Study On The Accumulation Characteristics And Control Technology Of Pollutants In The Recycling Of Printing And Dyeing Wastewater

In China,a large amount of printing and dyeing wastewater（PDWW）is discharged every year,and the primary goal of wastewater treatment is to meet the latest discharge standard limitation in GB 4287-2012 for dyeing and finishing in the textile industry.Recycling of PDWW is gradually forming scale.However,it is difficult to make the water reuse rate of enterprises meet the requirement of more than 40%specified in the"printing and dyeing industry standard conditions（2017）"by the widely used mixed treatment mode and double membrane regeneration technology.In addition,organic matter and inorganic ions accumulation could occur during PDWW recycling.In order to improve the wastewater reuse rate of printing and dyeing enterprises,a new framework of PDWW reuse,the accumulation characteristics of pollutant and the control technology were studied.The main contents and achievements of this paper are as follows:（1）In this study,a PDWW recycling system was established to investigated the organic and inorganic pollutants accumulation effect during closed-loop recycling.The results indicated that organic matter accumulation will preferentially affected the activated sludge system in the PDWW recycling system compared with inorganic ions at the initial stage.Four types of bio-treated organic matters in the PDWW recycling system were characterized as fatty alcohol polyoxyethylene ether（AEO）,volatile fatty acids（VFA）,soluble microbial products（SMPs）and other organic matters mainly composed of organic dye intermediates.According to GC/MS and constrained distance-based redundancy analysis（db-RDA）,organic dye intermediates were the critical organic matters responsible for the activated sludge system deterioration.In addition,phenylalanine metabolism,synthesis and degradation of ketone bodies,butanoate metabolism and pyruvate metabolism were the four influenced significantly metabolic pathways based on metabolomics analysis in PDWW recycling system.It was also revealed that gene number of feaB,DDC and E2.3.3.10 exhibited down-regulation so that phenol and naphthalene accumulated due to the impaired degradation ability,which was the main reason for activated sludge system deterioration.（2）The dissolved ozone flotation is optimized to effectively control the accumulation of organic matters during PDWW recycling.Compared with the traditional air flotation control,the retention time of activated sludge system under dissolved ozone flotation control is 1.5 times longer.The accumulate rates of COD,UV₂₅₄,fluorescence peak A and B,protein and other organic compounds in the two stage effluent were1.4mgCOD/L d,0.018cm^-1/d,11.1R.U/d,4.4R.U/d and 0.213mg/L d,respectively,which were 58.6%,53.8%,93.1%,89.1%and 25.8%lower than those under the traditional air flotation control.The proportion of benzene ring carbon and fat carbon in secondary effluent is increasing gradually.At the beginning of the cycle,the protection function of extracellular polymer substances（EPS）counteracts the influence of ion accumulation;when the ion concentration exceeds 5g/L,the continuous increase of inorganic ions results in significant inhibition of the function of activated sludge system（note to the decrease of gene number）,and the accumulate rate of COD in secondary effluent reaches 3.85mg/L d.Macrogenomic analysis showed that accumulate ions interrupted the pathway of glycan biosynthesis and metabolism,glycan biosynthesis and metabolism,xenobiotics biodegradation and metabolism,and finally the pathway of lipid metabolism.Different from the enrichment of organic matter,the inhibition and toxicity of ion enrichment on microbial function are based on the interaction of long-term,slow inhibition and microbial function.（3）Based on the accumulation model of inorganic ions,a bypass membrane separation and treatment technology for the regulation of inorganic ions enrichment was developed,which effectively controlled the enrichment of inorganic ions,saved the construction investment to the maximum extent,reduced the treatment cost,and provided technical guarantee for the normal operation of the biological system for the recycling of printing and dyeing wastewater.With the combination of dissolved ozone flotation and bypass membrane technology,the COD of the effluent of the system has been kept lower than 50mg/L for a long time,and the proportion of organic functional groups tends to be stable,eliminating the phenomenon of organic matter and ion enrichment in the secondary effluent,which is conducive to improving the reuse rate of printing and dyeing wastewater and ensuring the quality of reuse water.（4）Based on the field investigation,the water quality and quantity characteristics of different printing and dyeing processes are determined.The treatment characteristics of different printing and dyeing processes are obtained by using the water quality matrix theory normalization,and a new framework of"source separation process and sequential reuse per water quality level for PDWW"is constructed.According to the water quality and treatment characteristics,PDWW can be divided into special wastewater,high concentration wastewater and low concentration wastewater.Special waste water and high concentration waste water is treated up to the discharged standard.Low concentration wastewater treatment aims at recycling,producing general reclaimed water and high-quality reclaimed water.The construction of this model lays a foundation for improving the wastewater reuse rate of printing and dyeing enterprises.（5）The technology developed in this project has been applied to the practical project of PDWW recycling.The results of long-term operation show that the sensory index（chroma,transparency and SS）,organic matter index（COD）and salt index（TDS,iron and manganese）of the reclaimed water can reach and surpass the limitation requirements of the standard for water quality of textile dyeing and finishing industry（FZ/T 01107-2011）.The dyeing effect of reclaimed water is not significantly different from that of industrial water supply.The research of this paper can effectively improve the recycling efficiency of PDWW,ensure the capacity growth of enterprises,and provide a technical example for the closed-loop recycling of printing and dyeing industry cluster wastewater.