Abstract EN:

In order to decrease probabilities of contaminations of aquatic "systems, processes of treatment need to remove or to immobilise contaminants. The paper industry, one of the most water consuming industry with agro-alimentary, uses lagoon assisted by metallic salts to treat wastewater. These treatments are efficient but temperature dependant. Among the numerous substitutions processes offered, one of them is promising the biolfocculation by a natural product, the chitosan. The main objective of this work was to develop and to study the performance of chitosan in the decontamination of paper mill’s wastewaters and to assess the environmental impact of the process. Laboratory scale biofloccluation assays demonstrated the effectiveness of chitosan with respectively 45 to 80 %, and 71 to 94 % COD and turbidity removal while conventional treatment removed 25 to 68 % and 45 to 80 % respectively. As a consequence, semi-industrial scale assay have been run. Contrary to PAC, chitosan also removed metals and wastewater coloration. Environmental impact study of the process was carried out using Gamrnarus pulex (Crustacea, Amphipoda). Ecotoxicological studies in semi-controlled conditions demonstrated that wastewaters treated by chitosan were less ecotoxic than the conventionally treated ones (less locomotor activity inhibition or aluminium accumulation). It is possible to conclude that bioflocculation by chitosan is a chemically effcient and an environmentally interesting process. Its economic viability is conceivable but this point has to go further into in order to take into account the benefits generate by the structuralisation of the producing industry and the savings of scale.