Study On The Cause And Control Of Sludge Bulking In Activated Sludge Process Of Textile Dye Wastewater

The textile dye industry contributed the development of China.And the waste water discharge in cloth dyeing process occupies a large proportion in the whole industrial production department.The textile dye wastewater contains toxic substances and high concentration of organism and it has the characteristic of high chroma,high alkalinity,and treatment difficultly.For the past few years,although the technologies of textile dye wastewater process have been developed rapidly,the demand for stability and upgrading treatment has been growing gradually.Most of textile dye wastewater treatment plants(TWTPs)own the biodegradation system as major process.However,the sludge bulking in activated sludge process affects the stability of treatment efficiency frequently,and the studies on sludge bulking of textile dye wastewater treatment have been less reported from domestic and overseas so far.This paper aimed at the cause of sludge bulking,and the schemes were proposed to support the stable operation of treatment system.The daily operation of TWTPs had been studied for three years.And the key factors of sludge bulking had been studied by morphology,ecophysiology and community structure of microbial cell.High-throughput sequencing,characterization of activated sludge and CCA(Canonical Correlation Analysis)analysis had also been used.Meanwhile,the investigation through bench-scale settings operation was carried out by actual dying and printing wastewater.Based on the inner optimum regulating,the outer forced control had been put forward and at last attained the anticipative aim of bulking control.The study on TWTPs operation indicated that sludge bulking was influenced by the variation of temperature of season.Sludge sedimentation performance deteriorated in winter and improved in summer,and was extremely unstable in autumn.At genus level,Haliscomenobacter?Thiothrix and Leptothrix were the principal bulking bacteria detected in TWTPs.The result of bench-scale settings operation indicated that:the sludge bulking with actual dying and printing wastewater was worse than synthetic wastewater.During the whole process,temperature was 20?,the value of original activated sludge SVI was 571.1 ml/g.SVI decreased as the influent organic loading which contained starch from synthetical wastewater increased,the mean value of SVI decreased to 469.0 ml/g when influent organic loading raised to 1.08 gBOD/(L·d).Conversely,SVI increased as the influent organic loading increased.And the SVI of original wastewater treatment system grew more sharply,the mean value of SVI increased to 1140.1 ml/g when influent organic loading raised to 0.72 gBOD/(L·d).No matter how the temperature changed,when the DO contained more than 4 mg/L,SVI went down in all reactors,but it was uneconomical because of the dramatic increase of aeration intensity.By CCA analysis,there had close connection such as temperature and Haliscomenobater,DO and Zoogloea,influent load and Hyphomonas.Both Hyphomicrobium and Thiothrix had weak correlation with environmental factors.This result indicated that various of filamentous bacteria evolved independently by environmental factors.And they jointly maintained the stable existence in zooglea.In addition,the result of sequencing batch operation indicated that it was difficult to improve the characteristic of sludge sedimentation by the method of SBR operation.FC-200(Fe oxides agentia)type(particle sizes were 200-250 meshes)which was synthesized by iron and activated carbon performed better than other Fe oxides of different particle size types.When the dosage of FC-200 type was 0.1%,the value of SVI dropped from 474.2 ml/g to below 200 ml/g by only one minute reaction.The principle might be that tiny FC particulate matters with weakly magnetic were retained in the surface of zooglea.Then by the effect of the slight magnetism and gravity of FC,sludge floc gathered and compressd each other to improve the characteristic of sedimentation.Meanwhile,ultrasound was also effective but restricted by factors such as frequence,the character of sludge,power density,action time.Above all,various of filamentous bacteria with diverse physiological properties colud construct the stable ecosystem in the sludge bulking system.And the cause of formation could be more complex if the mixed type bulking occurred because of conditional variant such as the composition of influent.The condition of high DO concentration was benefit for alleviating bulking but uneconomic.The methods of FC types and ultrasound were effective,and possessed broad-spectrum,high-efficiency,low-cost.It was also security because of their physical way.But the application of ultrasound may be limited by the interference of various of factors.