Study On Pollution Characteristics And Environmental Risks Of Chlorophenols In Textile Dyeing Sludge

Chlorophenolic compounds(CPs)are organic compounds that are widely used in the textile dyeing industry.They have teratogenic,carcinogenic,and mutagenic properties.They can enter the textile dyeing wastewater during the production process and accumulate in the sludge,causing potential threats to the ecological environment and human health during the following disposal process.In order to conduct a more comprehensive assessment of CPs in textile dyeing sludge,the characteristics and risks of CPs in sludge from five typical textile dyeing wastewater treatment plants in the Pearl River Delta of Guangdong Province were investigated in this study.In terms of the pollution characteristics of CPs,19 CPs in the sludge were identified by GC-MS.The results of content detection and component analysis showed that the total concentration of 19 CPs(?₁₉CPs)varied from 170.90 to 6290.30 ng g^-1dry weight(dw)with an average of 1682.45 ng g^-1dw,among which high-chlorine phenols accounted for the greatest proportion.Cluster analysis and principal component analysis of 5 textile dyeing factories and 19 CPs were carried out and pollution characteristics were analysised by combining with the properties of textile dyeing factories and CPs.Five textile dyeing predominated chlorophenols(TD-CPs)including 2,3,5,6-Te CP,2,3,4,6-Te CP,2,3,4-TCP,PCP and 4-CP were proposed as well.Regarding the environmental risk of CPs,the CPs ecological screening levels proposed by the US Environmental Protection Agency(US EPA)were used to evaluate the inherent risks of CPs from the aspect of pollution.The risk quotient(RQ)method was used to analyze the risk of CPs acting on three trophic organisms of green algae,daphnia,and fish.The results showed that CPs had a medium to high risk and also revealed the amplifying effect of CPs'toxicity in the food chain.The species sensitivity distribution(SSD)method was used to analyze the ecological environment risk at the system level.Weibull,Burr?,and Log logistic models were applied to mathematically fit the toxicity data of multiple species at different nutritional levels and construct an SSD curve.The concentration levels of CPs under different species protection degree(HC₁?HC₂₀)were obtained(HC₅of 30?3082?g L^-1)and a reference for the formulation of ecological and environmental risk standards was provided.2,3,4,6-Te CP was used as the representative of TD-CPs to calculate the conversion yield of dioxins(3.64?18.2 ng PCDD g^-1dw)under different sludge incineration ratios from 20%to 100%to provide a reference for the risk avoidance of incineration disposal.The most widely used Fenton method was used as the textile dyeing sludge conditioning method in this study.The results showed that the content of?₅TD-CPs in the sludge increased 104%after the conditioning process.On this basis,a single factor experiment was carried out for reagent concentration,reagent ratio,reaction p H and reaction time.A lower rate of CP increase was achieved with a reagent dose of 180 mmol L^-1,H₂O₂:Fe²⁺=1:1,p H of 3?4 and reaction time of 30 min under the premise of ensuring the Fenton oxidation efficiency.A new insights for environmental risk control were put forward as controling the increase rate of CPs maybe more important than increasing the degradation rate of CPs on the purpose of reducing the overall toxicity of textile dyeing sludge and controlling the environmental risk.The work identified the pollution characteristics and environmental risks of CPs in textile dyeing sludge,and provided basic data and reference directions for subsequent research.