Treatment strategies for printing and dyeing wastewater
1. Adsorption method: The predominant strategy in physio-treatment is adsorption, which entails mixing p...
Treatment strategies for printing and dyeing wastewater
1. Adsorption method: The predominant strategy in physio-treatment is adsorption, which entails mixing powders or particles of porous substances such as activated carbon and clay with wastewater, or allowing wastewater to traverse a filter bed fabricated from its granular materials, thereby enabling pollutants in the wastewater to be adsorbed on the surface of the porous substance or to be filtered out. The adsorption rate, BOD elimination rate, and COD eradication rate of activated carbon attained 93%, 92%, and 63%, respectively.
2. Coagulation method: There exist primarily coagulation precipitation methodology and coagulation air flotation technique. The coagulants employed are predominantly aluminum salts or iron salts, among which basic aluminum chloride (PAC) exhibits superior bridging adsorption performance. The primary advantages of coagulation method are straightforward process flow, convenient operation and management, modest equipment investment, compact footprint, and high decolorization efficacy for hydrophobic dyes; The disadvantages are elevated operating expenses, substantial sludge production and challenging dehydration, and subpar treatment effect on hydrophilic dyes.
3. Oxidation method: Ozone oxidation method can yield commendable decolorization effect on most dyes, but displays poor decolorization effect on insoluble dyes such as sulfurization, reduction, and coatings. From domestic and international operational experience and outcomes, this method possesses good decolorization effect, but it incurs significant electricity consumption and presents certain challenges in large-scale promotion and application. The oxidation method exhibits a high decolorization efficiency in treating printing and dyeing wastewater, but equipment investment and power consumption still necessitate further reduction.
4. Electrolysis method: Electrolysis exhibits a robust treatment effect on printing and dyeing wastewater containing acidic dyes, with a decolorization rate of 50% -70%, but the treatment effect is deficient for wastewater with dark colors and high CODCr.
5. Biological method: In the biological treatment of printing and dyeing wastewater in China, surface accelerated aeration and contact oxidation methodologies predominate. Additionally, the blast aeration activated sludge method, jet aeration activated sludge method, and biological turntable have also been implemented, and the biological fluidized bed remains in the experimental application phase. Given the low color removal rate of organisms, generally around 50%, when the color requirements for the effluent are stringent, physical or chemical treatment is indispensable.
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