Study On Simultaneous Treatment Of Nitrate Nitrogen And Hexavalent Chromium In Water By An Aerobic Denitrifier,Pseudomonas Aeruginosa Strain G12

With the acceleration of urbanization and the speedy improvement of industry and agriculture,wastewater containing diverse varieties of pollutants discharged by way of human beings in manufacturing and living activities together with organic pollutants,inorganic pollutants and heavy metallic pollutants,etc.It is easy to form complex pollution into the water body.Combined pollution not most effective damages the ecological environment of the water,however additionally brings top-notch damage to human health.An inorganic pollutant due to nitrate nitrogen in water and heavy metallic pollution caused by Cr?VI?is one of the greater not unusual composite pollution.Inside the present sewage treatment method,the treatment methods for nitrate nitrogen and Cr?VI?pollutants respectively there are numerous researches.The techniques for casting off nitrate nitrogen consist of membrane separation method,ion exchange method,redox method,catalytic reduction method,and microbial method.The removal strategies of Cr?VI?specifically include adsorption method and solvent extraction separation method.Chemical precipitation techniques,etc.,but the above techniques are most effectively directed to pollutants due to a certain sort of pollutant.How to use effective measures competitively low cost,energy-saving,safe and environmentally friendly to remove the complex pollutants because of nitrate nitrogen and Cr?VI?in water has acquired extremely good attention.The microbial technique has great ability in dealing with environmental pollution problems.This paper focuses on a form of the microorganism which can simultaneously reduce Cr?VI?in aerobic denitrification for the treatment of complex pollution caused by due to nitrate nitrogen and Cr?VI?.The motive of this study is to observe the capability of strains to concurrently reduce Cr?VI?and nitrate and its reaction and metabolism mechanism,so that the isolated and decided on bacteria play a position in the actual sewage treatment,and offer a principle for enhancing the efficiency of nitrate and chromium treatment in sewage.According to the cardio denitrifying strains involved in this paper were isolated from the activated sludge of the oxidation ditch process secondary sedimentation tank of a sewage treatment plant in Chongqing.After acclimation and cultivation in the laboratory,the subsequent studies have been performed:16S rRNA gene identity of strain G12;initial Cr have a look at Cr?VI?The effect of concentration on the denitrification performance of aerobic denitrifying bacteria and the effect of nitrate concentration on Cr?VI?reduction;various influencing elements consisting of carbon source,nitrogen source,inoculum size,and coexisting binary heavy metal ions have been studied.The consequences of strains on nitrate and Cr?VI?reduction procedures;FT-IR,XRD,and XPS were used to analyze Cr?VI?and to study the simultaneous metabolism of Cr?VI?reduction and aerobic denitrification,a mechanism for the reduction of products.The consequences confirmed that:?1?At the denitrifying solid medium,the surface of the colony become neat,and the surface was smooth,moist,opaque and faded yellow.Using the 16S rRNA gene sequencing,it changed into showed that the pressure G12 belongs to Pseudomonas aeruginosa strain?Pseudomonas aeruginosa?and turned into named Pseudomonas aeruginosa stress G12.Stress G12 turned into inoculated at a ratio of 1%?v/v?to aerobic denitrification medium containing 500 mg/L of nitrate nitrogen and 10 mg/L of Cr?VI?,after which at 30?,120 rpm.The situations had been continuously cultured for 96 h.The strain G12 entered a strong stable growth at 48 hours,and its OD600 value reached a maximum of approximately 1.7.Nitrate nitrogen becomes absolutely removed in about 72 h,the elimination rate reached 98%,and the nitrate-nitrogen concentration became approximately 10 mg/L after 96 h.At 96h,the reduction rate of Cr?VI?reached 93.32%and Cr in the supernatant.The concentration of Cr?VI?is about 0.668 mg/L.?2?While the preliminary nitrate concentration is 100,300,500,700 mg/L,the nitrates are all decreased after 72 h of culture,and the elimination rate are 95.8%,99.5%,97.2%,70.3%,respectively;whilst the preliminary concentration of nitrate concentration turned into 500 mg/L,the reduction conversion rates of Cr?VI?of strain G12 to at least 1,5,10,15,and 20 mg/L had been 86.6%,94.9%,98.4%,99.1%,and 99.2%,respectively.%,the corresponding elimination rate of nitrate nitrogen had been 96%,96.5%,97.2%,96.7%,and 97.4%,respectively;the reduction impact of Cr?VI?changed into definitely correlated with the nitrate concentration within the medium;Cr?VI?The reduction and nitrate reduction were carried out simultaneously,focusing at the logarithmic growth phase of strain G12.?3?The outcomes of different environmental impact elements at the metabolism of strain G12 confirmed that:1 below distinctive carbon assets,the growth of strain G12 and the elimination impact of nitrate nitrogen and Cr?VI?had been distinctive,and one of a kind carbon source pairs The primary and secondary order of the consequences of strain G12 metabolism have been:1 sodium citrate>sodium succinate>glucose>sodium acetate,so sodium citrate changed into chosen because the carbon source;2 Inside the case of ammonia nitrogen,nitrate nitrogen,and nitrite nitrogen respectively.inside the case of a single nitrogen source,the primary and secondary ordering effects of various nitrogen sources on the metabolism of strain G12 had been:nitrate nitrogen>ammonia nitrogen>nitrite nitrogen,so nitrate changed into used as nitrogen source for subsequent research;3 After 1%,5%and10%?v/v?,the OD₆₀₀ value of stress G12 and the removal fee of nitrate nitrogen and Cr?VI?had been basically the equal after 72 hours of continuous culture.The impact of inoculum on strain G12 turned into higher.Small,so immediately inoculated in a ratio of 1%?v/v?;4 in the presence of binary heavy metal ions Cu²⁺or Mn²⁺coexistence,the growth of strain G12 reached a stable time frame,but its increase and the nitrate nitrogen and The reduction impact of Cr?VI?is not Influence,the presence of Cu²⁺or Mn²⁺improves the elimination rate of Cr?VI?to a certain extent;?4?it can be seen through instrumental analysis which include FTIR,XPS and XRD:1 the primary floor of G12 is carboxyl,hydroxyl,amino,amide,etc.Functional groups,these Functional groups are associated with the removal of Cr?VI?;2 within the XPS spectrum of the Cr2p orbitals of chromium,the 2p^1/2 and 2p^3/2 hybrid orbitals,which especially represent Cr³⁺,at binding energies of 577.36 and 583.01 eV,Cr The valence state of the decreased production of?VI?is in particular Cr???,this is,the strain G12 reduces Cr?VI?to a positive trivalent state;3 the reduction product Cr???of the strain G12 inside the cell is trivalent chromium,The crystal form of CrCl₃ exists.