Analysis On Dyeing Wastewater Of Cotton Knitted Fabric And Study On The Reuse Probability Of Treated Wastewater

It is estimated that the emission of textile industrial wastewater ranks NO.3 in all industries in China,accounting for 10.60%of the national industrial wastewater emission.But the wastewater emission from printing and dyeing industry accounts for 80%of the whole textile industry.With the discharge standards in terms of wastewater becoming increasingly strict and the fee of tap water and sewage discharge rising,printing and dyeing enterprises pay more and more attention to the clean production and the wastewater reuse also gradually arouses people's interest.Hengda printing and dyeing limited company carried out the project of reclaimed water reuse several years ago.The dyeing wastewater of the factory is classified according to the level of water pollution.Highly polluted wastewater directly is discharged to wastewater treatment plant and light polluted wastewater firstly is treated simply and then is used as washing water of deep-color fabrics.But the present problem is that the treated wastewater can't reach the standard of reuse water because of certain color and smell in it.So the rate of reclained water reuse is low and the project doesn't bring about many benefits for the company.This article mainly aims at the dyeing wastewater of' cotton knitted fabric in the factory.It is divided into three parts.Firstly,the quality of washing water after hydrogen peroxide bleaching and different concentration of reactive dyes dyeing xwas analyzed.The testing indexes included the value of pH?CODcr?chromaticity and conductivity Second,the light polluted wastewater was treated by means of coagulation followed by adsorption method.In coagulation process,the effects of the dosage of PAC and wastewater pH on the removal of COD and chromaticity were investigated,and in adsorption process,the effects of the dosage of activated carbon powcder?stirring time and wastewater pH were investigated.Finally,the treated wastewater was reused in fabric washing process.The whiteness of fabric and capillary effect were evaluated when the reuse water was used as washing water after hydrogen peroxide bleaching,and color difference and some fastness were evaluated when the reuse water was used as washing water after reactive dyes dyeing or disperse dyes dyeing.The results showed that the cotton knitted fabric through hydrogen peroxide bleaching and reactive dyes dyeing needed to be washed several times,but the water quality of each washing water was different.The pollution degree of the front part of washing water was higher than the back part of washing water.In general,the washing water after bleaching and soaping was suitable for recycling.In coagulation process,when the dosage of PAC was 800mg/L,the pH value was adjusted to 6.09 and the stirring time was 15min,the CODcr of wastewater was decreased from formerly 380mg/L to 123mg/L and the chromaticity of wastewater was decreased from formerly 2000 folds to 100 folds.In adsorption process,when the dosage of activated carbon powder was 450mg/L,the pH value was adjusted to 2 and the stirring time was 60min,the final CODcr of wastewater dropped to 78mg/L and the chromaticity of wastewater dropped to 1 fold.The wastewater through appropriate treatment was used in certain washing processes and some indexes were evaluated.When the treated wastewater was used as washing water after hydrogen peroxide bleaching,the whiteness of fabric was almost not affected,but the capillary effect was poorer compared with that using fresh water.When the treated wastewater was used as washing water after dyeing,the washing effect of all tested dyes is good except Reactive Turquoise Blue MZ-GR.