were obtained for all plants vegetative parameters in soil amended with vermicomposts, compared to the control (unamended soil). Indeed, a significant increase of the chlorophyll level (a, b) was noted in the beans having undergone sludge spreading. However, worm-stabilized sludge for 7 days (set-1) showed the highest chlorophyll a and b levels about 16.1 and 24.64 μg/g, respectively, against 10.13 and 4.38 μg/g in the control. For the carotenoid, a significant decrease was observed compared to the control. Our experiments have also showed that the application of vermicomposted sludge significantly increases the number of nodules, leaf weight and plant height of Phaseolus Vulgaris L . snap beans .

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The immunotoxicological effects of polychlorinated dibenzo-p-dioxins/dibenzofurans (PCDDs/Fs) mixtures on Eisenia andrei earthworms have never been studied. In this work we investigated these effects both for in vitro and in vivo exposure, using the viability and the phagocytic activity of coelomocytes as immunological biomarkers and the flow cytometry was used for analysis. The in vitro exposure revealed a cytotoxic effect of PCDD/Fs mixture (C2) containing 50¥10 -3 ng/mL of 2, 3, 7, 8-TCDD and an induction of the phagocytic capacity at the mixture (C1) containing 25¥10 -3 ng/mL of 2, 3, 7, 8-TCDD. In the in vivo filter paper exposure, the immunocompetence of earthworms was assessed after 3 h-exposure to mixtures of PCDD/Fs at the levels of C1, C2, C3 and C4 containing about; 0.05, 0.3, 0.5 and 0.83 ng of 2, 3, 7, 8-TCDD/cm², respectively. Morphological observations showed an excessive secretion of mucus and body surface lesions in worms exposed to higher concentrations (C3 and C4), which revealed that these organisms were affected by PCDD/Fs either through skin and/or by feeding. The levels of the extruded cell yield decreased significantly at all the concentrations tested. However, the cell viability was shown to be unaffected by PCDD/Fs concentrations. It was also shown, that exposure to the highest PCDD/Fs concentrations; C2, C3 and C4 inhibited both phagocytic activity and efficiency.

In this study, we assessed in vitro the effects of PCDD/Fs on the NK-like cell activity in Eisenia andrei earthworms using flow cytometry for analysis. NK-like coelomocytes isolated from E. andrei and used as effectors were exposed to various concentrations of PCDDs/Fs mixture, C1 (6.25x10-3 ng 2378- TCDD/mL), C2 (12.5x10-3 ng 2378-TCDD/mL) and C3 (25x10-3 ng 2378-TCDD/mL), before adding them to human tumoral cells (K562) used as targets. We evaluated the percentage of targets lysed by Nk-like cells. The results showed a significant stimulation of the NKlike activity at C3 when PCDD/Fs were not removed from effectors before contact with targets, while no effects were noted when the effectors were washed (PCDD/Fs removed) or fixed. Assessment of the viability of the targets (K562), exposed alone and separately from effectors, to the three concentrations of PCDD/Fs, C1, C2 and C3, showed that all these concentrations were cytotoxic for K562. Results suggest that PCDD/Fs concentrations tested in this assay may be considered too low to induce suppressive effects on the immune function such as the NK-like activity in E. andrei earthworms