Treating textile effluents by coagulation - flocculation method using different dosing compositions

This paper discusses fast yet simple method of treating effluents of textile industry by simple chemicals. Textiles industry produces substantial toxic, often loaded with color (from residues of reactive dyes and chemicals), acidic and alkaline contaminants having high pH, high concentration of organic materials etc, which requires proper treatment before being released into the environment. Removal of such toxic materials from waste water is more important because the presence of small amounts of dyes in effluent disposed into the land and river water reduces the depth of penetration of sunlight into the water environment, which in turn decreases photosynthetic activity and dissolved oxygen (DO). The adverse effects can spell disaster for aquatic life, soil, and detrimentally affects the water quality. In this research work different coagulants like Alum, Lime, Ferrous Sulphate, Ferric Chloride, and poly-electrolytes for flocculation were employed to select the most suitable composition which has optimal removal efficiency. Settling characteristics of the flocs formed in the coagulation process were studied at laboratory scale. Parameters such as colour, COD, Hardness, Total Dissolved Solids (TDS), and Total Suspended Solids (TSS), and settled sludge volume have been studied. The optimal coagulant dose volume and pH were determined by comparing the effectiveness of these coagulants [Amirtharajah, A. M., et. al]. Results showed that coagulant like lime eliminated colour and COD effectively. However ferrous sulphate was chosen as effective coagulant for colour removal as it required lowest coagulant dose, minimum settled sludge volume and maximum decolourization. It was also observed that higher percentage of suspended solids was removed by using a combination of iron salts with lime at pH 10 to 11 as compared to alum in a very short time period.