| Hubei province is called as "Province of Thousands lakes",with a humid climate as well as abundant water resources,locating in the middle reache of Yangtze river.Eutrophication of surface water such as lakes and rivers caused by excessive release of phosphorus(P)through wastewaters is a serious environmental problems in recent years,due to rapid industrialization,urbanization,and population growth in Hubei province.As an important industrial and agricultural cultivation base in the country,agricultural non-point source pollution in Hubei Province has been the main factor causing water eutrophication.Industrial wastewater and agricultural non-point source pollution to farmland,rural and other production and living sewage,often contains a high concentration of phosphate and organophosphorus pesticides,has been the difficulty of sewage treatment due to large pollution area and high cost.Therefore,efficient treatment of industrial wastewater and agricultural non-point wastewater is an important approach in curbing the aquatic eutrophication.In this study,twelve Phosphate-accumulating organisms(PAOs)(MEW09,MEW23,MEW55,MEW78,MEW89,MEW90,MET29,MET63,MET64,MET70,MET83 and MET84)were screened from the samples in Hubei province,by using traditional plate screening techniques,in combination with high throughput screening method.All these PAO strains above were tested for their dimethoate-degrading ability by HPLC,a efficiently dimethoate-degrading bacterial named MET70 which isolated from activated sludge collected from a wastewater treatment pool in Huangshi,with degradation rate of 77.3%.The colony morphologies and axonomic properties of strain MET70 were as follows: colony diameter 1~1.5 mm round,with ammonia odor,pale yellow,smooth surface,central uplift,opaque and sticky;gram-negative;oxidase was not produced;starch was not hydrolyzed;nitrate reduction,positive;contact enzyme,positive;lysine decarboxylase,positive and hydrolysis of gelatin,negative.According to T-A cloning of its 16 S r RNA sequence,its morphological and biochemical methods identification,the multifunctional bacteria of MET70 which can accumulate phosphate and degrade organophosphorus pesticide was identified as Stenotrophomonas maltophilia.Then the process of accumulating phosphate and the degradation characteristics of organophosphates by the newly isolate were studied.MET70 genomic sequencing shows that,the size of genome is 4.55 Mbp,the GC% amount is 66.54%,the scaffold number is 22,the max scaffold size is 1,241,852 bp,the min scaffold size is 1,471 bp,the mean scaffold size is 206,815 bp,the N50 value is 1,100,072 and the N90 value is 327,820.The predict gene number is 4116,t RNA structure is 66,r RNA structure is 6,TRF structure is 228,SSR structure is 45 and no CRISPR structure.Effect of biological phosphorus removal in synthetic waste water(SWW)was studied using dissociative MET70 organisms and its immobilization in calcium alginate.The result showed that MET70 has a good potential in phosphate-accumulating.The phosphorus accumulating rates were 97.8%,96.3%,85.3% and 70.7%,respectively,after treated 24 h with dissociative MET70 for 5,10,15 and 20 mg/L phosphorus-containing wastewater.When P?10mg/L,the treatment could meet the sewage discharge standards in 24h(TP<0.5 mg/L).In the treatment of 5 mg/L and 10 mg/L phosphorus-wastewater by calcium alginate immobilized-MET70,the rate of phosphate-accumulating was the highest at 12 h,which was 99.9% and 98.9%,respectively.In the treatment of 15 mg/L and 20 mg/L,the highest phosphorus accumulation rate was 98.2% and 98.54% at 48 h.The ability of the immobilized was further increased,that the treatment time was shortened to 12 h at the same condition,and when 10 <P?20 mg/L,the wastewater can be safe discharge in 48 h.Capability of OPPs-degrading of MET70 was studied,the results showed that MET70 had strong tolerance and broad-spectrum degradability to five kinds of organophosphorus pesticides(omethoate;dichlorvos;parathion-methyl;chlorpyrifos;dimethoate)commonly used in agricultural.The order of tolerance to pesticides is: dimethoate> omethoate ? dichlorvos> methyl parathion> chlorpyrifos;The optimum p H of MET70 in degradating omethoate,dichlorvos,methyl parathion,chlorpyrifos and dimethoate were 8.0,8.0,9.0,7.0 and 9.0,and the degradation rates were 64.8%,46.36%,50.22%,31.36% and 84.01% under optimum p H,respectively;The optimum temperature of MET70 in degradating omethoate,dichlorvos,methyl parathion,chlorpyrifos and dimeth and the degradation rates were 30?,35?,30?,30? and 35?,and the degradation rates were 64.21%,47.83%,45.8%,32.98% and 77.7% under optimum temperature,respectively.Overall,the degradation ability of MET70 was stable in the range of p H(7.0~9.0)and temperature(30~35?).The study also found that MET70 could utilize dimethoate as the sole carbon source for growth.In flask test strain MET70 degraded 89.7% of dimethoate(50 mg/L)within 120 h,and no new intermediate was found during the degradation by HPLC technique,further resulting in complete mineralization of dimethoate by MET70.The study also found that,MET70 has a strong hydrolysis capacity on lecithin in the range of p H 7.0~11.0.Sprinkling MET70 culture in the field,the results showed that the content of available phosphorus in soil increased from 8.42 mg/kg to 16.84 mg/kg in 72 h,and the ability of phosphorus-providing of soil was significantly increased,which was beneficial to improve the absorption and utilization of phosphorus of plants in soil.After the activation of MET70 for 20 days,the growth of pakchoi was significantly higher than that of the control group,weight increased by 34.63%,plant height increased by 12.43%,root length increased by 24.36%,and stem diameter increased by 51.79%.Above all,the ability of accumulating phosphate and reducing the toxicity of OPPs make S.maltophilia MET70 an ideal candidate for its application in curbing the phosphorus chemical industry wastewater as well as the development of biological agricultural.In order to improve the processing efficiency and reduce operation cost,an idealized treatment of industry wastewater wastewater has been formulated to remove phosphate and OPPs at the same time.The aim of this study is finding a new way to achieve phosphorus resource recycling and providing theory evidence for the production and application. |
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