Optimization Of Anode Electricity Producing Microorganism Of Drainage Microbial Desalination Cells And Effect Expression In Temporary Water Treatment

Water is not only the source of human survival and development but also an indispensable natural resource for life and economic development.People pay more and more attention to the lack of water resources,water pollution control,and purification technology.The lack of freshwater resources will seriously restrict the development of the economy and society.Therefore,people pay attention to desalination.Desalination of seawater to produce freshwater is an open-source incremental technology to realize the utilization of water resources.At present,the recovery and utilization of seawater are too low,the treatment cost is too high,and the energy consumption in the treatment process is huge.The disposal of seawater will cause pollution and waste.Therefore,the rational use of saline water resources,increasing the total amount of resources,and reducing energy consumption has become the main means to solve water resources and save energy.Microbial desalination cells（MDC）is a bioelectrochemical technology developed in the field of bioelectrochemical systems（BES）,which uses electricity producing microorganisms as catalysts to convert salt containing wastewater into electrical energy and fresh water output.At the same time,as an innovation on the basis of microbial fuel cells（MFC）,this technology has opened up a new technology for the treatment of saline water by directional migration of charged particles.So far,most of the MDC research is still at the laboratory level,and the results applied to the actual wastewater treatment are rarely reported.In this paper,the MDC treatment method is used as the operating principle,and MDC and salt stress method are combined to create a Drainage Microbial Fuel Cell,D-MDC),screening salt-tolerant and electric producing microorganisms,combining target bacteria with denitrification bacteria,discussing the efficiency improvement and optimization of the overall performance of the combined bacteria group coupled D-MDC,and the synergistic effect of application in the treatment of salt-containing temporary water in marine products.The long-term operation of the reactor was further evaluated from the aspects of electrochemical activity,desalination effect,system operation efficiency,and pollutant degradation The stability and practicability provide theoretical guidance and technical support for the application of MDC in the actual salt-containing wastewater treatment process.The results are as follows（1）As the core of MDC,electrogenic microorganisms can release electrons by oxidizing substrate,and then transfer electrons to receptors along the transfer chain,and obtain energy in the transfer chain.They have good response ability while ensuring the development of microbial community.In this study,D-MDC system combined with salt stress method was used to isolate and screen salt tolerant strains from sediment samples collected in the East China Sea.The strains were identified by morphological observation and 16S r RNA,and their physiological and biochemical characteristics were explored.The results showed that Halobacillus sp.T4 could enhance the efficiency of MDC and the potential feasibility of its application in desalination of saline alkali wastewater,which provided theoretical guidance and technical support for the high efficiency of MDC and the diversification of electricity producing microorganisms.（2）In this study,1.2L D-MDC strain Halobacillus sp T4 as the core of anode electricity production,its electrochemical indexes were calculated to evaluate its electricity production and desalination efficiency:both D-MDC-0 and D-MDC-5 could produce electricity,which verified the electricity production efficiency of strain T4,and the existence of salinity made the electricity production operation of D-MDC system more stable;the maximum power density of the two groups of D-MDC-0 and D-MDC-5systems were 6.6615 w·m^-3 and 8.36 w·m^-3 respectively,its electricity producing effect has no obvious advantage compared with some current electricity producing bacteria.However,as a halophilic and salt tolerant microorganism,T4 can play its role in organic matter degradation and electricity generation under salt pressure,which provides an idea for the screening and application of MDC system in multi environment anode electricity producing microorganisms.With the passage of T4,the upper limit of salt tolerant electricity generation is expected to be further improved.After stable operation,the desalination rates of D-MDC-0 and D-MDC-5 reached 82.89%and 85.63%respectively,and then the growth of desalination rate slowed down,which reflected the characteristics and expression of salt tolerant strain T4:the salt tolerance and halophilic of strain T4 had a large space for the improvement of D-MDC system efficiency.（3）D-MDC is used to treat the salty temporary aquaculture water of seafood.The initial response of D-MDC to the start-up voltage is fast,but the peak value of the initial period is low.The voltage curve of the steady decline and the voltage curve of the second operation period show that the adaptability of D-MDC to the anode environment is gradually enhanced.At present,the voltage output of D-MDC can reach 302m V,and the power density can reach 5.42 W·m^-3.When the system was applied to the actual treatment of seafood temporary culture water,its electricity output was lower than that of single bacteria T4 anode,but the nitrogen removal effect was relatively strong,which proved that the D-MDC anode complex bacteria group had a good degradation effect on nitrogen,and also verified that Halobacillus sp.T4 could promote the assimilation and nitrogen removal in the proliferation of bacteria groups.（4）D-MDC can complete the effect of organic matter degradation and desalination in the application of salty temporary water treatment,and the desalination effect is better.However,in terms of electricity production,the peak value of electricity production after the combination of bacteria is lower than that of a single bacteria anode.Therefore,it needs to be verified in the follow-up research to explore the micro changes of bacteria or the appropriate extension of the operation cycle.Generally speaking,the capacity of D-MDC system is relatively small at present,which can not meet the actual scale application temporarily,and needs further optimization and improvement.