The Construction Of A Bacillus-zeolite Complex And Research On Its Application In Wastewater Treatment

Zeolites,crystalline porous solids,are readily available tectosilicates consisting of corner-sharing Al O4 and Si O4 tetrahedra,resulting in their molecular sieve,ion exchange,and catalytic features,which determine their ability to remove pollutants from industrial,processing waters and wastewaters.Bioremediation,the use of microorganisms or microbial processes to degrade and detoxify environmental contaminants,is becoming quite an attractive alternative to consume and break down environmental pollutants.Based on these properties and advantages,it is possible to attach the microbial cells to the surface of zeolites,hoping to exert a combined removal effect of pollutants.In this study,Bacillus amyloliquefaciens Z9 and Bacillus polymyxa Z11 were used as adsorbed microorganisms.The main components of natural zeolite I and II were determined by X-ray diffusion method,after which the modification of natural zeolite was carried out to increase the adsorption rate of microbes.Four different types of modifier including acid,base,salt and surfactant were used to modify the zeolites which was conducted under the same condition and the adsorption rate was determined to select a better modifier,which turns out to be DTAB,a type of surfactant.Secondly,different concentrations of DTAB were used to modify the zeolites and likewise the adsorption rate was determined to get an optimum DTAB concentration of 8 g/L and 6 g/L for Z9 and Z11,respectively.It took about 4h and 2h for Z9 and Z11 to reach the maximum adsorption rate,and the proper p H of adsorption buffer was 7.0 and 7.5,respectively.In order to obtain the amount of microbes absorbed onto per gram of zeolite,standard curve was created using biomass as x-axis and optical density under 600 nm as y-axis to establish a corresponding relationship between them.E-test was applied in the counting of microbes and the culture was spread on plate.The absorption capacity of modified zeolite was calculated within the range of 3.58×10¹⁰-2.06×10¹¹ CFU/g for Z9 and 8.20×10⁹-9.19×10¹⁰ CFU/g for Z11.In addition,in order to determine the adsorption of the cells on zeolite,the complex was observed by Scanning Electronic Microscopy.For the sake of verifying the effect of the complex on the treatment of the wastewater,the removal efficiency of two kinds of dyes: aniline blue and methyl blue,ammonia nitrogen and nitrite were determined.When the concentration of the two dyes were 200 ppm,300ppm and 400 ppm,the removal efficiency reached 98%,70%,50% respectively.When the ammonia nitrogen content is 0.33g/L,the removal rate of ammonia nitrogen is about 42%,and the removal rate of bacteria or natural zeolite powder can only reach 30% and 20% respectively.Similarly,when using the Z11 and Z9 complex,removal rates for nitrite achieved 81% and 97%,respectively,compared to 20% when Z11 was used alone,with a final removal rate of 97% relative to Z9 alone,but the speed increased by 30%.In summary,the combination of bacillus species and zeolite increased the removal rate of wastewater contents.