Study On The Co-treatment Of Acid Mine Drainage And Mineral Processing Wastewater By Biological Remediation And Heavy Metals Recycling Process

In the process of mining and flotation of non-ferrous metal minerals,large amount of acid mine drainage（AMD）and mineral processing wastewater（MPW）are produced.AMD contains high concentration of heavy metals and sulfate,while a variety of flotation reagents remain in MPW.It has been considered promising to treat AMD with sulfate reducing bacteria（SRB）.Considering of the characteristics of AMD and MPW,a bioremediation system for the co-treatment of AMD and MPW were constructed.The co-treatment permits the occurrence of neutralization process and the dissolved organic carbon（DOC）in MPW can sustain the bioactivity of SRB.In this study,the feasibility of the co-treatment of AMD and MPW was explored through laboratory-scale and pilot-scale experiments,and the design parameters of each unit were optimized,meanwhile,the heavy metal recovery process was also researched.（1）The biodegradability of MPW was evaluated by BOD₅/COD and Shaking Culture method.The results showed that MPW was easy to be biodegraded,and the biodegradation process of DOC in MPW conformed to the first-order reaction kinetic model.（2）Batch and continuous-flow experiments were conducted to exam the efficiency of bioremediation for the co-treatment of AMD and MPW.Previous to feeding into the bioreactor,the reduced concentration of Cu,Fe,Zn and Mn reached 78.55%,82.91%,63.42%and 71.66%as the AMD and MPW were mixed at the ratio of 1:2.Batch experiments revealed that the organic carbon in MPW could sustain the bioactivity of SRB.When the p H of influent and hydraulic retention time（HRT）were 5.00 and 18 h,the sulfate removal reached 46.10%,whereas the removal of Cu,Zn and Fe reached 99.46%,99.68%and 96.40%.In continuous-flow reactor,the concentration of heavy metals in influent had a negative influence on the performance of bioremediation.Microbial community analysis of the sludge showed the bioreactor contained less bacterial richness and evenness at higher heavy metal concentration in influent.The co-treatment system of AMD and MPW showed the synergism between the SRB and fermentative bacteria.The fermentative bacteria are more sensitive to the fluctuation of influent water qualities.（3）The co-treatment of AMD and MPW is verified through the pilot test.As the p H of influent and HRT maintained 5.00 and 18 h,the sulfate and DOC removal reached 47.50%and 71.8%,whereas the removal of Cu,Fe,Zn,and Mn reached 98.30%,91.56%,97.07%and 49.85,respectively.The results of pilot test are consistent with the laboratory-scale experimental results,and the co-treatment of AMD and MPW is supposed to have important value of engineering application.（4）To achieve the recovery of heavy metals from AMD by taking the advantage of H₂S,the technological process of“alkali addition—anaerobic sulfate reduction process”was carried out.The p H gradient experiments showed that the optimal influent p H was 4.50 for the high anaerobic reaction efficiency and highest concentration of H₂S.The design parameters such as C/S ratio,HRT,and gas/water ratio were optimized through pilot studies.When the C/S ratio and the HRT were 1.5 and 24h,the anaerobic reactor reached the highest utilization efficiency.The removal rate of DOC and sulfate reached more than 80%,and the concentration of H₂S was more than 140mg/L.The removal of Cu,Zn,Fe,and Mn reached99.19%,96.46%,95.67%,and 71.48%,respectively.