TREATMENT OF A WASTE-WATER RESULTING FROM DYES MANUFACTURING WITH OZONE AND CHEMICAL COAGULATION

The degradation of the compounds present in a previously chlorinated w astewater resulting from the production of azoic dyes has been studied in this project. Towards this end, the first step developed was the c haracterization of the spillage water by GC/MS and GC/FID. Secondly, a combined ozone + Ca(OH)(2) treatment was carried out, determining its efficiency on this wastewater. The majority of compounds found in the wastewater are aniline derivatives and azo compounds. Also, as a resu lt of the chlorination treatment which is carried out by the factory, some organochloride compounds were identified, being the most importan t those which are subjected to legislative control, namely: chloroanil ines, chloronitrobenzenes and chlorophenols. After ozonation, the conc entration of the compounds present is reduced to good percentages. The by-products formed after this first treatment were, mainly, nitrobenz ene derivatives and organic acid compounds. The following treatment wi th Ca(OH)2 leads to almost total elimination of the remaining compound s in the ozone treatment. However, aniline and chloroanilines are form ed after chemical coagulation due to the strong basic medium at which the sample in this process is set. C.O.D. is reduced 25% after ozonati on, while it decreased 50% after the complete treatment. T.O.C. remain ed constant during ozonation, but a 42% reduction was obtained after c hemical coagulation. Color decreased gradually during ozonation reacti on, and after the final treatment the reduction was 62%. The complete process of ozonation and chemical coagulation with Ca(OH)2 is, in gene ral, very effective to treat this kind of wastewaters. (C) 1998 Elsevi er Science Ltd. All rights reserved.