| As a new kind of trace contaminants which has the characteristic of great consumption and complex biological activity, antibiotics has gradually aroused people’s wide attention, the removal of antibiotics is very important to improve ecological environment and alleviate the water crisis. As a kind of effective wastewater regeneration technology, MBR shows certain advantages on the removal of conventional pollutants and micro pollutants. This study selected the crop waste straw as a biodegradable biofilm carrier, by adding this new type carrier with unmodified(2#) and modified state(3#), forming three sets of parallel comparison with blank MBR(1#). By adding low concentrations of trimethoprim and sulfamethoxazole to artificial water, after a long run, the removal of the routine water quality indexes and two target drugs, as well as enzyme activity, bacteria index have been monitored to observe the relationship between removal efficiency of conventional pollutants and antibiotics. The advantage and mechanism.of compound system to eliminate the antibiotics residues were explored by the batchtests. The main research results are as follows:The modified way of straw was alkali treatment. After modification, the surface of straw coarse, porous cellulose exposed, the chances of contact with microorganisms was increased, the function of carbon source was well played. From the point of COD release ability, the carbon release of straw within 30 d before and after alkali treatment was respectively 178mg/g and 323mg/g, the average carbon release rate was respectively 5.93mgCODg-1d-1 and 10.77 mgCODg-1d-1. After alkali treatment, the amount of carbon release and carbon release rate were increased significantly, the straw could play a role in the function of carbon source slow-release.During the stable operation of reactors.the removal rate of COD in 1#,2# and 3#MBR were respectively 92.48%,94.14% and 95.30%, the removal rate of NH1+-N were respectively 89.05%,96.91%and96.46%, this illustrated that the MBR has strong ability of organic metabolism and nitrification. The dehydrogenase activity of sludge which was added with unmodified straw and modified straw, as well as the function of carrier was well achieved, which could provide good adhesion environment, nitrification ability is improved. The removal rate of TN were respectively 89.05%,96.91% and 96.46%, the main reason is that through the carbon source slow-release ability of straw, denitrification process was enhanced, modification of the straw could release more carbon source, which could be used by microbial more easily.During the stable operation of reactors, the removal rate of trimethoprim inl#,2# and 3# MBR were respectively 40.82%,82.10% and 87.50%. The removal rate of sulfamethoxazole in 1#,2# and 3# MBR were respectively 91.92%,95.79% and 95.77%. As you can see, the MBRs which was added unmodified straw and modified straw could get a better removal of trimethoprim and sulfamethoxazole, which showed that the impact of modification was small.By simulating the static adsorption and reaction kinetics of sludge in MBR, the main research results are as follows:the trimethoprim and sulfamethoxazole both showed slow adsorption by inactivated sludge and straw, and the adsorption effect was limited, which meaned trimethoprim and sulfamethoxazole were mainly removed through microbial degradation. The degradation of organic matter in MBRs were all in line with the first-order kinetics. The degradation rate constant increased with increment of organic load. The degradation of ammonia nitrogen were in line with the zero order reaction kinetics. The degradation of trimethoprim and sulfamethoxazole were all in line with the first-order kinetics. In the case of the sludge nitrification inhibition, the degradation rate of trimethoprim and sulfamethoxazole were decreased significantly. In pure denitrification environment, trimethoprim could be degradated regularly, while the degradation of sulfamethoxazole was restrained. Correlation analysis showed that the degradation rates of two target antibiotics and nitration reaction rate constant were significant correlation, while there was no significant correlation with organic compound rate, the contribution of organic co-metabolism was little. We can see trimethoprim is degradated by both the nitrification co-metabolism and denitrification co-metabolism, sulfamethoxazole biodegradation is mainly done by nitrification co-metabolism. |
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