| Nowadays,the problem of water resources crisis,energy crisis and environmental pollution have become increasingly prominent,constraining the development and progress of human society.Microbial fuel cells?MFCs?,as a new wastewater energy technology,can achieve the recovery of electrical energy while treating wastewater,accord with today's"green development"concept and construction of ecological civilization.Energy microalgae is a clean and environmentally friendly biomass energy that can replace traditional fossil fuels.It can be used as a cathode biocatalyst for MFCs to increase the system's output power density,reduce the cost of MFCs construction,and harvest energy microalgae.On the other hand,China is a big producer of pork,the wastewater generated during the rapid development of pig farms accounts for 3/5 of the total discharge of poultry wastewater in China,swine wastewater contains high concentrations of COD,ammonia nitrogen,and TP,the direct discharge of untreated swine wastewater seriously damages the ecological environment.However,high concentrations of organics in wastewater is an ideal matrix for MFCs.Therefore,in this paper,we construct microalgae MFCs to treat swine wastewater,study the effects of key parameters such as pH and substrate concentration on the electrical production performance and organic pollutant degradation of the system,and confirm the feasibility of microalgae MFCs in efficiently treating piggery wastewater while producing electricity.At the same time,study the growth and purification of Chlorella in swine wastewater.?1?Based on the existing research,adopting artificial simulating wastewater to activate the microalgae MFCs at an optimum operating temperature of 30°C and an illumination intensity of 5500Lux,the system can get 165±5mV stabilized voltage during 20 days of startup,it indicates that the selection and enrichment of electrodes for electrolysis microorganisms has been completed,the system has been successfully started up and operated stably.The maximum output power density is 231.64mW/m3,the electricity generation cycle is about 80h,and can effectively degrade the organic matter in the wastewater,the removal of COD reaches 87.75%.?2?On the basis of stable operation,study the effects of key parameters pH and substrate concentration on the electrical performance of microalgae MFCs and the degradation of organic pollutants.The results show that the anolyte of microalgae MFCs is beneficial to improve the performance of the system in an alkaline environment,When the pH is increased from 6 to 10,the micro-algae-type MFCs have improved electrical production performance.When pH is 10,the system produces the best electrical performance,the power density is534.84mW/m3,which is 2.12 times the maximum power density when pH is 6.The pH has little effect on the COD removal rate,and it is above 90%.The removal rate of ammonia nitrogen increased with the increase of pH value.When pH is 10,the removal rate of NH4+is93.54%.The substrate concentration has little effect on the open circuit voltage of the system.The variation trend of the stable output voltage and power density with the concentration is consistent with the variation law of the Monod equation.With the increase of the substrate concentration,the system's Coulomb efficiency is gradually reduced,and the two are fitted.The curve equation:y=55.869x-0.36?R2=0.9848?,the Coulomb efficiency decreases from5.97%at COD=510 mg/L to 2.86%,which decreases about 52%;COD removal efficiency increases with substrate concentration Increasing gradually,the removal rate of NH4+and TP gradually decreases with the increase of substrate concentratio.Comprehensive analysis and evaluation are performed from the aspects of electricity generation performance,pollutant degradation capacity,and efficiency,when the initial concentration of substrate COD is950mg/L,the performance of the system is the best.Therefore,microalgae MFCs is running under the conditions of temperature is 30°C,light intensity is 5500Lux,pH is 10,COD concentration is 950mg/L,and the system have the best performance of electricity generation and organic degradation.?3?The MFCs running with artificial simulating wastewater is used to treat the actual swine wastewater,the system has reached a stable state after three power generation cycles.It indicates that the stable output voltage is 220mV,the power generation cycle is about 120h,the output power is 432.44mW/m3.At the same time,the removal rates of COD,ammonia nitrogen and TP are 85.61%,90.50%and 38.97%respectively,and the coulombic efficiency is 6.28%.Compared with the effect of artificially simulated water distribution with different concentrations,the output voltage is slightly reduced,but the Coulomb efficiency has increased,indicating that the system has a higher utilization rate of pig-raising wastewater and can effectively degrade the organic pollutants in swine wastewater and produce electricity at the same time.?4?This paper analyzes and compares the growth of Chlorella in different water bodies and the effect of water purification.It draws the conclusion that Chlorella isn't able to grow normally in the raw water of swine wastewater due to its high concentration,the degradation of organic matter depends on the original microbial.Under the purification of Chlorella,the effluent quality of 8 times diluted swine wastewater and anode effluent reaches the water pollution standard for livestock and poultry breeding industry?GB18596-2001?.And Chlorella is able to quickly enter the culture in diluted 8 times of swine wastewater and anode effluent,the dry weight of the cells are 0.397g/L and 0.258g/L respectively,the specific growth rates are 0.286/d and 0.196/d respectively. |
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