| As for pollution of printing and dyeing wastewater, this thesis describe the status quo of its treatment in China, analyze the source, component, characteristics and contamination, introduce a variety of treatment technology as well as their advantages and disadvantages, subsequently decolorization experiment was conducted by using coagulation-flocculation and Iron filtration process with simulated printing and dyeing wastewater.Coagulation-flocculation experiment showed that regular aluminum and ferrous coagulation is very effective in removing hydrophobic dyes, with 90% decolorization efficiency for sulfuric black, direct black and disperse black, while coagulation is less effective in removing hydrophilic dyes, only 50% decolorization efficiency was achieved by aluminum for reactive and acid dyes. Ferric coagulation is a exception for decolorization of hydrophilic dyes, in the experiment color removal efficiency reached as high as 95% and 65% for reactive red and acid blue, respectively.Jar test for color removal of printing and dyeing wastewater with iron particle showed that main factor connecting with color removal are raw wastewater pH, dosage ratio of iron to water, reaction time, aeration, raw wastewater color and type of dye. The effect of pH value is much greater during the earlier time of reaction, while decreasing gradually with reaction time. Ferric ion increase dramatically when raw wastewater pH is 3.0. High color removal efficiency was achieved when dosage ratio of iron to water was increased, however, there is no distinction between high and low dosage ratio of iron to water when it increased to 0.5gram iron per ml wastewater. Color removal efficiency can be increased by 10% when wastewater is aerated. Low color wastewater is more easilydecolorized than high color wastewater. This process is effective in removing color caused by reactive dye, acid dye and disperse dye, but different dye is decolorized with different mechanism, for different simulated dye wastewater with 300 dilution multiple, when 90% color removal efficiency was achieved, reactive red, reactive blue and acid blue needed 8minutes, acid red and disperse black needed 12 minutes, 20 minutes respectively. With 1.0 mm to 2.5 mm sponge iron, decolozation curve is much same as with 0.5鈥?.6 mm regular iron particle.Orthogonal experiment was conducted by using pH value, dosage ratio of iron to water, reaction time as three pitch, aeration or not as two pitch. The result showed that factor affecting magnitude of decolorization efficiency was reaction time, dosage ratio of iron to water, pH value and aeration in sequence.Pilot-scale experiment showed that fine iron particle as filter sand can easily be compressed and blocked, and it is nonfeasible for application. For low color raw wastewater(300 dilution multiple), 93% color removal efficiency was achieved with sponge iron as filter sand at 5 m/h filtration rate and pH5.0, while for high color raw wastewater(500 dilution multiple), it is only 77%. When effluent color is constant, the effect of pH for color removal is obvious, the lower pH was, the higher color removal efficiency was. Filtration rate has a significant effect on decolorization efficiency, low filtration rate is more effective. Raw wastewater pH value play an important role in lengthening filtration period. Repeative experiment indicated that high pH value can easily result in inactivity of iron particle with decolorazation efficiency decreasing dramatically, and this process can't be operated under neutral conditions. Static regeneration couldn't restore its decolorization performance to that of the very beginning of the experiment. When the system was backwashed 20 minutes with intensity of 251/s.m2 , sponge iron can not be compressed, and no gap flow was observed, the optimum size of iron particle is 1.0-2.5mm. When the system was operated at pH5.0~6.0 with filtration rate 5~10m/h, the effluent pH was neutral around, and total ferrous was less than 6.0mg/l.
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