| With the development of economy and urbanization in China, the amount of municipal sludge increased dramatically. How to scientifically deal with the municipal sludge has been concerned widely by environmentalist at home and abroad. Among most of the residual sludge treatment methods, land utilization is one of the most potential methods. But the heavy metal is a main factor limiting its effectiveness. For the heavy metal pollution, the phytoremediation technology has been developed rapidly for its low cost and good environmental effect, but the study about this technology is now focused primarily on the soil contaminated by heavy metal.For the different characters of sludge compared with those of the soil, the mechanism and effect that plants remedy heavy metal of the residual sludge need to be explored and validated by experiments. This thesis has taken the residual sludge from four different scale and type sewage plants as research objects, conducted the analysis and experiment of heavy metal contents and speciation in the residual sludge, and carried out screening test of the heavy metal pollution remediation by ornamental plants in the residual sludge and the activation of the earthworm in the residual sludge polluted with the heavy metal. Based on the analysis the thesis has put forward the eisenia foelide and Chlorophytum comosum combined remediation technique for the heavy metal in the residual sludge. The research had important theoretical meaning and potential application value for the heavy metal remediation of the residual sludge and would provided a new way for the sludge detoxification. The main conclusions of the thesis include:(1)The analysis of heavy metal content shows that: the contents of heavy metals in the sludge from four different types of sewage plants are different. The Jingmahe sewage plant in Xuzhou city has the highest contents of Cu, Zn and Pb (the values are 2013.48mg/kg, 4862.18mg/kg and 541.79mg/kg).The Yaozhuang sewage plant in Xuzhou city has the highest content of Cd (the value is 25.42 mg/kg). The Huaibei sewage treatment plant has the highest content of Cr (the value is 462.19 mg/kg). Meanwhile, the contents of Cu, Zn, Pb and Cd in the sludge from all plants exceed prescribed discharge standards of Discharge standard of pollutants for municipal wastewater treatment plant (GB18918-2002).(2)The analysis of the heavy metal speciation in the residual sludge shows that: all kinds of heavy metal in the sludge from four sewage plants mainly exist in stable states (sulfide-bound state, residual form). The most speciation of Zn are carbonate state(from 20.26% to 27.11%) and residual form (from 45.08% to 61.70%).Cu, Pb, Cr mainly exist with the speciation of sulfide-bound state(the proportions of 51.79%～60.87%, 23.12%～31.45% and 61.28%～78.36% respectively) and residual form(the proportions of 27.43%～34.62%, 55.68%～63.50% and 21.64%～38.72%).Most of the Cd exists in sulfide-bound state(the proportion of 38.45%～51.60%) and Fe-Mn-bound state(the proportion of 15.69%～30.20%).(3)The screening test of ornamental plants shows that: For its vigorous growth Chlorophytum comosum has the ability to accumulate the heavy metal of Cu, Zn, Cd and Pb to some extent without the symptom of being poisoned, thus it is suitable for the combined remediation of the heavy metal pollution. In the period of experiments, the Chlorophytum comosum has the largest total accumulation amount of the heavy metal of Cu, Zn, Cd and Pb which is 5.70mg plant -1,14.53mg plant -1 0.340mg plant -1和0.580mg plant -1 respectively with the sludge treatment(3:0,2:0).(4)The activiation experiments of the earthworm show that: The earthworm Eisenia fetida Andrei can grow normally in the sludge added with certain proportion concentraition of Cu, Zn, Pb and Cd. This kind of earthworm can change the physical and chemical character of the sludge and improve the bioavailability of the heavy metal in the sludge. The bioavailability of the heavy metal will be most improved by the acitivity of the earthworm when the proportion concentration of Cu is 150 mg/kg and that of Zn is 200 mg/kg and that of Pb is 400 mg/kg.(5)The combined remediation experiments by the earthworm and the ornamental plants show that: The earthworm Eisenia fetida Andrei can change the physical and chemical character of sludge, accelerate the growth of the Chlorophytum comosum and enhance the absorption of the heavy metal in the sludge. For the sludge with different Cu proportion concentration, the total accumulation amount by the Chlorophytum comosum has increased 0.99 mg plant -1, 4.69 mg plant -1, 1.62 mg plant -1 and 8.03 mg plant -1 respectively. For the sludge with different Pb proportion concentration, the total accumulation amount by the Chlorophytum comosum has increased 4.81mg plant -1, 1.13mg plant -1, 3.707mg plant -1 and 0.45mg plant -1 respectively. The earthworm Eisenia fetida Andrei has raised the enrichment coefficient and the transfer coefficient of the stem and leaf and the root of the Chlorophytum comosum. The enrichment coefficient of the root of the Chlorophytum comosum is larger than 1 when the proportion concentration of Cu is 50mg/kg or100mg/kg and the proportion concentration of Pb is 0mg/kg. There are 73 figures, 46 tables and 215 references in the thesis. |
PDF Full Text Request