Overview

Textile industries receive and prepare fibers; transform them into yarn, thread, or webbing; convert the yarn into fabric or related products; and dye and finish these materials to the final product. Textile manufacturing consumes a considerable amount of water. The principal pollutants in the textile effluent are recalcitrant organics, color, toxicants and inhibitory compounds, surfactants, soaps, detergents, chlorinated compounds, and salts. Dye is the most difficult constituent of the textile wastewater to treat. The type of dye in the effluent could vary daily, or even hourly, depending upon the campaign.

The various processes in a textile mill that generate effluent are desizing, scouring, bleaching, dyeing, and printing. Effluent from the desizing operation produces the most chemical oxygen demand (COD) (40%) and effluent from the final rinsing operation the least (7.5%). The suspended solids load is highest in the effluent generated from desizing (47.7%) and the least from the scouring and bleaching operation (7.3%). The volume of effluent produced is highest from the combined scouring and bleaching operation (53.9%) and the least from the final washing (7.5%) (see Figs. 11-1 to 11-3). The typical cotton textile effluent stream will have a pH of 8.9 to 9.9, a biological oxygen demand (BOD) of 90 to 170 mg/L, a COD of 1,018 to 1,062 mg/L, suspended solids of 110 to 180 mg/L, a total kjeldahl Nitrogen (TKN) of 20 to 57 mg/L, a phosphate concentration of 0.9 to 2.4 mg/L, sulfate concentration of 1.9 to 6.4 mg/L, Cl ^- of 557...