Specific Integrated Biochar – Microbial Fuel Cell Bioreactor for Removing Antibiotics from Swine Wastewater
- Publication Type:
- Thesis
- Issue Date:
- 2020
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Swine wastewater is an important source of antibiotics in the environment due to their large-scale application in swine industry. High levels of antibiotics in swine wastewater have become an increasing global concern considering their potential risks to the environment, human and animal health. The integration of biochar and microbial fuel cell (MFC) is a promising technology for the treatment of swine wastewater containing antibiotics and producing electricity simultaneously. The aim of this study is to investigate the potential of a specific integrated biochar-MFC system to treat swine wastewater containing antibiotics. In this scenario, it is necessary to identify the removal process and mechanism of antibiotics in the anaerobic sludge that used in the anode chamber of MFC. Through a series of batch experiments, the results indicated that the removal of tetracycline antibiotics (TCs) in the anaerobic sludge contributed to the biosorption of sludge, while biodegradation was responsible for the removal of sulfonamide antibiotics (SMs). The adsorption data of TCs in anaerobic sludge fitted well with the pseudo-second order kinetic and the Freundlich isotherm modes, which suggested a heterogeneous chemisorption process. Cometabolism was the main mechanism for the biodegradation of SMs and the process fitted well with the first-order kinetic model. Microbial activity in the anaerobic sludge might be curtailed due to the presence of high concentrations of SMs.
The performance of a double-chamber MFC for treating swine wastewater with the addition of different concentrations of SMs was investigated under the anode self-circulation operating condition of MFC. It is observed that chemical oxygen demand (COD) could be effectively removed (>95%) and almost not affected by the presence of SMs in MFC. A stable output of voltage was also observed. The removal efficiency of sulfamethoxazole (SMX), sulfadiazine (SDZ), and sulfamethazine (SMZ) in the MFC was in the range of 99.46% to 99.53%, 13.39% to 66. 91% and 32.84% to 67.21%, respectively, which were higher than those in a traditional anaerobic reactor with 97.45% - 98.89% for SMX, 11.96% -31.24% for SDZ and 23.85% - 33.49% for SMZ. The biodegradation process of SMs in MFC was fitted to the first-order kinetic model. Hence, MFC revealed strong resistance to antibiotic toxicity and high potential for the treatment of swine wastewater containing antibiotics.
For industrial application of the MFC in the treatment of swine wastewater containing antibiotics, the MFC was conducted in continuous operating modes under different conditions. Voltage can also be successfully generated during the continual operation with the maximum value of ~550 mv. Effective removal of COD can be achieved in both single continuous (>80%) and sequential anode-cathode (> 90%) operating modes. Nutrients can also be removed in the cathode chamber of the MFC with the maximum removal efficiency of 66.62% for NH4⁺-N and 32.1% for PO₄³⁻-P. The removal efficiency of SMs under the sequential anode-cathode operating mode of MFC was around 49.35% - 59.37 % for SMX, 16.75% - 19.45% for SMZ and 13.98% - 16.31% for SDZ, respectively. The inhibition of SMs to pollutants’ remove in both chambers of MFC was observed after SMs exposure, suggesting that SMs exert toxic effects on the microorganisms. Moreover, a positive correlation was found between the higher NH₄⁺-N concentration used in this study and the removal efficiency of SMs in the cathode chamber. Results suggest that it is feasible to use the continuous anode-cathode MFC to treat swine wastewater with antibiotics, while the removal efficiency of antibiotics required to be further improved.
The addition of biochar into the MFC is a promising method for enhancing the removal of antibiotics in continuous flow MFC. Biochar adsorption is an effective method for the removal of antibiotics from wastewater with advantages of low cost, easy production and environmentally friendly. A new pomelo peel derived biochar was developed in this study. The biochar activated by KOH displayed a large surface area (2457.37 m²/g) and total pore volume (1.14 cm³/g). SMs are favorable absorbed onto the heterogeneous surfaces of biochar thorough pore-filling and π-π electron donor–acceptor (EDA) interaction. The biochar’s addition to a certain concentration (500 mg/L) could enhance the removal efficiency of SMX, SDZ and SMZ to 82.44% - 88.15%, 53.40% - 77.53% and 61.12% - 80.68%, respectively. Moreover, the electricity production and COD removal were increased by increasing the concentration of biochar. The improved performance of MFC could be due to the role of porous biochar as an adsorbent and biocarrier of the growth of microorganisms.
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