Study On Degradation Characteristics Of Two Nonionic Surfactants And The Influence On Soil Physic-chemical Properties

Two nonionic surfactant-degradating bacteria designated as B-2 and T-1 were isolated from the surfactant-polluted water(in pollution-outlets) from detergent factory by repeated subculture in liquid medium with Brij-35 and Triton X-100 as the sole carbon and energy source respectively.The bacterial characteristics,molecular biology identification,degradation rate of nonionic surfactant impacted by different environmental facto's were reseached in this paper.The effects of nonionic surfactants on activities of enzyme and microbe,nitrification and amonification in tested soil were studied through incubation experiments.The main results were summarized as follows:The shape characteristics of two nonionic surfactant-degrading bacteria were abserved by scanning electrom microscope(SEM).The results showed that the individual's shape of B-2 was short bacilluses,no flagellum,non-sporeforming;T-1 was short bacilluses,flagellum from one side.The analyse of the phylogenetical analyses of 16S rDNA sequence showed that strain B-2 and T-1 were identified as Burkholderia and Ochrobactrum sp.The results indicated that the optimal pH value and temperature for T-1 growth were 6～8 and 25℃,B-2 were 7 and 30℃respectively.A significant positive relationship was found between bacterial growth and concentration of nonionic surfactant degradation.In a mineral salts medium with 100 mg/L nonionic surfactant,the highest degradation of Triton X-100 was obtained after 60 h,but that of Brij-35 was obtained only need 36 h.When the concentration of nonionic surfactant at 200～800 mg/L,the degradation rates of Triton X-100 was higher than Brij-35 after 72 h.The optimal pH value and temperature for T-1 growth were 6～8 and 25℃,B-2 were 7 and 30℃respectively.The two strains were able to use a broad of nitrogen sources.Zn²⁺, Ca²⁺,Al³⁺,Fe³⁺ could inhibit the growth of the strains and biodegradation of Triton X-100 and Brij-35 slightly, but Cu²⁺ had inhibitory effect.The urease activities were inhibited in vegetable garden soil and tea garden soil after treated with surfactant,and the results of the effects of surfactants on urease activities in soils were the same.In vegetable garden soil,the urease activities were stimulated when the soil was added surfactant-degrading bacteria in 1 d and then inhibited quickly and then decreased to background value.The urease activities were inhibited in 1 d and then stimulated quickly in sea garden soil added bacteria,which can arrived the max value in 16 d.There were effects on soil breathing intensities with two nonionic surfactants.The breathing intensities were increased in 4 d and then decreased in soils adding bacteria,but slightly changes can be finded in soils without nonionic surfactants degrading bacteria.The study on the different of influence of two nonionic surfactants on the number of ammonifiers and nitrifiers in two so ls added bacteria or not was also discussed in this dissertation.Results showed that the number of ammonitiers and nitrifiers were increased in evidence in the soils added bacteria compared with in which not added bacteria.The aminatation was inhibited apparently in soil by nonionic surfactant in this study.The concentrations of NH₄⁺-N were changed differently in two soils in 32 d:The concentrations of NH₄⁺-N changed fluctuating,and the whole trend is minus in vegetable garden soil added nonionic surfactants.Adding nonionic surfactants degrading bacteria in vegetable garden soil can weaken the effects of inhibition to aminatation by nonionic surfactants,the concentration of NH₄⁺-N can approach the background value after 32 d,but different results can be finded in tea garden soil.The nonionic surfactant could still inhibite the nitrification apparently in soil in this study.The concentration of NO₃^--N decreased at initial stage in 8 d in two soils.The difference of the nitrification changed in two soils added nonionic surfactants degrading bacteria were finded:the nitrification in vegetable garden soil was stimulated quickly in(?)d and then changed fluctuated,but the reverse result was finded in tea garden soil and persistent inhabitation was finded in the tea garden soil added Triton X-100.