Influence Factors Of Humic Microbial Reduction And Its Applications In Pollutants Removal

Humic substances are heterogeneous high-molecular-weight organic materials which are ubiquitous in terrestrial and aquatic environments.Some microorganisms found in soils and sediments are able to use humic substances and its model compound AQDS as an electron acceptor for the anaerobic oxidation of organic compounds and hydrogen to support growth,which is named humus respiration.A number of microorganisms which can reduce humus were found in sediments abundant of organic materials,contaminated soils and activated sludge.And many studies reported that by microbial humus reduction,humus and its model not only as electron acceptor support anaerobic microbial oxidation of organic acids and phenolic compounds, but also can shuttle electrons to support bio-reducion of the noxious (e.g.,metals,azo dye and nitroaromatis compounds)as electron shuttles.So microbial humus reduction has important significances for biodegradation of pollutants and biorestoration of contaminated sites.In this paper,sludge enriched with humus-reducing bacateria was obtained after 21 days by improved acclimation methed,and acclimation time was shortened compare with previous methds of task groups.The following studies contained the influence factors of humus reduction by acclimated sediments with AQDS as humus model compounds,the influence factors of Cr(â…¥)reduction by acclimated sediments with AQDS as electron shuttles,and biodegradation PNP by sludge with AQDS as electron shuttles.The present studies could be helpful in remediation of contaminated sites by microbial humus reduction.The results of influence factors of humus reduction suggested that acclimated sediments can reduce humus during 15～45℃,and the optimum temperature is 30～37℃.At initiative pH 4～9,humus reduction was occurred,and the optimum pH is 7. humus reduction was partially inhibited in the presence of O₂ or light.The degree of humus reductive activities caused by different nitrogen sources is NH₄Cl＞CO(NH₂)₂＞NaNO₃＞NaNO₂.Mg(â…¡),Mn(â…¡)enhanced humus microbial reduction, but Fe(â…¢),Zn(â…¡),Ni(â…¡),Cu(â…¡)showed partial inhibition for humus reduction,and Hg(â…¡)completely inhibited humus reduction.The result of influence factors of Cr(â…¥)reduction showed:Cr(â…¥)reduction was promoted in the presence of AQDS,and accumulation of AH₂QDS was delayed. The rate of Cr(â…¥)reduction was affected by carbon resource concentration,AQDS concentration and initial Cr(â…¥)concentration.NO₃^- or SO₄^2-inhibited Cr(â…¥)reduction. Mg(â…¡),Mn(â…¡),Fe(â…¢)enhanced Cr(â…¥)reduction,but Zn(â…¡),Ni(â…¡),Cu(â…¡), Hg(â…¡)inhibited Cr(â…¥)reduction.Long-term Cr(â…¥)reduction could be occurred when carbon resource is enough.PNP can be biodegraded by sediment of West Lake,acclimated sediment of West Lake and acclimated sludge sample from SiBao wastewater treatment plant with external carbon resource as electron donor,and biodegradation of PNP was enhanced with AQDS as electron shuttle.The degradation was continues with enough carbon resource.Acetate was better than glucose as electron donor.The time of complete degradation was prolonged with high PNP concentration.HPLC analyse demonstrated PNP was reduced to PAP owing to -NO₂ reduced -NH₂ by AQDS shuttle electrons between batefia and PNP.The multidimensional approach to degrade PNP by sediment or sludge:first,direct degradation of the chemicals;second,indirect degradation by reducing AQDS which act as electron shuttles to transfer electrons to the cyclic nitramines.The present study could be helpful in determining the fate of PNP in the environments rich in HA.