Study On Residual Characterization Of Antibiotics In Aquaculture Wastewater And Its Removal Technology

This study took a certain large-scale aquaculture farm in Changzhou city of Jiangsu province as the research object. The antibiotics in aquaculture water were determined by using solid-phase extraction-liquid chromatography-tandem mass spectrometry (SPE-LC-MS/MS) approach and its residual characterization was analysed. The occurrence, spatical distribution and seasonal variation of antibiotics in aquaculture water were investigated and the enviromental risk was also assessed in this study.. The removal efficiency of typical antibiotics applied in aquaculture was investigated. The effects of substrate, plant, flow state, and hydraulic retention time (HRT) which contributed to the removal efficiency of antibiotics were explored by setting up different surface flow constructed wetlands and subsurface flow constructed wetlands.The main conclusions were as follows:(1) Four kinds of antibiotics (enrofloxacin, sulfamethoxazole, oxytetracycline and florfenicol) were detected in the aquaculture water of this research. Results showed that florfenicol had the highest content of detected antibiotics (average concentration of 973.21ng/L), followed by sulfamethoxazole (average concentration of 110.84ng/L) and enrofloxacin (average concentration of 55.85ng/L) and Ge Lake had the highest content of oxytetracyline (average concentration of 667.73ng/L). Florfenicol, sulfamethoxazole and enrofloxacin were the major antibiotics in fishponds, Florfenicol, sulfamethoxazole were the major antibiotics in yielding river channel and oxytetracyline was the major antibiotic in Ge Lake. The results of seasonal variation of antibiotic concentrations indicated that the content of enrofloxacin, oxytetracycline and florfenicol in spring and winter were higher than that in summer and autumn, while sulfamethoxazole had the highest content in summer (average concentration of 249.66ng/L). The results of environmental risk assessment showed that all the four kinds of antibiotics posed potential medium risk to the aquatic organisms at least (risk quotient^0.18), while sulfamethoxazole showed high risk.(risk quotient≥3.17).(2) The removal efficiency of typical aquaculture antibiotics from wastewater by hydrous ferric oxide modified bamboo charcoal was investigated. Results showed that sulfamethoxazole had the highest removal efficiency of 97.84% in 48h, followed by enrofloxacin (removal efficiency of 59.32% in 48h) and florfenicol was hardly to remove (removal efficiency of 4.79% in 48h). Results revealed that the modification method is feasible according to the characterization results by X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy(FTIR). The removal efficiency increased with decreasing the initial concentration and the increasing removal efficiency was accompanied with higher initial pH(pH8>pH4>pHl), indicating that the removal of sulfamethoxazole is more easier when it exist as anion specie in aqueous solution. Luminescent bacteria toxicity test showed that luminescence inhibition rate of the reaction system decreased from 96.1%(0h) to84.2% (144h), which revealed that the application of HFO modified bamboo charcoal for the removal of sulfamethoxazole may contribute to weaken the toxicity of the reaction system.(3) The application of surface flow constructed wetlands could reduce the antibiotics from aquaculture wastewater and the removal efficiency was in the following sequence: enrofloxacin (69.7±6.9%)>sulfamethoxazole (24.4±12.8%)>florfenicol (13.9±9.1%). When the HRT was 4 days, the surface flow constructed wetland was efficient for the removal of enrofloxacin (66.7%),while sulfamethoxazole and florfenicol were partially eliminated by the surface flow constructed wetlands. But the removal efficiency of sulfamethoxazole and florfenicol increased with increasing the HRT. The wetland plants could not be its main elimination pathways and most target antibiotics were removed slightly. The wetland substrates played an important role in the removal of antibiotics from aquaculture wastewater. When the HRT was 4 days, the integrative substrates-surface flow constructed wetland was significantly more efficient for the removal of enrofloxacin(67.6%), while the soils-surface flow constructed wetland was superior to that of integrative substrates-surface flow constructed wetland for the removal of sulfamethoxazole and florfenicol.(4) The application of subsurface flow constructed wetland could reduce the antibiotics from aquaculture wastewater and the removal efficiency was in the following sequence: enrofloxac in(80.4±4.5%)> sulfamethoxazole(30.4±12.4%)> florfenicol (17.0±8.9%). When the HRT was 1 day, the subsurface flow constructed wetland was efficient for the removal of enrofloxacin(82.9%), while sulfamethoxazole and flofenicol were partially eliminated by the subsurface flow constructed wetlands. But the removal efficiency of sulfamethoxazole and florfenicol increased with increasing the HRT. When the HRT was 3 days, Iris Pseudacorus wetland showed more efficient for the removal of sulfamethoxazole and the removal efficiency was 60.2%. Flow types could affect the elimination rate of sulfamethoxazole from aquaculture wastewater. Horizontal subsurface flow constructed wetland was proved more efficient for the removal of sulfamethoxazole and florfenicol than vertical subsurface flow constructed wetland and integrated vertical subsurface flow constructed wetland.