Silk Lycra

This paper concerns the treatment of wastewaters produced during printing matrix washing and by dyestuff leakage in the silk and Lycra printing industry. The objective was to obtain effluent of a quality that would allow water reuse. The raw wastewaters contained a high concentration of ammonia nitrogen (from urea, ammonium sulphate and tartrate used for the dyestuff preparation together with organic compounds. A high BOD5/COD ratio determined the possibility of a biological treatment of the wastewaters by nitrification denitrification. To achieve complete denitrification, however, it was necessary to add an external carbon source. A mixture of methyl and ethyl alcohols from pharmaceutical industry wastes was used to achieve a BOD5/N ratio of about 3.5. High temperature (23–26°C) and low inhibition enabled good rates of treatment to be achieved in a single-sludge system, equal to 0.042 kgN/kg MLVSS × day and 0.12 kgN/kg MLVSS × day, respectively for nitrification and denitrification. After this stage the effluents were characterized by COD