At present, the textile industry pollution mainly from the production wastewater, exhaust gas and noise in the process. From the three aspects of the environmental pollution of the textile industry in recent years Chinese.

Printing and dyeing wastewater is the main harmful, refractory wastewater is one of the main pollutants, dyes, additives, fiber pulp, impurities, oil, acid and inorganic salt. Its characteristic is the characteristics of large amount of wastewater, water quality is complex, high concentration of organic matter, bio degradable, color depth, water quality change quickly without the law, among which the dye pollution is the most serious, the residual dye component even at low concentrations, may also cause water transparency reduced, leading to ecological environment the destruction of.

Printing and dyeing wastewater is the main pollution source of textile industry. According to incomplete statistics, daily wastewater of printing and dyeing enterprises in China is about 300 ~ 4000000 t per 100 m, printing and dyeing processing fabric, will produce 3 to 5 t, the amount of waste water. With entrainment of fiber raw material itself in discharged water, and used in the process of slurry, oils, dyes and chemical additives, has the following characteristics: (1) change of COD, high up to 2000 ~ 3000 mg/L, BOD is as high as 2000 ~ 3000 mg/L. (2) pH high, such as sulfur dyes and vat dyes wastewater can reach more than 10 pH. (3) high chroma, high organic content, containing dyes, auxiliaries and a large number of wastewater viscous slurry. (4) the water content changes, due to changes in processing varieties, yield, can lead to the water temperature at 40 DEG C, thus affecting the efficiency of wastewater treatment.

In addition, the traditional process of printing and dyeing processing will produce toxic large amounts of sewage, wastewater processing after some toxic dye processing aids or adhere to the fabric, have a direct impact on human health. Such as formaldehyde, azo dyes, fluorescent whitening agent and softening agent with sensitization; polyvinyl alcohol and polypropylene pulp is not biodegradable; chlorine bleach pollution; some carcinogenic aromatic amine dyes; dye has all kinds of harmful heavy metals; formaldehyde finishing agent and printing and dyeing auxiliaries have toxic effects on the human body. If such wastewater without treatment or after treatment fails to reach the prescribed emission standards on direct emissions, not only directly endanger people's health, but also seriously damage the water, soil and ecological system.

(two) review of printing and dyeing wastewater quality characteristics and processing technology

Printing and dyeing wastewater source, water quality, water in

1 Sources

The four processes are discharged from the printing and dyeing wastewater, the pretreatment stage (including singeing, desizing, scouring, bleaching, mercerizing process) to discharge the desizing wastewater, wastewater scouring, bleaching wastewater and mercerizing wastewater, dyeing process and dyeing wastewater discharge, waste water and discharge printing process printing soap wastewater, finishing is the process of finishing wastewater discharge. Printing and dyeing wastewater is mixed wastewater over all kinds of wastewater, or in bleaching wastewater outside the comprehensive wastewater. In

2.. Quality and quantity

Depending on the type of fiber and the processing quality of printing and dyeing wastewater with different components, pollutants. General printing and dyeing wastewater pH value of 6 ~ 10, 400 ~ 1000 increase in CODCr mg/L, BOD5 for 100 ~ 400mg/L, SS 100 ~ 2 00mg/L, chroma is 100 ~ 400 times. But when the dyeing process and the type of fiber and the processing technology of the waste water after the change, there will be a big change. For example, when containing alkali reduction wastewater produced in the process of polyester silk printing and dyeing wastewater, wastewater COD La Cr will increase to 2000 in the above 3000 in the La ~ La in mg/L, BOD5 increased to more than 800mg/L, pH value of 11.5 ~ 12, and the water quality simulation with adding polyester silk dyeing wastewater the increasing deterioration. When the amount of 20% CODCr alkali reduction wastewater added amount of more than CODCr in wastewater, biochemical treatment will be very difficult to adapt to the. The drainage is generally: the process of printing and dyeing

(1) desizing wastewater: a small amount of water, but the high concentration of pollutants, which contains all kinds of slurry, slurry decomposition, lint, starch and various additives. The waste water was alkaline, pH value is about 12. Sizing to starch based (such as cotton desizing wastewater), COD, BOD values are very high, good biodegradability; sizing with polyvinyl alcohol (PVA) mainly (such as polyester cotton warp) desizing wastewater, C OD high and BOD low, wastewater with poor biodegradability. The

(2): boiling water, wastewater with high concentration of pollutants, which contains cellulose, wax, oil, acid, alkali, surfactant, nitrogen-containing compounds, wastewater is strongly alkaline, high temperature, brown. The

(3) bleaching wastewater: water, but less pollution, which contains residual bleach, acetic acid, oxalic acid, sodium thiosulfate, etc..

