Research On The Treatment Of Printing And Dyeing Wastewater By Anaerobic Baffled Reactor

Printing and dyeing wastewater is refractory organic wastewater, and exerts great threat on the environment. Its characteristics, such as large water volume, complex composition, changeable water quality, deep chromaticity, high alkalinity, poor biodegradability, and containing some toxic substances, make it become the focus of industrial wastewater treatment.In this study, ABR with five compartments was adopted in the small-scale experiment to treat printing and dyeing wastewater discharged from a printing and dyeing enterprise in Changshu, Jiangsu Province. Then, a pilot-scale study using ABR with five compartments was performed to study the integrated wastewater which was mainly composed of printing and dyeing wastewater. The removal effect of the major pollutants in the printing and dyeing wastewater and removal characteristics of ABR were investigated. Main conclusions are as follows:(1) ABR is feasible and applicabe for printing and dyeing waste water treatment. It can be started very fast. The start-up influent included complex printing and dyeing wastewater and glucose, which were mixed according to a certain proportion. The amount of glucose was gradually reduced to zero. After continuous operation about 50 days, the color of wasterwater was changed from the original reddish-brown to pink. BOD5/CODcr of printing and dyeing wastewater was raised from 0.21 to 0.36, indicating the improvement of its biodegradability and that the ABR was started successfully.(2) ABR has a good effect on COD of printing and dyeing wastewater. The shorter the hydraulic retention time (HRT), the lower the COD removal rate became. When HRT was 32 h,24 h,18 h,14 h and 10 h, COD removal rate differed greatly from one chamber to another. The highest removal rate of ABR was observed in the first grid chamber, which accounted for around 38.5%～54% of the total removal rate. When shortening HRT, the relative COD removal rate in front-end compartments of ABR decreased while it was observed to increase in back-end compartments.(3) ABR has good color removal effect. ABR was not affected when the color of influent was fluctuated greatly. The average color removal rate was about 60% when color of influent and effluent was 380 times and 150 times, respectively. As HRT being shortened, the color removal rate declined slowly, but it was kept above 50%. The color decreased along the way in every compartment. The highest removal rate of ABR was observed in the first grid chamber; followed by the second grid chamber.(4) ABR can effectively improve the biodegradability of printing and dyeing wastewater. The average B/C was increased from being about 0.2 (input water) to around 0.35 (output water), indicating that the biodegradability of wastewater has been improved and the burden of post-aerobic treatment sequence has been reduced.(5) ABR maintained a relatively stable treatment effect in the low temperature. When the HRT was 24 h, the COD removal rate decreased about 6.6% when the temperature was 15℃, compared to the rate when the temperature was 30℃.(6) The performance of ABR-A/O system was investigated when the HRT was 24 h. The average COD of aerobic effluent was 124 mg/L, and the removal rate reached 80%; oammonia nitrogen of output water was 4.05 mg/L, less than 5 mg/L, and met the standard of DB321072-2007; decolorization rate reached 76%. This system provided a way to meet the standards by further treatment.(7) GC-MS analysis showed that the structure and species of the organic compounds changed significantly after ABR treatment. The variabliilty of organic component in the effluent declined as most organic compounds were further degradated after aerobic treatment. The performance of the system was restricted because some benzene and phenol could not be removed through aerobic biological processes. Thus, advanced treatment process was still needed in order to satisfy discharge standards DB32.(8) Pilot-scale study of using ABR to treat printing and dyeing wastewater.was conducted. The result showed that:With the prime HRT 24 h, the system was operated for two months. COD of influent and effluent was 630 mg/L and 376 mg/L, respectively, and the average COD removal rate was about 40.4%. Color of influent and effluent was 380 times and 110 times, respectively, and the average color removal rate was about 70%. The average B/C of printing and dyeing wastewater was increased from 0.28 to 0.41, indicating the biodegradability of printing and dyeing wastewater was improved greatly.