| Biochemical oxygen demand(BOD) is one of the important indexes of water organic pollutants such as aerobic content. Now five days biochemical oxygen demand is commonly used as standard method for the determination of biochemical oxygen demand. The samples are cultured in 20℃±1℃ for 5 days and dissolved oxygen is measured before and after the training samples, the difference between the two is the biochemical oxygen demand of 5 days. This method is a very complex biochemical process, which is influenced by many factors. Because the test cycle is too long, low efficiency, unstable test results and poor reproducibility, so the method has many limitations. Microbial sensor rapid determination method overcomes the drawbacks of the standard method,which is fast and convenient. The entire test cycle is shorten, test results can be directly printed and the method can monitor on-line, which is becoming more and more widely used.This paper describes not only the generation of microbial sensors,principle and composition of microbial sensors but also the research progress of microbial sensor, including the type of microbial sensors and microorganisms,immobilization methods. It also introduces the application and their use of microbial sensors and BOD Tester in this paper. The research is focused on the core of the sensing element, including the current research situation of the sensing element biofilm, the problems in the preparation process and the sensor performance analysis of microbial pellets. The focal point of this study is the choice of strain, temperature and immobilization methods.In this paper,making sensitive material chooses the traditional biological membrane method at first, and selects four factors, namely bacteria, embedding medium, temperature, and strain ratio embedding medium. Each factor has three levels, namely the strains: 1#, 2#, 3#; temperature: 25℃, 30℃ and 35℃; embedding agent: polyvinyl alcohol, polyacry amide, sodiumal ginate;strain ratio:1:2,2:1,1:1.The orthogonal design is selected to do the experiment about the four factors and three levels, and Microbial film is produced according to the experimental arrangement, using BOD Tester to value the BOD of the standard solution(BOD=2000±160mg/L). Then the degree of influence of the each factors about the test index is obtained by using orthogonal analysis, including the range analysis and variance analysis, and they ranked by influence of size: Strains, temperature, immobilization materials, materials and cell immobilization ratio. Where in the selection and cultivation temperature strains have obvious impacts on the results, followed by the other two. The optimal scheme is selected for analysis of strain 3#,strain temperature 35℃, embedding agent, polyvinyl alcohol immobilized material and cell ratio of 1:2.Finally, by testing 2000±160mg/L standard solution and the actual water samples, It is proved that optimal solution is to meet the requirements, which is the most effective solution.Under optimal solution corresponding to the experimental conditions,we can obtain the date by testing 2000±160mg/L standard solution and the actual water samples with microbial pellets as the sensing element. For data analysis, results showed that: under the same experimental conditions and microbial beads, as the sensitive element, the microbial beads have better effect than microbial film,the test results also show that numerical fluctuation amplitude is smaller and stabler. So microbial pellets can be used as the better sensitive components.Then identify 3# strain who has better ability on organic matter degradation selected from the the optimal solution.First, stain the 3# strain with Gram, then after doing the DNA extraction, PCR amplification using 16 S r DNA sequence homology analysis, the 3# strain will be sented to Shanghai Sonny Biological Technology to complete sequencing reaction. Finally the identification of the strain get the results: Bacteria、Firmicutes、Bacilli、Bacillales、Bacillaceae、Bacillus.sp. |
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