This paper presents the results of wastewater coagulation with the use of polyaluminium chloride (PAC). The examined wastewater contains the following reactive dyes: turquoise DG, black DN, red DB-8 and orange OGR. It has been shown that the efficiency of dye removal depends on the type of dye, a coagulant dosage and the sample pH.
The highest efficiency coagulation was found for turquoise DG. The reduction of the dye was observed from 95.4 mg/dm³ to 0.6 mg/dm³. The dose of PAC was 0.6 mg Al/mg dye. However, the least effective dye removal was reported for reactive red DB-8. In this case, the PAC dose of 2 mg Al/mg dye resulted in the reduction of the dye from 107 to 35.9 mg/dm³.
It was found that the adjustment of the sample pH at 6.5 lowes the effectiveness of dye reduction but it improves the phosphate removal. The amount of organic substances that were removed, measured by the reduction of COD, ranged from 40 to 70%, regardless of sample pH.