| In recent years, new types of organic pollutants such as endocrine disrupting chemicals (EDCs) have become a rising challenge in wastewater treatment. Researches show that the concentration of EDCs in surface water and sewage treatment plant effluents had reached dozens of μg·L-1 or even higher. These pollutants cannot be removed effectively through traditional methods.It’11 be a big threat to ecological environment and drinking water safety when the EDCs are discharged into receiving water body. Therefore, it’s of great significance to search for economical and effective techniques for EDCs removal. This thesis focused on typical steroid estrogens, the characteristics of removal process by floc sludge and aerobic granular sludge and the performance of aerobic granular sludge process treating steroid wastewater containing estrogens were studied with the application of FTIR, LC/MS and high-throughout sequencing technique. Main conclusions are as follows:1. Study on the adsorption characteristics of estrogens by floc sludge and aerobic granular sludge were performed via batch tests. Results showed the adsorption process of estrogen by floc sludge and aerobic granular sludge were similar. Adsorption equilibrium was reached after 4 hours when the initial estrogen concentration was at 250 μg·L-1～4000μg·L-1. The adsorption isotherm was followed by Langmuir equation and Freundlich equation with the correlation coefficients at 0.924-0.959 and 0.949-0.975, respectively. Adsorption process of E2 and EE2 by aerobic granular sludge was followed with pseudo-second order kinetic with R2>0.992, indicating this process was a physical and chemical process where chemical adsorption was the major role. MLSS, pH and temperature were all the crucial factors on estrogens adsorption.2. Study on adsorption and degradation process of E2 and EE2 showed that with the initial concentration of 4mg·L-1, E2 removal efficiencies by floc and aerobic granular sludge were above 94%, among which biological degradation percentages were at 66.5% and 68.8%, respectively. Results showed that E2 was mainly removed by biological degradation. EE2 removal efficiencies by floc and aerobic granular sludge were 75.5% and 88.9%, among which adsorption percentages were 67.1% and 69.3%, respectively. Results showed that EE2 was mainly removed by adsorption degradation.Results of SEM and FTIR showed that the core structureand large surface aera and complexation reaction of chemical functional groups (amino, hydroxyl radical, carboxyl) of aerobic granular sludge favor the adsorption and microbial enrichment.3.In order to test the efficacy of aerobic granular sludge to remove estrogens. reactors were set up with influent COD, NH4+-N and E2/EE2 concentration of 1.5kg·m-3·d-1,0.08·kg·m-3d-1 and 0.03·g·m-3-d-1.Mean diameter of aerobic granular sludge after 120d running reached 685±35μm, while MLSS and SVI were at 5.8±0.1g·-L-1 and 34ml·g-1, respectively. COD, TN and NH4+-N efficiency were 94.6±0.2%,73.5±0.3% and 97.5±0.1%. Meanwhile, E2 and EE2 removal were 88.6±0.7% and 73.2±0.5%, confirming that aerobic granular sludge removed estrogens effectively.Results of microbial community succession showed that the shannon index of granular sludge reactor increased from 3.58 to 5.65. Compared to regular reactor R2, Proteobacteria and Actinobacteria were dominant microbies in R1 reactor with a proportion of 60.1% and 27.2%. At the same time, Sphingomonas spp. increased from 1.02% to 13.50%, and Pseudomonas spp. increased from 0.02% to 10.38%. It’s speculated that these two strains are important in estrogen degradation.The results reveal the microorganism mechanism of estrogen degradation by aerobic granular sludge. |
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