Studies On Bioremediation Of Nonionic Surfactant In Soil

Nowadays the research on ecological environment of nonionic surfactants hasbecome a focus at home and abroad. The nonionic surfactants can seriously harm theaquatic plants, the aquatic animals, and the microorganisms, impair theself-purification capacity of the water body, speed the water eutrophication process.Therefore, it is of great importance to control and remediation the nonionicsurfactants' pollution.To develop a simple and effective bioremediation method to treat the nonionicsurfactants in soil, the bacterial strains were sifted from the waste water (inpollution-outlets) of Hunan Lichen Detergent Factory and of Changsha Towel Factory,respectively, which had a prominent degradation effect on the nonionic surfactantsBrij-30 (the correspondent bacterial strain B30), Brij-35 (the correspondent bacterialstrain B35), and TX-100 (the correspondent bacterial strain T100). Through theselection and study, the main results were as follows:1. KI-I₂ Spectrophotometry was used in the study of the absorption behavior ofthe three kinds of nonionic surfactants (Brij-35, Brij-30 and Tx-100) on naturalabsorbing agent, and the results showed that the saturated absorptive capacity ofBrij-35 was 7600 mg·kg^-1, bigger than that of Brij-30, which was 6000 mg·kg^-1. Inaddition, it was also explored the KI-I₂ Spectrophotometry's influences on thenonionic surfactants in water body under different experiment condition. Resultsproved the KI-I₂ Spectrophotometry was simple to operate, it had a good correlationcoefficient of calibration curve, a wide check linearity, the satisfactory stability ofacid, and little disturbance of the majority of salt and the soil humic acid.2. Three bacterial strains (B30, B35 and T100) highly degraded on Brij-30,Brij-35 and TX-100 correspondingly. Through the experiments, the results of thestrain growth regulation, the strain degradation rate, and the strain degradationregulation showed that 1) the bacterial strain B30 growed fastest; 2) comparing withB30, the bacterial strain B35 growed relatively slowly; 3) as for the growth curve ofthe bacterial strain T100, there was a lag phase at the early stage of growth and anacceleration phase after 12 hours from the beginning of the growth. The growthcurves were fitted well with the degradation rate curves. The degradation rate curvesof the nonionic surfactants indicated that the degradation process of the bacterialstrains corresponding to Brij-30 was the fastest, which could be finished in about 12 hours; the degradation process of the strain corresponding to Brij-35 was the second,which could be finished after 24 hours; and TX-100 degraded the slowest on theinitial stage of degradation process, it sped prominently the degradation after 12hours' interval, and degraded completely to its end within 48 hours. The degradationrate of TX-100 was the slowest among the three types of nonionic surfactants,because TX-100 had relatively great toxicity to the bacterial strain, and the growth ofthe bacterial strain needed a suitable period at its early stage.3. Various environmental factors, such as temperature, the pH value, differentsubstrate concentration, the nitrogen source and the mental ions, influenced thegrowth and the efficiency of the surfactants' degradation of the three kinds of bacterialstrains(namely B30, B35 and T100). The study showed that the degradation effect ofthe bacterial strain B30 was the best at 30℃,with PH=5～8 and the substrateconcentration being below 0.2g.L^-1, along with the protein peptone used as thenitrogen source; Mental ions Zn²⁺, Ca²⁺, Al³⁺ and Fe³⁺ could contribute to the growthof B30 and B30's degradation rate of Brij-30; Bacterial strain B35 growed anddegraded well at 30℃, with PH=7 and the protein peptone used as the nitrogen source,and the mental ions Ca²⁺ and Al³⁺ could speed the growth of B35 and improve thedegradation rate of B35; The degradation effect of T100 was strong at 25℃, withPH=6～8 and the protein peptone used as the nitrogen source. When the density ofZn²⁺ was 0.2mg.L^-1 and the density of Ca²⁺, Al³⁺ and Fe³⁺ was 30mg.L^-1, these mentalions could improve the degradation rate of T 100 to a great extent.4. The shape structures of B30, B35 and T100 were under observationrespectively with the aid of the transmission electron microscope (TEM) and thescanning electron microscope (SEM). The result showed that the individual's shapeof the three kinds of bacterial strains was all brevis bacilluses or long bacilluses (themajority). The individual length of B35 was about 1.078～1.705μm and the widthwas 0.338～0.456μm; The individual length of B30 was about 1.131～1.820μm andthe width was 0.385～0.560μm; The individual length of T100 was about1.05～1.586μm and the width was about 0.359～0.427μm. The majority of theindividual size of B30 was a little bigger than those of B35 and those of T100. Theflagella of both B30 and B35 growed on the periphery of them, the flagella of T100belonged to polar flagella, some of T100's individuals growed like a chain.5. PCR-based cloning and sequencing approaches were applied in the molecularbiological identifications on the three high-efficiency degradation bacterial strains, corresponding to nonionic surfactants Brij-30, Brij-35, and TX-100, respectively. Theresults showed that 1)B35 belonged to Burkholderia, rather similar to Burkholderiavietnamiensis strain LMG 10929 and Burkholderia cepacia strain ATCC 55792, theserial homology degree reached 99%; 2)B30 belonged to Pandoraea, rather similar toPandoraea sp. LB-7, the serial homology degree reached 99%; 3)T100 belonged toOchrobactrum sp., rather similar to Ochrobactrum sp. CGL-X, the serial homologydegree reached 99%.6. The study on the influence of three highly effective bacterial strains on the soilmicroflora and the capacity to degrade the nonionic surfactants in soil was alsodiscussed in this dissertation. Results showed that the three highly effective bacterialstrains had remarkable degradation effects on nonionic surfactants, which couldobviously reduce its soil pollution. An immediate inoculation with the soil polluted bynonionic surfactants was much better than the 168 hours' inoculation. Compared withthe non-inoculated soil, the surfactants in soil remarkably reduced its residual quantitywhen the soil was inoculated and cultivated 168h soon after it was polluted bynonionic surfactants. The percentage of B30's degradation Brij-30 was over 85%. Asfor the degradation rate of B35 to Brij-35 and T100 to Tx-100 varied from 69% to75%; Compared with the immediate inoculation, the inoculation after168 hourscaused the degradation rate of the surfactants to vary from 60% to 70%. Thedegradation rate of B30 to Brij-30 decreased the most, from 85% to 68%. In differenttypes of soil, the degradation effect of highly effective bacterial strains on nonionicsurfactants was remarkably different. The three kinds of nonionic surfactants hadinhibiting effect on the growth of microorganism, namely, Brij-30＞Tx-100＞Brij-30and the inhibiting effect on the growth of actinomycetes＞the inhibiting effect on thegrowth of bacteria＞the inhibiting effect on fungi.