Islarion And Identification Of Penicillium Chrysoqenum ZG-16 And Its Role In Removal Of Heavay Metals From Sludge

By the end of 2014,China has built 3717 sewage treatment plants with the daily sewage treatment capacity of 157 million m3 in major cites and counties.It is expected that the annual yield of sludge?with the moisture content of 80%?from urban sewage treatment plants will reach the amount of 33.59 million t by 2015,which means that these plants produce 92,000 t sludge every day.Sludge has the characteristics of high water content,high content of heavy metal and pathogenic pollution,etc.Many researches have demonstrated that heavy metals in sludge severely hinder the disposal and utilization of sludge because these heavy metals may be enriched into the human and animal body through the food chains.Thus,heavy metals in sludge are obviously harmful to human health.Recently,many studies have found that low molecular organic acid produced by filamentous fungi could dissolve heavy metals from the environment,thus removing heavy metals from contaminated soils or sludge by using filamentous fungi.This study isolated a strain of Penicillium chrysogenum with the ability of producing small molecular organic acid from sludge.The feasibility of using the isolated filamentous fungi to remove heavy metals from sludge was studied..The influences of the addition of extra carbon sources and the solid content of sludge on the solubilization of heavy metals during the fungal treatment of sludge using filamentous fungus Penicillium chrysogenum were also investigated.Furthermore,the usefulness of combing fungal treatment and bioleaching driven by Acidithiobacillus sp.in enhancing the solubilization of heavy metals from sludge was explored.Based on results obtained,following conclusions can be drawn:?1?Four strains of filamentous fungi,that is,Mucor,Penicillium chrysoqenum,Penicillium simplicissimum and Penicillium crustaceum,respectively,were isolated from sludge collected from the thickening tank of Taihu New Town Wastewater TreatmentPlant.A filamentous fungus named as ZG-16 produced several kinds of small molecular organic acid such as oxalic acid,citric acid,and pyruvic acid,and thus is was selected as a suitable candidate for the fungal treatment of sludge.The optimal temperature for its growth was 20?35?,and the optimal pH value for its growth was 3.0?8.0.The concentrations of Zn²⁺,Cu²⁺and Cd²⁺ for inhibiting the growth of the filamentous fungus ZG-16 by 80%were 200 mg/L,300 mg/L,and 500 mg/L,respectively.During its growth in pure culture system,the yields of oxalic acid,malic acid,citric acid,pyruvic acid and succinic acid were 3.2 mmol/L,9.8mmol/L,23.3 mmol/L,6.9mmol/L and 3.5mmol/L,respectively.?2?The treatment of sludge using Penicillium sp.ZG-16 can effectively solubilize heavy metals form sludge.The addition of extra carbon souces influenced the solubilizatin of heavy metals during the fungal treatment of sludge using Penicillium sp.ZG-16.After ten days of treatment,almost no heavy metal was solubilized when treating sludge using Penicillium sp.ZG-16 but without the addition of sucrose as extra carbon source.But when sucrose was added into sludge as extra carbon source,the solubilization,efficiencies of heavy metals were 4%?Cd?,0.1%?Cr?,2.1%?Cu?,15%?Ni?,3.7%?Pb?,and 28%?Zn?,respectively,during the fungal treatment of sludge using P.chrysoqenum ZG-16.?3?The solid content of sludge also impacted the solubilization of heavy metals from sludge during the fungal treatment of sludge using Penicillium sp.ZG-16.The final sludge pH reached decreased with the lowering of sludge solid content.The final pH values of sludge with 1.1%,1.7%,and 3.4%of solid content were 2.1,2.5,and 2.9,respectively,after the fugnal treatment using Penicillium sp.ZG-16.More organic acids were produced and higher solubilizatin efficiencies of heavy metals can be achieved when treating sludge with lower soild content.When the solid content of sludge was 1.1%,the solubilization efficiencies of heavy metals reached the maximum?Cd 62%,Cr 81%,Cu 20%,Ni 40%,Pb 57%,and Zn 95%?,which were close to that of treating sludge with the solid content of 2%.However,the solubilization efficiencies of heavy metals were extremely low when treating sludge with the solid content of 3.4%.Regression analysis was used to study the relationships between the solubilization of heavy metals and organic acid produced and sludge pH.It was found that citric acid,pyruvic acid and sludge pH had important impacts on the solubilization of each heavy metal.In the sludge with 1.7%of solid content,the yields of pyruvic acid and oxalic acid were the main factors controlling Cd solubilization.The solubilization of Cu was slightly effected by organic acids produced.Nevertheless,the solubilization of Ni and Zn were strongly effected by sludge pH,and the values of R2 of their linear correlation models were close to 1.Moreover,the yield of citric acid has the greatest impact on the solubilization of Pb.?4?It was proposed that different microbes,such as A.ferrooxidans LX5 and/or Penicillium sp.ZG-16,shoud be used to treat sewage when different heavy metals are present in sludge,because autrophic and heterotrophic microbes possess distinct meahanisms responsible for heavy metal solubilization.It was found in the present study that A.ferrooxidans LX5 and Penicillium sp.ZG-16 synchronization is the best way to dispose the sludge containing high content of Cd.A.ferrooxidans LX5 should be used to solubilize Cr,Cu and Ni from sludge,while either P.chrysoqenum ZG-16 or A.ferrooxidans LX5 are usrfull for the leaching of Zn in the sludgeThis study is able to aid the development of method dissolving heavy metals of sludge by using filamentous fungi.