Research On Comprehensive Purification Technology Of Printing And Dyeing Wastewater

Printing and dyeing wastewater is one of the largest industrial wastewater in China,with complex components,high organic concentration,high chroma,high salt concentration,and poor biodegradability.Some aniline and azo dyes contained in the water are highly carcinogenic and seriously harm the water environment and human health."Textile Dyeing and Finishing Industry Water Pollutant Discharge Standards"(GB 4278-2012)sets stricter requirements on the discharge standards of ammonia nitrogen,suspended solids,chromaticity and COD of printing and dyeing wastewater.Current printing and dyeing wastewater purification treatment technologies include Physical,chemical and biological methods,among which denitrification,flocculation and decolorization are the.three key technical links in the purification process.The water quality characteristics of printing and dyeing wastewater have led to a sharp increase in the difficulty of wastewater treatment.Although biological methods have the characteristics of low cost and no secondary pollution,in high-salt environments,metabolic activities of microorganisms with poor salt tolerance are easily suppressed,reducing wastewater treatment efficiency in order to improve the efficiency of comprehensive purification treatment of printing and dyeing wastewater,this paper intends to study the effect of enhancing the denitrification effect of mixed bacterial flora,selection of flocculants and optimization of conditions,and screening of high-efficiency decolorizing strains by Halomonas to achieve comprehensive purification treatment of printing and dyeing wastewater.Halononas sp.B01 and Halomonas sp.H02,which were suitable for high concentration of ammonia nitrogen and good SND denitrification effect,were used to enhance the denitrification ability of mixed bacteria,which was used to simulate the denitrification of printing and dyeing wastewater and optimize the denitrification conditions.The optimum nitrogen removal conditions were:sodium acetate as carbon source,C/N of 7.5,DO of shaker speed of 90 rpm,SND nitrogen removal for 96 h,initial ammonia nitrogen content of 2000 mg/L,and nitrogen removal rate was up to 99.3%.The selection of flocculants and the study of flocculation conditions were the key to achieve good flocculation effect.This paper compared the flocculation effect of the chemical flocculants which were included polyaluminum chloride(PAC),polyaluminum ferric chloride(PAFC),polyferric sulfate(PFS),andpolyacrylamide(PAM),and the biological flocculant ?-PGA to the simulate high-salt nitrogen-containing printing and dyeing wastewater on the optimized flocculation conditions.Comprehensived economic cost and flocculation effect,the biological flocculant ?-PGA was selected.When the dosage was 4%(w v),the flocculation time was 6 minutes,and the flocculation temperature was 30?,the flocculation effect was the best and the flocculation rate was 96.2%.Halomonas sp.B01 was as the high-efficiency decolorizing bacteria for methyl orange by selected.The response surface method was used to optimize the decolorization conditions.The optimization results of the main influencing factors were:pH 7.04,NaCl 25 g/L,(NH4)2SO4 12 g/L,decolorization culture at 30? for 48 h.The decolorization rate of methyl orange azo wastewater which the concentration was 55 mg/L was 95.07%.At the molecular level,the reason why Halomonas sp.B01 could be decolorized for the methyl orange azo dye was the bacteria contained the azo reductase gene.And this conclusion was explained by used the construction and functional verification of gene recombinant expression vectors.According to the optimized conditions of denitrification,flocculation and decolorization determined above,combined with hollow fiber ultrafiltration technology,the printing and dyeing wastewater from a printing and dyeing plant in Dalian was comprehensively treated.The treated wastewater had an ammonia nitrogen concentration of 18 mg/L and suspended solids concentration of.32 mg/L,color was 70 degrees,COD was 54 mg/L.It provided theoretical and technical support for the comprehensive purification treatment of printing and dyeing wastewater.