Degradation Of Oorganic Pharmaceuticals By Dissimilatory Metal Reduction Bacteria

Pharmaceutical and personal care products (PPCPs), including organicpharmaceuticals, have become a hot area for recent years. Organic pharmaceuticals enterinto the aquatic environment mainly through the sewage treatment plant discharge, becausethe conventional wastewater treatment process (such as biological, physical or chemicalmethods) cannot effectively remove organic them. Most of the urban sewage treatmentplants only have two-stage processing, and only a few using tertiary treatment or advancedtreatment processing (such as ultrafiltration, flocculation, ozone oxidation, advancedoxidation or reverse osmosis) which need higher cost. As a result, most of the organicpharmaceuticals are released into the aquatic environment, and will have adverse effects onthe aquatic ecosystems. Even at low concentration, organic drugs may have potential harmon the environment and human health.Dissimilatory metal reducing bacteria can use Fe (III) and Mn (IV) as the soleelectron acceptor coupling oxidation of organic compounds, and gain energy to supportgrowth; Fe (III) and Mn (IV) can be restored, but will not be assimilated as cellcomponents. Because of the higher geochemical abundance of Fe(III) and Mn(IV) on theearth, the dissimilatory metal reduction can be found in almost all the anaerobicenvironment, and different dissimilatory metal reduction microorganisms have been foundand isolated from various anaerobic environments, such as fresh water, groundwater,sediments, lake sediments, the basement soil, acid wastewater and activated sludge, etc.Dissimilatory metal reduction microorganisms distribute through bacteria and archaea, andthey are of diversity on phylogeny and Physiology and ecology. they can ferment oroxidizing H2, organic acids or aromatic compounds using electrons supplied by Fe (III) orMn (IV).In the soil, groundwater and water sediments, metal reduction coupling organicmatter oxidizing and its potential role in environmental restoration have arousingincreasing concern. Applying metal reduction reaction for the removal of organicpharmaceuticals in water has significant importance on the degradation of organic drugs inwater and on in-situ remediation of sediment environments. The research appliedGeobacter metallireducens and concentrated dissimilatory metal reduction microorganismsfor the degradation of organic pharmaceuticals, which used iron and manganese oxides aselectron acceptor.Degradation of carbamazepine by Geobacter metallireducens was studied by using ferriccitrate as electron acceptor and carbamazepine as the sole carbon source and electrondonor. Through analysis and discussion, conclusions are drawn as follows:(1) The system composed by the dissimilatory bacteria and ferric citrate can remove61.8%carbamazepine. Under anaerobic conditions, carbamazepine was degraded by the dissimilatory reaction of G.metallireducens and ferric citrate. The removal rate ofcarbamazepine carsed by the bacterial was30.1%.(2) Fe(II) produced by iron reducing reduction will inhibits iron reduction reaction byadhering on the surface of bacteria and iron oxide. As Fe(II) and Fe(III) will generatemagnetite precipitation, iron reduction process is terminated, as a result the degradation ofcarbamazepine cannot continue.Degradation of carbamazepine by concentrated dissimilatory metal reductionmicroorganisms was studied by using different iron or manganese oxides as electronacceptor while carbamazepine and diflofenac as the sole carbon source and electron donor.Three sediments from different locations along Jialing river were chosen to enrichdissimilatory metal reduction bacteria, and synthetic amorphous iron oxides Fe(OH)3,synthetic amorphous manganese oxide δ-MnO2, hematite powder (α-Fe2O3) andmanganese dioxide β-MnO powder were used as electron acceptors, respectively.1#C-Fe、1#A-Mn、2#C-Fe、2#A-Mn in enriching experiment were chosen for the degradation oforganic pharmaceuticals. The degradation experiment used corresponding iron ormanganese oxides as electron acceptor and carbamazepine and diflofenac as the solecarbon source. Through analysis and discussion, conclusions are drawn as follows:(1) Sediments from3different locations can reduce iron or manganese oxide. theconcentration of soluble Mn (II) reached the maximum on the second day in systems whichused A-Mn and C-Mn as electron acceptor, while soluble Fe(II) reached the maximum on4~5d in systems which used A-Fe and C-Fe as electron acceptor. The concentrations ofsoluble Fe(II) were higher in A-Fe while Mn(II) were higher in A-Mn.(2) In enriching experiments, OD600were on the rise and stayed stabal after7days.pH were also on the rise because of the accumulation of Fe(II) and Mn(II) and theconsuming of acidity.(3) In degradation experiments, enriching dissimilatory metal reductionmicroorganisms can degrade carbamazepine and diflofenac using hematite as electronacceptor. The carbamazepine and diflofenac removal retas were3.35%and2.73%for1#-Fe, and2.08%和2.09%for2#-Fe, respectively.(4)The system which used δ-MnO2as electron acceptor can oxidizing carbamazepineand diclofenac. The initial concentration of the two pharmaceuticals are1.715mg/l and1.520mg/l, respectively, and the effective manganese content is2.0g/l. carbamazepine anddiclofenac were removed by chemically oxidation or oxidation catalyzed by dissimilatorymetal reducing reaction.