Chemical Coagulation Is Used In Dyeing Wastewater

Treating dyeing wastewater is a difficulty both at home and abroad. A series of coagulants/flocculants, such as inorganic coagulants: polyaluminum chloride(PAC), ferrous sulfate(FeSO₄.7H₂O); organic flocculants: polydimethyldiallylammomum chloride(PDMDAAC) , decolouring flocculant(BT-03); composite flocculants of inorganic-organic: PAC-PDMDAAC, decolouring flocculant(BT-04), was used to treat disperse dyes, reactive dyes simulation wastewater and real dyeing wastewater. Factors influencing color and COD removal were studied by using jar test, including the consumption of coagulant, pH value , the time of stirring and depositing etc. The coagulation/flocculation mechanism was also investigated.The study shows that PAC-PDMDAAC and BT-04 has a better decolorization result towards wastewater of reactive dyes simulation, disperse dyes simulation and real dyeing wastewater under suitable condition. The color removal rate to the disperses dyes simulation waste water can reach 96.4% in a high degree, to reactive dyes simulation wastewater can be 93.6% and to real dyeing wastewater can also be 54%.In addition COD removal rate can be 66.3%. PH has little influence on BT-04. Inorganic coagulant PAC and FeSO₄.7H₂O has great effect on decoloring the disperses dyes and has less effect on decoloring thereactive dyes and real dyeing wastewater. pH has great impact on PAC and FeSO4.7H2O . The color removal rate of organic coagulant PDMDAAC and BT-03 is high , but it costs a lot under the same investing amount. The study also finds that a variety of coagulant has better impact on simulation wastewater than on real wastewater. The reason is that the components of real wastewater is complicated, and it demands the combination of other methods in order to achieve the satisfactory effect.A composite flocculant of inorganic-organic combined the advantage of the inorganic and the organic coagulant. It has the advantage of low consumption , low cost , wide range of application, high removal rate and high COD removal rate . Hence, it has good application prospects.