(4) mercerizationwastewater: high alkali content, the content of NaOH is 3% ~ 5%, the majority of printing and dyeing factory concentrated by evaporation recovery NaOH, so mercerizationwastewater rarely discharged waste water after repeated use of the final discharge process is strongly alkaline, BOD, COD and SS were higher. The

(5): a large amount of water, the water quality of dyeing wastewater with different dyes, including slurry, dyes, additives, surface active agent, the general was strongly alkaline, high chroma, COD higher than BOD, poor biodegradability. The

(6) printing wastewater: a large amount of water, waste water in printing process, including printing after soaping, washing wastewater, high concentration of pollutants, including slurry, dyes, additives, BOD, COD were higher. The

(7): finishing wastewater containing a small amount of water, fiber and resin, oil, slurry etc.. The

(8): is to produce alkali reduction wastewater polyester alkali decrementprocess process, mainly containing polyester, ethylene glycol and terephthalic acid hydrolysate, the acid content of up to 75%. Not only the high pH value of alkali reduction wastewater (general > 12), and high concentration of organic matter, alkali deweighting process of CODCr wastewater emissions can be as high as 90000 mg/L, organic polymer and dye is difficult to be biodegraded, the wastewater is a high concentration of refractory organic wastewater. In

(three) methods of dyeing wastewater treatment

At present, the domestic means of printing and dyeing wastewater treatment by biochemical method, some chemical methods and series. Abroad is also basically the same. In recent years, the development of chemical fiber fabric and dyeing finishing technology, PVA slurry, new additives and other refractory organic compounds in dyeing wastewater, to increase the difficulty of treatment. Most of the existing biological treatment system from the original 70%COD removal rate dropped to about 50%, or even lower. The color removal is a big problem in dyeing wastewater treatment, biochemical method in old decolorization has been unsatisfactory. In addition, by PVA chemical slurry COD dyeing wastewater accounted for the proportion of total COD is quite large, but because they are hard to be used by common microorganisms and the removal rate is only 20% to 30%.

Aiming at the above problems, in recent years at home and abroad have carried out some research work.

Printing and dyeing sludge generally inert high sludge concentration such as denim washing and bleaching wastewater produced is very high, and the organic matter, bacteria content is less sludge, low calorific value, high content of heavy metals than urban sludge in general. The printing and dyeing industry itself due to the use of raw materials, varieties of products, products of different processing methods, components of the sludge produced are not the same, such as the use of sulfur dye enterprises, sulfide content is high. The printing and dyeing sludge treatment agent selection and dosage according to the different sources of sludge. To the scale of sewage treatment, sludge production, drug sources, dosage, operating cost, moisture content of the cake and so on, according to local conditions, comprehensive consideration.

At present, the domestic printing and dyeing mill by the size limit, the amount of waste water is generally not more than 50000 cubic meters / day, a large area of land natural drying or incineration facilities are not desirable, especially in the southern region, the rainy and humid climate makes the dry field useless. On a small scale sewage treatment plant sludge, if used after the initial conditioning centrifuge triple Zhejiang environmental protection machinery equipment Co Ltd production, dehydrated solid containing rate of more than 25%, reached the transport requirements, in the investment, operation and disposal methods of sludge on the owners can accept.

Working principle

The suspension through the feed tube from the helix outlet into the drum, the centrifugal force generated by the high-speed rotation, a large proportion of solid particles deposited on the inner wall of the drum, and the drum helical blade continuously the relative motion of the solid particles deposited on the drum wall scraping and launch discharging port. After the separation of the supernatant liquid layer by adjusting plate opening overflow drum. The relative motion between the body and the spiral drum (i.e. differential rotation) is realized by differential, its size is controlled by the auxiliary motor, so as to realize the continuous centrifuge separation process of materials.