Wastewater treatment using flocculation method and water reuse for dyeing of polyester fibers

Abstract

Textile industry uses and pollutes large quantities of water, especially for chemical treatments of textile materials, like bleaching, desizing, dyeing, printing and finishing. After each process, the water is usually drained into the sewage system and fresh water is used for new process of textile treatment. Re-using of wastewater for further processing would be of great importance in term of saving fresh water and diminishing the environmental burden. The goal of our research was to find out whether treatment of dye-house wastewater with flocculation could be efficient enough for water re-use in further dyeing of polyester fabric.Wastewater collected in Slovenian dye-house was treated with a cationic flocculant. Treated water was analysed for chemical oxygen demand (COD), total organic carbon (TOC), spectral absorption coefficient (SAC) and dry matter and further used for laboratory dyeing of polyester fabric. The fabric was dyed comparatively using technological and treated water under the same conditions in light, medium and dark shade. The colour of dyed samples was evaluated on spectrophotometrically. Wet fastness and colour fastness to perspiration (acid and alkaline) of differently dyed samples were investigated. Change of colour was acceptable for all dyed samples. Fastness to washing and perspiration were good, very similar when comparing samples dyed in technological and those dyed in cleaned water. The colorimetric and fastness results showed a high efficiency of flocculation for dye-house wastewater treatment and reuse of treated water in production.