Textile wastewater is a combination of various chemicals and different types of dyes and has a salty nature. In this study, an SBR (sequencing batch reactor) was used to treat synthetic and real textile wastewaters in a 24 h cycle time. Remazol Brilliant Blue R, a reactive dye, was used as the model dye. Dye concentrations ranged from 125 mg/L to 500 mg/L, and TDS (total dissolved solids) concentrations ranged from 1000 mg/L to 10,000 mg/L in synthetic wastewaters. For the highest dye concentration (500 mg/L) with low TDS, an 80.71% COD removal efficiency was obtained; at a TDS concentration of 5000 mg/L, a 59.44% COD removal efficiency was obtained. When the TDS concentration of wastewater was raised to 10,000 mg/L, COD removal decreased to 14.92% and reductions in MLSS (mixed liquor suspended solids) and MLVSS (mixed liquor volatile suspended solids) concentrations were observed. According to the results, increasing the TDS concentration of wastewater up to 5000 mg/L did not affect COD removal efficiency of the activated sludge microorganisms in the treatment system.

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Sorghum bicolor and Trifolium repens extracts as plant coagulants can be used for wastewater treatment instead of chemical coagulants. This study investigates the effects of pH and coagulant dose on COD and turbidity reduction by natural coagulants. In the optimum treatment conditions of 100 mg/L coagulant dose and pH 7, high turbidity (81.34%), and COD reduction (62%) (Compared with Alum and FeCl3) were obtained. The percentage of COD reduction is higher in Trifolium repens than the other plant coagulant and the percentage of turbidity reduction is higher in Sorghum bicolor. FT-IR spectra were performed on the plant extracts to identify the existing factors in active extracts. Also, outlet COD and turbidity values can be calculated according to computational equation in similar treatment systems where using the same plant coagulants. It should be mentioned that the only applied solvent for extracting the natural coagulant seeds, was distilled water and none of the other solvents such as NaCl and NaOH were used. According to the results, the characteristics of the treated effluents by the plant extracts make them appropriate alternatives for textile wastewater treatment.