> Basic aluminum chloride (pac) iswaterOne of the most commonly used flocculants in the treatment of dyeing wastewater in the most widely used in Shanghai the first pool of silk printing and dyeing dyeing biochemical regulation waste water, is mainly reactive dyes, direct dyes, giving a high color, high-strength wastewater, such as the use of coagulation Su Yuping this wastewater treatment, when pac dosage of 700 ~ 900mg / l, ph value control in the 5.4 ~ 6.6, the decolorization rate of up to 93%, and compared with other pac alum flocculant produced by large, fast settling velocity, in addition, the study also found that for the reactive dye-based printing and dyeing wastewater, pac dosage than when dealing with hydrophobic dye feeding to more investment. Lujun Rui flocculation process using bromine acid reactive dye wastewater, when pac dosage of 2g / l, the decolorization rate and cod removal rates were above 90%. In addition, the quarter of the people and so on decolorization of dyeing wastewater coagulation mechanism study further suggests that decolorization of poly-aluminum coagulation wide range of ph values, for most of the dye waste water, are available to more satisfactory bleaching effect, but the single azo, low molecular weight water-soluble groups containing more hydrophilic dye, you can not use poly-aluminum coagulant bleaching 1.2 Flocculants ferric iron flocculant poly bleaching performance, therefore, ferric coagulant commonly used in printing and dyeing wastewater decolorization. Qinmei Jie, etc. with ferrous sulfate, sulfuric acid, aluminum as the basic raw materials in sulfuric acid medium to mno2 as a catalyst, obtained by air oxidation of a high degree of polymerization of inorganic polymer flocculant PFS, printing and dyeing wastewater treatment, wastewater decolorization rate of 98%, cod removal rate of 75% or more, to meet the national emission standard. Du Yang Min to inorganic salts, for different types of printing and dyeing wastewater flocculation bleaching, printing and dyeing wastewater after coagulation flocculation increases, the average rate of decolorization up to 94%, cod place the average rate of 74.3%, of dyeing wastewater treated colorless, transparent, and meet emission standards. Chen Fu roots using ferric sulfate (pfs) plus coagulant mz textile printing and dyeing wastewater treatment, after several years of production practice runs showed that the treated water cod, color and other key indicators to the national emission standards. 1.3 composite flocculant recent years, many scholars have developed the use of composite flocculants slag waste, and for the treatment of dyeing wastewater. Wudui Hu and other self-made Boron clay composite coagulant, printing and dyeing wastewater decolorization experiments, when the dosage of 0.3g / l, its removal rate of 67% cod, bleaching and ss removal rate reached 98%, this method with less dosage, simple process, and high efficiency. Wuqi Fan and other use of copper slag Preparation of solid coagulant fas, hydrophilic dye wastewater treatment, the decolorization rate of 95% or more, to achieve a utilization purpose. Ji Ya Ying found containing home-made magnesium compound bleaching agent, high-color printing and dyeing wastewater, the decolorization rate of up to 99%, cod removal rate of nearly 70%, bod removal efficiency of 90%. Liu Three Studies developed the use of aluminum sulfate ash, silica , magnesium and other elements fh iron coagulant complex, and for the treatment of dyeing wastewater, decolorization rate of> 90%, cod removal efficiency of 60% to 70%, the effect is better than pac. Jiang Jun Mao developed the xb-iv complex flocculant, the flocculant both combination reaction, charge neutralization, bridging adsorption effect on the various types of printing and dyeing wastewater have good flocculation. 1.4 silicate polymer flocculant flocculant is an application of polysilicate flocculant earlier, because of its poor stability, it is seldom used, on this basis, people developed a polysilicate flocculant, and for waste water treatment, and achieved good results. high developed a gem and other metal ions bleaching polysilicate flocculant (psma), of dye wastewater decolorization with good flocculation effect of reactive dye wastewater, when psma dosage of 90mg / l, the decolorization rate of 95 %, and for the dispersion and acid dye wastewater, when psma dosage of 45mg / l, the decolorization rate can reach 95%. Shih-Wen Li, also developed a poly-silicate flocculants, and applied to the dyeing wasteWater , and achieved good results.>