The main contribution of our research was to compare the impact of the conventional dyeing process and the power ultrasonic technique on dye-bath exhaustion and, consequently, on dye-bath effluents during the dyeing of four dissimilar fabrics (cotton, viscose, wool and polyamide) using chemically-different dyestuffs (reactive, direct, acid and 1:1 metal complex) at two concentrations, regarding different operational parameters, in order toestimate the environmental impact of numerous parameters and dyeing systems.The efficiency of various dyeing procedures was verified by measuring on-line absorbance, followed by the calculation of exhaustion rate. After dyeing, the selected pollution parameters were monitored in dye-baths effluents, i.e. pH, total organic carbon (TOC), chemical oxygen demand (COD), and biochemical oxygen demand (BOD5). The obtained results indicated superior exhaustion of dyestuffs during ultrasound assistance in comparison to conventional dyeing, thus causing a reduction in dyeing time and energy consumption. Moreover, the selected pollution parameters were diminished in all the dye-baths effluents after ultrasonic dyeing, thus also enhancing environmental protection
