Coagulation of indigo blue present in dyeing wastewater using a residual bittern

This work presents an experimental study evaluating the reuse of a bittern wastewater (BW) as coagulant for clarification of dyeing effluent. Comparison with other coagulants was also considered. The zeta potential and morphology of the flocs were investigated. Despite the importance of magnesium ion (Mg2+), other ions contained in the BW also contributed to the clarification of the effluent sample. The removals of turbidity and color of the effluent with 200 mg Mg2+/L were higher than 95% and 80%, respectively. The morphology of the flocs in the coagulation with BW was somewhat different in relation to the flocs obtained with just MgCl2. The adsorption mechanism of particle was observed to be different for each coagulant. According to the results obtained in the clarification of the dyeing effluent, the bittern wastewater can be applied efficiently and economically as a coagulant in the physical–chemical treatment of alkaline textile effluent.

► The wastewater of saline industry was applied to treat textile effluent.
► The treatment was efficient to clarify effluent with indigo blue dye.
► Morphologies of the flocs with bittern were different than the flocs with MgCl2.
► The magnesium ion was important in the clarification with bittern as coagulant.
► The coagulation mechanism of Mg2+ occurred mainly by charge neutralization.