Posted 21 Dec 2010 02:12
Dyeing and Printing Wastewater large printing and dyeing wastewater will adversely affect the drainage, which is a toxic substance colored contaminants. In printing and dyeing wastewater treatment engineering design, not just consider the color of the discharge standards, taking also into account other pollutants color and COD removal. I think the best decolorization of dyeing wastewater by biological treatment. Bleaching is the use of biological oxidation or reduction microbial enzymes to dye molecules, and the destruction of the unsaturated bond chromophore. Microbial Decolorization of dye adsorption and enrichment first, followed biodegradable. Dye molecules through a series of oxidation, reduction, hydrolysis, compounds and other activities, and ultimately degrade into simple inorganic or converted into a variety of nutrients and protoplasm. Subtle changes in molecular structure of dye will affect the decolorization rate, and different microbial removal efficiency of different structures are greatly different dyes, dye concentration on decolorization rate also have some impact, high concentrations of dye (dye itself has a strong biological toxicity) will be inhibit microbial activity and affect decolorization. Aerobic process is a common treatment process, but the dye molecules are strongly resistant to biodegradation, processing BOD5/COD ratio decreased (biodegradability of variation), resulting in a normal aerobic process of wastewater color, COD removal rate is not high (60 ~ 70%). To the aeration **** by adding iron salts, such as activated carbon adsorption material, refractory material may extend the residence time in the system to improve the aeration **** of activated sludge concentration, reduced sludge loading, thereby enhancing the rate and the bleaching system COD removal rate. In recent years the development of anaerobic (Hydrolysis) - aerobic treatment process to a certain extent, compensate for the lack of aerobic processes. However, biological treatment processes alone can not meet the color and COD remained stable compliance requirements. Production for the enterprise and the different water quality, wastewater pretreatment and follow-up treatment, to ensure color and other pollutants to meet emissions standards. Woven fabric dyeing process usually desizing wastewater, waste water scouring, dyeing wastewater. Such a large water alkalinity, high color, COD high, and the water temperature is higher, the use of a wide range of dyes, and sometimes the use of sulfur in the production process will be a certain amount of sulfide, as if the use of PVA slurry, mixed waste water will contain a certain amount of very poor biodegradability of PVA. The class of pure water anaerobic - aerobic or such extended aeration process, the effluent COD, color are difficult to compliance, investment and strengthen the oxidant water in the system, the sulfide is converted to elemental sulfur precipitation, the water was like thin rice soup milky white, color or difficult standards. Wastewater treatment in the class, if the increase in the physico-chemical treatment prior to biological treatment facilities, voted to ferrous sulfate and PAC-based bleaching agent, can remove about 80% color, 95% of the sulfide , and 40% of the COD, which also removes some of the macromolecular refractory dye, if matched to design a good biochemical processes, such wastewater COD and color are stable standards. Denim Yarn and Dyeing Wastewater with high color, COD high, such a large number of wastewater used in the dyeing process of sulfur, therefore, waste water contains large amounts of sulfur, often as high as 200 ~ 1000mg / L, color up to 2000 ~ 3000 times . Materialization of such waste must also be pre-dosing, and then biological treatment, to stabilize the discharge standards. Jeans rinse wastewater containing dyes, pulp and surfactant additives. Large quantity of such waste, concentration and color of the low, if only using the physico-chemical treatment, the effluent COD only at 100 ~ 200mg / L between the color but also to meet the emission requirements, but has greatly increased the amount of sludge, sludge higher cost of treatment, likely to cause "secondary pollution", and therefore should also consider using biochemical processing. Knitted fabrics (yarn) printing and dyeing wastewater of dyeing wastewater and sweaters, and more use of cationic dyes, reactive dyes, disperse dyes and so on. Decolorization of such physical and chemical treatment in the primary, the use of the ferrous sulfate-based bleaching agent, coagulant often used hydrated lime powder, but the addition of lime scale will lead to pipeline blockage, resulting in system maintenance workload increase. In addition, water and oxygen in the air once the combination of divalent iron ions will be oxidized to ferric ions, rendering the water turbid yellowish rust color. Knitted fabrics (yarn) dyeing wastewater and dyeing wastewater is generally sweater directly anaerobic - aerobic-based biological treatment, but sometimes occur in the aerobic system, the phenomenon of color increases, then that biochemical system is running well, But this time in addition to strong oxidants, other bleaching agents to remove the results are not satisfactory, strong oxidizer and waste water should be controlled the contact reaction time from 30 to 60 minutes. Decolorization of the class should also consider the impact of fluctuations in water quality, number of enterprises receiving orders for printing and dyeing sulfide, often in 1 week or 10 days of the discharge of wastewater containing sulfide, and other reasons due to microbial adaptation, sulfide in the waste water will strongly inhibit microbial activity, resulting in effluent COD and color of different degrees of overweight, this part of the physical and chemical pretreatment of wastewater should be carried out for biological treatment.