Treatment of textile wastes utilizing a lime-polyelectrolyte system

Abstract

The feasibility of the excess lime process for color removal from textile dye wastes was evaluated. The lime dosages were optimized by using anionic, cationic, and nonionic polyelectrolytes as coagulant aids. The effect of the process on the removal of organic pollutants was determined. The time interval between coagulant additions was analyzed.

Color reductions of at least 94 per cent were obtained by the lime and lime-polyelectrolyte processes. The lime dosage of 980 to 1,060 ppm was decreased by at least 30 per cent using 5 ppm polyelectrolyte dosages. The processes reduced the Total Organic Carbon concentration by 73 per cent approximately, the Chemical Oxygen Demand by 50 per cent, and suspended solids by about 85 to 90 per cent. The excess lime process was more efficient in removing organic matter than the lime-polyelectrolyte processes, and also incurred the least chemical coagulant cost. The excess lime process was most effective at 30 minutes flocculation and 30 minutes settling. The lime-polyelectrolyte processes were more effective when the polyelectrolyte was added after about 30 minutes lime flocculation and settled for 5 minutes. The lime-polyelectrolyte processes produced a floe which settled rapidly.

The volume of sludge produced was about 8.1 to 12.8 per cent, resulting in a sludge to supernatant ratio range of 1:7 to 1:11. The lime-polyelectrolyte sludge volumes were usually higher than the lime sludge volumes.