The Study Of Metal Ion Effect Anammox Bacteria Second Messenger C-di-GMP

The anaerobic ammonium oxidizing(anammox)process has received more and more attention because of its bright application prospect in the field of high nitrogen wastewater treatment.It has been demonstrated that the operation and startup of anammox reactors are closely related to numerous external environmental factors such as pH,temperature,and heavy metal concentration.Among them,the widely studied metal ions Ca2+,Mg2+ and Fe2+ have significant effect on the anammox process.However,studies on the mechanism of metal ions affect anammox process had encountered many difficulties since anammox bacteria cannot be purely cultured.This experiment explored the effects of different concentrations of Ca2+,Mg2+ and Fe2+ on the denitrification performance of anammox reactors.The mechanism of Ca2+,Mg2+and Fe2+ effect on the anammox process was analyzed from the perspective of molecular biology using biological information analysis based on the metabolic changes of the second messenger cyclic diguanylate(c-di-GMP).The main results are as follows:(1)The increase of Ca2+ concentration within a certain range can promote the removal of TN(Total nitrogen)when the MgL.concentration was maintained at 30 mg/L.The variation of Mg2+ concentration in the anammox reactor had little effect on TN removal rate when the Ca2+ concentration was maintained at 49 mg/L.TN reached an optimum removal rate when the Ca2+ concentration was 98 mg/L meanwhile Mg2+concentration was 30 mg/L in R5 reactor.The TN removal efficiency of the reactor was the best when the added nano-zero-valent iron(nZVI)concentration was 50 mg/L.(2)The anammox bacteria abundance was significantly higher than other reactors as the Ca2+ concentration in the reactor was maintained at 98 mg/L and the Mg2+concentration was 30 mg/L.The abundance of the anammox bacteria had no significant changes but the abundance of the autotrophic denitrifying bacteria was increased when the Ca2+ concentration in the reactor was 49 mg/L compared with the blank group.The abundance of anammox bacteria was significantly increased when the concentration of nZVl in the reactor was 50 mg/L.The richness of anammox bacteria was declined in the reactor which nZVI concentration was 1 g/L compared y\with the reactor which concentration was 50 mg/L.(3)The gene content of c-di-GMP metabolism-related enzymes was positively correlated with the content of extracellular polymeric substance(EPS)and TN removal.This suggests that the enhancement of c-di-GMP metabolism can promote the removal of TN by the anammox process.Ca2+ and Fe2+ can promote the synthesis of c-di-GMP by promoting the abundance of Diguanylate cyclase(DGC)which function is to express c-di-GMP.The influence by the Ca2+ and Fe2+ to the enzyme abundance of phosphodiesterase(PDE)gene is not significant.The effect of Mg2+ on c-di-GMP metabolism is not significant.(4)Bioinformatics analysis showed that the addition of low-concentration nZVI(50 mg/L)can promote the communication of microorganisms in the reactor and nitrogen metabolism,thereby promoting the formation of anammox granular sludge and the treatment efficiency of the reactor.The formation of granular sludge promotes the efficiency of the treatment of the reactor.