Treatment of wastewater from dye manufacturing industry by coagulation

Chemical coagulation was used to remove the compounds present in wastewater from dye manufacturing industry. The character of wastewater was determined. Most compounds found in the wastewater are phenol derivatives, aniline derivatives, organic acid and benzene derivatives, output from dye manufacturing. Various polyferric chloride coagulants were investigated. Results showed that high extent of Fe(III) hydrolysis was not always suited for chemical oxygen demand (COD) removal in our wastewater, that electrostatic interaction between flocs and organic contaminants played an important role in removal of organic contaminants, that copolymers of Al(III), Si(IV) and Fe(III) were helpful for high flocculating effect, that COD removal efficiency of poly-silicate-aluminium-ferric chloride (PSAFC) and polyferric chloride (PFC) coagulant increased with increasing dose of coagulants, and that the performance of PSAFC and PFC coagulants was superior to PAC coagulant. This difference in efficiency may also be attributed to the copolymers of Si(IV), Al(III)and Fe(III). However, compared with PFC, PSAFC can easily reach high COD removal efficiency below coagulant dose 0.3 g/L. Thus, from the economic point of view, PSAFC is more suitable for treatment of wastewater effluent from dye manufacturing.