Textile sludge application to non-productive soil: physico-chemical and phytotoxicity aspects

As part of an assessment study on the risk of spreading textile sludge onto non-productive soil, the sorption behaviour of some sludge-metal constituents [Cr(VI), Cu(II), Pb(II), and Zn(II)] in the soil was studied. In addition, the sludge stabilization effect was evaluated by the biodegradation of organic compounds and phytotoxicity tests. Metal-soil sorption was assessed using soil columns and by sorption isotherms (i.e., Freundlich and Langmuir). In relation to the phytotoxicity of Eruca sativa L., there was a biomass inhibitory effect for the fresh sludge and a biomass stimulant effect for the stabilized sludge. Thus our results show that after stabilization, the tested loading ratio of 33% sludge: 67% soil (v/v) (equivalent to 85 Mg ha(-1)) did not significantly increase the risk of groundwater contamination since only small amounts of metals applied to the soil underwent percolation and almost all the organic compounds were degraded.