Electrochemical treatment of industrial wastewater and effluent reuse at laboratory and semi-industrial scale

Abstract

This study is based on the electrochemical decolouration of exhausted dyeing effluents which contain dyes and salts. The treated effluents were reconstituted and reused in a new dyeing process. Initially, synthetic effluents containing one of the reactive dyes Novacron Yellow, Ruby and Deepnight were treated in the laboratory pilot. In all cases, the dye decolouration follows a pseudo-first order reaction. Subsequently, seven industrial effluents which contain mixtures of these dyes were collected in a Spanish mill and treated in the laboratory pilot. Two methods for the electrochemical treatment and further effluent reconstitution and reuse were studied. The first method consisted of an electrochemical treatment followed by an acidification and a stripping step to remove the carbonate ions. In the second method, the acidification was carried out before the electrochemical treatment; subsequently, the generated CO 2 was removed during the decolouration process. Finally, the optimised process was applied in situ in a Spanish mill by means of a semi-industrial pilot plant (400 L). No significant colour differences were appreciated between reference dyeings and the fabrics dyed with the treated exhausted effluents. The reuse of the dyeing effluent achieves the reduction of 70% process water consumption and 60% salt discharge.