Study On Advanced Treatment Of Yarn Dyeing Wastewater By Aerated Bological Activated Carbon Filter

The effluent of yarn dyeing wastewater after secondary biological treatment was studied by upflow aerated biological activated carbon filter as advanced treatment. The optimal process condition of BAC, microbial properties in filter and changes of pollutants were researched. Some results of research were concluded.1. The four factors of gas-water ratio, hydraulic loading, HRT, temperature and pH were studied. The optimal process parameters were obtained:gas-water ratio was 3, hydraulic loading was 0.19 m3/(m2·h), HRT was 9.8h, temperature was 25℃～30℃, pH was at 7.0 to 8.5. Under the condition of optimal process parameter, the average removal rate of COD, chromaticity, UV254 and turbidity were 80.7%,92.5%,83.8% and 81.7%, and the corresponding average COD, chromaticity, UV254 and turbidity of effluent were separately 19.1mg/L,6.8,0.25 and 2.82NTU which met the reuse standards of reclaimed water. The optimization of process parameters supported the evidences of its practical application.2. Through the study of hydraulic loading and gas-water ratio, the effect of filter material on the degradation pattern of organics, chromaticity and was UV254 researched. The results showed that considering the effect of gas-water ratio and hydraulic loading on the every stage removal rate of COD, chromaticity and UV254, the height of activated carbon media chose 120cm as best under the condition of gas-water ratio of 1:3 and hydraulic loading of 0.19m3/m2·h.3. Through the detection of biomass and bioactivity in different height of BAC, the microbial properties of activated carbon as the carrier were studied in order to understand the mechanism of organic removal by BAC and support the application of activated carbon. The results showed that through the detection of biomass by phospholipids method, the content of phospholipids contained in unit of activated carbon along the filter and the height were in inverse relationship. The inverse ratio decreased greatly below 110cm of filter, but the content of phospholipids increased slightly above 110cm. The correlation coefficients between the three pollutants along the filter and biomass were high and separately 0.9636,0.9931,0.9981. The pollutants got the most significant decline at the 110cm of filter, while they reduced slightly above 110cm.Takeing the TTC-dehydrogenase activity as bioactivity index, the results showed that the bioactivity of activated carbon decreased as the height of filer increased. At the 110cm of filter the reduction of bioactivity tended to gentle, and it reduced to the minimum of 33.1μgTF·gdwC-1·h-1 at 150cm of filter. The biofilm of activity carbon at 150cm still had bioactivity.4. Through the UV-visible scans, infrared spectra and GC-MS spectra, the structural change of organic pollutants along the BAC system were studied in order to understand the microbial degradability and discuss the degradation pattern. The results showed that the UV-visible scans could be used to judge biomass and structural change in advanced treatment system of yarn dyeing wastewater after secondary biological treatment. Below 80cm of filter the chromaticity could be removed greatly, while the organism containing Conjugated double bonds and benzene could be removed in the whole reactor except the top of reactor. Through the infrared spectra of samples along the filter, the broken of double bond and appearance of new saturated methyl group were important way of biodegradation. The generation of small molecules decreased microbial metabolic loading and promoted the metabolism of microbiology to reduce the amount of organism in'the wastewater. Through the GC-MS spectra of samples along the filter, the small molecules such as alcohols, alkanes, ketones, acids were easily degraded in BAC, while the organics that had retention time more than 20min such as 3-methyl-tetradecane and 4-methyl-heptadecanoic were not easily removed.The basis of selecting the optimum operation conditions of biological activated carbon filter treating yarn-dyeing wastewater were provided by this research. The basis of reuse of yarn dyeing wastewater and textile wastewater were also laid. This study provided design parameters and the biological basis for the practical application and engineering and deepened the understanding of degradation mechanism of organic pollutants by activated carbon.