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Textile effluents are considered among the most polluted wastewaters all over the world. Among different textile processes, dyeing is the operation that produces the most important amounts of chemical pollution. Many studies have been carried out toward the treatment of these hazardous effluents, and a variety of techniques have been applied for this aim. In this work, the effluents coming from different steps of the dyeing cycle were treated following different mixtures of baths using membrane technology. Nanofiltration (NF) experiments were performed for color removal, but membrane fouling still a major limitation. To enhance NF performances, microfiltration (MF) was carried out as pretreatment to NF. The results showed almost above 99 % of color and turbidity removal and also an important decrease in COD, chloride and salts contents with an improvement in the MF and NF stabilized fluxes of different mixtures compared to that corresponding to the dyeing effluent treated separately. In order to accomplish a full reuse cycle, dyeing experiments were performed using the combined system (MF/NF) permeates. Results were evaluated regarding total color difference between samples and a standard test done with fresh water.

A combined system of coagulation and membrane processes was investigated in this study for reactive dyeing wastewater treatment. Microfiltration (MF) and ultrafiltration (UF) membranes were tested in order to study the effect of the membrane type on the hybrid system performances. Additionally, membrane resistance analyses were conducted in order to understand the membrane fouling mechanism. Two different coagulants were used: Al 2 (SO 4 ) 3 (Alum) and Amerfloc445. The influence of the coagulation conditions including coagulant nature and shear rate and duration on the UF behavior was studied. Indeed, a procedure of flocs breakage-reformation under different shear intensities was followed in the coagulation step, during these tests, flocs size and sensitivity to breakage as well as their regrowth ability were examined. The filtration results indicated that the coagulation step did not enhance the MF performances. The coagulation/ultrafiltration system was found to be better not only in term of permeate quality but also in fouling minimization. Although, Amerfloc445 generated the largest flocs with the best regrowth ability, but these flocs were more sensitive in increasing shear rate. As a result, the flocs breakage dropped the UF normalized flux by at least 22% with Amerfloc445 against a maximum of almost 12% with Alum. The extension of the shear duration from 5 min to 10 min affected the UF behavior especially in the presence of Amerfloc445; indeed the normalized flux decrease reached 14% against just 3% for pre-coagulated effluent with Alum.

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