Treatment Of Acid Mine Drainage By Sulfate Reducing Bacteria Using Sludge As Carbon Source

At present,SRB process can be used to treat acid mine drainage with good removal effect for heavy metal ions,but the effect is not ideal in terms of economic benefits.The common organic acid carbon sources such as ethanol and acetic acid are expensive,which has a certain impact on the treatment of acid mine drainage by SRB process.Therefore,how to improve the removal rate of heavy metal ions and reduce the cost of carbon source has become the key to the application of SRB in AMD treatment.In this paper,the process of treating acid mine drainage（pH=2.5）with sulfate reducing bacteria（SRB）inoculated with activated sludge without additional neutralizer was investigated,and the effect of sludge dosage on the treatment process was analyzed,so as to provide guidance and methods for low-cost treatment of acid mine drainage（AMD）.When SRB uses sludge as carbon source to treat simulated acid mine drainage,the alkaline substances in sludge can quickly neutralize part of the acidity of wastewater at the beginning of the reaction,and make the pH value of the reaction system rise to the level suitable for SRB growth.Sludge can effectively adsorb the main heavy metal ions in acid mine drainage.When the input amount of sludge is 7.8 g/L,the removal rates of Cu²⁺,Ni²⁺,Zn²⁺are 99%,91%and 95%respectively.Before SRB acclimation,the removal of Cu²⁺、Ni²⁺、Zn²⁺was mainly attributed to the adsorption of sludge,activated sludge has a good adsorption effect on Cu²⁺、Ni²⁺、Zn²⁺.When the three ions coexist,the adsorption order is Cu²⁺>Zn²⁺>Ni²⁺.Changing the proportion of sludge in the system will affect the change of pH in the system,and then affect the sulfate reduction,because the acid neutralization capacity of the reaction substrate is mainly related to the dosage or concentration of sludge.When adding different amount of sludge,the removal rate of heavy metal ions increases with the increase of sludge amount,but it does not show a linear change.When the pH of the system increased from 2.5 to more than 5,it was beneficial to SRB growth,SRB domestication and sulfate reduction.However,when the pH rises to a level that does not inhibit the SRB activity,the sulfate reduction degree will be affected by the sludge input in the system.With the increase of sludge amount in the reaction system,the contents of DOC,acetic acid and butyric acid in the system with higher sludge content were correspondingly higher,acetic acid and butyric acid produced in the reaction process had a certain role in promoting the increase of dissolved organic carbon in the system.Using sludge as carbon source can realize low-cost acid mine drainage treatment,which has practical significance for remediation of mine environment.It was found that temperature,pH value and other factors restricted the growth activity of SRB.The optimum growth temperature of SRB was 30～36℃,high or low temperature could inhibit the growth of SRB,and the optimum pH was 7.Inoculation of5%,10%,15%and 20%SRB can remove SO₄^2-from simulated acid mine drainage.Comprehensive comparison shows that inoculation of 10%SRB can remove ions from acid mine drainage better.