Research On The Application Of Microbial Sensors For The Detection Of Toxic Substances In Water

With the rapid development of industry and agriculture,the severe water pollution situation urgently requires fast,sensitive and simple methods for water toxicity detection.Microorganisms have received extensive attention due to their high sensitivity,low cost,fast response and easy storage.Electrochemical and optical methods have become research hotspots in this field due to their high efficiency,good reproducibility and other advantages.However,there are still problems such as cumbersome detection procedures and low sensitivity that need to be solved.In this paper,several water toxicity detection sensors were constructed using RGB technology,absorption spectroscopy and bioelectrochemical system,in which microorganisms were used as model bacteria.Based on the optimization of experimental conditions such as concentration,reaction temperature and reaction time,the artificial simulated wastewater was detected simply,quickly and sensitively.The results indicated that the constructed water toxicity detection sensors possess broad application prospects in the field of water pollution detection.Specific research contents are as follows:1.A colorimetric biosensor was constructed by RGB technique to assess water toxicity,the indicator,dark brown quinone hydroquinone（QHQ）,obtained from a rapid color reaction between Escherichia coli DH 5α（E.coli）and p-benzoquinone（BQ）.Toxicity inhibition ratios were calculated from the RGB（red,green,blue）values of the samples or the oxidation currents of the hydroquinone（HQ）.The results suggested that the biosensor-based RGB method has an obvious dose-dependent response.This biosensor can be used to quickly detect the toxicity of wastewater containing Cu²⁺or Hg²⁺without complicated operation steps,which possesses certain promising applications.2.A high-efficiency colorimetric biosensor for water toxicity assessment was constructed using Fe³⁺of culture medium.Photobacterium phoshoreum T3 spp.（T3）and Prussian blue（PB）were used as the model bacteria and indicator of the biosensor,respectively.In order to accurately detect acute toxicities of wastewater,the experimental conditions,including concentrations of T3 cell,K₃[Fe（CN）₆]and Na Cl,reaction temperature and reaction time were optimized.On this basis,the single toxicity tests were performed on simulated wastewater containing Hg²⁺,Cd²⁺,Zn²⁺,3,5-dichlorophenol（DCP）or formaldehyde.A toxic unit（TU）model was applied to evaluate the biotoxicity of Hg²⁺+Cd²⁺,Hg²⁺+Zn²⁺and DCP+Zn²⁺for T3,which all showed antagonistic effects with reduced toxicities.The practicality of the sensor was validated by testing the composite biotoxicity of dry battery leachate and real water samples.3.An online monitoring sensor for water toxicity was constructed using a single-chamber Microbial electrolytic cell（MEC）reactor with a penetrating anode and a transmissive cathode.Through cell comparison of performance,platinum sheet was selected as the cathode.On the basis of optimised experimental conditions,cell impedance,redox performance,power and current density were tested,and the toxicity detection experiment was performed with 1.25 m L min^-1 of flow rate,and 20 mmol L^-1 Na AC as the nutrient substrate of the sensor.The results illustrated that the sensor can provide a rapid response to0.05%formaldehyde with good reproducibility.