Study On Treatment Of Printing And Dyeing Wastewater In A Textile And Printing Factory

A textiles printing and dyeing Co., Ltd. in Guangdong province has four wastewatertreatment plants. These plants adopted a combined process of coagulation sedimentation,hydrolysis acidation (HA), biological contact oxidation, Decolorization (Bleaching) and Sandfiltration. However, COD of effluent was from110to180mg/L, which was hard to meetdischarge standard. In order to achieve effluent to the new water pollution emission standard,a pilot plant composed of facultative contact reactor (FCR), coagulationsedimentation (CS),biological contact oxidation (BCO) and two stage ozone biological aerated filter (O3-BAF)was used to treat printing and dyeing wastewater. This process was simple, stable and efficient.It was suitable to treat this wastewater.The study adopted FCR to pretreat the wastewater. The result of experiment indicated thatFCR possessed strong resist impact load capability. Besides, the dissolve oxygen (DO) below0.3mg/L could effectively inhibit multiplication of sulfate reducing bacteria. FCR unit had abetter efficiency of COD and SS removal than HA. During the start-up, COD of effluent wasabout400mg/L and the highest COD removal rate was65.9%. SS of effluent was form50to105mg/L and removal rate was93.3%. Moreover, the average COD removal rate from50to60%was obtained in optimal hydraulic retention time of10.36h.Through coagulation sedimentation experiment of different kinds of coagulants,FeSO4·7H2O and H2O2were selected for the pilot study, and optimal dosage were0.5g/Land0.22g/L, respectively. The coagulation sedimentation and biological contact oxidationcombined process was adopted as secondary treatment of wastewater. The result showed thatafter further treatment the effluent of secondary process could meet the requirement ofinfluent of advance treatment. The combined process had a good efficiency of COD, NH3-Nand SS removal. At optimal HRT of9.81h, COD of effluent was stable from150to180mg/L,and removal rate was form50to60%. NH3-N removal rate of60to90%and effluent SS of10to32mg/Lwere also obtain at optimal HRT.The two stages of O3-BAF process was used as advance treatment in pilot study. In thisexperiment, total dosage of ozone, ratio of ozone dosage and HRT were investigated. Theoptimal total dosage of ozone, ratio of ozone dosage and HRT were60mg/L,2:1and6.25h, and COD of effluent was about40mg/L. Energy consumption of two stages O3-BAFassociated with the type of air source. Using a liquid oxygen as the oxygen source of ozonegenerator, energy consumption of two stages O3-BAF was about a quarter of the use of airsource.And removal of organic pollutants in wastewater was slightly increased.During the period of stable operation, the influent flow rate of conventional treatment andadvanced treatment were0.9m3/h and0.8m3/h, respectively. COD of influent was from550to1100, and COD of effluent was stable under40mg/L. The result meant that pilot system had agood effect on removal of organic pollutants. The pilot system also did well in removingchromaticity of wastewater. Chrommaticity of influent was from500to700times,chromaticity after treated was just about40times. Operation cost of the pilot system wasabout2.18to2.48yuan per ton wastewater. Besides, operation cost of ozone decreased withthe scale of treatment increased.