Effect Of Heavy Metals On Paracoccus Versutus LYM In Aerobic Denitrification Process

In recent years, with the rapid development of economy and industry, human activities have seriously interfered with the balance of nitrogen circulation, with the skyrocketing quantity of ammonia nitrogen, nitrate nitrogen, nitrite nitrogen and nitrogen oxides in natural environment, leaving serious nitrogen pollution. As a new type of denitrification technology, aerobic denitrification with its inherent advantages has gained widespread attention. In this paper, the Paracoccus versutus LYM screened from seabed sediment with function of heterotrophic nitrification and aerobic denitrification was studied, and the research was done over the aerobic denitrification removal process of two kinds of nitrogen pollutants:NO3-and NOx respectively.Wastewater containing heavy metals generated in industrial processes will inevitably enter the biological sewage treatment system also some special high-nitrogen wastewater contains large quantity of heavy metals, while excessive content of heavy metals shows to be toxic to microorganisms, thereby lowering the treatment effect. The first part of this research explores the effect of common heavy metals as Cd(Ⅱ), Cu(Ⅱ), Zn(Ⅱ), Ni(Ⅱ) at concentrations of0.2mM and0.5mM respectively on the process of NO3-aerobic degradation by LYM strain, the conclusions are as follows:(1) The growth condition of strain LYM directly affects the NO3-degradation effect: Cu(Ⅱ) and Ni(Ⅱ) have significant influence on the strain growth curve under two levels, which can lead to large differences in inhibition extension of NO3-degradation effect; Cd(Ⅱ) has a great inhibitory effect on the growth of strains in two levels, leading to poor NO3-degradation effect; Zn(Ⅱ) influences the growth of the strain comparatively weaker, and even revealed to have slight promote effect, meanwhile NO3-degradation process is also slightly affected accordingly.(2) The gaseous product during NO3-aerobic denitrification degradation process by LYM is N2and N2O hasn’t been detected.(3) In the experimental period, the orders of constraint influence of heavy metals differs under concentrations of0.2mM and0.5mM, which can be ordered from strong to weak: Cd(Ⅱ)> Ni(Ⅱ)> Cu(Ⅱ)> Zn(Ⅱ) under0.2mM; Cd(Ⅱ)> Cu(Ⅱ)> Ni(Ⅱ)> Zn(Ⅱ) under0.5mM. Generally flue gas containing nitrogen oxides also contains oxygen. Aerobic denitrifying bacteria owning to its ability of denitrification in oxygen condition shows its advantages in this scenario. While the NOX in flue gas comprises mainly of NO which is poorly soluble in water, which makes aerobic denitrifying bacteria to be favorable in the flue gas nitrogen treatment. The first issue required to be solved is screening out proper oxygen resistant complexing agent. The preliminary study found that CoEDTA has certain ability of catalyzing and oxidizing NO into NO3-and NO2-. Thus the second part of this research mainly inspected the effect of CoEDTA on NO3-and NO2-degradation process by strains LYM, the conclusions are as follows:(4) CoEDTA has less inhibition effect on NO3-degradation process.(5) Adding CoEDTA into NO2-degradation system can significantly increase the lag phase of strain LYM, while the NO2-degradation rate in degradationstage is the same to control group when strain LYM gets adapted to the environment containing CoEDTA.