Research On Activation Of Manganese Oxide Bacteria And Removal Efficiency Of Pharmaceuticals By Biogenic Manganese Oxides

In the recent decade,because of the production and use of human beings,pharmaceuticals have been found in water bodies around the world,and continuously endanger the safety of human and ecological environment.The regular sewage treatment process have poor biodegradation performance on pharmaceuticals.Although AOPs,active carbon adsorption,membrane can remove pharmaceuticals effectively,but the cost,toxic by-product,production waste make it difficult to be further applied.Biogenic manganese oxides are metabolites produced by manganese oxide bacteria in aerobic environment.Because of its high specific surface area,high redox potential,biogenic manganese oxides can remove organic contaminant.Therefore,it has great scientific and practical significance to study the degradation of pharmaceuticals by biogenic manganese oxides which can reveal the migration and transformation rules of pharmaceuticals in the environment and provide a cost-effective treatement technology wastewater containing pharmaceuticalsIn order to find the optimal bacteria source and medium,aerobic sludge from sewage plant,paddy soil,freshwater sediment from Qingshuixi and surface soil from manganese ore field were chosen as the inoculation bacteria using Letpothrix medium,K medium as medium.Afterwards,the best bacteria source was activated under difference pH and difference Mn2+ dosage,the activation condition was optimized and the changes of microbial communities and the products were also analyzed.Four typical pharmaceuticals namely diclofenac,naproxen,17α-ethinylestradiol,carbamazepine,were chosen as target pharmaceuticals.The removal efficiency of target pharmaceuticals degraded by biogenic manganese oxides produced after activation were investigated under different pH and biogenic manganese oxidesd dosage.The main conclusion were as follows:(1)Aerobic sludge and Leptrothrix medium were chosen as the best bacteria source and medium.The manganese oxide bacteria were activated best at pH=7.0.Manganese oxide bacteria were more suitable for acidic conditions,and alkane conditions would inhibit their growth.The best activation result was obtained when the Mn2+ dosage was 1mM.When Mn2+ dosage was increased by 5mM,it would strongly inhibited the activity of manganese oxides bacteria.(2)The biogenic manganese oxides produced by manganese oxide bacteria is complex and mainly contained Na3Mn(PO3)CO3、Mn3O4、MnO2.Seven genus with manganese oxide bacteria,Areomonas,Exiguobacterium,Flavobacterium,Acinetobacter,Sphingobacterium,Pseudomonas,Bacillus were found.The relative frequency of the seven genus was significantly increased after activation,and the total relative frequency was 18.25%.(3)The removal of pharmaceuticals by biogenic manganese oxide depends on pH.The removal efficiency and rate of pharmaceuticals gradually increased with the decrease of reaction pH and the increase of the dosage of biogenic manganese oxide.When the dosage of biogenic manganese oxides was 20mg/L and the reaction pH was 4,diclofenac,naproxen,17α-ethinylestradiol had the best removal efficiency.After 48 h reaction,the removal efficiency of the three pharmaceuticals was 100%,65.5%,100%,in which 75.5%,35.7%,78.3% was removed by biogenic manganese oxides.When the dosage of biogenic manganese oxide was 20mg/L and the reaction pH was 3,carbamazepine had the best removal efficiency.After 48 h reaction,the removal efficiency of carbamazepine was 29%,in which 21.2% was removed by biogenic manganese oxides.