Mini CW-MFC Electricity Collection And Applied To Power UV Lamp For Sterilization

At present,rational utilization of biomass energy to realize resource utilization has become an inevitable trend in the development of sewage treatment technology.Constructed Wetland-Microbial Fuel Cell（CW-MFC）is a new environmentally-friendly wastewater treatment technology emerging in recent decade in which microbial fuel cells（MFC）are coupled with conventional constructed wetland（CW）.Under the action of electrochemistry,the sewage treatment capacity is strengthened with the use of microorganisms to degrade organic matter while generating electrons and releasing energy.The electric energy generated by CW-MFC has certain utilization potential.However,due to the low power level of the experimental device in operation,the maximum output power of a single CW-MFC is0.8m W-1.0m W,which is not enough to drive conventional electrical equipment.As a result,there are few studies on the utilization of electricity generation at present.The uses are limited to lighting small bulbs,driving sensor detection and other aspects.Some scholars have carried out scale-up studies on CW-MFC,but the output power cannot increase proportionally with the increase of the volume of a single CW-MFC or the area of the electrode.This experiment tries to establish the optimal power generation mode through debugging several mini CW-MFCs,and carry out stacking and enlargement processing.Through the power management device,the collected electric energy is supplied to power an ultraviolet lamp in intermittent mode,thus it can be used for killing E.coli and achieve a breakthrough of effluent disinfection from the CW-MFC.The main conclusions of this study are as follows:（1）A new device of mini CW-MFC was constructed using a 200 m L syringe.The effective height of the device was 12 cm,the bottom diameter was 5 cm,and the effective volume was 40 ml.During the initial trial,the influence of electrode,substrate,inlet mode and water inlet load on the electricity generation of a single CW-MFC device was explored,and the optimal device structure and operating parameters were then determined to obtain the best electricity generation performance.It has been demonstrated that intermittent water feeding was applied,while carbon felt+metal mesh as electrode material was used with the anode and cathode area ratio of 1:1.Biochar mixed quartz sand（thickness 5 cm）is used at the bottom to increase the packing density in the anode area to provide an anaerobic environment.Biochar is filled in the middle（thickness 5 cm）,and conductive activated carbon（thickness 2 cm）is used at the top to enhance the conductivity of the cathode.（2）A multi-combination stacked CW-MFC system was constructed to improve the power generation capacity.In order to improve the power collection,the mini CW-MFC was stacked in hybrid mode.The influences of different connection modes and the number of batteries in the battery pack on the output voltage and the maximum power density of the battery pack were studied.The results show that,under the same number of devices,the overall current output of parallel connected devices is higher than that of series connected devices,while the series connected devices have a more obvious effect on voltage improvement.Finally,in the case of no voltage inversion,a 5×2 series and hybrid connection is established to obtain a stacked CW-MFC with a power density of 271.1 m W/m²and a current density of 58.2 m A/m^2.（3）The UV-UV lamp is driven by the CW-MFC system using the booster conversion module.The static energy collection module is designed in the experiment.The power input terminal is boosted by the DC-DC booster conversion module,and the battery（capacity is 1000m Ah,3.7 V）is charged by the battery management terminal（TP4056）.Thereafter,the DC-DC booster conversion module is used for secondary voltage boost.The electric energy generated by the device is stored in the lithium battery through the DC-DC booster circuit.When the electric energy accumulates to a certain extent,the switch is used to control the discharge and boost the voltage twice to provide the required electric energy for the ultraviolet sterilization lamp.The results show that the radiation intensity of the UV lamp meets the requirements of the germicidal lamp.Under the condition of theoretical power generation,the system works for60 s and can provide 18 s for the UV lamp.（4）Ultraviolet UV lamp driven by electricity generation was used to sterilize E.coli in water samples.The UV lamp with the power of 2 W（wavelength 254 nm）and the UV intensity of 3 m W/cm²（zero distance）was used to treat the water sample with the number of Escherichia coli of 60 CFU/m L in the laboratory.The experimental results showed that the system had good bactericidal disinfection on Escherichia coli,and the disinfection rate could reach more than90%after 120 s of irradiation.